Like I said in the title. I just got the car back from the mechanic and on the way home it acted like crap, missing and backfiring. I pulled over and it stalled out, and would not start back up. Later I went back and it started right up and ran like crap after i got home and left it running. Also, my cat was glowing bright red. It was running rich and blowing back smoke and sut out the tailpipes with pieces of cat. We replaced most of the distributor components including cap, rotor, pickup, and module. After starting it back up we got the same thing, and the same codes. code 41 and 23. The car ran fine since i bought it till i took it to the mechanic. also, he replaced the MAT sensor (code 23) very recently...and we noticed it looked old. but this sensor would not be causing such a serious problem. the car was changed from a 305 to a zz1 350, but a hypertech chip was put in. i was thinking of calling up my friend and getting his 350 tpi computer into my car to see if it will begin running fine, and if so i need a new computer. what do you guys think is wrong?

 

Code 41 either was set when the timing was being adjusted (meaning you need to clear the codes), or there's something wrong with the circuit that provides the distributor signal to the ECM.

Code 23 may be the TPS.

Sounds like it runs okay in open loop, then goes nuts in closed loop.

Is the check engine light on all the time, or only when it runs badly?

 

we got code 41 before we even messed with the distributor also. the check engine light only comes on when it starts to run like crap. also, its always had a really stumbling idle and i figured the iac or tps might have something to do with it, but it never did this backfiring and running at 250 rpm stuff until i got it back from the mechanic. im thinking its the computer. if i can get one for like 30 bucks i think it would just be best to do that. of course ill try out my friends computer first (also tpi 350) just to make sure it runs ok like that. i know something went bad, because the car ran fine for months and now it runs like crap. like if it was the wrong computer or something, it would have always done that (corvette motor and dist). thanks for the help.

oh yea, do you need to reset the tps after you change a trans...i doubt it but maybe. i also guessed the closed loop thing, which is why i figured it was the computer. thanks again.

 

My guess would be a fuel issue. I had the exact same problem when I went from a 430 HP engine to a 525 HP one. I swapped my 26# Accels to my new combo and had the same problems you're seeing. Try stepping up your FP if you have an AFPR, to see it that helps. I'm guessing the 19# 305 squirters are just too small. Kinda weird.....but injector size has a great importance on starting, and drivability, you'd think it would just act up at WOT, but that wasn't the case for me.
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I missed the part about the car running good for a few months after the engine change...... scratch my theory on your problem.

 

the previous owner installed the new engine in 1991. i bought the car in june, so i know from since then it ran fine. and i assume it ran fine all throughout as well. do you guys agree that it is a computer problem? if not, what should i look at? should i blame the mechanic who installed the tranny...(maybe he bent the distributor on the firewall since it was never removed and ive heard that it needs to be). thanks for all the suggestions.

 

As always, you need to determine what all happened between the time it ran well and the time it started running poorly. If the major event is the transmission replacment, then start looking at what could have happened during that event. The distributor could have been damaged, the harness damaged, etc.

I would start by looking back by the distributor for anything obvious. Typically, the cap only needs to be removed in order to drop the tranny, so he may have done something to the cap, or something else beyond the typical may have occurred. Cap cracked, rotor cracked, harness damaged - they all make some sense.

 

right. but i replaced cap, rotor, pickup, and module in the distributor and it still doesnt work. so you think it could be the wiring harness? maybe it got squashed on the firewall or something?

 

OK, now it wont even start at all. even after sitting for a day or two. i got some pictures of some kind of connector for a sensor or something, but its not connected to anything. its on the passenger side, very close to the distributor.

 

I've squished one between the trans and the block before. Found out when we were putting it back together and missing the dist. connector.

 

thats funny. i have that one end and nothing to connect it to ...you think im missing the other end to that...or maybe just something else with the wiring harness.
also, i just took off the cat and it reeked of gas. still no start though. whats weird is that before we beefed up the distributor it would start and then eventually die. now with the distributor in all good, it wont even start up again, but it did that one time. is this a different problem now?

 

Looks like the EGR solenoid. Normally, it mounts under the coil. A malfunctioning EGR will make your car run crummy when in closed loop, and make it act like it is running rich, but should have no effect on a cold motor. Perhaps the coolant temp sensor (For ECM) is on its way out? Do you have a scanner that you can look and see?

 

no, i dont have a scanner to check. the thing i want to bring up again is that it ran absolutely fine before. and immidiately after i get it back from the tranny install it starts. its not like i drove it for a week or anything. i picked it up right after the install and it immidiately sucked. i know this could be possible, but i wouldnt put my money on it. i think im just gonna run it over to the mechanic and see what he says. also, remember, now it wont even start. and i just took the cat off thinking it might be the clogged cat, but it still would not start.

 

ok, im taking it in today or monday. what kind of response could i expect...maybe my injectors went bad, computer went bad, wiring harness was squashed...anything else i could expect?
also, when i try to start it, it smells stongly of gas under the car (out of the headers i assume).

 

I'd pull the plugs and see how gas fouled they are and then just replace them. You need to figure out what's making it that pig rich. I'd start by checking the fuel pressure regulator (pull off vacuum hose and see if gas comes out) and the coolant temp sens (disconnect and measure the resistance). Somewhere on the board is listed what the resistances are at different temps. If it's off, it's gonna be way off, like the ecm sees -40 below when it's really 70.

 

so you think i should hold off on bringing it to the mechanic? is it possible that one of these problems occured during the tranny swap. like maybe he cracked the fpr or something?

 

Today is friday, you have until monday to mess with it, why not? If the plugs are gas fouled (high probability), even if you fixed the problem it would not start, so go ahead and change them. You've got all weekend to save yourself some $$ by trying to fix it yourself. If it's still not running sunday night, then you know where it's going on monday.

 

well, theyre open tomorrow also. so doing it tomorrow would be dumb, but today wouldnt be a terrible idea.