• The site migration is complete! Hopefully everything transferred properly from the multiple decades old software we were using before. If you notice any issues please let me know, thanks! Also, I'm still working on things like chatbox, etc so hopefully those will be working in the next week or two.

97 Grand Prix 3.8 n/a, P0171, P0174

R

rlervin

New member
Hi folks, I'm new and really appreciate all the technical information I have already read about. I have a problem with a 3.8 throwing these codes for lean mix on both banks. It started shortly after I had replaced the intake gaskets and PCV valve. When I removed the upper intake, I found a 3/8" tube that had fallen out and was laying on the lower intake. It appears this tube goes back up to where the PCV valve is located. If this tube falls back out can it cause these lean mix codes? Can an aftermarket PCV valve cause these codes. I haven't had a chance to check the fuel pressure yet but I plan to sometime this week. I have replaced all the vac hoses going to the intake and checked the other ends at the solenoids and modulator etc... Another problem I am having is when you crank this thing up after a hot soak the engine will have a roll to the idle. If you put it in gear it will actually jerk the car forwards or back depending weather it is in drive or reverse. My LTFT are reading over 10% so I know I do have a problem. I did replace the fuel filter recently and cleared PCM memory and reset fuel trims but they came right back up showing the PCM is trying to richen the fuel mixture up. Are there any common problems on these engines that cause these lean mix codes. This car has over 190000 on the meter but runs like a new one other than the lean mix problem. I bought the car with around 180000 on it and no codes. This lean mix problem just slowly started coming on and has gotten worse over the past year. I do believe I may have a leaking brake booster but I have tried unhooking and plugging the vac line to the booster and the STFT and LTFT don't change. Any ideas?
 


engine at idle spray carb cleaner at the vac lines and tb vac lines and the injectors. if the idle jumps up you found the leak area.
 
I've tried looking for a vac leak with carb cleaner and cannot find it. I will try cleaning the MAF and popping in a new air filter to see if that changes the readings. I've already checked for damage at the MAF connector and everything checked good.
 
Yes, sprayed around injectors, seams where manifolds meet, vac hoses, solenoids, modules etc... I even checked for high crankcase vacuum in case I had a lower intake gasket failure. Saw that one on a 5.7 Vortec few years ago. Like I say, I'm going to clean MAF and check fuel pressure when I can pry my wifes hands off the steering wheel for a few minutes. LOL!
 


You must log in or register to reply here.
Back
Top