Off boost stumble
05-03-2018, 11:30 PM
#1
Rennlist Member
Thread Starter
Off boost stumble
Car stumbles after it is up to normal operating temperature. I can be cruising or accelerating lightly when it happens. Under hard boost in never does this.
The AFR goes rich (~11.1) just prior to and after this condition. I am thinking TPS.
What do you guys think?
89 951
2.83 Hybrid Stroker
M Tune (Earlier version)
The AFR goes rich (~11.1) just prior to and after this condition. I am thinking TPS.
What do you guys think?
89 951
2.83 Hybrid Stroker
M Tune (Earlier version)
05-04-2018, 12:50 PM
#2
Three Wheelin'
Car stumbles after it is up to normal operating temperature. I can be cruising or accelerating lightly when it happens. Under hard boost in never does this.
The AFR goes rich (~11.1) just prior to and after this condition. I am thinking TPS.
What do you guys think?
89 951
2.83 Hybrid Stroker
M Tune (Earlier version)
The AFR goes rich (~11.1) just prior to and after this condition. I am thinking TPS.
What do you guys think?
89 951
2.83 Hybrid Stroker
M Tune (Earlier version)
05-04-2018, 07:25 PM
#3
Rennlist Member
Thread Starter
05-04-2018, 08:00 PM
#4
Drifting
Not a good idea to disconnect the tps and drive. It's one of the five main sensors to make an engine run. I would look into your tps Idle switch or your FPR for a start. Also your potentiometer part of your tps may be going bad and you may just need a new tps altogether. And seeing how it happens in cruise where your tps usually sets at while cruising I would think that the tps would be the issue. 30+ years of the tps sweeping back and forth and setting at the cruise location for most of its life that would be a high probability that it's wore out. You can test it with an analog ohm meter not a digital meter.
https://rover.ebay.com/rover/0/0/0?m...2F391844555430
https://rover.ebay.com/rover/0/0/0?m...2F391844555430
05-04-2018, 09:40 PM
#5
Three Wheelin'
Not a good idea to disconnect the tps and drive. It's one of the five main sensors to make an engine run. I would look into your tps Idle switch or your FPR for a start. Also your potentiometer part of your tps may be going bad and you may just need a new tps altogether. And seeing how it happens in cruise where your tps usually sets at while cruising I would think that the tps would be the issue. 30+ years of the tps sweeping back and forth and setting at the cruise location for most of its life that would be a high probability that it's wore out. You can test it with an analog ohm meter not a digital meter.
https://rover.ebay.com/rover/0/0/0?m...2F391844555430
https://rover.ebay.com/rover/0/0/0?m...2F391844555430
05-04-2018, 10:40 PM
#6
Rennlist Member
Does it happen consistently or just once in a while? If you can induce it, take a video. You say it goes rich before and after -- how about during? And do you have any logging ability? If the TPS pot is lying to the KLR, you car could be running off WOT maps, which would send it rich. Ever have a bad idle? Bad temp sensor or harness might be adding too much fuel for the motor to burn until you floor it. Scratchy AFM is possible too. FPR good? Injectors clean? Cracked solder joints in DME or KLR always possible. O2 sensor could be going full rich. Bottom line, could be lots of things...the more info you supply the more likely we'll help you figure it out. 
05-04-2018, 11:01 PM
#7
Rennlist Member
Thread Starter
Does it happen consistently or just once in a while? If you can induce it, take a video. You say it goes rich before and after -- how about during? And do you have any logging ability? If the TPS pot is lying to the KLR, you car could be running off WOT maps, which would send it rich. Ever have a bad idle? Bad temp sensor or harness might be adding too much fuel for the motor to burn until you floor it. Scratchy AFM is possible too. FPR good? Injectors clean? Cracked solder joints in DME or KLR always possible. O2 sensor could be going full rich. Bottom line, could be lots of things...the more info you supply the more likely we'll help you figure it out.
Idle surges between 950-1000 (always has even with reseal of throttle body and new ISV). I can’t log right now as my netbook is acting up but I may load the software on my Son’s laptop. I have a M Tune with Rogue DME. Replaced o2 sensor last fall. Injectors were sent to Witchhunter 1.5 years ago. FPR is good. The TPS was replaced 5 years ago and I have another known good one being sent to me.
Trending Topics
05-04-2018, 11:46 PM
#9
Rennlist Member
Thread Starter
05-05-2018, 12:22 AM
#10
Rennlist Member
If you have an older version of the M-tune you may have a small pressure/vacuum leak after the MAF sensor due to cracks or deformation of the original plastic M-tune intake pipe. I had a similar stumble during acceleration with my M-Tune, and it turned out that the issue was with the M-tune plastic pipe leaking air. I replaced the plastic pipe with the LR aluminum M-tune pipe and problem solved.
05-05-2018, 11:48 AM
#11
Rennlist Member
Thread Starter
If you have an older version of the M-tune you may have a small pressure/vacuum leak after the MAF sensor due to cracks or deformation of the original plastic M-tune intake pipe. I had a similar stumble during acceleration with my M-Tune, and it turned out that the issue was with the M-tune plastic pipe leaking air. I replaced the plastic pipe with the LR aluminum M-tune pipe and problem solved.
05-06-2018, 02:34 PM
#12
That's not the point - if you unplug it, your car goes into open loop, which is the mode your car runs in while it is warming up. If you have no stumble after doing this, you can eliminate every sensor and component that runs in open loop. If it does stumble, you can focus on only the things in open loop.
This is how you eliminate a whole bunch of suspects in a hurry. Else we can randomly ask you if you think it is this or that.
This is how you eliminate a whole bunch of suspects in a hurry. Else we can randomly ask you if you think it is this or that.
05-06-2018, 03:11 PM
#13
Three Wheelin'
That's not the point - if you unplug it, your car goes into open loop, which is the mode your car runs in while it is warming up. If you have no stumble after doing this, you can eliminate every sensor and component that runs in open loop. If it does stumble, you can focus on only the things in open loop.
This is how you eliminate a whole bunch of suspects in a hurry. Else we can randomly ask you if you think it is this or that.
This is how you eliminate a whole bunch of suspects in a hurry. Else we can randomly ask you if you think it is this or that.
05-06-2018, 06:21 PM
#14
Rennlist Member
Thread Starter
05-06-2018, 06:27 PM
#15
Three Wheelin'