Need Help: Engine Miss Firing

kengorden · 09-11-2002, 05:05 PM

Here is the short part of a long story:

87 944S, engine is miss firing. Pulled the wires one by one, with plug wire pliers, to see if the engine sounds changes. When he pulled the wires on the two middle cylinders, no change. On the first and last cylinder, the idle changes and almost dies (like it should) with the wire pulled.

So basically the two middle cylinders (2 and 4) are not getting spark. Actually they do get a spark ... but it is like once every 3 or 4 seconds instead of constant.

Besides changing the wires could it be anything else?

Now here is the long story:
Took the car to a mechanic to get an oil change and turn up (I was feeling lazy). When he had the rotor off, they accidently turned the engine. So he had to pull the belt cover and brought the cam belt up to TDC. Question is ... Could the second belt be off as well causing the miss fire? What do you guy think? Besides the obvious ... get a new mechanic

Ken

Paul Stewart · 09-11-2002, 05:45 PM

I'd make sure the rotor, distributor cap, and spark plug wires are installed properly.

Scott R · Scott R's Garage

I have had just about every miss-fire condition under the sun on my 951. Here are the root causes:

1. Broken vacuum lines, borken vacuum connections and t's

2. Holes in the intake boot

3. Worn cap and rotor

4. Broken electrical harness to the AFM

5. Leak in brake booster

6. Faulty injector

Keep at it you'll figure it out. Mine runs smoothe as glass these days.

kengorden · 09-11-2002, 07:48 PM

I'm sure it has something to do with the electrical system. Remember pulling the wires on the 2 and 3rd cylinders causes no change in engine idle and they are only sparking every 3 to 4 seconds. The wires on 1 and 4 are sparking normally.

Does any one have the spark plug wire location on the distributor for the 944S? I'm going to the mechanics tomorrow and want to make sure he has it right. I am thinking cylinders 2 and 3 maybe switched.

Scott R · Scott R's Garage

That would not cause a miss. On a 4cyl that would cause a no-start condition. But its 1-2-3-4 front to back. #1 on the distributor is in the 1'oclock position. Getting the wrong signals to the DME is most likely your culprit. I.E. AFM. TPS, or inproperly gapped reference sensors.

kengorden · 08:51 PM

That would cause cylinders 2 and 3 to not get a spark?

Maybe a better question would be ... Why am I not getting a spark to cylinders 2 and 3?

Cylinders 1 and 4 are fine. You pull the wires on 1 and 4 and they spark away. You pull the wires on 2 and 3 and no spark.

todwic · todwic's Garage

Broken/mishapen/corroded rotor tips/dist. notches? The plug wires have slipped off the metal contacts inside the boot? Dist. installed upside down? Lots of little stupid things can go wrong with dist. cap. Plug wires grounding out.
I don't see why it mattered that you turned it over with the cap off, it still goes on the same way, and the rotor only fits on one way. There's more to timming these cars that having it at TDC. AFJuvat has posted a nice post about it recently. Use the Search capability.

Lawrence Coppari · 03:45 AM

Check to see if distributor cap is securely fastened. While you're at it, remove it and look inside to see if anything looks messed up on the inside. It sounds like you have a ham fist for a mechanic.

kengorden · 09-12-2002, 09:19 AM

Thanks for your reply Lawrence ... Its my own fault for being to lazy to do a simple tuneup myself.

The cap and rotor are both new and securely fastened, I stood there as he put it together. I am going to make sure he tried putting the old cap and rotor back on to see if 2 and 3 were still not getting spark. If that is still the case, I'll have him swap the wires (he already checked them on the meter) i.e. take the wire from number 1 and switch with the wire from number 2. That way if all of a sudden 1 is not getting spark and 2 is we know its the wires. If not I am back at square one.

Lawrence Coppari · 09-12-2002, 09:37 AM

When I first got my 944T, I opened the distributor to have a look see. I did not fasten the cap properly and really messed the rotor and cap up. I had to buy a new cap and rotor. Engine was also missing.

kengorden · 09-13-2002, 07:17 PM

Well the saga continues ... the mechanic replaced the wire, still no spark to cylinders 2 and 3.

I'll let everyone know what the problem was once its fixed ... this one has me puzzled.

todwic · todwic's Garage

The allen head screw on your rotor? I got a fiver that sez it's your dist. cap. Zim's has a Bosche Cap and Rotor kit for $43.95 and Neighbor, that's a helluva deal.