Need assistance with diagnosing hesistation problem
Thread Starter
Teching In
Joined: Jul 2005
Posts: 2
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Need expert help for hesitation unable to diagnose I recently purchased a 1998 camaro z28 with the 6spd trans. The car has 57000 miles. It has a new granatelli MAF sensor, K/N Filter, and the catalytic converters are gone. Recently the car has developed a bad hesitation on 75-100% throttle while driving. In neutral the car revs fine. I had a fellow use his HPTuners computer program to check what was wrong. He is telling me that there is good air, fuel, spark, and slight knock retard but nothing significant. He flashed the computer, deleted the rear O2 sensors code and the 2nd Air Pump codes. The car idles fine and is not setting any codes off while hesistating. Do you have any suggestions on how to proceed with diagnosing? We are confident there are no tranny issues as a final note.
Thread Starter
Teching In
Joined: Jul 2005
Posts: 2
Likes: 0
Need assistance with diagnosing hesistation problem I recently purchased a 1998 camaro z28 with the 6spd. After some routine tune ups, part changes the car has developed a hesitation on 75-100% throttle. A friend with HPTuners has been unsuccessful in finding any problems with AIR/FUEL/OR SPARK problems using his computer. There is no hesitation while in neutral with throttle input, only while in gear. As a side note, we don't believe there is a tranny problem either. We are limiting our focus to internal engine, computer problems. The car has a K&N filter, granatelli MAF sensor, catalytic converters are gone. I am in need of help, I can't enjoy the car at all right now.
TECH Veteran
Joined: Dec 2004
Posts: 4,012
Likes: 1
From: Beaumont, TX
How in the world do these kind of threads end up in the 'Signature Testing & Design' forum?? The forum's only been here a couple weeks and this is the second time already! 
I hope you get your problem solved, so I was going to send this thread to a more relevant forum, but I see you already posted in the PCM forum ten minutes later 
So this is being merged with that thread to get all your information together.
I hope you get your problem solved, so I was going to send this thread to a more relevant forum, but I see you already posted in the PCM forum ten minutes later So this is being merged with that thread to get all your information together. 
Teching In
Joined: Jun 2004
Posts: 40
Likes: 0
Bump~
i too have this same problem with my 98 ls1/m6(02 ls6 cam) in my 90 miata... idle is fine, revs fine, no codes, but has a hesitation from 60-100% throttle... i have not yet figured it out. tried new plugs/wires/pushrods, each seemed to make the idle even smoother, but didnt help with the hesitation... new walbro255lph, new 3/8" lines, new vette filter regulator, new k&n filter... any ideas? i too have hp tuners, extra stuff is turned off, fans kick on at 190 and off at 180... might my car be running too cool???
thanks!
Karl
i too have this same problem with my 98 ls1/m6(02 ls6 cam) in my 90 miata... idle is fine, revs fine, no codes, but has a hesitation from 60-100% throttle... i have not yet figured it out. tried new plugs/wires/pushrods, each seemed to make the idle even smoother, but didnt help with the hesitation... new walbro255lph, new 3/8" lines, new vette filter regulator, new k&n filter... any ideas? i too have hp tuners, extra stuff is turned off, fans kick on at 190 and off at 180... might my car be running too cool???
thanks!
Karl
The GMAF is always to be suspected. Its output is just
not right relative to stock. But on opening throttle it is
taken offline for a bit, you run in speed density mode
until MAP stabilizes and then the MAF comes back. I
always suspect the VE table is off (especially if the car
is modded without tuning) and you're stumbling until
the MAF comes back and gives a more proper airflow
reading. KR on tip-in comes from lean VE table in my
observation. KR persists too long and jumps up too
quick, a few good hits and you'll pay for it over the
next couple of seconds.
These cars' factory tune is a bit over-enriched at WOT
but voodoo tweaks such as GMAF can push this either
way (lean by nature, rich by trim overcorrection).
180 is not too cool. 140F is the closed loop ECT limit.
not right relative to stock. But on opening throttle it is
taken offline for a bit, you run in speed density mode
until MAP stabilizes and then the MAF comes back. I
always suspect the VE table is off (especially if the car
is modded without tuning) and you're stumbling until
the MAF comes back and gives a more proper airflow
reading. KR on tip-in comes from lean VE table in my
observation. KR persists too long and jumps up too
quick, a few good hits and you'll pay for it over the
next couple of seconds.
These cars' factory tune is a bit over-enriched at WOT
but voodoo tweaks such as GMAF can push this either
way (lean by nature, rich by trim overcorrection).
180 is not too cool. 140F is the closed loop ECT limit.
