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ECMlink Intermittent Hesitation/ Bogging/ Bucking

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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!
 
Posting a log and filing out the ECMlink log file help request will answer many questions and help us possibly solve your issue. Help us help you.
 
Does the concern feel more apparent in different weather conditions? Is it going into open loop when this happens?

Intermittent concerns are usually related to loose connections/high resistance in a circuit. So don't rule stuff out just because a component was replaced.

A log would definitely help.
 
Thanks I will post up a log shortly. It has been running good again lately haven't had an issue. But I know it will be back LOL.

I changed out my fuel injector Resistor box and it didn't help. I have lots of logs I can post so here goes...

This log shows how when its running awful it will sit and idle at 20:1 and extremely cammed out. It sounds good but it isnt! Look at the end of the log to see this..
 

Attachments

  • wideband 20.elg
    945.1 KB · Views: 62
Last edited by a moderator:
Here is a log with plenty of misbehavior. At 277 seconds you can see the bucking hesitation on part throttle. Also at around 417 seconds some light throttle 4% does nothing in terms of raising rpm and WB stays at 20:1 for quite some time again.
 

Attachments

  • log.2015.04.30-01.elgsputter.elg
    376.6 KB · Views: 54
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