91 3.4 Not firing on 2 and 5

[19jettadad97]

My '91 GP 3.4 has no spark on 2 and 5. Wires are good. I changed the coil pack and it seemed to have a faint spark. I had problems like this last year when the timing belt tensioner failed. I guess it was a defect when I had the timing belt and all parts replaced. This time it all started after I changed the oil pressure sensor b/c it was leaking. With oil on the wires for the ignition module, would that cause the module to not work right? Is there a way to check the module while it is still in the car? Or does this sound like it would be the timing belt tensioner again? I can't use 5th gear unless the RPMs are up over 3000. Plus I'm only getting about 9-12 MPG b/c it's running soooooo much like sh!t.

[tblake]

I would double check to see that all the coils are firing.

May I ask how you determined it was number 2 and 5 missfiring? I didnt know scan tools for OBD1 cars were able to tell you this. Did you do a cylinder drop test?

Have you ohm checked the injectors?

[19jettadad97]

The way I know it is 2 and 5 is, I pulled the plug wires off and arched them to the intake and got no spark on 2 and 5. The injectors are fine, I'm not getting any SPARK on those two. I changed the 2 and 5 coil with a known good one and same thing happens. I also switched the plug wires around and same thing happens so I know it's not the two plug wires. I need to know how to check the module while it's in the car or I'm gonna have to just change it and see if that fixes it. But if not I can't return it. This weather better change soon so I CAN work on it. It's costing waaaay too much in gas.

[tblake]

Any Advance or Autozone can test out the ignition module. Just pull it off and bring it in. Have them test it a few times to get it nice a cookin'.

[19jettadad97]

[quote=tblake;5925756]Any Advance or Autozone can test out the ignition module. Just pull it off and bring it in.quote]
Good advice but, there's not one in walking distance for me, this is my only car. That's why I was asking if it can be tested in the car. I guess I'll change it out and if that's not it then I'll change it back and try to return the new one. Gotta wait till it warms up anyway, we're supposed to get 12 inches of snow tonight.

[richtazz]

Since you swapped coils and wires, and the no spark condition stays on the same cylinders, then I would bet it is the ignition module. It's a pretty expensive part to trial and error swap, so unless you're going to drive this car running on 4 cylinders to get the new one, take it with you and have them test it.

[tblake]

I agree with Rich, be carefull running on 4 of the 6. Raw fuel will burn up your cat converter.

Plus most parts places will not return electrical parts, so you might want to ask them about their return policy before you buy.

[19jettadad97]

Originally Posted by tblake

I agree with Rich, be carefull running on 4 of the 6. Raw fuel will burn up your cat converter.Plus most parts places will not return electrical parts, so you might want to ask them about their return policy before you buy.

Yeah I know, but gotta do what I gotta do. It's been like this for a few months now. I never have the time, cash, and good weather all at the same time. The fuel smell is pretty bad sometimes, especially if I'm sitting at a light. I can get the module for about $85 and if I have to return it, I think I can fanagle it somehow. Would I be able to test it with a test light or multimeter somehow while it's still installed? As for the cat, I plan on taking it out soon after I take it through emissions.

[Fortune50]

Went thru the same thing on my '90 Olds 3.1's ICM, it was bad. It wouldn't fire one of the coils at all. Swapped coils, wires and even mesed w/ the ICM's wiring, ended up replacing the ICM and all was well again . Let us know what you find out...

[tblake]

i can usually finangle returns at this one shop where I always get my parts. I have been going there for years, they all know me by name, and if I package it up exactly how I got it, and it isnt greasy or dirty, they usually take it back with no problems.

Why are you taking the cat off?

[19jettadad97]

Originally Posted by tblake

i can usually finangle returns at this one shop where I always get my parts. I have been going there for years, they all know me by name, and if I package it up exactly how I got it, and it isnt greasy or dirty, they usually take it back with no problems.Why are you taking the cat off?

I always go to the same place also, so it shouldn't be too hard to return if I have to.
I meant changing the cat, not taking it out. (my mistake)
I probably won't get this done for another few weeks b/c of finances and weather.

[19jettadad97]

Originally Posted by 19jettadad97

I probably won't get this done for another few weeks b/c of finances and weather.

I've decided to (maybe) change the ignition module on Sat. The weather is supposed to be almost 60*. I guess I'll hold off on my rent untill next week. The car is more important. I'll post on Sun. for what I find.

[19jettadad97]

Well, I changed the ignition module today, beautiful weather. It didn't fix it. I still got a very very faint spark on 2 and 5. What the hell could this be? I changed it back to the old one and returned the new one with no problem, the idiot didn't even look in the box. I really hate the electronics of a vehicle. I should have asked b/f but with the new module, does it have to relearn itself somehow?
Here's a very stupid question but, this all happened the same day that I changed the oil presure sensor, even though that's new it's not working, it's pegged up over 80 pounds. would that somehow send a signal to the ECM and make it not fire right? I know that sounds crazy but I'm sooooo confused with this. The only other thing I can think of would be the timing belt tensioner. I feel like bringing it to the stealership and paying them the $90 diagnostic charge.
Any other ideas from anyone?

[BNaylor]

Originally Posted by richtazz

Since you swapped coils and wires, and the no spark condition stays on the same cylinders, then I would bet it is the ignition module.

I guess that was a no go. Good thing you didn't go to Las Vegas to bet but good advice considering at times you have to replace the components to rule them out. ....... Yeah I know I am a pompous "a" hole.

I recall the early 90s GPs were notorious for flaky ECU modules. Since the ECU is mounted on the passenger side front strut tower and was subject to the weather elements, corrosion and wiring issues as a result. So that is a possibility.


However, before replacing the ECU module I would check the ignition control circuits wiring point to point between the ICM and ECU using a reliable wiring diagram and to the crank position sensors (24X and 3X). Concentrating on IC and Bypass mode wiring. Plus inspect the back of the harmonic balancer and how the 24X crank sensor is mounted or aligned. Thats all I can think of without the car being in front of me.

[tblake]

so 2 coils provide good blue spark, and the 2&5 coil has a weak spark? How are you determining "weak" spark? By using a spark tester on the spark plug end of the ignition wires?

Have you ohmed the wires out by chance? I'm not sure of the spec, but I think anything over 10,000 ohms and the wire is shot.