Engine misses, surges or bucking (FI related only)


woodyvw9

New member
I have 78 westy with a new engine and at about half throttle and in the midrange of rpm's I get an intermitant skip. I've check the airflow meter, timing, and all my vaccum lines, am I missing something obvious. (It did sit for a while so I just got a good fuel system cleaner and hope that will do the fix.) If I stay hard on the gas it does not do it. It isn't stalling or really losing power just kind of hiccups at that perfect rpm/throttle position. Thanks for the help...

[ 07-23-2001: Message edited by: Capt. Mike ]
 

Capt. Mike

Moderator
There is a good Type II troubleshooting chart for fuel injection posted on my pic site linked from the home page. Look in the technical diagrams folder. That will check out the FI with nothing more than a volt-ohmeter.

You symptom sound like the air-flow meter may have a burned spot in it's control "switch" section as it works on the principle of constantly changing voltage. Something like a rheostat that has a burned section. But isolate everything else out first; they're expensive compared to other sensors & components.
 

Capt. Mike

Moderator
Car bucks & stalls. Turning off and restarting solves the problem.

Has anyone else experienced this? I don't want the mechanic to replace the fuel injection system part by part, hoping he'll eventually stumble on the cause. No one in this area has any real expertise in vanagons. There aren't many!

By the way, we did get a tune-up last week too.

Capt. Mike Moderator Member # 11 posted 05-20-2001 10:18 PM

Have you done the full FI system check-out with a volt-ohmmeter per the Bentley? Replacing parts until one works is not the way to test! I can sympathize if you can't find a good mechanic, but the troubleshooting is far more complex sounding than in practice.

A shot in the dark would suggest you see the post on Vanagon Syndrome. Although the usual symptom of Vanagon Syndrom is working only at start or full throttle, the CAUSE is incorrect voltage through the air-flow meter. If the voltage does not change with deceleration, the air-flow would stay on.

An '88 should have the fix harness; and you'll note in that post that a fix harness is not forever. We have found the harness cures some mighty weird FI problems that aren't anything like the tech bulletin description.

Serious wet weather grief with my van

miket Member # 430 posted 06-05-2001 07:20 PM

I’m having some serious wet weather grief with my van. It is a 1988 VW Vanagon Syncro, manual transmission, 195,000 Kms.
During rainy weather (some accumulation of water on road), the van will gradually lose power (in 10-15 sec.) until it either idles roughly (below 500 RPM) or stalls. Will re-start easily, accelerate, then repeat the power loss. This cycle continue until road is less wet, then runs normally. This problem used to be more intermittent, but now consistently happens on rainy days.

One other thing: When the van starts to lose power, an initial regain of power can be had by flooring the accelerator or switching the ignition off and on again.

In dry weather, no problems. Van idles steadily at 800 RPM, steady engine power thru RPM range.

Recent new parts:

1. Distributor assembly with Hall sender unit
2. distributor cap (with shield) and rotor
3. ignition wires
4. ignition coil
5. fuel filter
6. air filter
7. spark plugs
8. ground strap from engine block to chassis
9. muffler and oxygen sensor connection pipe

Maintenance:

Cleaned and packed with lithium grease all accessible connectors inside engine compartment, including:

1. Fuel injector connectors
2. Fuel pump connectors
3. Air flow meter and auxiliary inline wiring harness connectors
4. Ignition coil primary connectors
5. Idle stabilizer connectors
6. Sensor connectors
7. Ground wire connectors on left side of engine compartment

Other:

Cleaned airflow meter (AFM) internal copper spring contacts. Added some spring load to contact

Checked function of AFM according to Bentley manual - ok

Cleaned and checked throttle valve switch according to Bentley manual - ok

Even wrapped and taped a plastic bag around the distributor. I'm getting desperate!!

I have done most of what I believe can do to fix this, but I don't want to replace the entire FI system! Any suggestions as to next steps?

Capt. Mike Moderator Member # 11 posted 06-06-2001 10:03 AM

Your condition brings to mind two items. First is Vanagon Syndrome. See the post on that subject elsewhere, as at your mileage and age, a failure of the harness module is a possibility. Since it functions as a signal stabilizer & rerouter, it could be beginning to become moisture sensative. That's easiest to check, just borrow a good harness upgrade from another Vanagon for a test run under the condition you describe.
2nd is the throttle valve switch. They seem to be susceptible to water and moisture. Last I checked, P/N 025 906 011A. They are in an area that also seems to trap moisture. That one happened to me; a new switch cured the problem.

