so basically i swapped a stock 94 z28 LT1 into my 84 vette. its running but really rich and once in a while it backfires or it shuts off as i try to drive it.

I DO NOT have a diag port on the car and do not know how to hook it up. my buddy wired up the motor for me and forgot to hook that up.

PCM has had the VATS and EGR tuned out of it. and has been tuned for my long tubes.

New parts:
GM opti
plugs
MSD wires
coil
MAP sensor
vacuum lines
MAF
o2 sensors
knock module


The car runs all wierd. when its idling at 700-800rpms and i rev it or drive it, it runs fine but when it starts to idle up around 1000-1100 and i try to rev it or drive it. it will either fall flat on its face or backfire like crazy.

i was thinking that the ignition control module was goin out.

heres a video of it running. at that moment it was idling at about 7-800rpms.

 

Looks like PCM and engine management might not be working correctly. Seems like the tune of the engine which the PCM does is way off. I don’t think the ICM is of any concern now since the engine is basically running and does have spark.

You need to have the temperature sensor in the water pump connected so the PCM can perform normal. If you don’t have the digital readout as on the 94, you really have no clue what its doing to the PCM especially without the ALDL connector and serial output to connect to a scanner. You need to know some basics like if it is going into closed loop and what the fuel trim is. Are the O2 sensors operating properly in their voltage swings. And if it runs to rich for to long time it will destroy the O2 sensors.

You have a boat load of unanswered questions. Without that diagnostic connector and knowing what is going on in the PCM, you are really working in the dark. There is a huge amount of input to the PCM for engine management and if an input is missing it is not going to be happy.

I would like to know if it is going into closed loop, if the IAC, TPS, MAP, MAF and temp sensors are working. I would suggest to try figure out how to install the correct diagnostic connector so you can do a scan. It may take some work but that may be a way to figure out what’s going on. Having a FSM for the engine you have would be a good road map in getting thing connected properly.

 

yeah i know i need to hook the diag port up. and i got one of those universal GM scanners.

when the car is running i can pull the maf off of the intake and itll still run the same(if that means anything).

guess i gotta wait until my friend is able to hook up the diag port.

 

how do i make this work with my scanner? i repinned the OBD1 connector to kinda match up but i have 4 wires on the connector and only three prongs on my scanner.

 

What I say here is based on some assumptions and best opinion.

If your scanner mates up with the DLC then your is good shape for starters (wish the pictures were more in focus). The important wires are the serial data pin M, ground pin A. I don’t believe all the wires are shown in your picture for the DLC. I think one of the pins should be 12 volts which is probably power for the scanner. Probably other pictures in the FSM will show the full connection of wires for the DLC.

You will need to trace the serial wire from the PCM back to the DLC to connect to the right pin. And so will you have to do for all required wires. Knowing what each pin is for on the scanner would be helpful in correlating the wiring but don’t know if that information is available to you.

 

i tried to match up the wires the best i could. but like you said it would help if i knew what the pins were comming out of the scanner. maybe i can try to email the company and see if they can tell me.

 

ok good news and bad news.

Good news:
got all the wiring up and the check engine light seems to be working

Bad news when i try to scan for codes the check engine light doesnt flash or anything.

now what?

 

Aight so the vette is runnin good now. hooked up a obdII scanner and scanned it up. found out the engine coolant temp sensor wasnt getting a correct signal causin the car to run like ***. guess somewhere in the harness a wire broke. so we jsut ran a new one. fired it up and the car idles fine and sounds great.

only problem now is the ALTERNATOR and my belt.