surges when motor is warm

[38v62]

I installed a 2001 3.4 litter egine in my1997 lumina that had a3.1 egine.It runs good when it is cold and starts fine cold ,but when it is warm and you start it you have to rev it up or it surges and dies if you rev it up it runs just fine. I have change O2 sensor,TPS,IAC,off old engine.It did help some.No check engine light is on but it was before I changed the O2 sensor .Please help if you can 38v62

[bszopi]

Check the coolant temp sensor.

http://60degreev6.com/showthread.php?t=25015

Also, which KS (knock sensor) did you use? There shouldn't be a difference between 97 and 01, but you never know. The KS has to match the PCM.

Did you ever pull the codes to see what triggered the SES light in the first place?

Also, since it is OBD2, there are 2 O2 sensors. Did you change both of them? Since its a closed loop issue, I would be leaning somewhat towards the O2.

[38v62]

I used 2001 knock sensor ,I changed collant sensor from 3.1 old motor.I changed O2 sensor near motor not behind converter . what does the other O2 sensor do? Thanks for your help .I will change the knock sensor.What about the cam sensor?I never pulled the codes.

[bszopi]

The cam sensor would cause issues no matter if it was warm or cold, so I would take that out of the equation.

I just thought of something that I noticed on my car (94 Beretta with a 01 3400) awhile back... I actually have a vacuum "leak" on my car. A few years back, I was messing with a standalone ECM which had a built-in MAP sensor. I ran a vac line to the ECM when testing, and never removed it after that, even though I had pulled the ECM out. Earlier this year, I just happened to be looking at my engine and noticed the vac line, and then realized it was open on the opposite end inside the car. Well, I took it off and plugged the port on the plenum. The next day, when I was driving, I came to a stop light (first time I had to stop after starting the car and it had warmed up) and the car died. Started it again, and it died again. For the rest of the time I drove it until I stopped, I had to keep it rev'd to keep the engine running. After that, I took the cap off the plenum vac port (there is a spare one) and have run it that way since without any issues... Not sure why I have never thought of that before when people have similar issues. It might be something you try for a day or so.

[38v62]

Thanks for your help

I am going to try the vacuum leak ,Thanks for your help,

[t3hchad]

The cam sensor would cause issues no matter if it was warm or cold, so I would take that out of the equation.

I just thought of something that I noticed on my car (94 Beretta with a 01 3400) awhile back... I actually have a vacuum "leak" on my car. A few years back, I was messing with a standalone ECM which had a built-in MAP sensor. I ran a vac line to the ECM when testing, and never removed it after that, even though I had pulled the ECM out. Earlier this year, I just happened to be looking at my engine and noticed the vac line, and then realized it was open on the opposite end inside the car. Well, I took it off and plugged the port on the plenum. The next day, when I was driving, I came to a stop light (first time I had to stop after starting the car and it had warmed up) and the car died. Started it again, and it died again. For the rest of the time I drove it until I stopped, I had to keep it rev'd to keep the engine running. After that, I took the cap off the plenum vac port (there is a spare one) and have run it that way since without any issues... Not sure why I have never thought of that before when people have similar issues. It might be something you try for a day or so.

Sounds like your IAC (idle air control) is sticking... But for the poster of this thread... im having the same problems with my 96 GP 3100.... replaced both O2's, MAP, MAF, IAC, TPS, cleaned injectors, cleaned EGR... and still is making a surging after warmed up...

[t3hchad]

the only thing that made it less surge for me was the EGR valve... by cleaning it...

also just found this info...

Too much EGR flow at idle, cruise, or cold operation may cause any of the following conditions to occur:

* Engine stalls after cold start.
* Engine stalls at idle after deceleration.
* Vehicle surges during cruise.
* Rough idle.
* DTC P0300 (misfire detected).

[Joseph Upson]

Yes, the EGR is a perfect place to start since it is only functional mainly during Idle and surging is characteristic of it inappropriately cycling. Solenoids and diaprhagms wear out and maybe that's the root of the probrlem, a worn out EGR and an ECM trying to compensate with increased cycling to obtain the right AFR change it expects to see with EGR activation.