Kick me in the nutz!!

[jeremiahkellam]

I've posted this elsewhere (explains some of the explaination), and I figured I wouldn't leave my buds out on all the fun!

I'll start with the facts:
94 gt built for NASA road race series
It has the original high mileage block (150+)
GT40 heads with about 70k on them, they were disassembled, hot dipped and cleaned, new freeze plugs and Crane springs installed
E303 cam, new timing chain, new balancer (FR stock replacement)
Stock MAF w/ BBK Intake (elbow cut off to locate filter in engine bay)
Stock injectors (new orings and caps, and cleaned)
stock throttle body, 94-95 cobra intake
the wiring harness from computer to engine bay (and CCM) was untouched, everything else was completely gutted and rewired. The grounds are good
I know i doesn't mean anything, but other new parts include:
Dist
coil
TPS
fuel pump

A local shop did some of the work and the tuning for me. The timing was set at 16 btdc (with spout out) and about 28 at 3000rpm, fuel pressure is reading about 35 psi

I just got the car back from the shop early this week and looked over everything they did, it looked good. I ran the car yesterday on a short 1/2 mile road at my house. I ran it up to 6000 in both 2nd and 3rd with no problem at all. I did this about 6 times. Loaded it up and dropped it off at the dyno shop. I was not there today when they did the pulls, but here is what I was told (I did get the dyno graph): 4th gear pulls
first run (wtr temp about 180) 250hp / 285 tq - graph looks nice and smooth - reves up quickly - A/F 16:1 (high...)
2nd run (185) 159 / 200 - started cutting out as soon as they got in the gas
A/F 20:1 WTF??

Killed car - checked under hood to make sure nothing came loose, everything was fine

Restarted car
3rd pull - 254 / 287 - A/F 15:1
4th pull 170 / 205 A/F 20:1

Just so you know, I'm not trying to make crazy power. Again this is a regulated road race series. 260 / 310 are the optimum numbers. And before I forget to mention, NO COMPUTER TUNING ALLOWED.

I'm guessing that because it isn't a constant problem, it has to be something self adjusting (computer). So either the computer isn't working right, or it is not recieving the correct signals from the sensors (HEGO, MAF...) As stated before, the grounds are good. The grounds from the computer and MAF are grounded directly to neg post on battery. Fuel pressure holds steady at 35 psi during all pulls. So now it is a process of elimination, and who ever finds the problem in the fewest steps wins. So... any ideas???

Given the fact that I can't tune the computer, would it be a benefit to retro a A9L (Fox) computer?? If so, what all is involved?? The fan is not an issue as it no longer exist.

Not sure if I left anything out or forgot to ask any questions, just looking for input

Thanks

[Todd Covini]

Put new O2 sensors in it and try again.

-=-T

[mitchntx]

Got a K&N air filter?

On my old street car, the oil used in the K&N got on the MAF filaments and caused all kinds of problems.

[jeremiahkellam]

We are going to try O2 sensors tomorrow. It is the BBK filter that came with the kit. The MAF has been cleaned about 10 times in the last 6 months

[Adam Ginsberg]

Grounds to the battery are one thing, but you need a good ground to the body.

Additionally, check/replace your ECT and ACT sensors.

[marshall_mosty]

Replace the coil as well. I had a problem with mine and I traced it back to either a faulty ECT or Coil. Don't know which one was causing the ultimate problem since I replaced them at the same time.

OBD won't show a bad coil.


Good luck.

[jeffburch]

What does the On Board Diagnostic feature of the ecm tell you?
Any codes?
jb

[jeremiahkellam]

I haven't yet bacause when I drove it, it seemed fine, no worries. I guess it is just allergic to the dyno. I reference to that question though, The way the car is wired, when the ignition is shut off, there is no power going to the computer (90% sure) to help retain programming. I was not a 1000% sure which lead to the computer handled this power, so nothing was done to make sure it had a constant draw even with ignition off. I think I know which lead it is now, so I may try to wire it up seperatly. If that is the case that the computer is getting wiped clean everytime the ignition is shut off, could that be causing a problem?? I have a very detailed schematic and I have narrowed it down to 3 wires that supply power to the computer. But for any one who knows, doesn't the Constant Control Module relay power to computer for this function?? Would it matter if I piggybacked a power lead to supply power constantly??

Village Automotive is doing a few diagnostic test today, so I'm sure they will try to check for codes while it is running, but if power to the computer is killed with ignition off, I guess it would erase codes.

[jeffburch]

JK,
Your statement above contains a myriad of uncertainty.
I would get a factory service manual and get to know what you have.
Does the check engine or service engine soon (idiot) lite illuminate when you turn on the ignition (bulb test)?
If it is setting codes after a run period you need to do everything to try to get them. This is why diehard efi guys like me love efi. The damn thing is trying to tell you what's wrong and you ain't listening. The provisions given by the designers of your efi system make it SOOOoo simple.
Now, I know zero about your application specifically.
Maybe a fomoco efi guru here will chime in.
If I owned it, I'd get a Ford manual and dive in.
jb

[evarner]

Put new O2 sensors in it and try again.

-=-T

Closed loop vs. open loop

.02 When an internal combustion engine is under high load (e.g. wide open throttle), the output of the oxygen sensors are ignored, and the ECU automatically enriches the mixture to protect the engine. Any changes in the sensor output will be ignored in this open-loop state, as are changes from the air flow meter, which might otherwise lower engine performance due to the mixture being too rich or too lean, and increase the risk of engine damage due to detonation if the mixture is too lean.

[evarner]

IMHO sounds like the MAF like was stated earlier.. something on the elements causing the wrong voltage/signal to be sent to the EEC or a really bad vaccum leak. Been there done that, especially since the first pull was smooth and then a nanospec of debris could have been sucked onto one of the wire elements.

.02