88GT Stuttering at Cruise (Page 1/1)
Nathan A JUL 30, 08:22 PM
Hi, I have an 88GT and it has a stutter like issue at cruising RPMs, even in park when throttle is held at around 3k rpm the car will stutter down sometimes to 2k or lower. It seems to run fine at both idle or under medium-heavy acceleration. EGR valve, plug wires, and fuel filter have been replaced with no change. Also tried unplugging the O2 sensor with no change, cannot hear any obvious hissing from vacuum. If anyone has any ideas as to what it could be please let me know.
Gall757 JUL 31, 08:11 PM
I would suspect the TPS. Check for codes.

http://www.gmtuners.com/tech/TPS_IAC.htm

[This message has been edited by Gall757 (edited 07-31-2021).]

Nathan A JUL 31, 09:03 PM

quote
Originally posted by Gall757:

I would suspect the TPS. Check for codes.

http://www.gmtuners.com/tech/TPS_IAC.htm




I just checked TPS wide open voltage is right where its supposed to be closed throttle is 0.2V higher but I'm guessing this may be due to it having a Holley throttle Body. No codes atm.

[This message has been edited by Nathan A (edited 07-31-2021).]

Patrick JUL 31, 10:26 PM

quote
Originally posted by Nathan A:

I just checked TPS wide open voltage is right where its supposed to be closed throttle is 0.2V higher...



I'm not absolutely sure about this (but it's easy enough to check in the archives), but I believe the idle voltage is the most critical. I'd adjust the TPS (by rotating it) to get it spot on. If the current TPS doesn't have slots to allow rotation, they're easy enough to create. It isn't the best idea to bend the "tang" instead.

What you also need to check for is a smooth voltage transition from closed to wide open. In other words, make sure there are no dead spots.