Help with 98 Chevy 5.7 misfire not running right

90

Asked by Feb 03, 2015 at 01:50 PM about the 1998 Chevrolet C/K 1500 Silverado Extended Cab LB

Question type: Maintenance & Repair

Hello. I have a 98 chevy 1500 5.7. The truck doesnt run right at all. Msifres bad under acceleration. Idle ok when misses when reving and accelerating. I did a full tune up including plugs, wires, cap rotor and a new distributor. With key on i have about 60psi fuel pressure but idleing i only had 50psi. I put a complete new fuel pump unit in and changed fuel filter. Same problem. no different fuel pressure. I changed and replaced the spider injector with the new updated system. changed all intake gaskets. That didnt make a difference either. Replaced tps sensor and map sensor. Removed egr valve and it isnt sticking or anything. I cleaned it and used new gasket and put back on. Still same. I know these trucks need 60psi when idling. Cant figure out why i only have 50. I replaced everything in the system. I removed the fuel line where id goes into the spider system and plugged it and have 80psi when i turn the key. then i disconnected the return line by the distributor and plugged it and had 90psi there when idling but engine ran the same. i dont know where to look next. please help
Thank you
Jon

3 Answers

90

also to add, i was getting a p300 misfire and a p122 tps sensor code. thought it had a bad sensor thats why i replaced it. sensor code hasnt come back yet but just did that this morning and still messing around with it. could i have a bad spider injector causing the low fuel pressure?

4 of 4 people found this helpful.
40

What's the battery and alto stir like? If one or the other is bad it may not be getting enough voltage.

2 of 2 people found this helpful.

I have a 98 1500 with 5.7. Have same issue. I have replaced everything I can think of and still misfiring. My next move is to replace timing chain. Hopefully that'll fix it. Did you ever figure out your problem?

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