i've been trying to get this car running right for some time now. the engine is a '93 LT1 from a Z28. i put it in an '88 firebird. at first, it ran fine, except for a knock in the pass. head. I pulled the intake and replaced a dead lifter. I had it tuned twice.
the first time, i had the EGR, AIR, VATS, deleted, shorty headers, 160* stat.,high flow cat. it seemed to run fine like that...except for the lifter.
after i changed the lifter, i got another tune at the same time. same as above, except with Smog and A/C codes deleted and the power tune option (91 octane). now it runs so rich, the car will die after about 15 minutes of ideling.
i changed the O2's with AC Delco's and changed the plugs with new TR55's. changed the fuel filter and the temp. sensor. it still runs this rich.
nothing has been changed inernally on the engine. FP has always been a Walbro 255.
also, the fans don't kick on. i took the temp up to 224 or so and still no fans. there aren't any codes and the fans turn on when i check for codes.
it was a mail order tune from Ion Soltan (Madtuner i believe).
what should i check now?

 

not exactly sure but it sounds like you changed the usual suspects, have you plugged a scan tool in to see what the pcm temp sensor is reading, if thaqt thing is malfunctioning wouldn't that cause both of your symptoms of rich A/F and fans not working right??

 

check to make sure there are no exhaust leaks. A leak near the o2 sensor could cause the pcm to think there is more oxygen in the exhaust and will then send more fuel, causing you to run rich.

Also check the intake elbow to the throttle body and make sure there are no tears or rips.

 

i don't have a scanner, but lately i've been thinking about getting something. maybe datalogging software. any sugestions?
there aren't any exhaust leaks...everything is welded except for the collectors, and i checked those when i changed the O2's. the intake is good also. it's a k&n CAI. i took it out when i took the intake manifold off, then put it back in. i'll double check it anyway.
thanks for the replies.

 

I dont think it would be a bad idea to check ur fuel pressure, and make sure the regulator hasnt gone bad. Not 100% sure on the Speed Density cars but i think they are the same as the MAF cars as far as FP goes. Should be around 40 to 42 pounds WOT. If its much higher than that it wont have a good spray pattern at the injector, and if its much lower itll make it rich. May not be the problem but like i say its something to check.

 

Definitely check the coolant temp sensor FIRST. The one in the water pump housing is the one the PCM uses, not the one in the driver's side cylinder head. If it is malfunctioning it would cause exactly what you are describing, rich A/F mixture and fans not coming on. Any scanner that connects to the OBDII port should be able to read coolant temperature. Also check it visually, broken/frayed wires etc.

 

Coolant temp, Exhaust leak at the heads, intake leak on the elboe at the intake, too high of fuel pressure, too low will NOT cause a rich condition, it will cause it to lean out and missfire at WOT. Also I would have a REAL tune put on the car, not the mail order crap! Let someone with a good reputation, and a good following to hook up and tune it correctly! Hope you find the problem!

 

i changed the sensor yesterday, disconnected the battery, reconnected it and tried again. still rich. i'm not sure what the vlotage going to the sensor should be, but i got 1.27 volts in "run". the third gen ref. voltage s/b 1.7 to 1.9 volts.
the computer is a '93 OBDI. i've never messed with scanners or tuners before, but i think i'm about to.

 

i'd love to get a real tune, but i'm hours away from the closest place to do anything...which is the reason for a mail order tune. also, i didn't think a lot would be different since it's basically a stock engine.

i'll check the fuel pressure and see where that takes me.

 

Oops, I just noticed it's OBDI. I'd still want to see what the PCM was seeing for temperature, even if the sensor is good there could be a short/bad wire/something causing an inaccurate reading.

 

i ordered an ALDL cable from moates. as soon as that comes in, i'll finally be able to see what the computer is seeing. i haven't checked the fuel pressure yet, and it will probably be monday before i get the chance to check it. thanks for the input so far.

 

Sounds to me like you may have gotten a bad tune...

 

i don't believe that it's a bad tune. Ion is good at what he does, plus there was no reason to change the fuel on a stock engine. the ALDL cable should be here tomorrow. depending on if it's still cold and raining, i may get some datalogging done tomorrow.

 

i finally got a chance to see what's going on. the engine temp. is reading 17.00 C. constantly. if i unplug the temp. sensor, it reads 67.25 C. constantly. even though i replaced the sensor, i'm going to do it again and see what it reads.

 

ok, changed the sensor...again...and now the fans work and it's not running rich.
i have a question though. the program i'm using is Tunerpro RT. when at operating temp, the ECM temp sensor is reading about 105 C to 107 C (roughly 221 to 225 F). the temp. gauge is reading about 160 F. the fans turn on at 80 C or so...which is right, but it's no where near that on the temp gauge...it's a little over 100 F.

why is this? i believe the temp gauge on the cluster is pretty accurate, since the stat is a 160* and that's about as hot as it gets, since both fans are on. so i'm lead to believe that the fans are turning on way before the stat is open...but at the right temp that the ECM says.
could the ECM temp sensor be that much hotter than the gauge temp sensor?? what voltage should i be seeing at the wires going into the ECM temp sensor with the car off and key in the "on" position?

 

i believe it's in the sensor or wiring now...
i looked at the datalog i did. before the engine is on, the IAT sensor reads 21*C and the ECT sensor reads 48*C.

 

How is the IAT sensor related? An intake air temp of 21*C (70*F) sounds pretty normal.

 

lol, sorry if i mislead you...
this is while the car has been sitting for a long time...i believe that the engine temp sensor should be close to what the IAT sensor is reading if the car is not and has not been running. but 27*C more is too much. the coolant isn't warm at all...it's cold. so, reading 48*C (118*F) is incorrect...because of this, my fans are on before the stat is open...and when the car is really 160*F, the computer thinks its 225*F.

 

the wiring going into the ECT sensor is only at 4.3 Volts...which is causing the sensor to read high...any ideas?

 

are you still runing the single wire o2 sensors if so try converting them to 4 wire. that might help, it did for my 93. good luck