Go Back   Corvette Forum > C4 Corvettes, 1984 - 1996 > C4 Tech/Performance
Sign in using an external account
Register Forgot Password?
Register Search Today's Posts Mark Forums Read FAQ Vendor Directory
Search
C4 Tech/Performance
L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Reply
 
 
 
 
Thread Tools Search this Thread
Old 08-10-2005, 10:34 AM   #1
Jim85IROC
CF Senior Member
 
Jim85IROC's Avatar
 
Member Since: Jul 2001
Location: Stamford VT
Send a message via AIM to Jim85IROC
Default part throttle stumble in 91 TPI Corvette

my 91 has developed a habit of having a nasty dead spot and/or stumble in the throttle at part throttle during acceleration. If I accelerate very easily it doesn't do it, and if I accelerate at WOT or close to it, all is fine. It's when I'm anywhere inbetween that it's having fits. It doesn't do it all the time, but it's doing it often enough to irratate the hell out of me. A while back I tried blocking the EGR to see if that helped, and it didn't. Just recently I replaced the 02 sensor, which also didn't help. When using my Auto X-ray, I couldn't find anything out of the ordinary, but I was concentrating on 02 voltage and knock sensor data more than anything else, so I may not have noticed a MAP problem if there is one.

I'm going to check the X-ray again, but has anybody else had this sort of problem? Right now by process of elimination, I've got to think that it's MAP related, but so far I've gotten no codes, my gas milage is unaffected, and drivability other than part throttle acceleration is totally normal.

Thanks for any help.
Jim85IROC is offline   Reply With Quote
Old 08-10-2005, 11:48 AM   #2
65Z01
CF Senior Member
Cruise-In II Veteran
 
65Z01's Avatar
 
Member Since: Dec 2000
Location: SE NY
Send a message via AIM to 65Z01
Default

I'm not sure if a dirty TB would do that or not??
You could try cleaning the bores and blades and then resetting the base idle.

Also, check the ignition for any loose wires.

Do you have any fuel pressure leak down issues?
__________________
My 1988 Z01 #65 Site

------------------
65Z01 is online now   Reply With Quote
Old 08-10-2005, 11:55 AM   #3
Alvin
CF Senior Member
St. Jude Donor '05
 
Alvin's Avatar
 
Member Since: May 2003
Location: Charlotte NC
Default

I'll bet it can just use a computer tune up.. Do you have any datalogs?
Alvin is offline   Reply With Quote
Old 08-10-2005, 03:19 PM   #4
Jim85IROC
CF Senior Member
 
Jim85IROC's Avatar
 
Member Since: Jul 2001
Location: Stamford VT
Send a message via AIM to Jim85IROC
Default

I forgot to mention that I also swapped the TPS with the one on my IROC with no avail, and I swapped the throttle body with no improvement as well.

Why exactly would my car need a "computer tune-up"? I've made no changes to it that would require a PROM change.

I haven't checked any fuel delivery issues because typically fuel problems don't dissapear at WOT. Ignition could potentially be an issue, but again, I would expect that at cruise and WOT conditions, not just part throttle acceleration. The car has a new coil, cap, rotor, plugs, wires, and distributer ignition module. About the only part of the ignition system that I haven't replaced recently is the ESC.
Jim85IROC is offline   Reply With Quote
Old 08-10-2005, 03:29 PM   #5
Alvin
CF Senior Member
St. Jude Donor '05
 
Alvin's Avatar
 
Member Since: May 2003
Location: Charlotte NC
Default

Has it always had this?

alot of the speeddensity cars come tuned from the factory with something left on the table.. alot of them have like a surge, deadspot, whatever.. Usually apparent to whoever owns the car and takes a sensitive driver to feel however it is still there.
Alvin is offline   Reply With Quote
Old 08-10-2005, 03:30 PM   #6
65Z01
CF Senior Member
Cruise-In II Veteran
 
65Z01's Avatar
 
Member Since: Dec 2000
Location: SE NY
Send a message via AIM to 65Z01
Default

Have you checked manifold vacuum for a leak (though something like a leaking EGR valve usually gives idle problems too)?

You might check inside the dist cat to verify that the rotor is still securely attached and check all plug wires for firm "snap" into position.

I'm not familiar with SD setup so don't know what issues with the MAP might bring.
__________________
My 1988 Z01 #65 Site

------------------
65Z01 is online now   Reply With Quote
Old 08-10-2005, 05:22 PM   #7
Jim85IROC
CF Senior Member
 
Jim85IROC's Avatar
 
Member Since: Jul 2001
Location: Stamford VT
Send a message via AIM to Jim85IROC
Default

I can try checking vacuum, although I'm not sure how I'd diagnose the vacuum when the condition occurs.

It did this before and after my new cap and rotor change.

This problem hasn't always been there, it's something that developed rather slowly over time.
Jim85IROC is offline   Reply With Quote
Old 08-10-2005, 05:56 PM   #8
65Z01
CF Senior Member
Cruise-In II Veteran
 
65Z01's Avatar
 
Member Since: Dec 2000
Location: SE NY
Send a message via AIM to 65Z01
Default

You can lay the vacuum gauge hose under a wiper blade with the gauge face taped onto the windshield.

I use this method with my FP gauge when I want to check for fuel delivery problems and it works well.
__________________
My 1988 Z01 #65 Site

------------------
65Z01 is online now   Reply With Quote
Old 08-10-2005, 05:56 PM
 
Go Back   Corvette Forum > C4 Corvettes, 1984 - 1996 > C4 Tech/Performance
Reload this Page part throttle stumble in 91 TPI Corvette
 
 
 
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
No acceleration/ bogging bigj177 C4 Scan & Tune 13 12-09-2013 02:25 PM
At idle; Engine stumbles and surges after warmup! AZBlackC4 C4 Tech/Performance 40 07-22-2012 10:15 PM
1994 LT1 conv. Engine stumbles and idle surges after warmup AZBlackC4 Intros 11 01-11-2012 10:34 PM
Auto Xray scanner (long) SS409 425HP C4 Tech/Performance 16 08-18-2005 06:59 PM
Stumbling during acceleration White91 C4 Tech/Performance 3 08-21-2001 10:22 PM


Tags
c4, corvette, stumble, stumbling, throttle, tipin, tpi


Thread Tools Search this Thread
Search this Thread:

Click for Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Forum Jump

Corvette Store
 
 
C7 Parts & Accessories
C6 Parts & Accessories
C5 Parts & Accessories
C4 Parts & Accessories
C3 Parts & Accessories
C2 Parts & Accessories
C1 Parts & Accessories
Wheels & Tires
Sponsored Ads
 
 
Vendor Directory
 

All times are GMT -4. The time now is 07:03 PM.


Emails & Password Backup