Problems at WOT

[james85z28]

It started happening last weekend. When at WOT my car starts off fine but then starts to bog, stumble, jerk, etc. I originally though my cat was plugged because i keep slamming it on the ground but I check it and it looks good. I attached a FP gage ==> idle pressure is fine and when driving at WOT the max pressure I saw was ~42 PSI. regular driving I see no problems but once I gun it it starts to bog.

fuel pump?

any suggestions?

I'll drive to georgia and pay B $50 to change it for me.

[WS6 VERT]

Sounds like you have good fuel pressure, so I don't think its the fuel pump. Even when my fuel pump was bad, I didn't get a bog, I just shaved like .2 and gained 3 MPH from a new pump.

You can't really tell if the converter is plugged by looking. You need to remove the O2 sensor and install a backpressure guage to be sure.

[james85z28]

It dosn't happen at WOT exclusively. At part throttle high load it happens as well.

hmm.

I first noticed it when I was leaving a junk yard after I banged my exhaust on an unmarked speed bump. Then on Sunday I went to the track. First run was 13.9. I thought I'd go faster. But it was 95*+. On the second run I missed 3rd and when I was coming down the return lane my car kept wanting to die and stall. I then left because I thought I killed my car. Now it only does it when under load (WOT, PT).

[james85z28]

follow up:

I did some work today but haven't figured out the exact problem. I disconected my MSD and went back to straight HEI, no change. I did more observation on my FP, looks good. I checked my timing, looks good. I looked for vacuum leaks/breaks/line damage, looks good. I swapped PROMs, carriers, no change.

I then scanned my car while it was happening, checking TPS voltage, speed, RPM, and MAF rate among all the other variable like EGR cycling, temp, O2, voltage, BLMs, knock, spark, etc. I then noticed that my MAF rate is significantly down. At 4800~5000 RPM at WOT (TPS@ > 4.6v) I usually have 230~235 gps (grams per second). But now I am only showing around 142 gps. A significant difference indeed.

One of my initial beliefs was that my CAT is broken up inside and blocking my exhaust because I first noticed the problem after I nailed my undercarriage on a speed bump. I wonder if the blockage in my exhaust would hinder my intake airflow that much or if my MAF sensor is just bad?

Another thing I examined that seemed odd is that the exhaust comming out of my tailpipe is freaking hot as hell. I mean if I left my hand there I would burn myself. I don't seem to recall my exhaust being that hot before. I believe that if my CAT was blocked my exhaust temp would rise.

Before I take a metal rod to my CAT tell me what y'all think.

[WS6 VERT]

Don't you have emissons though? I didn't think you could gut your cat.

You can also check for restricted exhuast w/ a vacuum gauge.

[james85z28]

I just took my emmisions test, so I'm good for two years. If 1969 camaros don't need stinkin' CATS neither do I. The funniest thing about our emmisions tests is that all the state owned vehicles are exempt. Busses, Police cars, Fire vehicles, state inspector cars, any govt, doesn't get smogged. So screw 'em.

what's a good vs. bad pressure for testing? I don't have any experience on that stuff.

[james85z28]

well I wouldn't trash a CAT that didn't deserve. it without checking first. I unbolted the rear flangeand ground down the spot weld at the Y and remove the CAT. The CAT looked fine. Could see right throught the polarized biscuits no problem. It's not the CAT.

By flogging it I can get the problem to surface and perhaps permanently fail, instead of intermittently. It even has a hard time idling when its doing it thing. I still want to check the MAF reference voltage, 5v I believe. I had a similar problem when my TPS was dying but wasn't dead. But the scans of that look good.

Right now my car won't idle but maybe the gremlin will leave by tomorrow morning. Right now I'm thinking MAF or ECM.