A way-out possibility, your fuel breather system through the charcoal cannister. If the cannister is old and the media breaking down, it might not allow full breathing in soggy conditions. Cannsiters are basically a service item and fuel overfills can eventually cause them to break down & clog. Thus your tank is getting airbound.

I realize both of these can give temporary test OK's but the moisture relationship may only come into play under the wet driving conditions. Please let us know the results so I can then move this post to its correct topic.
miket Member # 430 posted 06-28-2001 04:28 PM

I confirmed yesterday that the oxygen sensor was causing my wet weather problems. Here's the sequence of what I did:

1) Installed a lawn sprinkler underneath the van, to simulate water splashing around during driving in the rain. Ran all tests with sprinkler on.

2) Ran the engine at 2800 RPM, with oxy sensor disconnected for several minutes. No problem.

3) Ran the engine at 2800 RPM, with oxy sensor re-connected for several minutes. Engine stalled out

4) Ran the engine at 2800 RPM, with oxy sensor disconnected for several minutes. No problem.

So, based on these results, I figure the oxy sensor was getting wet, or water was getting drawn into the exhaust and screwing up the signal to the FI computer, causing my engine to stall. Until I get a new exhaust system, I'm leaving the oxy sensor disconnected.

Buck or bolt at 2800 rpm

dwolterd Junior Member # 47 posted 08-26-2000 08:37 PM

I want to thank everyone for helping me solve significant problems (dialogue is now archived).

One problem remains with my 1985 Westfalia camper. When 2800 rpm is sustained for any length of time, the engine bolts. We got around this by trying to quickly pass through this speed on a recent trip through Ontario. But I know the times when we were unable to avoid this rpm, and the engine has bolted, have not done the engine's longevity any good. When viewed from behind (from another vehicle) it looks like the muffler and tail pipe are shaking loose for a moment. What really is happening is that the whole engine is bolting for a moment. Any ideas will be appreciated. Third engine was installed earlier this year. Ecu and throttle pos sensor/switch were recently replaced.

Doug Wolterding, Woodbridge, Virginia

jpquick Member # 121 posted 07-03-2001 10:13 AM

MY 85 WESTY bucks at approximately, 1800 to 2100 RPM. It drives me crazy. I Just down shift and tach up to avoid the bucking bronco. This usually happens when in a parking lot, otherwise ,I just tack it up, CASTROL style.

I have tried fuel injection cleaner, to no help.

I once had an 83.5 water cooled 1.9 liter that bucked all the time after a fillup at a not so great gas station (Pilot). I received plenty of water which, I combated with heet, cured the problem 5 bottles later through two fill-ups.

I think the airflow meter section contains
info. related to this problem.

Hey, If I learn about a fix, I'll post.
Let's hope we get some attenion of the
others out there.

JP

Capt. Mike Moderator Member # 11 posted 07-04-2001 05:50 AM

That your throttle valve/deceleration/idle switch assembly was replaced does NOT mean it was properly adjusted. The full throttle enrichment switch (Bentley 24.34) requires adjusting and could give your symptom.
The pressure regulator could also give similar symptoms if you are not getting the normal increased pressure above idle vacuum. It could be enough to get you to 2800 RPM, but not enough for more until you pass through with the full throttle enrichment phase.

This presumes you have already checked for proper CO levels and temperature sensor I specifications.
 

Capt. Mike

Moderator
Transferred from another post to consolidate similar topics.

Water related Vanagon Syndrome

Earthlinkmike Junior Member # 1209 posted 09-09-2001 10:27 PM

I just got another new 1991 Westy and its going to be the final one (4th so far). After reading the info on the ignition board regarding rain and the syndrome, I felt right at home. I've had this van about 3 months and every time I wash it for the next 30-40 minutes or several miles it looses power until I reset the ignition switch. I have heard a bit about a harness and not sure if mine has it opr not. I'm not nearly as knowledgeable as most and probably not able to troubleshoot beyond the basic level. Any clue where to start for a novice?
 

Capt. Mike

Moderator
As to whether you have the Vanagon Syndrome fix is well covered in the Vanagon Syndrome topic. All you have to do is look for the harness as described there. That doesn't mean the harness hasn't failed; that possibility is also covered there, along with references to a picture of the harness module.

First, your symptom is not typical Vanagon Syndrome -- and Vanagon Syndrome isn't usually water related. Reread that thread.

Two questions. If you immediately shut down and restart, does the symptom go away? If not, it's not "reset" related.

