Oh yeah I remember on these trucks when the coolant sensor went bad it would make the trucks run rough. Might look into that. Shamrock knows more about it.

Thanks, I will pick up a new sensor and try that.

Which coolant sensor? The temp sending unit or the one by the therm inlet?

It would be the one by the therm housing.

I unplugged the temp sensor and noticed no difference. Of course, I don't know what that would do anyway. Probably just easier to replace it.

Do you guys think that this could be a fuel pump problem? The fact that I can get it to run smooth and rev in park kind of kept me awayy from the pump but not so sure of anything now. I need to get a couple of fitting to adapt my fuel pressure gauge the truck. Should it just go inline at the fuel filter area? If so, do you turn on the key and see what it pressures up to or should I tee te line so it can be read while running? I do LS1's and not too familiar with these engines.

Last, when you turn the key on after the truck has sat for a day or so, how long should the fuel pump run to pressure up the line??

Thank you guys very much.

Thanks RUFFNECK4LYFE for the suggestion, but the temp sensor didnt do the trick. I thought at first it did, it seemed to run better after the swap.

All the things listed i have tried at the start of this post, they all seem to change the way it misses. But nothing takes it away. I dont know anything else to change other than the ECM.

I would guess the fuel pump. I just read your 4th post and it describes what my brothers truck was doing to the "T". Actually his is an 89 also. I guess sometimes the pump was providing enough psi and other times not. We thought it was bad gas b/c we ran all the gas out and went and filled up and it started running good again. Then all of a sudden ran bad again until it just quit one day. Luckily it was in his driveway. I helped him pull the bed and replace the pump and it has ran like a champ for the last 8 months. You need an adapter that goes in place of the fuel filter to check the fuel pressure on the TBI trucks. I would definitely check that first. Even a few pounds low can throw these truck for a loop. If you decide to go that route I have all the test procedures and PSI ratings. Good Luck!