Have a U4PO computer.. looking for base settings to start with? Any help appreciated!

stangmanok · 09-05-2002

I just installed heads on my 94GT. I now have a horrible part-throttle mis-fire. When I hit WOT the engine will run smooth, but anything less than 3/4 throttle will miss like crazy. I have searched the car over, and cannot find a vacuum leak, or arcing plug wire. The plugs are new, and the timing is set correctly. I'm running out of ideas to try. Any help would be appreciated. I have the following mods:

Edelbrock Performer RPM intake
Motorsport "E" Cam
GT-40 Iron heads (ported)
BBK shorty headers
Hollowed Cats
Flowmaster Mufflers
Built AOD-E
2500 Stall
Shift Kit
4.10 gears
MSD 6AL
Accell Coil
Taylor wires
Smog pump eliminator (all emissions removed)
K&N
Stock throttle body, MAF, and infectors. (next upgrade)
Oh Yeah 150hp NOS

Vortex · 09-05-2002

...possible problem with your throttle body or TPS? did you remove it with the intake or take it off seperatley?

Redhook_98 · 09-05-2002

Try something emissions-wise, (such as O2 sensors, EGR, etc) that are not sampled or used at WOT.

stangmanok · 09-06-2002

Welll I took my car to a buddies shop today, and had him connect a scope to the computer. What he found was that my car is running way lean at part throttle. I have an EEC-Tuner, but I'm not sure where to start programming to get this desired effect. He suggested that I use the tuner to change the injector pulsewidth at part throttle. I'm kinda of newbie with the tuner, so anyone who has experience with it I'd love some input.

Thanks Again,
Tyson

Redhook_98 · 09-07-2002

The question is: Why is it running lean? There must be something telling the computer to make it run lean..... Don't start adjusting your computer before all options are checked.....
My 2 cents....

stangmanok · 09-07-2002

He (the mechanic) told me that my car was probably running borderline lean before I put the heads on. Now that I have the extra airflow, the injectors duty cycle isn't long enough to supply the proper amount of fuel for the extra air. He's not familiar with the EEC-Tuner, so he doesn't know how to tune with it. He just told me that if I could adjust the injector pulsewidth at part throttle, that I should start tuning there. He also said that my car is actually running pretty lean on the top end (WOT) also, but not quite enought to cause a mis-fire. I'm pondering the idea of going ahead and upgrading to some 24# injectors and a 75mm MAF. So to make a long story short, I'm still not sure about what I'm going to do. I'm sure I'm not the only person who has run into this before, so hopefully someone will read this that knows what's going on. Thanks again for your help. Anymore ideas are welcomed.

Tyson

Vortex · 09-07-2002

you probably are out of your Fuel Injector range like you thought.. 24's would help regardless.. but it sounds like thats the issue, if its running even more lean when you need the most fuel..

stangmanok · 09-07-2002

I have been previously posting the 5.0L Tech forum.

http://www.allfordmustangs.com/forum...&threadid=4580

I noticed that you helped someone out with MAF function and injector slope. I have not changed anything related to the engine. (only my tranny due to the gears and stall). Also, my idle sucks too. (surges like crazy since I put the cam in.) I did raise my drive and neutral RPM to compensate, but it's a pain in the A$$ with an auto when you want to slow down. My mods are listed on the posts in the other forum. If there is any way you could give me some base settings to start with it would be appreciated greatly. BTW I have a U4PO computer.

Thank you so much!
Tyson

GTRaptor · 09-08-2002

I merged your posts to have all the info about you car / problems in one post.

You have a "healthy" list of mods, so let me start by asking you to ATTACH your moded EEC Tuner file to your next post. That way i can have a baseline. Please comment all the lines that have been modified.

stangmanok · 09-09-2002

Well I don't have my file handy, and my laptop is dead at the moment. I can tell you exactly what I've moded tho. I haven't changed ANYTHING except shift points in the tranny, my Neutral and Drive RPM, and my PIP to disable rev-limiter. I've got the MSD box to take care of the over revs, cause cutting fuel while running nitrous can be disasterous. I can find the U4P0 file bundled with the EEC-Tuner software that has the stock setting for my computer in it. Then you could have the base settings for everything as my car is setup.

Thanks for your time and consideration.

Tyson

stangmanok · 09-09-2002

I have attached the stock U4P0 .eec file. I just changed the extension so I could upload it. Hope this helps out.

GTRaptor · 09-09-2002

See if this does it for now:

OPEN_LOOP_FUEL_MULTIPLIER 1.05 # Global open loop fuel multiplier

LOW_INJECTOR_SLOPE 26.7997 # Low Injector slope lbs/hr
HIGH_INJECTOR_SLOPE 18.6416 # High Injector slope lbs/hr

stangmanok · 09-09-2002

Rob,
The increase in
OPEN_LOOP_FUEL_MULTIPLIER 1.05 # Global open loop fuel multiplier

Helped at WOT quite a bit. I tried 1.1, but that was too much and it dogged out the motor, so I changed it back to 1.05.

The injector slope high and low I changed also per your recommendation. I don't know how much they helped. I still have a mis-fire anything short of about 1/2 throttle. But these settings did seem to help some. I'm assuming this is due to the injector slope.

Oh I did change my MAF_VOLTAGE to 5. I don't know if my meter is accurate at 5 or not, but I figured I'd try it anyways since my heads, cam, and intake flow so much better.

In your opinion do I need to do something with the MAF function? Mine is still stock, but if I'm not mistaken the MAF pretty much determines the amount of fuel.

Or what about the A/F tables?

Like I said I'm pretty much a newbie. I've read alot of stuff on the net, but there's not a good source of info that's laid out in newbie terms.

GTRaptor · 09-10-2002

you could try raising flow values on the maf table at the trouble spots, that will increase fuel. do this on a percent basis, say 2.5 percent increment until you get it right.

86Cobra · 09-13-2002

If it runs fine at wot but misses at part throttle it's not the injectors. If your 19s can supply enough fuel at wot, they're going to be fine at part throttle. You still should step up to 24s but that's not your problem.

I wouldn't even mess with the EEC Tuner until you fix this problem. It's not a "normal" thing that you should just try to tune out with the EEC Tuner.

Have you checked your O2 sensors? The EEC ignores the O2s at wot so if they are bad it would only show up at part throttle. The O2 sensors basically control the a/f ratio at part throttle.