And second, what are you doing when you wash the car that would get water into a FI system component? Does the problem happen in just ordinary rain? Although the water-cooled Vanagons can easily get wet, there is very little of the FI system that gets wet following a normal wash job. (I am presuming you are NOT sending it through one of those infernal automatic washes whose sole purpose is to ruin paint, & every external accessory in the shortest possible time!) About the only places that get routinely wet in a normal wash would be the O² sensor and the wiring harness that runs from front to back.

The possibility of an O² sensor getting wet is already covered in this post along with miket's excellent and methodical efforts to track it down. That's a good place to start.

Elsewhere on the site is a post about how Vanagons are subject to harness damage from extended driving on gravel or dirt roads. Forget where it's posted at the moment, but the net result is there are a couple of places where the harness runs side-to-side on the 'front' side of frame members and spray and gravel from the wheels will eventually abrade the harnesses. Get underneath and thoroughly inspect your wiring as it runs from to rear and up into the engine compartment. The one I had to protect was at the left rear just in front of the LR wheel about the area of the fuel pump. The harness went up to feed the rear seat heater fan and the FI system brain.

I'd suspect if your problem occurs for just the first 30-40 minutes, it's a matter of it drying out. But that also raises another possibility -- water in the intake systems.

Vangans get their engine intake air from the RR quarter panel grill. Are you running a lot of water into that area? And have you checked your air filter system after a wash? If you are getting your filter wet, it will severly restrict flow (with resultant loss of power) until it dries out.
 

WestyLover

New member
fuel. We manually made the connection for the relay and she started right up and ran fine all the way home (300 miles).

I bought a new relay once we got home and the car wouldn't start. We checked as many connections and grounds as we could and they seemed fine. So off to the VW mechanic we went. He said it was the computer. There were some burnt areas on the board itself. He had a used one that he charged me $200 for, he put it in, she started right up, and he called me to say that she was fine and we could pick it up tomorrow. The next morning he calls, he took it for a test drive and she was not fine. She would stall at lights, when she ran the RPMs would go from 3000 to 0, 3000 to zero. It would get worse as she warmed up. He checked all of the grounds, they were fine, he checked sensors, found the idle stabilizer control unit was fried. One of the little parts had actually melted a bit. That little bugger was 249 dollars! So that goes in. No improvement whatso ever. He had a working Vanagon in the shop so he swiched the temperature sensor and the airflow meter. No improvement. After 3 grueling weeks in the shop (he wasn't just working on my car) my husband and I drove her home. She barely made the 1/2 hour ride.

We did check the AFM by prying off the lid and cleaning it and checking the arm. We bought the syndome fix harness for $150 dollars. She doesn't stall at lights anymore but those RPM are still dropping and rising while we drive. When we put her in park the RPMs will often rise to 2000, we tap the gas and she returns to normal. Now pre-problem she would hesitate a bit when she was cold (like at the first light I'd stop at but that was it). She did do the RPM dropping once, a week before our trip, I was pulling away from a stop light and she almost stalled.

Sorry to ramble on a bit, I'm just hoping some tid bit of info may help. Do you think it could have anything to do with the used computer?
 

Capt. Mike

Moderator
What year?

The mechanic is checking first hand what we can only guess at second hand. When there is surging or fluctuation with idle, it's often related to the O² sensor system. Remember that's its function -- to adjust FI back & forth as exhaust characteristics change. See the O² sensor topic for further info.

Your indication that a blip of the throttle will let it idle back down is more closely related to idle stabilizer, or the throttle valve/idle switch system which will depend on which model you have.

I know it's frustrating, but every part of the FI system can be checked by other than the 'parts changer' method. Since you have a new air flow meter & CPU, chances are now that its down to a sensor or adjustment.
 

anitalennon

New member
My 87 Westy is hesitating until RPMs reach 3000+. It ran great and wasn't doing this until after we did a tune up (new plugs, distributor cap & rotor, fuel filter) and added the "vanagon syndrome" harness fix. The timing has been adjusted and we reconnected a hose which was disconnected from the front opening of the pressure regulator. It seems that when the pressure regulator hose is disconnected, it idles more smoothly at 1000 RPM (instead of about 900) and the hesitation is reduced or negligible. Does this mean the pressure regulator is in need of replacement? Also, with the hose connected, the OXS and battery light on the dashboard stays on when the engine is started until I rev it up a bit. When the hose is disconnected...lights don't stay on. What's going on?? Any input would be helpful. Also, for a little background, prior to the tune-up we had experienced the Vanagon syndrome twice randomly on long trips in the form of surging while in 4th gear while driving along the highway. Each time, stopped van, restarted and no problem thereafter. Other than those instances, we had no hesitation problems. Actually, the installation of the "fix" is what prompted the whole tune-up idea, "while we were at it." Thanks for all the info provided on this forum...it has been invaluable.
 

