it as a 383 LT1 in a pickup if that helps.

what is happening is this. my truck sits all winter due to where i live. so every spring for the past 3 years, i charge it up, and get it running..... not well, but running. last summer, it wouldn;t start for me at all. i had fuel and spark. i changed the IAC motor and the TPS sensor. it ran. then it wouldn't charge. without going into great detail, i replaced the alt ( i runed the other one by mistake) and it seemed ok. new battery too. then it sat for a few months. fast forward to yesterday.
the truck has sat for 3 months. charged her up again and she started. now i read somewhere if the computer sits without power for a long time, it has to "relearn" itself . i let it run for a good 20 min, and headed out to see what problems i had this year.

it seems to be running rich. always has.
at higher rpms (4000+) there is a popping like a backfire and it looses at least 60-70 % of its power. this also happens if i am on the highway and i punch it in 5th or 6th gear. he truck will almost "buck" and the tach jumps all crazy. it will also spit smoke which is fuel. its not antifreeze or oil. i already replaced the headgaskets last year
my friends say its fuel, it'll make your eyes burn.
even when its not doing the popping thing, it seems like it isn't burning the fuel right.

now for the computer. i can't use my auto ex-ray !!. the plug from my new (4 years ago) street and performance harness will not work no matter what i type into that xray. i've had it on other computers, and they can;t scan it either. i'm thinking the harness was built wrong, (there was a problem with the O2 sensor connectors i found a few years ago.) OR the computer is bad. i sent it to pcmforless when i did the inital install, and the damn thing ran like a champ. but i could never ever scan it. this has to be fixed. any where that i can get a diagram of the harness, so i can trace the wires and check the connector? i know there was something funny bout obd1 and 2 on this year. like obd2 software but an obd1 connector? i can't remember. please help.

so from reading on the site , it seems like it could be any number of things. a bad MAP (original) , and bad ICM (original), bad spark plug wires/placement ( THE WIRES ARE NOT AT ALL NEAT, AND HAVE TO BE MOVED DUE TO HEADERS) , prolly a bad opti spark. maybe a bad crank sensor?

so, read this again cause i dumped a ton of stuff on you, and let me know the course of action you would take. i can't afford to take it to the local shop and have them look at it. i'm looking at well over 1200.00 for that. they will do the final flash on the pcm when i'm ready, and dyno tune.


ps. i have an af meter, the dynojet one. it's installed in my h-pipe. it reads 14-15 af ratio, and spikes when i let off the gas.

i have 30lb svo injectors due to the stroker.

ther is also an msd 6a running on it now.



any help at all would be much appreciated! thanks

 

Hard to respond to so many items ... but I'll try the easy ones.

There is nothing "funny" about the 94 LT1 PCM in an F-Body. Did your engine come from an F-Body a B-Body or a Y-body? From an F-body, it is OBD-I, and the 94 cars had a normal 12-pin OBD-I ALDL connector. It is the 1995 cars that had the oddball 16-pin OBD-II style connectors, and the same OBD-I PCM used in the 1994's.

Shoebox has PCM wiring diagrams of the 95's. While the data wire from the PCM will go to a different pin in the 95 ALDL connector, it will still originate at the same pin on the PCM, and will be the same color.

http://shbox.com/1/4th_gen_tech2.html#1995_pcm_wiring

http://shbox.com/1/dlc1.jpg

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Who tuned the PCM for the 30# injectors? If you don't have the correct tune for the injectors, it would explain the hard start, running poorly after storage and running excessively rich at WOT.

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Yes, when you remove battery power from the PCM for more than 30 seconds, you lose the stored/learned long term fuel corrections. If your tune is forcing the PCM to make large changes to the long term fuel corrections when it running "OK", if you lose the stored values during extended storage, you will be starting the engine with the wrong corrections and it could run excessively rich.

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The jumping tach could be a problem with the Opti, or a critical engine or PCM ground. That would certainly cause a loss of power, missing, etc.

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Misfires and exhaust leaks will cause it to run excessively rich. Your jumpled plug wires might explain that. Have you checked the exhaust for leaks before the O2 sensors?

 

I start my car once a week during the winter. You should not let it sit all winter without starting it unless you have no choice.

 

the motor and pcm are from a 94 F-body, or at least thats what i was told.
brian at pcmforless did the original tune after i installed the new stroker. (i had a hotcammed LT1 before this motor). i am 99% sure he tuned it for my mods, i spoke with him back then and got him all the build info.
thanks for the links! i will do some further research on the harness and call street and performance later this week. how much would it matter if it was a 95 motor, and a 94 pcm?? could that be a bad thing? is there a difference between a 94 and a 95 pcm? if so, that could have gotten messed up when i swapped motors.

just for troubleshooting, would it harm the motor if i swapped in the oem injectors for a few?

i DO have a header leak at the heads, and that is on my list of things to fix, as well as my grounding situation, so i will make them a priority over everything else.

have you ever seen anyone use 0 guage wireing for the engine to chassis ground? i would like to get the best ground i can and i'm wondering if that will work better then the crappy "woven" oem style ground thats on there now.

as far as the exhaust leak, i am using truck (oval port) headers due to my situation. i will have to change to actual LT1 headers and bite the bullet for cost to have something custom made. maybe i'll get lucky and the f-ody headers will fit down under the truck.




thanks very much for the quick reply guys! the truck is stored off my property for most of the year, and i get over to start it as much as i can, just not as much as i like

inj, your post explains a lot.
thanks. anymore advice, shoot it my way.