JM993

The heat sensitivity, in my mind, is a good sign. Not that we can rule other possibilities out yet, but your problem is probably external.

I had to run down a similar problem down in my old BMW. The PO had changed fuel filters, injectors, various sensors, fuel pumps, spark plugs, etc etc. I purchased the car (at a big discount) and nearly drove myself crazy - even trying the engine wiring harness from another car. The last place I looked (duh!) was the cap and rotor because it was new! Turns out it was bad, but would only show signs when the engine is really warm.

If you haven't already, renew your caps and rotors. I'm guessing your problem is probably ignition related.

HTH,
Joe

Mike J

Another good idea! I just happen to have a spare set of rotors/caps that I replaced on the engine just before the rebuild...I can swap those out and try again. Its early morning so the engine is cold...I am going to start up the car and confirm that it runs fine with a cold start...

My timing light had gone for a crap so I have borrowed a friends. I will use it to see the "steadiness" of the spark for cyl 6 --- that might give me a hint...

Thanks for the help!

Cheers,

Mike

Mike J

Yes, but with this weather I would rather be driving the car than diagnosing it...this car is trying to kill me (mabye I should rename it "Christine"). I have not even put the interior into the car yet because I was too angry at it to get the energy together........

Cheers,

Mike

Adrienne

Hey, I renamed my car Pita when I was dealing with similar problems. Your symptoms still seem similar to mine. Mine was heat sensitive at first, but progressed to hesitating at any temp. Mine was a gentle hesitation, as if the car had dirty fuel. My idle was not rough, and I could rev the car smoothly. The hesitation was felt under acceleration. The car was driveable, but it was irritatingly noticeable.

Gweedo

You can try an old trick I use when I have ignition problems. Wait until night with the lights off, or in a dark WELL VENTILATED garage and start the car. Watch the distributor cap and wires for any sparking. You may have a cracked cap or bad wire/connection.

Matt

long_beach_968

Adrienne,

I think I am having he same problems with my 96' as I have noticed a hesitation at part throttle and I just threw my second check engine light. so what you are saying is that I should pull my positive treminal at the battery cut the cable, and just resolder a connector just a few inches short? seems to easy of a fix.

geolab

I bet a tenner that it is a spark-plug wire Cap that is craked and shortening on the cylinder cover. Please bare in mind that if one of the sparkplugs is shortenning on mass(negative), the other plug won't ignite as should be since the head (-) is getting juice(+) at the same time.
Please try to switch both spark plug cables and connectors from cylinder 6 with another cylinder. And if possible, clear error in PCM with a P System tester.

___________________________


'97 Carrera S 100% original

Adrienne

What's your CEL code?

I'd suggest checking the lead to see if it is suspect if the other ignition-related items check out fine. My mechanic had already checked ignition wires, spark plugs, distributors, and fuel injectors. We also checked ECU connections, ECU, and lifters. So I wouldn't suggest directly cutting the terminal lead without narrowing down the problem first. Hesitation could be caused by lots of items. The battery lead is just another item in your list of things to check. Make sense?

long_beach_968

the first time it was random misfires all cylinders, I never felt it while driving though. I will take her in tomorow morning to see what this cel is about. I guess I should be thankful I cant feel anything wrong to cause the light.

Mike J

I replaced the spark plug wires not that long ago and I still have the old set which I can temporarily use. The problem is of course is that Cylinder 6 is in the bloody awkward position that requires a whole bunch of work to get to, especially the top plug wire. If this is true would it also be true that I will not pickup a spark on the plug for piston 6 with a timing light if the timing light is clamped near the plug end of the wire? I will fool around with the car tonight and report back....

Cheers,

Mike

tam993

I would suspect that it would just need one wire and plug working correctly to idle correctly.....
wouldn't it? You would think it would run right too???

Mike J

I found that having one plug working per piston does affect the engine running quite a bit. If you have a 993 Try an experiment...disconnect one of the coils and start the car and you can see what happens to the idle when half of the ignition system is working...

A weird thing happened last night. I test drove the car from cold to operating temperatures and it worked fine...no surging, no rough idle. Disconnecting Injector #6 affected the idle. I parked it for 20 minutes just like last time to let the heat soak in...and started the car. It idled fine...no missing or roughness. It was quite late so I called it quits. I will try again tonight with an extended test drive and longer heat soak to replicate the problem. I borrowed a timing light and was all ready to check the spark on #6 but then its hides the problem....**sigh**

Cheers,

Mike


Cheers,

Mike

Mike J

Well I had some time to do some diagnostics. I had a hard time replicating the problem...I drove it last night and it drove like a champ. Tonight I went for a longish drive and no problems. I let it heat soak in the garage and then it started missing.

I used a timing light to "check" the spark. I had checked the engine when it was cold and the spark for cyl #6 was nice and steady for both upper and lower plugs. However, when its warm and starts to act up, I get the following:

Piston #6 - I plugged in the timing light as close to the plug as I could. Since the upper #6 has an insulating sleeve I put the sensor where the wire comes from the last holdown before it goes into the sleeve. For both the upper and lower plugs the spark on the timing light was steady but had the occasional "hickup" which seem synronized with the exhaust noise.

At the distributor - I plugged the timing light into the leads for piston #6 on both the main and aux caps and got a nice and steady pulse with no hickups. It was noticably steadier.

I switched back and forth and consistently found the that spark near the plugs for #6 was not steady. I tried piston #5 and #2 as well and they are steady at the distributor and the plug, definetly different than #6 FOR BOTH PLUGS!

Okay, so it appears something is wrong with the plugs wires or plugs. I then disconnected the top #6 plug at the cap and looked at the lower plug with the timing light...still erratic. I then did the opposite, disconnect the bottom and measured the reconnected top plug...still erratic. I thought maybe one would be in trouble but they appear both are...

The question is : How can two seperate circuits show the same symptoms especially in the instance that one was physically disconnected?

Next step: Examine the wire resistance for both upper and lower #6 wires. I have to wait for the engine to cool because, as wel all know, #6 upper is a bear and I have to drop the muffler...

Cheers,

Mike

geolab

Mike, please consider what I explained before.
2 options here.
Now we know the short is between the head caps and the cylinder head [#6].
1-you should try exchanging both cables, with a pair of another cylinder cables, The short could be anywhere on the cable from the distributor to the cylinder head, if problem persist,
2-It will definetly be one of the head caps,
keep us posted,


___________________________


'97 Carrera S 100% original

Mike J

Thanks!

I have the original set of wires/head caps (if you mean the screw in ends) on my workbench which I can use for testing. I can rough lay them out and put them in...the problem is of course its a bit of work to get to the top #6--- that is for tomorrow hopefully.

Will a resistance test show anything?

Cheers,

Mike