Capt. Mike

Moderator
You need to isolate several concurrent problems. Easiest first; the O² sensor. Testing is in the Bentely 24.54 but the light in the dash is controlled by a speedometer activated elaspsed mileage trip. You'll see more info on that in the O² sensor topic.

The battery light is a function of the voltage so a low idle will cause it to flicker; revving up will increase voltage to stop the light. That normally doesn't activate the O² light, but I'll never say never.

The pressure regulator adjustes fuel pressure in relation to the intake manifold pressure. This is engine speed related and could cause your symptoms. Testing is per 24.55. Note that the specs show a lower pressure connected and higher disconnected. Regulators typically throttle DOWN the pressure, indicating yours is throttling it down too much, thus the bad idle when connected. Also, as engine speed increases, you get into the higher pressure requirement range so the engine smooths out -- it's now getting the appropriate pressure.

Other parts of the FI system that can cause similar symptoms are the throttle valve switch & adjustment, and the idle stabilizer. Note 24.59 specifically says if the throttle is imporperly adjusted, the engine will surge under light throttle.

Often fixing one part of an interrelated system like the FI will show up other defects. The Vanagon Syndrome fix has taken away one problem and allowed the others to become apparent.
 

digitalmantis

New member
I'm having a terrible time with a too rich idle. It blows black smoke terribly.

It is a 90 Westy and this is what I have done so far, all with no improvement:
(1) Changed Temp II Sensor.
(1A) Plus checked wiring to ECU and resistence per Bentley graph.
(2) Changed the AFM.
(2A) Plus checked Temp I sensor per Bentley.
(2B) Plus changed the Aux AFM wire (Vanagon Syndrome).
(3) Changed the ECU.
(4) Disconected the Q2 sensor.
(5) Changed the Idle Stabilizer Control.
(6) Disconnected and reconnected the Idle Stabilizer Valve.
(7) Changed the ignition wiring.
(8) Resoldered every ground wire I could find and replaced the ground eyelets. Even changed the battery ground and engine ground.
(9) Checked timing.
(10) Checked air filter and air intake.

All of the above did not work.

The engine starts fine when cold. As it warms up the revs drop as expected and then it starts to stumble as it blows black smoke. Too rich.

If I disconnect the Temp II sensor, the revs go up as expected and the problem is gone.

The Temp II sensor provides the correct resistence throughout the temp range. This was done at the ECU.

With the Temp II reconnected, it spews black smoke again. If I shut down the engine for about 60 seconds, and then start up, the engine runs fine - no smoke for about 60 seconds, then the black stuff starts.

The O2 sensor connected or disconnected makes no difference.

Okay, so now I'm thinking about the Pressure Regulator. My local parts place will sell me a fuel pressure tester for $110 but I am reluctant to throw more money at this problem. So here's my question: How prevalant is a Pressure Regulator malfunction? Does a malfunction of this regulator make any sense regarding my problem?

I'm tired! Someone tell me what to do.

Thanks.
 

Capt. Mike

Moderator
Finally; someone who actually does some diagnosis before posting! Thanks.

Now the easy part first -- it's not likely to be the pressure regulator. First, that can be tested independently. And second, its function is to increase fuel pressure at high demands based on manifold pressure so there is no correlation to temperature & the Temp II sensor.

You're diagnosis narrows the problem to most likely still being a function of temperature and the cold start functions of the ECU.

It still sounds very much like you are getting a good cold start, and then as the system warms, it is not reverting to hot run condition.

Some thoughts: When you did the O² tests, did you disconnect with the ignition OFF to cancel the memory of the control unit?

The Vanagon Syndrome harness fix can fail and that particular harness seems to do some things to the FI far and above the items the official tech bulletin describes. It does contain a microprocessor. A common symptom of the Vanagon Syndrome is that it will reset and start fine with a shut off -- then goes into failure after a period of time. I'm not suggesting you run out and buy a new one, but the easiest test is to swap out the harness insert with some other Digifant equipped Vanagon owner for a test session.

I know you've replaced your idle stabilizer, but have you checked the new one for function and values? i.e. is it getting the right signals. Does it vibrate & hum?

I didn't see the throttle valve switch checking in your list.

