Plug wires

[Shimy87]

The car has a miss and transmission guy thought maybe plug wires. I have felt this miss for quite a while. I checked coil and it's 13 ohms across each, as expected as its new. Also plug wires are new. I checked them and each one reads .008 to .010 depending on length. I also kept the autolight wires that came on the car as they looked good. I tested those and they read 5.25 to 5.75 on the meter. Why are they so much higher? Both 7mm.

[Steve Wood]

Made differently, I guess. Amount of resistance in plug wire brands usually is unimportant as long as it is proportional to length on a given brand. If it changes while wiggling the wire, that is not good.

Swap between the two cars and see if the problem moves to the other car.

Swap the coil packs as well.

then, I would pull one injector connector at a time while idling to see if the miss got worse with each one you removed, or if it was largely unchanged on a particular cylinder.

[Shimy87]

Thanks Steve,

The miss is very small and only noticable when driving, in 4th with converter locked. You cant tell it has an issue at idle. Way back, soon after I got it running and discovered the problem I had the injestors proffesionally cleaned and  I did swap the coil and wires from other car and put new plugs in at the same time. miss gone with the parts from other car so I bought a new coil and plug wires then for this car. It got better but I did still notice it. Yesterday, the trans shop fixed the hard shifiting issue and when I picked it up he mentioned the miss and said he had alot of cars coming in a few years ago with a miss and usually it was a bad plug wire with people that just put new wires on. He thought it was from how they bend them tightly to fit in boxes. I pulled every one last night and while I held the tester I had my son bend around each wire from end to end to see if there was a bad place somwhere that was causing this.....readi ng remained constant with each one?

I guess this time I will put old wires on and keep new coil and see what happens, if it remains must be coil even though it tests well??

[Steve Wood]

"Must" is a pretty strong, and often wrong, term

Long ago, my GN had a light miss up in 4th gear.  Never figured it out.  It went away with a rebuild.  I still wonder what it was

[Scoobum]

Heat changes everything. I didn't call a coil pack/ignition module good until I did a WOT run at the track and it revved out clean. Stick with the stock wires and the stock plugs from a GM dealer gapped at a tight .030. I hate saying this, but I had known good parts...and if I ran into this situation, I'd swap them out one at a time till the problem rectified itself. ECM's will do funny shit as well.

[nocooler]

Steve will correct me if I'm wrong. But with it being waste fire wouldn't you have 2 misses if a coil was bad?
I'd start with a temp gun on the exhaust manifolds and see if they are consistent across the board, might drive it until it misses, and then check it again and see if you can spot the cylinder.

[Steve Wood]

Yep, does not sound ignition related to me, but, it's easy enuf to swap between cars and find out.

Brad might be right on the ecm...maybe an injector driver is a bit flaky and kicking a cylinder a bit lean up in fourth when there is a pretty good load on the engine at relatively low rpm.  I would not bet much on it but things do happen.  Another swap candidate.

[Scoobum]

Shimy, if you have PL bring up TPS on graph. Key on but engine not running slowly push the gas pedal to the floor and slowly release it. The TPS line should be smooth...not jagged. I had a miss in my car and the TPS line was jagged/saw toothed. Ended up being the fukn ECM. Something on the PC board had gone for a shit. Slapped a known good ECM in and all was well...smooth TPS line again.

[Shimy87]

Thanks guys, lots to try here, not lots of time available

[Steve Wood]

I would just swap module, coil, wires in one go to see if the miss goes away.

[Shimy87]

Tested coil when hot, 13.5 on all 3. put old wires on car, gets worse. put new wires back and put in new plugs, still there but very slight.  Swapped coil, module and wires over from my car, goes away.  At this pont I think its the ingnition module but I dont want to seperate coil/module from the one from my car just to see. Any way to test these modules? Dont feel like spending another $200 I dont need to

[Steve Wood]

Not aware of any practical way to test one.  I think I might have a new one on the shelf I can loan you (assuming I find it LOL) if you want further verification

Brad has stated that he had good luck with non turbo specific modules at the track.  He will have to provide the numbers he used.

I always used 11-13 k-ohm as the range.  The strange thing with yours is that ignition misses usually show up initially under boost where the load imposed is high.  While the load is higher up in 4th under cruise conditions, it should not compare with under boost conditions.  The modules are very complex, however so that may not always be completely true.  Interesting case.

[Shimy87]

Its the only thing in the loop that isnt brand new, I think I'm just going to get one. Amazon and Summit both have them for $160. If this one is original its got 150,000 miles on it.

[Steve Wood]

I bought one of these    https://www.highwaystars.net/module-ignition-control-acdelco-replaces-24503624/

or maybe he had one of these on sale, I don't recall   https://www.highwaystars.net/module-ignition-control-nos-acdelco-24503624/

[Shimy87]

Thanks Steve!