1999 ls1 compression results any ideas?
#1
1999 ls1 compression results any ideas?
Well my "supposed" 78k mile 1999 ls1 has started to act up a while back.... runs good for about 20-30 minutes before it starts to buck and misfire and backfire!... once it's up to operating temp. Pulled codes with no help until I took it back to my tuner to turn on the code reporting portion of my ECM got code for CSP, I replaced the CSP and the wiring looks good.... Pulled my cats and they were completely hollow! fuel trims won't record? had a code for maf sensor which they tuned out. it's staying in open loop and my b1 s1 has low mv vs b2s1 o2 sensor...he suggested doing a compression test and here are my results I did a "cold" compression test today....
cylinder:
1. 140
2. 135
3. 134
4. 129
5. 145
6. 140
7. 145
8. 135
would a "hot" compression test and or a leakdown test help? or do you think a bad coil would be my problem??
cylinder:
1. 140
2. 135
3. 134
4. 129
5. 145
6. 140
7. 145
8. 135
would a "hot" compression test and or a leakdown test help? or do you think a bad coil would be my problem??
#2
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Fuel trims won't record? What kind of software is he using? Your compression test is low but that could be cam or gauge and they are close enough together that I wouldn't think that was it if your car runs fine cold. Your best bet is to find a better tuner who can log the car when your issue happens or pick up HP Tuners and do it yourself. Turning off MAF codes sounds like your tuner guy is suspect.
#3
TECH Junkie
iTrader: (4)
If it runs good for 20-30 minutes then has problems it's not likely to be low compression related but I will ask.... Did you have throttle blade wide open during your compression test? Having blades in idle position will cause inaccurate readings.
Sorry for sounding dumb but what is a CSP ? It does sound like an electronic issue, Many electronic components take time to get hot enough to show signs of failure.
Popping and backfiring doesn't sound like a coil (Bad coil = dead cylinder)
Cam sensor maybe.
Sorry for sounding dumb but what is a CSP ? It does sound like an electronic issue, Many electronic components take time to get hot enough to show signs of failure.
Popping and backfiring doesn't sound like a coil (Bad coil = dead cylinder)
Cam sensor maybe.
#5
Fuel trims won't record? What kind of software is he using? Your compression test is low but that could be cam or gauge and they are close enough together that I wouldn't think that was it if your car runs fine cold. Your best bet is to find a better tuner who can log the car when your issue happens or pick up HP Tuners and do it yourself. Turning off MAF codes sounds like your tuner guy is suspect.
MODS if need be move to diagnostics!