Last -- don't laugh -- have you checked the power steering pressure switch? I think in unlikely since you can isolate it to the Temp II sensor, but if 'stuck on' it will enrich to compensate for load that doesn't exist.
 

digitalmantis

New member
Well here's the saga so far:

Here's what I've done since my last long list (2 messages up):
(1) Checked throttle switch - no problems.
(2) Installed new Pressure Regulator - no change.
(3) Checked idle stabilizer valve - okay.
(4) Checked steering switch - okay.
(5) Installed new Auxillary harness to the AFM - no change.
(6) Grounded the right side of the engine and grounded the AFM - no change.
(7) Checked for vacuum leaks - none.

An important hint is that if I remove the Temp II sensor connection (when engine is fully warm) the ECU thinks the engine is running cold and the engine runs beautifully but at 1100 rpm. Reconnect it and the black smoke returns.

Also, when it is warm and blowing smoke I can turn off the engine, start up again, and the engine runs well for about 30 seconds, then smoke again.

Any help would be very, very, very much appreciated.
 

digitalmantis

New member
Well it is finaly fixed. No more black smoke. Runs great!
/infopop/emoticons/icon_biggrin.gif

It was the Aux wire harness connected to the AFM. I even bought a brand new one to try solve the problem. But the solution was so remove the Aux harness altogether. I have the original setup now - no Aux harness - so I may have the Vanagon syndrome to sort out in the future.

When it was belching black smoke when warmed up, the AFM combined with the Aux wire harness was not a good mix as far as the ECU is concerned. This was the case even using a good AFM.

Anyway, after 2 months and many $ and a lot of learning, I am finally back on the road.
 

Capt. Mike

Moderator
Read the thread on Vanagon Syndrome. The harness fix can also fail, and you will probably face a return since the original problem of voltage stability is not addressed. I've had it happen to me and there is a picture of the failed harness microprocessor on the tech diagrams link from the home page.
 

westy87

New member
Well, I have a 87 camper with 170k miles that is still unhappy after 2 weeks in the shop. I posted previously in Vanagon Syndrome, but after replacing the harness with a new harness, there was no change.

The problem is as follows. When he leans out the engine and gets the required CO amounts, the engine will not accelerate with any amount of throttle. If he adjusts it very rich, it will accelerate through all throttle range except for full throttle, where the engine cuts out. It also backfires under the rich condition.

Here is the list of things that were checked out by a replace and try method.

O2 sensor and Plugs. The original problem, van died in town and didn't restart, it was running perfect right up to this point. He discovered the O2 sensor was bad and the plugs were fouled. After replacing these 2 items, we ran into the van runs very rich problem. He adjusted the CO down to 1.1% from 5% and the engine wouldn't run past idle.

Installed new wire harness, Rev A. - No change.

Computer - replaced twice, no change. Installed original computer.

AirBox - replaced twice with 2 different boxes, no change. Reinstalled original box.

Put in another new O2 sensor (just in case) - NO Change.

Replaced Temp Sensor - No change.

Fuel pressure checked out fine, he even had someone in back taking readings while driving it! Looked good. This would eliminate tank airlock and fuel filter and pump issues, right????

Fuel Filter - lots of brown powder in the filter, though the filter looked new on the exterior. Bought and installed new filter even though pressure was good, no change. Fuel Pressure still good.

"Fixed" the idle sensor switch. I guess it didn't always click like it was supposed to. He fixed it. No change.

What about exhaust leaks again? I have 2 or 3 leaks at exhaust pipe joints on the drivers side of the engine. I had installed new bolts and tightned down the joints, but there is still exhaust leaks at these joints. Could the new O2 sensor be more sensitive than the old worn one thereby making the exhaust leaks a first order problem?

Could the Cat be shot?

There are no holes in the exhaust, and I would hate to have to replace it because of the joints not sealing properly. Would an aftermarket High Performance exhaust suffice for now? I don't have $1000 to spend on a new exhaust.

What about the power steering pressure switch? Could this cause the engine to run bad under lean adjustment and "ok" under rich adjustment? I did notice a small power steering fluid leak, and the fluid is currently low. One of the hoses seems soft.

I am going to have it towed to the other VW garage in Town thursday. Hopefully he will not have to run through all of these checks again!

Running out of ideas.

