Thread: LTFT issue cured

Where to begin??? I bought my 97 Grand Prix SE V6 3800 for my Daughter from a “friend” for $500.00. I just wanted it to hold her over until I could repair her other car or buy her a new one. I was told there was a “fuel problem”. When I get the car home I find the Fuel pressure regulator is disconnected. Wow that was easy!!!
NOT!!! No luck the car stalled at HWY speed on my Daughter and left her stranded. It always restarted after a short rest and got her back home. At this time there were no codes. After some testing and reading a lot online (that’s how I found this sight) I replaced The MAF sensor. Then the MAP Sensor codes started popping up so I replaced that. Codes for map gone but no improvement in drivability. To shorten the story I replaced the O2 sensors the Plenum gaskets, a lot of bad Vacuum fittings, Cleaned the throttle body, replaced the bad PVC valve, the bad valve cover gaskets, power steering pump, Crank and Cam sensor, And bought some new scanner software. None of which fixed my problem. I’m getting a lot of P0171 codes. And on my last test drive I ran for a good 100 miles before it quit on me. I was looking at my scanner on the way to the service road when it started and it looked like my 02’s flat-lined as it chugged along on the HWY. When I checked the codes it gave me a P0131 and the good old P0171 . When I got home I removed the throttle body and looked into the plenum and it was soaked with coolant. I think that was what is causing my 02’s to go nuts and also causing my P0300 and P0171 codes and Killing my motor. Remember all the gaskets where replaced. I replaced the LIM and I’m waiting on the new UIM gasket and the Plenum. I’ll let you know how it turns out. This has been a real learning experience for me.

Update: after all that work plus some I haven’t added to my post I have found the last Gremlin in my Daughters car. When I completed the plenum I took the car out for a test drive. My STFT was looking good but my LTFT was still hanging around 16. I almost want to keep this to myself because I feel like a bone head for missing it. But the problem was the PCV O-Ring and the missing spring. I would never have found it if I didn’t go back to my repair manual and look real close at the picture. I didn’t know it had an o-ring and spring. The friend I bought it from had some work done on the car and the Mechanic must have forget to replace it. Well now my LTFT is between 4-6 which is good to me because it no longer has the P0171 code. I tried to get it inspected today and the only thing it failed for was the window tint. Which is now gone. Thanks for all the help this site is great.

Originally Posted by cn1151

I replaced the LIM and I’m waiting on the new UIM gasket and the Plenum.

What are the LIM and UIM gasket? My stepson has a problem with his car not revving past 3500 rpm and overheating. Some other issues: Gas gauge shows always full or always empty...fuel pump?

Glad you got it fixed up!

I overlooked swapping the PCV O-ring when I changed mine out. Been a liong time since I changed out a PCV like that style, anyway, I did not get a code but a loud whine/whistle!

I was baffeled, than it hit me in the middle of the night. I rememered seeing an O-ring on the old but not the new. The next day, sure enough, I found it and put it on the new PCV and all was good.

Originally Posted by 03GTPLE

Well, since we are reviving this old thread, I just replaced my PCV, threw away the old one (that didn't have an o-ring, nor did I remember to look for it as I tossed it out), and put the new one in.... hmm, guess it's another trip to the parts store.....argh.

Though, I'm not getting any whistling/whining from the PCV, maybe the o-ring was stuck in the supercharger.....

Jesse

The O-ring could have stayed in the intake manifold and the PCV just slid out of it and the new dropped in.

The whine I got sounded like one of theose party favor horns, or New Years eve party horns, and it happened within minutes of starting the engine at idle and does not go away.

You could pull the PCV out and check it, although if you do not have the noise, I think you are OK then.