My 2004 monte, 3.8 117,000 Starts but after warming up 2-3 minutes RPM's start to drop in at 850 but with slight bounce maybe 20 rpm's then ramps up ~1300 then shuts down, will not restart unless I hold accellerator down slighly then runs OK at normal R's for few seconds then drops out again, No codes set or other obvious signs. I did replace the TPS but that was no help.
Country: United StatesMake: GMModel: Chev Monte CarloYear: 2004Engine: 3.8 series 2
Test pump pressure ~ 45-50 PSI, replaced TPS.
Welcome to JustAnswer, my name is XXXXX XXXXX X'm here to help get your problem resolved. Fuel pressure is low, it should be at least 53 psi key on engine off. Replace the filter to see if that helps if not replace the pump. Let me know if you have any questions at all and only rate when satisfied, thanks.
Got the pressure tester and fuel p is at 54 psi about 52 when running. could this be idle control valve problem?
Are you able to keep it running by pressing gas or does it stall either way?
I can, but can't hold steady rpm's. pressure looks fine at occurance'
Thanks for info, Now that I know you can keep it running when you try does it seem like there is a rev limiter and not able to go over a certain rpm such as 3000 rpm. Let me know if you have any questions, thanks.
Would not start without holding pedal, really erratic but did see r's at 4000 momentarily but could not keep her running.
If car sits for a period of time it will start but after few minutes ramps up and down then stalls at low r's.
See if it can run on starting fluid good, if so this means computer is not pulsating injectors correctly. Next step is to make sure injectors have good resistance, they should be 11-14 ohms, check when warm and running rough. If resistance is good I would monitor power/grounds on PCM, make sure 5v ref is not shorting out, if good replace the PCM. Let me know if you have any questions, thanks.
Where is the pcm on this car? How do I run on starting, fluid just spray into intake?
The PCM is located in air filter housing and correct, just spray into intake. Let me know if you run into questions, thanks.
Please double check the pcm location as it is not inside the air filter housing.
Here are replacement instructions, let me know if you have questions. Thanks.
Do you recommend recycled parts, I have a friend in the buisness and he has not failed me yet ?
I did pull the PCM from its location and noticed I had mouse nest inside luckly no chewed wires.
I checked the connectors seemed OK so I started the vehicle up with out the filter assembly and it ran but at 2000 rpm's. So I reassembled the filter housing and it was right bak to no start. When I used accelerator to start it I thought I would see hom many rpm's, would not reach 4000.
Remove front oxygen sensor to see if it helps if so you have a clogged converter, if not its sounding like a bad PCM. I think getting a used/refurbished part is fine, but dealer will need to reprogram and install which is around $100. Let me know if you have any questions, thanks.
I will get back with you tomorrow Dan.
Sounds good, let me know how it goes. Have a good evening.
Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database