Thanks,

Jeremy
 

ben

New member
Good day,
I know that I have said that often but please double check every connector, even the injection one, I add many strange problem last year, including one similar to yours, same test where done whit similar negative result. The answer was a single loose wire!!! (that I found myself after $200 of test by a VW dealer), other problems where faulty connector (Contact). I am not saying that is your problem but it doesn't cost much to check (unplug and check for corrosion, even if you don't think that it's possible).
Also, the Vanagon (Westy) computer SHOULD go in a safe mode when the OS is defective and allow you to continue driving. I add this problem last year in Vancouver and the VW dealer assure me that even in a case of a faulty OS I could continue my trip.
He was wrong in some ways, leaving the faulty OS plugged gave bizarre info to the computer; the problem was gone when I simply unplug the connector. On a final note, I add another power related problem that (believe it or not) was related to a faulty stabilizer control box wire (not the control box), located behind the right brake light.

And yes, test the power steering pressure switch

Good luck, Ben /infopop/emoticons/icon_smile.gif
 

Capt. Mike

Moderator
You've gone at it very systematically and ben's advice -- a loose or missing connection somewhere sounds most plausible. I would doubt a small exhaust leak would cause the problem, even if it 'fooled' the O² sensor. Most exhaust joints use gaskets -- can they be replaced to cure your leaks?

Aftermarket OEM exhausts are considerably cheaper than OE from VW but I hesitate to recommend a cheapo 'performance' systems as they usually change the operating characteristics of the engine. Few are set up for the cat or O² sensors and you may run into future EPA inspection problems.

A clogged catalytic converter can cause those problems but that's easy enough to inspect -- remove the muffler and look in. It should be a soft gray, neat honeycomb. In a pinch, remove it to see if the problem goes away with an open exhaust.
 

westy87

New member
Well, you two were right. That same morning I posted, the mechanic called me and had FINALLY located the problem. The connector that plugs into the airflow meter wire harness had been tampered with. The previous owner had done some cutting, soldering, and installing of that 20-micro farrad capacitor under the boot. Well, his solder joint failed. The mechanic installed a new connector. Should have checked the continuity before installing the vanagon syndrom wire harness!!! Oops.

Anyway, I drove her out to Colorado Sunday at a dissapointing 13mpg. Found out today (no mechanics this time), with all of my new gained knowledge, that the mechanic did not attach the O2 sensor to the green wire!

Also, he had installed "cold burning" bosch plugs. My understanding is that these vans run better with the "hot burning" platnum plugs?? I installed the split-fire platnums today. The store was out of the bosch and the AC delco plugs.

Hope this fixes solve the mileage problem.

Thanks!

Jeremy /infopop/emoticons/icon_smile.gif
 

Capt. Mike

Moderator
Heat range is very critical and the "wrong" plug can cause major engine damage. 'Cold' plugs are for hot running engine conditions, for example high performance and racing. 'Hot' plugs are for engines that have low ignition qualities. Which is which and what all the code numbers mean is confusing and, unfortunately, constantly changing. Worse, there is no standardization. Your '87 digifant calls for Bosch W7CCO; the 7 is the heat range. You may substitute Beru 14L-7CU or 14L-7C, or Chamption N288. Most of the gimmick plugs such as the triple electrode do little in a VW. I'll try to elaborate further in the future in the Spark Plugs topic this forum.
 

Capt. Mike

Moderator
Transferred to consolidate same topics.

Bucking when cold out

jack 86 weekender Junior Member # 3382 posted 02-13-2002 06:42 PM

'86 weekender 2.1 L. I am currently touring the US and am having a problem with bucking. At high speeds (45+) I will notice my temp gage move from its usual position of 60% to 45%. It seems this only ocurs when is it cold (under 50) outside. Then it will seem to loose power and buck. Sometimes this will occur for seconds to minutes. I have replaced my coolant temp. sensor. No change.

I have read Bentlys cover to cover countless times without insight to this paticular problem. Could it be the O2 sensor not cycling? I am in Vegas now and on the way to the Grand Canyon. I fear it may get worse?

ben Member # 671 posted 02-14-2002 11:15 PM

1)- try to unplug the OS (connector). After, unplug battery (optional but do it anyway) for a minute or so. Connect the battery back but leave the OS unplug, the computer ""should"" go in a safe mode (defective OS sensor) and give a safe!!!! mixture to the engine.

2)- unplug and plug all possible connector (fuel injection, temp. sensor, power steering, idle stabilizer and so on), maybe you have a loose wire. (Believe me, I add a similar problem and most of my problem where wire related).

3)-check the air flow meter (Search this site for more info)

Buy a ohm meter, it is explain it the Bentley how to check many parts, including the airflow meter and OS sensor.

Is fuel pressure OK?
 

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