Having an issue, need help

[Tz44]

I was gonna post this on ls1tech but figured I could get some good advice here. My car is acting strange when I'm slowing down. rpm drop to +/-500 or so when I'm about to make a turn or come to a light. Ivan put the car in park and it goes right back up to 670rpm idling like normal and I can pull it down into drive and everything is normal up until I go to slow down and then it acts like it's gonna cut off on me and just barely runs.

The car is an 86 regal with a mild cammed 5.3 and a 4l60e, I know I've got a little vacuum leak and I've noticed the vacuum hose running from the back of the truck intake to the brake booster squeezes itself almost shut while it's running. I also have a couple of transmission issues but I don't believe they're related unless it could be a converter problem?

Any ideas?

 

[big reazon]

If the torque converter is trying to lock up it can cause this what kind of fuel system are you running?
.

 

[Tz44]

I just know the fuel pump is a walboro 255 and I'm using the Monte Carlo gas tank

 

[Tz44]

I fixed the vacuum leak but the problem is still there. One other thing I noticed is if I shift the car into drive and just let it idle itself around it acts like it's going to stall and rpm gets very low even down in the 450 range and it barely moves forward...

 

[Tz44]

Could any of this be due to a Misfire? Burnt valve maybe? I just don't know what else to check for. I've got another thread posted on ls1tech but I've had very little help over there.

 

[Chuck Leeper]

Data log it.....MAP reading, and LTFT are a couple items to look at.
Could be throttle cracker, throttle follower, IAC.
Is the PNP switch on the trans wired in?
Has it been tuned for the cam, cold air intake, etc????
Has the speedo been calibrated?
Stock injs?? Are they clean?
Exhaust leaks?
Fresh O2 sensors that are working?
MAF sensor clean, and properly wired in?
Most of these items can be checked when the scan/data logging is done. Without a logger/scanner, you are pretty much shooting in the dark...........

We use EFILIVE. The best tool we've found, for working/tuning on these engines...

 

[Tz44]

Just to update...

I replaced both o2 sensors and the car runs awesome again.
Thanks for the help everybody.