Oli928

I've searched with various key words and have not found this exact problem...so forgive if already answered. My 1989 928 S4 sputters after rain, washing or even high humidity (overnight). This starts usually within 3-5 minutes of morning start up or sometimes after driving 10-15 minutes during morning commute. Symptom goes away after sitting in sun a few hours or after engine heat(?) burns away humidity. This almost never happens during evening drive, unless it was raining. I already cleaned every contact at the battery including the ground strap. I'm thinking crack in one or both dist. caps or condensation on idle control valve contacts or engine ground strap or condensation on mass airflow sensor or...okay I don't have another idea. This is driving me CRAZY and is unsafe since it feels like it is running on 4 cylinders. Engine catches up eventually. Doesn't sputter during highway drive, only from initial acceleration to about 30 MPH. No backfiring.
-Sorry for long post...just want to list all details. Anyone experience this? Any clues? Thanks (new to forum)

Leon Speed

Hello and welcome!

It is weird that it takes some time from starting, but first things to check:
- is there a plastic cover on the hot post (engine bay front passenger side)
- sparks/fire flies anywhere on the ignition cables with the engine running at night/in the dark

SeanR

Check your coil wires too.

VehiGAZ

ICV has nothing to do with anything above idle, so that's probably not it. You are most likely on the right track focusing on electrics and ignition. There are a couple of directions to go on this based on your description...

1) Ignition/distributor wires. Do the "firefly test" to see if you have bad ignition wires.

2) 4-Cylinder mode. Locate the ignition monitoring relay/controller (p/n 928 618 175 00) next to the LH and EZK controllers in the passenger-side footwell and see if either the red or green LED comes one inside it when you feel like it's running on 4 cylinders.

Please post results of these tests...

Good luck!

z driver 88t

+1 on the coil. I'm not sure how prone 928s are to this, but VW coils are prone to small invisible hairline cracks that moisture will cause problems with.

I was trouble shooting a very similar issue with my wife's Jetta. A friend who is a local VW mechanic said to start the car, get it running and use a spray bottle to hit various items with a spray of water. As soon as I hit the coil (was the first suggestion) the car stumbled and died and would't start again for about an hour while it dried out. A new coil later the problem was gone.

Ed Scherer

FWIW, I've had three (that I remember within the last ten years or so) instances of similar problems that all turned out to be corrosion at a plug cable / distributor or plug cable / ignition coil connection. Very obvious when I pulled the cable: classic green powder at the connection. One time, it was so bad that I replaced the cable. Two other times, I cleaned the connection, applied some 100% DeoxIT (D100L, which I use on damn near every electrical connection I encounter on the car) and it was good to go.

I'm not sure that my problems were quite as humidity dependent, though, so the suggestion of looking for a bad (cracked or whatever) coil and/or distributor as well as dodgy plug / coil cables in general sound like possible problems, too.

Mrmerlin

OK to sum up what all of the others have posted and could be suspected problems do these tests in this order
First clean the battery ground cable and the power cable do all of the connections
Then open the 14 pin connector look for corroded pins then open the back of the connector and inspect the wires for shedding insulation and or corrosion fit a hot post cover if your is missing , if water get onto the connector this isnt good as power is always flowing through it, keep it dry.
Then open the CE panel cover and inspect the floor and panel for water traces if the floor is wet then the blower box may be leaking and should be resealed as well as the well drain cleaned, (this you can do after dropping the blower box)
Remove the fuses and all of the relays if you find water traces after you do the run test and clean them with an eraser.

Next remove the intake tubes and run the car in the dark look for jumping sparks around the caps the coils and wire leads.
Also inspect the relay at the CE panel to see if its illuminating red or green, this indicates one of the ignition systems has shut off

The coil wires are the most probable, they can rub on adjoining parts and cause ignition leaks as well as sparks jumping from the coil tips and the distributor caps
but look before you touch them so you can find the faulty connection, replace /clean the suspected parts.
If the wires are original get a new set of Berus.

If you follow this procedure you should be able to remedy the running issue

In the picture the hot post cover is fitted

WallyP

The design of the 928 means that rain or wash water runs down the fender edges and falls off on the coil connections. There should be small pieces of clip-on edging on the fenders to direct the moisture away from the coils.

