I know this is the wrong kind of truck to be posting in this forum, but was looking for some advice thinking that maybe some of you guys had one of the OBS before your NBS. I've posted this on "fullsizechevys.com" and thought I would post on here as well.

This is the what was posted:

As soon as my truck gets warm, the idle goes to hell. It's fine until it gets there, I replaced my coolant temp sensor just to see if there was any problem, but same result. I pulled off the egr and put a block-off plate instead, made it run a lot better than with it on. My truck has been losing power as soon as it gets warm, not sure where the problem lies? It did this before the recent mods also, so I'm thinking that something that is on it now is hurting it. Can anybody shed any light on this?

My recent mods are: '98 vortec heads, bowtie vortec intake, dual 21/2" exhaust, 21/2" x-pipe, no cat, Magnaflow 21/2 dual in/out muffler, msd 6AL, MSD start/retard module, MSD 3-step module, '94 Caprice "cop car" fuel pressure regulator, 100-150hp NOS kit.

Before I left my brothers, we had it on the scanner. The only thing that was goofing up was the TPS, which we replaced, everything else looked fine. I'm thinking that maybe it hadn't reached "closed loop" so nothing else showed up? It hasn't thrown a code yet or a CEL yet.

I pulled the IAC, cleaned it and squirted a little carb cleaner in the port, but still rough idle. I guess once we put it on the scanner again, I'll never know? It also has new plugs (Autolite 25's gapped @ .045), Accel 8.8 wires, Hypertech cap and rotor. I bought a new coil, but never put it on (it's still at the bro's house) it looks like the original one is still on there.

I also pulled the hyperping chip out and installed a stock '94 chip in it (mine is a '90) it feels better as far as more responsive, than the hypertec. I will be putting in a custom tune when the money becomes available.

As far as timing goes, I pulled the bypass, advanced it to 10 with a timing light and plugged the bypass back in.

Anyways, I hope this helps all you "expert troubleshooters" in helping me diagnose the problem. I don't want to throw money at it and not take care of the problem, so was hoping you guys could help.

Thanks, Bobby


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'90 Chevy C1500 short box
5.7L 350 TBI motor
Bowtie Vortec Alum Intake
'98 Vortec heads
100-150hp nitrous shot
custom 21/2" duals/Magnaflow muffler
Hypertec chip
5/7 drop

I'm not only talking "idle", it just seems to lack the snap that it has when she's cold. I know I need a custom tune to reap the benefits of the new mods, but I have a hard time believing that something isn't wrong with it as she is now. She still flies when you put your foot into it, but not like I think she will once I find out what's happening. Any help would be appreciated!

 

Try changing the gasket under the throtle body. I had the same thing happen to my old 89 Chevy.

Good luck,
Chris D.

 

Thanks Chris, I'll have to check it out. Thanks for the input!

Bobby