hoggel

I started my car cold and drove about half a block when it started running rough and the CEL came on flashing. I drove back home and shut off the car. After waiting about two minutes I started the car again and it was still running rough with flashing CEL. After the car sat for about two weeks (while I looked for my diag cables) I read the codes and found cyl 1 misfires. I checked the plug wires for security, looked for obvious plug wire damage and found nothing that looked wrong. I started the car and it ran smoothly with the CEL on steady. I cleared the codes and it didn't immediately return. I revved the car to 2000 rpm and then 4000 rpm and held for a few seconds. The engine ran smoothly. I drove the car to work (33 miles of freeway each way) and just as I returned home the CEL came on steady. Again with the cyl 1 misfire code.

Car is a 97 C2S with 98,000 miles. Steve Weiner programmed the ECU for me. The plugs, plug wires, caps, rotors were replaced for the second time (engine out) Jan 2011 at about 85,000 miles. I have owned the car since 2005 when it had 45,000 miles. As far as I know there has not been any fuel injector maintenance.

My amateur theory is there must be an intermittently shorted plug wire or a problem with the fuel flow at the injector. Or possibly a valve train issue? This guess is based on the misfire only occurring on cyl 1 and being intermittent. I think this makes the flywheel sensor, coil, coil wires, caps, rotors, plugs unlikely to be the cause?

The only way I can think of to troubleshoot this is to replace the most likely part and drive? Is there something that should be done with the fuel injectors? Any suggestions?

mpruden

There are others way more knowledgeable than me, but have you checked the distributor belt? I have to imagine that if it were to fail or slip, you'd have a very rough running engine...or worse.

JM993

I think you mentioned a few good places to start. Swap the plug and injector (one at a time - plug first - easier) to another cylinder to see if the codes move to that cylinder. If that doesn't work, perhaps you kept an old spark wire that you can temporarily install on the offending cylinder. The idea to is determine if the problem is specific to one cylinder.

BesideTheBox

You can't go wrong by checking all of the grounding points.
I had a very similar problem, reporting misfire on cylinder 6.
Tried lots of things, none of which fixed the problem.
Cleaning the grounding points fixed it for me.

More information at this link:
https://rennlist.com/forums/993-foru...0388201http://

pp000830

My experience is that if the rotor & cap are a few years old the car, among other things, can throw a misfire code on one or more cylinders. If the distributor belt checks out OK look at the underside of your rotor caps. If you see a faint carbon track running around the inside wall of the cap you may want to consider replacing the caps and rotors. If I leave the caps on for more than two years or so I get an occasional misfire code. You can check the distributor belt by pulling the coil wire from the center of the primary distributor, the one that has the attachment to the engine under it and try to start you engine with only the secondary attached. If it runs at all the belt is in place. If not the belt is likely broken. If you need to drive the car in for service with a broken belt you may want to consider leaving only the primary coil attached to avoid out of time fuel detonations from damaging your engine.

hoggel

Thanks for the good suggestions. I forgot to mention the distributor belt was changed when I had the engine out in 2011. I'll check it though, and the caps and rotors. I have Monday off so it'll be a holiday in the garage. Will swap the injector and plugs. I don't have any ignition wires. Will give them a good inspection when I can get around and under the car with my glasses on (I'm old). Grounding point issues? That sounds like a PITA. I hope I find something definite. I've never done anything with the injectors. I'll have to get out the manual. Thanks again for the suggestions.

hoggel

Found the upper spark plug boot not fully seated in the cover. Contacts in the spark plug wire and on the spark plug are corroded green. Will replace the plug and the wire and think that will solve the problem. Thanks for the suggestions.

nine9six

As I understand things, the primary distro is gear driven; if the belt snaps, the secondary distro will stop and there should be a definite loss of power, but the car will still run. Valves banging pistons is not a worry if the belt snaps.

Did you do any work on your car recently that included pulling the plug wires? Do you do your own work, or does a shop perform maintenance? Just curious as to how a plug wire comes off, unless it was not fully seated; or how all of a sudden it rears its ugly head.

I would think a plug wire not fully seated would show issues from day one, in the form of a misfire.

mpruden

Threads like this would lead me to check the distributor belt in the event of repeat misfires, just to rule it out while troubleshooting.

It seems possible that the ECU could tell the ignition system to fire, but the failing distributor could distribute the spark to the wrong cylinder causing damage. Then again, maybe I don't understand the ignition system on these cars.

Regardless, glad you have a good lead on fixing the problem!

nine9six

Yes, this is off topic, but in regard to the link provided above...

Lets say the circumference of the distributor is 12", and there are 6 ea., .250" contact tabs around the circumference of the rotor cap, plus maybe .500" width of the rotor contact point. The likelihood of the secondary distro rotor coming to rest over one of the six .250"contacts, seems less likely than not; however a check would seem prudent.
In any event, if I suspected a broken belt, and needed to drive the car, home or to a shop; peace of mind would come as pp000830 stated, by simply removing the coil wire to the secondary cap. No worries of holing a piston in this case.

hoggel

I'd bet the boot has been that way since early 2011. I do most of my own work but the job in 2011 was a swap from tiptronic to 6 speed. A friend who is also a Porsche mechanic did all but the wiring in his shop (I do not have a lift). I have not done any work that area since. As I was looking around in the engine bay with the air cleaner cover and heater fan out I noticed a few things that are not quite right. I'm going to take this opportunity to look everything over and get it sorted out.

The boot was not out much. I think the wire contact was up against the spark plug but not snapped on. It was probably making electrical contact until the corrosion got to the point where it is now intermittent. When I looked in there last week I never noticed that it wasn't fully seated. After I took the air cleaner cover off and could see all three boots at once I noticed that the boot on 1 was not in as far as the other two.

I had incorrectly assumed that a problem with one spark plug would not cause rough running and flashing CEL.

hoggel

Checked the distributor belt and it is good (still turning the second dist).

I replaced the caps/rotors/ignition wires/coil wires/spark plugs. I did not see any other obvious issues other than the corrosion on the ignition wire and spark plug on cyl 1. Now have driven the car to work and back, 66 miles, and the misfire CEL has not returned (fingers crossed while knocking on wood).

Since the engine was out in 2011 there has been a slight and irregular buzz on the driver's side. I could only hear it at idle and it sounded like it was coming from the muffler or exhaust pipes. I had checked all exhaust connections, even removed the muffler and shook it, finding nothing and not changing the buzz. When I had fan and ducts out to change the plugs I found a 1/4 inch ratchet and deep socket laying in the engine tin next to the spark plugs. Removing it cured the buzz. It was not my ratchet.

While I was in there I replaced the valve cover gaskets to see if I could stop a small oil seep but it looks like it might be coming from the right side cam chain cover. I didn't have that gasket on hand and I didn't feel like taking that on this weekend.

I'm old! After a weekend of lying down, sliding under the car, wrenching, sliding out from under the car, sitting up, standing up, leaning into the engine compartment and wrenching with arms over head, repeat about 100 times ... I can hardly move.

Mike J

Your older so treat yourself to a lift. I did and never looked back..

Mike J

When i took an engine rebuilding course years ago with Bruce Anderson, Gerry Woods had an example piston that was ruined to what they determined was a secondary rotor stopped due to a belt slippage.

From my thinking, if you look inside the cap and at the rotor, the edge of the rotor is quite long and stays within arc range of a post for quite a while while its passing - so the space between the posts of the cap where firing is not possible is not that large as it may appear.

Cheers,

Mike

hoggel

I'd love to install a lift. My garage is 7' 9" from floor to rafters. To raise the ceiling ... is a slippery and steep slope.