As has been suggested already, your first try should be to carefully clean and check the coils and their connections, especially the fat HV leads.

Make sure that the coil wires do not touch any metal or other wire harnesses at any point.

Oli928

Thanks for all the suggestions so far. I do have a cover on the hot posts and all seemed clean there. I have not done the firefly test. I am considering using a spray bottle and mist certain areas like the coils, caps and wires (one at a time). I suspect one reason (sometimes) it takes 10 minutes to show up is the release of steam (as engine gets hot) from water sitting somewhere. If I wash the car, it is pretty quick to show sputter (sometimes immediate upon start up). One odd item I forgot about, after I cleaned the engine 2 months ago, I noticed there was about 2 tablespoons of water sitting in the air filter housing bottom (while waiting for engine to dry, I removed filter to clean with compressed air). I thought this was maybe because I sprayed water directly on engine with hose (I didn't investigate air filter housing for cracks yet) . This is why I mentioned mass airflow sensor might have condensation (based on another post). Thanks for the LED on controllers suggestion, I'll post results when I have time to try this.

Is there any item in the cowl area, that if it gets wet, will cause this sputter? This looks like the only area that water gets into during car washing (maybe leaf clog is making water sit there?). I'm probably over analyzing this...based on high San Antonio humidity, it is probably a crack in a cap or coil/coil wires. I know exactly when the problem will crop up 90% of the time because when I sit at the first light on my morning commute the engine has a "miss" every 2-3 seconds. Then as I accelerate, I have the 4 cylinder syndrome. This morning there was extreme humidity and the sputter continued for first 10 minutes of driving, then went away. PS I did own a '85 944 for 9 years before I bought this 928, so I'm kind of used to gremlins, but this one is really annoying.

WallyP

"This looks like the only area that water gets into during car washing..."

"The design of the 928 means that rain or wash water runs down the fender edges and falls off on the coil connections. There should be small pieces of clip-on edging on the fenders to direct the moisture away from the coils."

Oli928

I didn't get to read Mrmerlin's post before posting my previous reply...very good suggestions there. FYI I did clean the ground strap and even slightly peeled back the heat shrink on the cable to check for the "green monster"...all looked good. One easy item to check from all the great suggestions, is looking for moisture at the fuse area after washing car. Based on all the relies so far, it sure is leaning towards cap/coil/wires...especially since humidity can even cause this issue.

auzivision

Mine used to do the exact same thing... new spark plug and coil wires fixed it.

Oli928

Forgot one ignorant question...what 14 pin connector? At foot well area? FYI what work I've done at fuse/relay area, nothing looks corroded / carpet looks clean / area under carpet looks clean. It may be coincidence, but this problem started after first wash after wires were re-run to fuel pump due to high resistance on original wires. Maybe something got disturbed during diagnose and repair. Over the next 3-6 days, I'll try the suggestions you guys offered and will check for any new ideas. I will post my findings for sure.

VehiGAZ

Any other salient facts like that we should know about?

You could even have a combination of causes & effects...

The ignition monitoring circuit measure temp in the exhaust manifolds. If it senses a disparity in the two temperatures, it switches on the ignition-protection, which cuts the fuel to 2 cylinders per bank (click here for more reading). You might be failing to fire a cylinder or a bank due to bad wires, which then causes a disparity between the exhaust gas temps, thereby engaging the 4-cylinder ignition-protection mode... suggesting two apparent problems, when only one is the real one.

Oli928

No other salient facts...Thanks for the tip on ignition monitoring circuit.

Based on the suggestions so far (and my technical abilities) I will try misting the coil/cap areas first, then wires to see if I can recreate the sputtering. If that doesn't get it going, I will spray car down like I'm washing it and check for moisture at fuse/relay area/ground straps. If I can recreate issue, but can't figure out the culprit, I'll pull it into the garage and and check for fireflies. If all this doesn't work, I'll probably give up and take it to Jones AutoWerks, my regular repair shop. If you see an error in my plan of attack, let me know. I don't know if cap & wires are original, but they do look old. I've only owned the car since March. Previous 2 years car was garaged and only driven 200 miles. Yes, the low mileage over the 2 years caused several gremlins...most I've fixed.