Franken5.0

91 Foxbody LX 5.0.

Previously Supercharged, 27lb injectors, MSD ignition, Trick Flow Intake manifold upper and lower, BBK Shorty Headers.

When I bought the car it had a chip, it ran unpredictably. Stalling, holding at 4k RPMs. A basket case of problems.

So I returned it to N/A, and stock injectors. Removed the Chip, but now it will fire, stutter, backfire. No matter what Sensors I unplug or replace. Now before running off and getting a stand alone ECU, or getting mine replaced I wanted some more opinions. I'm 99% sure its not a bad sensor, and the MAF wouldn't cause the motor to completely not work. I've scoured the Forum for an answer. Should I just do a standalone and hope for the best? Or is there a cheaper alternative to try first and fix the problem? Also new spark plugs, gapped and everything, and the gas has been in it for a while, but I have Stabilizer in it so I don't imagine that being the issue. Really thrown for a loop here.

Thanks for the help.

88 orangepeel notch

I'd start by checking the codes. See what's stored and go from there.

Then......

Reset timing to 10, give all vacuum lines a look over checking for any vacuum leaks, clean MAF sensor, verify TPS voltage at idle position (just to know, as this shouldn't cause your current issue's)

Post back with what you find .......good luck

Oh, and welcome to the forum and the world of modded Foxbody's lol.

Franken5.0

I tested my TPS and it was good, but I replaced it with a new one for piece of mind. Anyways, I ran the self test, and it told me I was getting 23 TPS Out of range, 12 idle speed out of specified range, 43 lean mixture (Which is not true my AF ratio was 24, really rich) and 21 coolant temperature out of range. I was able to baby the throttle and get the car to operating temp. I then replaced the TPS and retried the self test. This time to my suprise more codes. Fuel Pump Circuit, No MAF Signal, Thermactor Bypass, and what has led me to the problem? Code 31 Canister EGR Valve. I have a deleted EGR and Smog, with a stock ECU. It had a chip but it was for A supercharger, and 27lb injectors. I'm stuck here, is there a way to work around this? Or is it time for a new ECU? I even drove the car around the block, NO Power, but it would push itself through 1st and second as long as I loved up on the accelerator.

88 orangepeel notch

I'd clear codes and try again. Hard to know how or when some of those codes were thrown. Since you've made some pretty drastic changes, I'd just start over with a clean slate for codes and computer.

If all your emissions stuff has been removed, then just ignore the codes for those right now.

And a AFR of 24 is really lean. Usually AFR gauges don't even read that lean lol. What wideband gauge are you running ?

If it's really running that bad, I'd seriously look for a vacuum leak first as those can really cause problems.

And one more thing that came to mind. Check all your grounds. Make sure connections are clean and tight, cables and wires aren't damaged. I had similar issues with my car a couple years back, took me a week to find it was just a bad neg.cable connection at the block.

Franken5.0

Okay. So I replaced my TPS, timed the engine to 12 degrees. So after that I started it up, and I get a RICH reading 9.0-10.0. It running rough, then I let it die, I start it up again, back to really lean. I ordered an OEM Fuel pressure regulator, and a new IAC valve. I don't know what else to do. It runs fine when I ran the auto test, I just had to limp the idle with the accelerator.

mongolchuck

Check your plug wires and firing order again. Also take a look at the two main engine harness connectors behind the throttle body. The salt and pepper shakers. A bad or dirty connection in those can cause a ton of problems.

Franken5.0

Ill have to check those harness connectors. Im also going to get a new battery, the one I have is beat up from comstant starts and troubleshooting over the months. I think its shot, Im going to clean up all the grounds too. OBD2 sure would be nice about now