97bowtie

iTrader: (1)

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.

Z28Venom

iTrader: (13)

I'm thinkin you may have jacked a O2 sensor. How often do you run the open cutouts?

97bowtie

iTrader: (1)

I've only had the LTs on there for about 3 weeks. I have made 15 or so passes with the cutouts open and driven another 30 or so miles with them open.

GTS346

iTrader: (1)

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.

97bowtie

iTrader: (1)

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.

Z28Venom

iTrader: (13)

I think you just answered your own question...

97bowtie

iTrader: (1)

I hope it's that simple. It seems to me the cycling O2 readings would be the product of something else that isn't allowing the PCM to enter open loop. I hope I'm wrong.

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.

John_D.

iTrader: (2)

Yeah scan it, see if the tps readings are going to 100%. That would be a likely culprit. Maybe a bad maf or map sensor, but I think both would have to quit at the same time. On the surface, it sounds like tps.

fast98

iTrader: (16)

are they fluctuating when the cut-outs are open or when they are closed? or both?

97bowtie

iTrader: (1)

They fluctuate with the cut-outs open and with them closed.

97bowtie

iTrader: (1)

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.

qew9999

iTrader: (1)

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

GrannySShifting

iTrader: (10)

What are your LTrims under slight to moderate load with the cutouts shut? if you log those runs what were the ltrims and tps position going downtrack? If they are positive you found your answer. Shoot me a PM