3.4Twin Cam running real rough (Help)

[Camillo08]

Hey guys, Im new to the forum but not so new to cars in general. I own a 92 Lumina Z34. I bought it last year from a guy who had bent the valves in the original engine. I trailered the car home and put a semi-new engine into it. The engine itself has about 45000 on it and was running great and strong. I moved down to Blairsville PA for school and one night just abruptly started having problems. The car just started running of 5 cyliders, so we pulled the plugs off the coil and wasnt getting any spark. Replaced the coil and it was running on 6 again but not as well as it was. Then when driving it back from class things got bad again. Whenever the car drops below 2000rpms it gets a really violent shutter and loss of power. Once it breaks about 2300rpms or so it runs "better" but still not as strong as it did. A friend of mine down here said he had the exact problems with his monte carlo and said it was his coolent temp sensor so were going to scan it tonight or tomorrow and see where that takes us. I have not checked the spark again yet btw. Any ideas from you guys? I could really use the help?

[gpse3400]

Look into replacing the ignition module

[Camillo08]

Alright, but we just tested the spark coming from the coils and everyone was firing so doesnt that mean the ignition modual is its job?? We scanned it today with a OBDI sensor also and got nothing....

[GTP091]

you can get a spark plug wire tool that lets you see if the plug is getting spark from it's coil, much better than pulling the boot off the plug when the engine is running. It's dirt cheap less than $3. You could simply have a bad plug wire/s or all the way to a bad ECM, hard to tell with such little info. In my experience an ICM will work 100% or not at all. If you want to be sure it's not the ICM have an auto parts supply store test it for you NAPA does it for free. check the wiring first as the ICM is a bitch to get out the first time around (three bolts hard to see, or feel). I've collected a few ICM's over the years thinking they were bad and they ALL tested fine.

[Camillo08]

Alright thanks, I know all the coils are firing because we just tested it. I also asked around and was told an injector could be stuck open. Not to mention Im doing all of this work with the car up on stands in a parking lot... In 15 degree weather so I get fed up pretty quick. We know and have had the one bolt and one nut hold the coil pack block off already its just removing the starter to get to the bottom 2 thats the problem.. Is there a much easier way or what am I missing here?? Thanks

[GTP091]

Oh you don't need to pull the starter. Use a trouble light and a mirror to guide an extension up there. Then hold the extension on with your thumb and attach the ratchet. It's doable you just have to get positioned right and have lots of light for the mirror. Check the plug cables first at the end close to the plug. If the little light pluses bright you should be good. Ignition can be a pain in the ass to diagnose. You can also test the front three injectors by putting a screwdriver on it and putting your ear against the handle; engine running; you should be able to hear it tick. The back three are covered by the plenum. If you had a stuck injector it would be like this through the entire RPM range not just below 2300, though.

[Camillo08]

Right right, Dont get me wrong its when it drops below 2000 it shutters really violently, but its still gutless through all RPM ranges. A asked around and I was told I also might have a bad cat or O2 sensor. If I hold the car at 2600rpms I can physically watch the gas gauge go down .