924Board.org

[kris]

I finally got my 931 running at idle speed last night (twisting the ignition wires on the plugs I think enabled it to finally stay running). It seems to idle well, with an occasional miss every 2-3 minutes (may need to go ahead & replaces cap, wires, rotor & plugs). But at least she is finally running at idle.

Now the problem:

When I "hit" the throttle cam to open the throttle body (even barely), it starts to "die" (or WILL die). If I play with the throttle body (tweaking it slowly) I can eventually bring he car up to higher RPM's. But when I do this, the car will start to miss fire ALOT! The car will actually backfire (shooting flames out the exhaust), and the sensor plate on the air mixture control unit will "jump" as it miss fires.

My question is: Is there general area that I should check that maybe causing this problem? Could bad plugs, wires, cap or rotor cause this problem? Vaccum leak maybe (if so, any ideas where to look)? Timing?

Keep in mind too, that last night was the first time this car has ran in over 3 years!

Any ideas would be GREAT...

[Lizard]

check your vaccuum advance that could be causing it but yes get new plus and wires at least

[kris]

Are you referring to the vaccum advance on the distributor? The 81 931 I have is not equiped with vaccum advance.

I was also talking with Charles D. And he suggested that it could be the ECU (or O2 control Unit) under the steering column. There is a micro switch on the throttle body that is closed when you are at idle position that causes the ECU to use a
different circuit then when at cruise or full throttle position. The idle circuit could be ok but the other is possibly bad.

I am going to go ahead & change the cap, rotor, plugs & wires so I can properly adjust the timing perfectly. Any idea who may have one of these Lambada Units for the 81-82 931 series?

HEEEEELLLLPPPP!!!!

Chris

[Smoothie]

What year is your car? Put the year and model somewhere in your profile. Earlier ones have timing set at the distributor, later ones have digital ignition timing with a crank sensor. If you have an earlier one, check the distributor timing. For a later one, clean the connections to the ditc box on the hump behind the radio and to the ignition module on the front left wheel well.

I'd be checking the valve timing too. Also hook up a vacuum gauge and see what it's reading - should be close to 20"hg at idle. Of course look for vacuum leaks and you've got the right idea there replacing the plugs, wires, cap, etc.

[Smoothie]

Ok, you have an '81... You can't adjust the timing at the distributor on your car. It's controlled digitally - no way to adjust it. The distributor does still have to be positioned correctly though.

A common problem with these cars with ditc (digital ignition timing control) is the connector to the ditc box gets flakey and needs to be cleaned or at least unplugged and re-seated. I've had this problem. It causes backfires, misfires, stalling and tachometer flops around.

[kris]

I will go ahead & clean all the terminals & replace all the wires, plugs, etc tomorrow.

I am going to check the timing too obviously to make sure thats ok. I have never checked the timing on these cars before, but just to verify: I need to hook onto the #1 plug wire & the light should flash as the mark on the cam pulley hits the arrow tip on the top of the cam cover. Is that correct? They should appear in perfect alignment?!?

If the timing IS off, do I need to adjust the belt on the cam pulley to compensate for the bad timing?

[Smoothie]

No - you have valve timing and you have ignition timing. Two different things. The ignition timing on your car isn't adjustable. The ditc box takes care of that. Valve timing is "set" by the timing belt being installed properly - by the mark on the flywheel at TDC and the mark on the back of the cam sprocket lining up with the pointer. At the rear left of the engine there's a small window that lets you see the edge of the flywheel. That's where to look for the TDC mark. When that TDC mark is lined up -and- number 1 piston is on its' compression stroke, the cam's mark should line up (the flywheel spins twice for each single spin of the cam - if the flywheel mark is at TDC and the cam mark is off by about 180 degrees, then number 1 piston is at the top on its' exhaust stroke, so you need to turn the crankshaft another 360 degrees). It's probably easiest to have the car on a level surface and in about 4th gear so you can push the car while looking through that window for the TDC mark to appear.

You can go ahead and hook up a timing light if you want, just the way you said, but point it through the window to the flywheel. This is of course done with the engine running (ignition timing)(like I said - not adjustable). Valve timing is checked with it stopped - I guess you could get a rough look at valve timing too with the engine running and a timing light, but the marks won't line up - really need to check that with engine stopped.

[Paul]

You have changed the 3 year old oil and gasoline I hope....

[Lizard]

also if the car had old gas clean fuel injectors also make sure no air leaks around them

[jamesi]

i ran into a similar problem just a few weeks ago, turned out to be a loose ground on the wiring harness for the engine, i took it loose to replace a line and didnt tighten it back up, engine would not run, took a while to find it, after that, car ran fine.