Lost 4 MPH in a week! Gurus in here!! Any help is greatly appreciated!!
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Lost 4 MPH in a week! Gurus in here!! Any help is greatly appreciated!!
My SS ran a best of 13.3 @ 109.7 a week and a half ago. I ran the car last night, in almost identical conditions and only trapped 105.9. A buddy of mine ran his car on the same night I trapped 109.7 and ran it last night as well, and trapped nearly identical so it wasn't the conditions. This is with same driver, tires, etc....nothing has changed since the LTs were installed.
The car has felt sluggish for the past week or so...pretty much after the trip to the track where I trapped 109. I figured it was a psychological thing and the car was running just as strong.
Here are my mods: Whisper lid, Jet-hot LTs and dual cutouts 12-14" after the O2 sensors.
The car had also been idling rough (which it wasn't doing a couple weeks ago) so I hooked it up to my friend's laptop and drove around a little.
Here's what I have found out so far:
O2 voltage is normal at idle and part throttle (fluctuating between ~200 and 900 mv.).
O2 voltage does not stabalize at WOT. I made a few WOT pulls and the voltage was fluctuating the whole time.
No misfires.
4* of knock retard at one point, but y-pipe is hitting on floorboard pretty good.
Here's what I'm thinking so far:
Possibly running with both cut-outs open (being 12-14" from the O2s) could have 'fouled' the O2 sensors. I've read a little about this online and have seen a few people have problems with this.
Possible bad or dirty TPS sensor - if the TPS wouldn't read WOT, it wouldn't put the PCM in open loop mode...hence the fluctuating O2 readings at WOT.
Clutch is not in the greatest shape (slips occasionally)...could be slipping just enough to cause the drop in MPH (however....keep in mind I ran 4 MPH faster a week prior). A Spec stage 4 is in the mail.
A bad tank of gas...?
Bad fuel filter?
The fact that the car doesn't appear to be entering open loop worries me. What all could cause the car not to enter open loop at WOT?
Any help is greatly appreciated.
The car has felt sluggish for the past week or so...pretty much after the trip to the track where I trapped 109. I figured it was a psychological thing and the car was running just as strong.
Here are my mods: Whisper lid, Jet-hot LTs and dual cutouts 12-14" after the O2 sensors.
The car had also been idling rough (which it wasn't doing a couple weeks ago) so I hooked it up to my friend's laptop and drove around a little.
Here's what I have found out so far:
O2 voltage is normal at idle and part throttle (fluctuating between ~200 and 900 mv.).
O2 voltage does not stabalize at WOT. I made a few WOT pulls and the voltage was fluctuating the whole time.
No misfires.
4* of knock retard at one point, but y-pipe is hitting on floorboard pretty good.
Here's what I'm thinking so far:
Possibly running with both cut-outs open (being 12-14" from the O2s) could have 'fouled' the O2 sensors. I've read a little about this online and have seen a few people have problems with this.
Possible bad or dirty TPS sensor - if the TPS wouldn't read WOT, it wouldn't put the PCM in open loop mode...hence the fluctuating O2 readings at WOT.
Clutch is not in the greatest shape (slips occasionally)...could be slipping just enough to cause the drop in MPH (however....keep in mind I ran 4 MPH faster a week prior). A Spec stage 4 is in the mail.
A bad tank of gas...?
Bad fuel filter?
The fact that the car doesn't appear to be entering open loop worries me. What all could cause the car not to enter open loop at WOT?
Any help is greatly appreciated.
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Originally Posted by Z28Venom
I'm thinkin you may have jacked a O2 sensor. How often do you run the open cutouts?
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Correct me if I am wrong but when drag racing you are throttle flat to the floor?
Now the PCM should be working in open loop at this time which has set AFR values, so your O2 sensors shouldnt be affecting your drag racing.
Cruising around and idle will be another story though.
Now the PCM should be working in open loop at this time which has set AFR values, so your O2 sensors shouldnt be affecting your drag racing.
Cruising around and idle will be another story though.
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Originally Posted by GTS346
Correct me if I am wrong but when drag racing you are throttle flat to the floor?
Now the PCM should be working in open loop at this time which has set AFR values, so your O2 sensors shouldnt be affecting your drag racing.
Cruising around and idle will be another story though.
Now the PCM should be working in open loop at this time which has set AFR values, so your O2 sensors shouldnt be affecting your drag racing.
Cruising around and idle will be another story though.
At WOT, the O2 readings should stabalize...not fluctuate. They are fluctuating at WOT.
O2s absolutely affect drag racing and WOT performance. They affect your BLM values and affect how the car drives in all conditions.
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Originally Posted by 97bowtie
Did you read the entire post before responding?
At WOT, the O2 readings should stabalize...not fluctuate. They are fluctuating at WOT.
O2s absolutely affect drag racing and WOT performance. They affect your BLM values and affect how the car drives in all conditions.
At WOT, the O2 readings should stabalize...not fluctuate. They are fluctuating at WOT.
O2s absolutely affect drag racing and WOT performance. They affect your BLM values and affect how the car drives in all conditions.
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Originally Posted by Z28Venom
I think you just answered your own question...
I'm going to do some more scanning today and possibly swap O2 sensors from my buddy's car. I'll have some more info later today.
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Originally Posted by 97bowtie
Did you read the entire post before responding?
At WOT, the O2 readings should stabalize...not fluctuate. They are fluctuating at WOT.
O2s absolutely affect drag racing and WOT performance. They affect your BLM values and affect how the car drives in all conditions.
At WOT, the O2 readings should stabalize...not fluctuate. They are fluctuating at WOT.
O2s absolutely affect drag racing and WOT performance. They affect your BLM values and affect how the car drives in all conditions.
are they fluctuating when the cut-outs are open or when they are closed? or both?
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Originally Posted by 97bowtie
They fluctuate with the cut-outs open and with them closed.
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Let me know what you find I am having the exact same issue. I verified that it is not the tps. My next route is the o2's. When my headers were installed I did not spring for the o2 ext. I just used the cheap little splice kit that came from Pacesetter. I wonder if I might have a bad connection? Anyway let me know what you find out.
Thanks
Thanks
Originally Posted by 97bowtie
Checked the fuel pressure and it's fine. Holds 60 PSI from idle up to 6200 RPM. I'm leaning more towards the O2 sensors being the culprit.