928 GREMLINS beating me

[jim ross]

I have an 84'928s auto. For the last two weeks it has plagued me with intermittent rough running ( like a cylinder is out, or slightly out of timing ). Especially in the cool morning, but lately in the afternoon as well. It can run rough then magically smooth out and run perfect. I thought about the coil..its only a year old though..i replaced it with an older one thought to be good, problem still there.Voltage to coil seems good (14 volts).Checked resistors..within spec ohms.I have cleaned all known contacts in engine compartment concerning ignition and fuel.. Yesterday i searched again for vacuum leaks, thought i found a slight problem...fixed it, and the car ran awesome all day. After patting myself on the back all day..today problem returns! Fuel pump/ injection relays seem good.Even jumpered the fuel pump relay to check it, still running rough.Here is a list of things replaced in the last 2 months.....dist.cap, rotor,wires,plugs. cleaned fuel tank, replaced tank screen, new fuel pump, and filter. Pressure regulators, damper, aux air regulator (used), cold start valve, thermal time switch, temp sensorII.I have been using additives to remove deposits in fuel system..... I even removed and cleaned injectors and fuel rail ( found gunk, cleaned with berrymans) ran great that day, until next morning again.Could more gunk from fuel lines be accumulating in injectors again?? I am at a loss.....any help would be awesome.

[MrGST]

First of all, note that I am a newb when it comes to 928's but I would take a look at your distributor cap and rotor. Even though they are new, they could still have issues. Check the contacts. Also check the ignition wires for any signs of arcing along their length.

[nosnow4pc]

Have you checked the infamous "Green Wire" I have a simular problem with my 82 and I've done almost exactly the same as you.... Someone mentioned that I should replace the green wire as that causes problems. It ain't cheap at ~$100.00 and I'm not sure how you can test it.

[Danglerb]

If the green wire is old, safe to say it needs replacing even if its not the specific problem.

See if you can't hook up with one of the locals and maybe they will recognize the issue?

[jim ross]

Ive messed with the green wire to the distributor....very old and brittle. i had to cut off connector and solder the two seperate shielded wires together. is this a timing reference wire? could be it? By the way would it be safe to remove my injectors and fuel rail.....connect hoses to remaining fuel lines in engine compartment, for draining. Then connect fuel pump to a gallon of berrymans parts cleaner and just run it right through the entire system full strength, followed by a flush of pure gas. Would this work? could it hurt any filters or regulators????

[Danglerb]

Originally Posted by jim ross

Ive messed with the green wire to the distributor....very old and brittle. i had to cut off connector and solder the two seperate shielded wires together. is this a timing reference wire? could be it? By the way would it be safe to remove my injectors and fuel rail.....connect hoses to remaining fuel lines in engine compartment, for draining. Then connect fuel pump to a gallon of berrymans parts cleaner and just run it right through the entire system full strength, followed by a flush of pure gas. Would this work? could it hurt any filters or regulators????

That sort of describes the "Carbon Clean" system, HF sells a thing "like it", but if you suspect the injectors at all, its time to pull them, have them ultrasonically cleaned and replace the O rings and hoses.

I wouldn't do the Berrymans thing. Nothing in the fuel system except the injectors should have any trouble with chunks smaller than a BB, so cleaning it is a bit pointless. Flushing out the big chunks with normal gas and changing the filter should be plenty. I had my tank flushed more to get rid of 20 years of sediment etc. that might have collected.

[Normy]

Can you get the car to run rough like this while it is sitting idling?

If you can, you might want to try to pinpoint the problem to a certain cylinder by [carefully!] removing a spark plug wire at a time from the distributor until you can pull one and hear no change at all. That's the bad cylinder. The other trick you can try is to start your car in your garage with all the lights out, and then look at the engine. Do you see sparks flying from the wires? If so, they might be bad or at least need to be moved so that they aren't close to metal parts.

Most likely it is a rotor/cap/wire/plug issue, but it might also be a bad connector at the fuel injector, or a bad injector itself. I suspect that you should pull them and have them cleaned as he talked about above. Cruisinperformance in Michigan did mine for $15 each a few years ago.

Good luck-

N

[jim ross]

Thanks for all the help guys...i went the old school route and used a screwdriver to the ear to listen for clicking injectors..found the faulty one. Removed and did a quick cleaning...reinstalled..ran great for an hour, than sputtered again. I checked ohms reading...O.K. SO i let the injector soak all night in berrymans parts cleaner. In the morning was quite a bit of sludge in the bottom. Im now soaking in marvel mystery oil for a couple of hours befor reinstalling. I will tell you if this works this time. Thanks for all the help! J

[Danglerb]

The injectors are so loud a piece of rubber hose worked for me.

[jim ross]

I replaced cleaned injector, and it ran good and sputtered again, so i replaced its harness connector , so far so good. NOW when starting car, it will idle nicely for about i minute then just die..twice...then drive just fine,( intermittently ) my god what next? Sounds like something electrical again...maybe that green wire, or possibly the ignition switch (by key)? can that cause similar problems??

[Danglerb]

For $20 I bought a set of 8 injector pigtails off ebay, but with the under hood heat and lousy factory wire you may have troubles at other spots than the injectors.

BTW each time you do something on the motor, I "read" that as I wiggled the wires and hoses around some under the hood. No telling what causes what.

[dfishwillis]

I want to know how to post a problem
I looked at every page it is not user friendly
So can comeone point me where to start

[dfishwillis]

J
I have two 928 -82 and 97
With gas prices I found I had to be careful
Even had to add oct boast to clear up a problem
With gas so exp.
Where did you buy gas?
Might want to change out or add gas additive.

[Danglerb]

I don't believe in gas additives to boost octane.

I do use Techron and Stabil from time to time, and ran through one can of Lubro Moly "Ventil Sauber" (valve cleaner), but the reason I use them is that sometimes I don't drive the car for more than a month at a time.

Price of gas is tough, but its important to use the stuff that works best for your car. Best power comes from using the lowest octane that doesn't ping, so your 82 for example should work fine on regular 87 octane. Not sure on your other car.

************************* How to post a problem.

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At the left side of the screen just above the list of messages is a button "Post New Topic" click on it.

Type in the "Title" or subject of your message in the single line space, and the full message in the larger box below it.

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[Pauwl]

Jim,

I had similar problems when my car would be really patchy at starting in the morning. Engine would turn, just wouldn't get going, or would get going, but cut out a little later after running rough.
Some days of course there were no problems at all.

I replaced the fuel pump relay. If I remember correctly you can swap it out for the hooter (oops Horn in the US of course) relay to try.

PLEASE get someone to verify you can swap it for the horn relay before you actually try, as my memory's not that good.

Pauwl