What else could it be??

[stangeater]

Okay, I've been trouble shooting this problem for about a week, and still haven't gotten to the bottom of it.

I was driving home, and all the sudden my car seemed like it was running on 4 cylinders. I pulled over to see if a plug wire had come off, but nope. Here is a list of what I have done so far..:

Replaced the DIS with 3 different ones.....didn't help
New Plugs..didn't help
New plug wires...didn't help
New Coil....didn't help
New fuel filter...didn't help

When it originally happened, I had no check engine light either, but pulled the codes anyway, and got a 172..Oxy sensor lean, and
136...Oxy sensor lean
Now the only code I can get is a 157, which is a MAF ground issue?

Any ideas what it could be? I'm wondering if maybe it could be a bad injector or something??
Thanks in advance for your help!

 

[SHOCH]

Have you tried a different maf?

 

[frosho]

And have you done a cylinder balance test? I forget whether or not you've done that yet.

 

[Toolman]

Try another MAF. Also, did you verify that the other DIS modules were good? Have you checked to make sure you are getting spark from each plug?

 

[SuperHO]

unplugging the MAF might help diagnose as well. it'll throw a code, but it should run much better if that indeed is the problem.

 

[stangeater]

And have you done a cylinder balance test? I forget whether or not you've done that yet.

wow, thanks for all the good ideas. I did the balance test, and it was saying that there were problems with a lot of the cylinders....I need to do it again, for some reason, it didn't sound quite right.

Toolman, All the other DIS modules came off of running engines. I find it hard to believe that all 3 of them could be bad?? I think my dad has a timing light that I can use to see if all cylinders are getting spark, but if the plugs, wires, coilpack, and DIS are all working, then why else would I not be getting spark?

Thanks, Jeff

 

[stangeater]

I'm begining to wonder if my timing belt skipped a tooth or something...

 

[klobbs]

only one way to find out

 

[luigisho]

If you have running cars to monkey with you can try a different MAF, PCM, Relay Control Module ect.. You don't want to generally throw parts at aproblem unless you have parts available that you don't have to purchase.

 

[elarm1]

cps? what other symptoms do you have?

 

[stangeater]

Okay, here is an update.
It seems that the cylinders with the problem seem to be the both front an back cylinders on the drivers side of the engine. I pulled plug wires, and those 2 didn't seem to make the car run any worse, where the others did.

For those of you who aren't aware, the car has a horrible miss. I have replaced the plugs, wires, DIS, coil pack, and fuel filter, and no change so far.

 

[SHOtime2511]

Do you have an extra spark plug?
Try pulling the wire off the front driver side cylinder put the plug in it and ground it to the intake or valve cover and see if you have a good spark on that cylinder.
compare to the others.

 

[stangeater]

Okay, I was wrong on which two plugs. The 2 plugs that seem to not be firing are the back two closest to the passengers side. They seem to have spark, but it looks weak. I can pull both of those plug wires off of the coil, and there is no change in how the car runs.

I'm seriously stumped. Normally i would say DIS, but I've tried 3 different ones, new plug wires, plugs, coil, and NO change in how the car is running. Still has a horrible miss. I now have a 4 banger sho.....

 

[jonheese]

Okay, I was wrong on which two plugs. The 2 plugs that seem to not be firing are the back two closest to the passengers side. They seem to have spark, but it looks weak. I can pull both of those plug wires off of the coil, and there is no change in how the car runs.

I'm seriously stumped. Normally i would say DIS, but I've tried 3 different ones, new plug wires, plugs, coil, and NO change in how the car is running. Still has a horrible miss. I now have a 4 banger sho.....

Huh... That's really strange...

The two cylinders you're saying have no/weak spark are cyls 1 and 2, but you say that you can pull the plug wires for 1 and 2 each (or both?) and have no change in the way it runs.

This is odd because the way the SHO ignition system works, there are actually 3 separate coils in the coil pack, and the cylinders are paired up, with each pair sharing a coil. The pairs are 1&5, 3&4, and 2&6. Because of the way this works, if you unplug the cyl 1 plug wire, you break the circuit to that coil, and cyl 5 will also stop firing. Similarly, if you unplug the cyl 2 plug wire, cyl 6 will also stop firing.

Since the DIS (the most likely suspect in this kind of symptom) has already been replaced enough times with no change in the behavior, I think the next thing that could be bad is the ECU, and then maybe the wiring to the coil pack. I don't think it could be CPS or CKS, because the problem seems to be affecting certain cylinders only, and those are discreet signals, so they would either "work" or "not work"; they couldn't fail in a way to cause some cylinders to fire weakly/not fire.

Do you have a spare ECU, or know anyone nearby who could loan you one to try?

Good luck.

 

[stangeater]

John, I don't have an extra ecu! Dangit. I'll double check the plugs, and make sure I'm correct again. It's just so hard to tell when the car is chugging/lurching to run. The middle plug (5) in the back is definantly one of the culprits.
I'll have to try to find an ecu. I think there might be a sho in a local junkyard close by. I hate that yard, they always want almost new prices for their stuff...

 

[jonheese]

The cylinders are numbered as follows:

Firewall
1 2 3
4 5 6
Radiator

So the middle plug in the back is cylinder 2, not cylinder 5.

Do your plug wires still have the cylinder numbers on them?

 

[stangeater]

The cylinders are numbered as follows:

Firewall
1 2 3
4 5 6
Radiator

So the middle plug in the back is cylinder 2, not cylinder 5.

Do your plug wires still have the cylinder numbers on them?

Sorry, yes you are correct it would be 5. No, the new plug wires are not numbered like the OEM ones.
Jeff

 

[SHOtime2511]

Are you sure you have to plug wires on correctly?
It is very easy to mess up.

 

[stangeater]

Are you sure you have to plug wires on correctly?
It is very easy to mess up.

absoposituvily

 

[jonheese]

Sorry, yes you are correct it would be 5.

Nooo... it would be 2. Not cylinder 5. Cylinder 2.

Incidentally, I don't think you've got an incorrect plug wire routing issue, as that doesn't really make sense with your symptoms (especially since they started out of the blue, while you were driving the car), but out of curiosity, where did you get the plug routing diagram from? I know the Chilton manual is notorious for having the incorrect routing.