Hi all, we have 2 thirds here but this is about my 93 3500
454 tbi.

It has a miss bad enough that it is hardly driveable. The tach is moving around so I thought ignition. After trying different modules coils and pickup coils it has not changed at all. It is consistant, cold or hot, high rpm or low.

The injectors appear to have a nice cone coming out. Could fuel cause this?

The idle vacume is only 5" and will come up with throttle.

I plan to check fuel press but I do not think that could make the tach jump and spark with the light appears normal.
I am going to run a compression check but I am running out of idea's
I have not checked the ecm grounds but I will.
I did try the search here too. No codes present. I set the timing and that code42 came on after I disconnected the brn wht wire and I cleared it as I have in the past. (normal)

Thanks for any help fellow third gen'ers

I had this same problem with mine to the point where it would just shut the car down. I ended up replacing my distributer and VUALA! If that is the case, make sure to get a new module, too.

So, it could be your dist.

Thanks for the reply.

I removed the distributor and replaced the pickup coil. You have to take the shaft out to change this. I tried 2 pick up coils and 2 modules and another coil. Module checked good at napa. I guess the only part I did not change is the rotor or stator that is on the shaft. I am not sure what it is called but the other component that spins inside the pickup coil.

I am afraid that I may have bigger problems with the engine vacume low like that.
I will do a compression check tomorrow.


The way it runs reminds me of the way the 91 305tbi that I bought as a parts car.
Only on that car the tach was more stable and it had a lot of crankcase pressure blowing out the breather.
I could not believe it still ran when I went to get some parts off it and there was two rods and caps in the pan and the slugs stuck up in the bore!!