Background:

'96 TA gutted and built to Camaro Mustang Challenge specs
What that means is, all emmissions has been removed. No EGR, no AIR ... just a motor, an alternator, and a PS pump

The PCM is bone stock tune ... NOTHING has been altered in the timing curves or the fuel maps.

O2s are old, but appeared to work just fine.

The MAF is aftermarket and I picked it up and installed it (was in a CAI setup already) by mistake. Not sure of the brand or make. It is descreened, however.

I went to a dyno today just to get some baseline data.

252/302 at the wheels unrestricted. A/F ratio was pegged at 10!

Any ideas on why the car is running so rich? All vacum hoses appear to be fine or plugged. The EGR plates don't appear to be leaking. Fuel pressure hovered around 40psi.

Part throttle (2500rpm in 3rd gear) saw the A/F ratio just fine ...

Realize, the PCM is off limits. I cannot touch the tune per the rules and regulations.

TPS issue? MAF issue? O2 issue?

Any help would be most appreciated ...

 

How can you tell?

 

No SES light ....

I do not know if I have one now, though, as the com port and associated SES light are tucked way up underneath the dash (Painless wiring harness).

I am hooking up my Autotap today to see if there are any codes ....

 

i had bad o2's that did not set off the SES.

 

yea i would agree just because your not getting ses light doesnt mean they work properly

 

That's good info ... but I was hoping to not start arbitrary, best guess parts chasing ...

 

My 94 Z was running so rich at full throttle that I could smell the gas every time I stomped on the gas pedal. It turned out it was the O2 sensor, and I wasn't getting a code either (now it misfires like crazy due to the opti but that is a different story ) So, I think the O2 sensors would be a good place to start. Good luck.

 

I'll give that a try ...

I would welcome any other input, though.

 

So here is what I have done ...

I took the aftermarket MAF off and replaced it with a stock unit as well as the CAI tube feeding it. Not sure what I was thinking when I installed it. It's illegal in my class and I never intended to use it ...

I also did the TB by-pass mod. Not sure what I was witing on for this mod either ...

I replaced all the plugs that cap vacum ports that I no longer use. Nothing appeard to be leaking, but I was there and wanted to make sure.

I replaced the PCV hose feeding the TB. Again, all appeared to be fine. But, it was cheap, I was there and grasping at straws.

I replaced both O2 sensors.

I wish I was able to use my A-Tap to monitor the old O2s, but I could never get it to connect and give me a list of parameters to monitor. The rig works on my '98 TA and my '01 HD, but not this '96. Strange.

The old O2s were original to the car. And I noticed that there was a slight "rattle" to them when shook. The new ones didn't rattle at all. So, maybe they were both busted ...

I don't think any single item in that list was causing the problem, rather the cumlative sum of a couple or all ... again, wishfull thinking ...

Headed back to the dyno on Saturday ...

 

A/F ratio was spot on.

Must've been the O2s ....

 

Glad it all worked out for you.

 

So what did it end up putting down?

 

232/291 with a 37mm restrictor plate