psychbiker1966
15+ Year Contributor
- 96
- 1
- Aug 14, 2007
-
Houston,
Texas
I have been having an intermittent problem with my DSM that's been occurring more and more frequently and I can't seem to put my finger on the issue.I have a 99 GSX with a 6bolt head and G4CS block.I have had the car for 2 years and have had this intermittent hesitating problem that seems to be getting worse with time. The car has been built/tuned right by a local shop that is known for there work. The car runs perfect much of the time and the tune is spot on. After driving her for about 30 minutes it will start to hesitate a bit on part throttle. This trend has been getting worse with time and we have so far not been able to find the culprit despite a lot of different remedies. Its been driving us crazy so I'm putting this out there to gather some new thoughts as to what it could be. Here is a list of what we have tried so far with no luck...
1.) Boost leak test/ Compression test. All good!!
2.) new wires NGK plugs properly gapped 1 step colder.
3.) new coil /PCM/ CAS. (It had stopped sparking in 2 cylinders) fixed!
4.) new o2 sensor.
5.) fuel filters changed twice.
4.) new fuel pump. 255 Walbro.
5.) 1050cc Fuel injectors cleaned.
6.) Underhood camera mounted to watch fuel pressures. (No change in pressures during hesitation).
7.) Driveability tune adjusted from passenger seat. 45 minute session (Issue still persists).
8.) Changed Idle control sensor.
9.) Swapped in good ECU. (No better)
10.) Unplugged battery. Car drove perfectly for 1.5 hrs!! Problem resumed.
When logging and the car hesitates the WB shows lean. On throttle tip in or at idle it can lean all the way out to 20:1 and threaten to stall. I have actually seen it idle at 19:1 and correct itself after 30sec to a minute back to 13.8-1 then go to 15:1 etc. On full throttle car will run consistent AFR with no knock.
The Throttle position is logging ok from what I can see. No spiking or tweaking. The other weird thing I see is
my vehicle speed changes from 0 - 12 mph for example when I am parked and not moving. Just for a few seconds.
Voltage is good/ alternator is fine.
From point 10.) I get the feeling its a sensor problem messing with the ECU since I can reset it by unhooking the battery but I'm at a loss as to what to try next.
We are open for suggestions and will take everything into consideration. We must be missing something!
BTW its tuned on speed density. Timing is perfect, no leaks, boost is conservative 19-25 psi. Making 375 -433 awhp. 93 octane (depending on hot or cold weather.)
Thanks in advance!
1.) Boost leak test/ Compression test. All good!!
2.) new wires NGK plugs properly gapped 1 step colder.
3.) new coil /PCM/ CAS. (It had stopped sparking in 2 cylinders) fixed!
4.) new o2 sensor.
5.) fuel filters changed twice.
4.) new fuel pump. 255 Walbro.
5.) 1050cc Fuel injectors cleaned.
6.) Underhood camera mounted to watch fuel pressures. (No change in pressures during hesitation).
7.) Driveability tune adjusted from passenger seat. 45 minute session (Issue still persists).
8.) Changed Idle control sensor.
9.) Swapped in good ECU. (No better)
10.) Unplugged battery. Car drove perfectly for 1.5 hrs!! Problem resumed.
When logging and the car hesitates the WB shows lean. On throttle tip in or at idle it can lean all the way out to 20:1 and threaten to stall. I have actually seen it idle at 19:1 and correct itself after 30sec to a minute back to 13.8-1 then go to 15:1 etc. On full throttle car will run consistent AFR with no knock.
The Throttle position is logging ok from what I can see. No spiking or tweaking. The other weird thing I see is
my vehicle speed changes from 0 - 12 mph for example when I am parked and not moving. Just for a few seconds.
Voltage is good/ alternator is fine.
From point 10.) I get the feeling its a sensor problem messing with the ECU since I can reset it by unhooking the battery but I'm at a loss as to what to try next.
We are open for suggestions and will take everything into consideration. We must be missing something!
BTW its tuned on speed density. Timing is perfect, no leaks, boost is conservative 19-25 psi. Making 375 -433 awhp. 93 octane (depending on hot or cold weather.)
Thanks in advance!
.
