help with rough idle and hesitation at cruising

turbowagon_in_pa · Post by **turbowagon_in_pa** » 27 Nov 2011, 17:06

Ok, I'm hoping someone can help me with this, but first I'll give a little history of what I've dealt with. About a year ago, I bought a '95 850 glt. When I bought it, I could see that the tires were wearing very badly so I figured it needed aligned. No big deal right? The alignment shop tells me that it's so bad that it won't register on there machine. They tell me that the frame must be bent in the rear. I do a car fax report, and find that it had indeed been hit in the rear a few years back. I liked the car, but not the power, so I found a turbo 850 cheap that needed work. I towed it home, and began the work. The main issue was the transmission codes, and the fact that it was in limp mode. The glt was parked at this point, so I switched the pnp switch to no avail. The transmission fluid was completely black, and flushing it didn't help. I ended up switching transmissions with the glt. Transmission problem fixed. While removing the old tranny from the "new" car, I saw that some engine mount, and transmission bolts were either hand tight, or not threaded in completely. many of the vacuum lines were either missing, or connected incorrectly. There were also various miscellaneous pieces on the vehicle that were missing, or broken. The glt bacame a donor vehicle, and all the broken, or missing pieces were switched out. To my problem, When I start the vehicle cold, it idles rough, and the rpm's are slow to climb. The rpm's don't spike for an instant, and than drop like I believe they should at start up. There is a slight delay at start up, and then a slow climb to 800 rpm's. The rough idle is almost gone at operating temp, but not completely. Also, When cruising at around 2400 rpm's, I feel a stumbling hesitation feeling in the car, but not under heavy acceleration, and only around that rpm. A couple sensors were switched over from the glt because it ran perfectly, but this is a list of what I've done.

Replaced cam sensor from glt
Replaced MAF sensor from glt
replaced upstream o2 sensor from glt
replaced all vacuum lines except those for the pcv system, but I checked those for blockages
new plugs, cap, and rotor
replaced IAC valve from glt

I ran two bottles of techron through the tank, and also did the seafoam treatment in the crankcase, and intake. I did this because when I had the intake off, I could see that there were a lot of deposits on the intake valves.
Also, I put the smaller wheels from the glt on the car, because the tires were brand new, and two of the tires on the factory turbo wheels needed replaced. would the smaller wheels cause the stumbling feeling, maybe because of the gear ratio change? I'm replacing the pcv system this weekend, and also the TCV because I believe that to be bad as well. The boost is not what it should be, and when the waste gate is unhooked, I get boost. The actuator moves freely.

I know this is alot, but hoping that someone can help.

Post by **rspi** » 27 Nov 2011, 17:31

Do you have any codes?

turbowagon_in_pa · Post by **turbowagon_in_pa** » 27 Nov 2011, 18:03

I don't have any codes right now. Something else, I know that the check valve on the fuel pump is bad, but I didn't see how that would effect anything.

turbowagon_in_pa · Post by **turbowagon_in_pa** » 28 Nov 2011, 15:23

Something I noticed when I pulled in the driveway tonight. When I put the car in park, I noticed that the idle was jumping slightly from 900 to almost 1000rpms. The rpms kept going up and down, but only slightly between that range, and the engine was running smoothly. I'm stumped, any ideas?