98 GMC 5.7L Vortec surges while accelerating and driving

[ndwinters21]

I have had this problem for quite some time. I've been trying to narrow it down one test and one part at a time with no luck.

It will occasionally drive great with no problems but other times it surges while accelerating and driving down the road. I've had the timing checked, replaced the spark plugs, replaced the wires a while back, replaced the EGR valve, and replaced the cap and rotor.

The truck will idle fine except for the occasional rough idle in gear during the times the truck is running badly.

 

Any suggestions would be appreciated.

Thanks.

[Mossyoakglock]

O2 sensors? Have you tried cleaning the throttle body or replacing the fuel filter? Maybe the fuel pressure regulator?

 

Run some techron through the tank just to clean things out.

[ndwinters21]

I was reading the thread below, 96-98 Fuel Pressure Spec, and my pressures read the same, 60 with key on and 54 running. Could this cause this problem. I replaced the fuel pump a year ago with a Airtex I believe.

Edited June 12, 2015 by ndwinters21

[ndwinters21]

I ran some 44K Fuel Injector and Top end cleaner thru it. I have cleaned the throttle body and the Mass Air Flow Sensor.

[2018GMC]

I was reading the thread below, 96-98 Fuel Pressure Spec, and my pressures read the same, 60 with key on and 54 running. Could this cause this problem. I replaced the fuel pump a year ago with a Airtex I believe.

Your fuel pressure is fine. I didn't notice a difference when replacing my fuel pump, but at least my fuel gauge is fixed!

[2018GMC]

Have you checked the computer for any codes?

[1997SierraSLT]

Faulty TPS or MAP sensor perhaps. Unfortunately the ECM is always intelligent enough to throw a code.

[operator556]

Could it be your idle air control? My 99 Tahoe did the same thing and I replaced the iacv and it ran like a top after that

[ndwinters21]

The codes that have been coming up most is P0300, Random Misfire, & P0303, Misfire Cylinder 3. A few weeks ago code P1404, Exhaust Gas Recirc. Valve Closed Pintle Position, came up. I replaced the EGR valve in December so I took it back under warranty thinking maybe by chance I got a faulty valve but it the new valve didn't change anything.

I've had the ECM checked out and it is working fine and about the only sensor I haven't changed is the Idle Air Control Valve so its probably worth a shot.

[ndwinters21]

I ended up putting a new spider injector in which improved the performance but did not cure the misfire. So I put in new distributor, cap, rotor, wires, and plugs. It ran like brand new for a couple days and now it is starting to misfire again. I ran the codes and it came up with the same P0300 & P0303. Still not sure whats going on. It does run a lot better but loses power at low speeds.

[AsphaltMan87]

I ended up putting a new spider injector in which improved the performance but did not cure the misfire. So I put in new distributor, cap, rotor, wires, and plugs. It ran like brand new for a couple days and now it is starting to misfire again. I ran the codes and it came up with the same P0300 & P0303. Still not sure whats going on. It does run a lot better but loses power at low speeds.

[AsphaltMan87]

If this helps anyone I had the same issues and replaced sensors n sensors n sensors traced wiring n didn't think it was fuel related because my pump was not even a year old and I had good pressure not running and idling but when I plugged in the datastream and went for a drive I found out under a load the fuel systems would close and I'd either have to stop all the way or turn off the truck n start it again so I ran some tests to narrow it down n found it was a damn faulty fuel pump, that was still under warranty tho ? hope this helps some poor guy save some time n money

[Branjo]

Tps throttle position sensor can act up and cause intermittent surging  or stumbling at any speed. 

[bronyaur]

Have you properly set the cam r e t a r d offset?  That can cause all kinds of stumbling and misfires.

Edited May 12, 2020 by bronyaur