Fordvette

Ok here goes. Trying to read OBD codes with a Inova 3120b and no connection present, Also have a Laptop with USB to GM OBD cable, and Scanmaster software. Unable to interface

2.8 MFI 1985 Camaro

Diag port paper clip shows code 12
Diag port voltage a and b shows 5.05volts
Diag Port voltage a and e shows a fluctuating but kinda steady around 3.8volts

ECM seems in good working order, chip is seated and no visable damage is present

So my guess is the the ECM is bad or the memory chip on the ECM is bad.

Symptoms of car .. Rough to start when cold, have to press pedal for first 20 secs to keep a idle going, then it starts to idle ok, but still rough. Under acceration, 70mphs, sluggish and unresponsive. Having to downshift from 5th to 4th going up a looong hill..

Replaced all the sensors except the MAF, which I don't have a spare. Same conditions. Now I have been trying to diag the MAF, but Im not sure. Ran the CODE 34 MAF trouble code diagram, (even thought I can not say for sure it is a code 34) on page 6e3-45 of the GM shop manual. Start engine, Light is off. Says to check th MAF, looks ok, but since I don't have one to compare it with .. very slight blistering on the center part, where there is 15 copper wires in a line.. Tried to run a HZ test on the MAF but the connectors are sealed and I guess I would have to cut the wires themselves to gain access.

So what do you guys think, bad ECM, or bad MAF ?

87IROC420

i needed a 10k resistor to start reading . 87

Fordvette

Thanks .. tried that tonight... no luck..

Also switched out the MAF, found a spare I had, car ran a little smoother but still throws a check engine light, Also found another computer in one of my boxes, same number 1226870 and swapped computers... Still not able to read any codes.

Funny think is with the old computer the car idled around 700-750ish, manual transmission.. I should note that the car was originally a Auto and I did a manual swap. The two wires on the gear selector that tell the engine its in gear where left unconnected.. Swapped in the second computer and the car now idles at 1800-2000ish.. Paper clip test on the second computer does not throw a a code 12 or any codes...

Ill take it for a road test tomorrow with the 2nd computer and see what happens..

87IROC420

are you picking a com port? usually com3 for me .

Tuned Performance

iTrader: (92)

on the second ecm have you looked to see what prom and calpak are in that ecm ? The 1226870 was used on tpi v8 in 85 as well. if the engine light is rapidly blinking you have the incorrect prom and calpak installed. The prom will have 3 letters on it as a identifier. Win aldl will connect to this ecm but you will need to at least enter field service mode first.

Fordvette

Yep I get com 3 showing up... Scanmaster trys to scan the port, at 38,000 baud ? then 112,000 baud. no luck.. Unable to interface. Although I read somewhere the ecm only communicates at 160baud

Both computers are 1226870. The calpak are both identical. 16046461 and prom numbers are both Delco FRF 9839

Althought the second seems to have a dealership service number on it.. written in pen

First ECM is below



2nd ECM is

Tuned Performance

iTrader: (92)

The frf is the correct prom, the 870 connects through e of the aldl at 160 baud. I'm unfamiliar with scan master, you might try to connect with winaldl.

Fordvette

Thanks for your help btw Tuned proformance

Ok got winaldl installed and working.. Now to learn how to read it lol

I have no error codes right now showing up which is good, Idle is sitting at 1200 semi warm..

this is a screenshot of it with the car runnin

Tuned Performance

iTrader: (92)

Thats connected ?

Fordvette

yes and idling at 1100

Tuned Performance

iTrader: (92)

There is no sensor data and no reps in the screen shot.

Fordvette

Ocassionally I get a blip in the IAC CT and EGR col.. but only say once ever 20 secs maybe.. that's about all the data it gives me so far..

Tuned Performance

iTrader: (92)

Try lowering the baud rate, that ecm is super slow

Fordvette

2400 is as slow as the program will let me go .. I have the 10k resistor setting as well ..

Fordvette

Tuned Performance

iTrader: (92)

It may just be how it is, Im not sure that ecm need a 10k resister to enable the data stream. Even if you go to a 302 ecm it will be slow. Learning how to reprogram and going to the 1227730 ecm and changing to speed density would be a big improvement or talk to six shooter.

Fordvette

will do

thanks

Fordvette

ok lots of looking around found a site http://forums.corvetteforum.com/c4-s...-corvette.html et to set the baud at 4800 with 10k resistor installed.. Now I am getting data in all col's

Tuned Performance

iTrader: (92)

Nice , glad you made big progress

Fordvette

Ok just a quick update, now that I got the computer to read the codes, fixed the two bad sensors, EGR solenoid, and MAT. Reset the timing, (was not aware at the time last year to disconnect the EST wire). Car still ran lean, and after some more testing, came to the conclusion that the Injectors needed replacing..

Car runs like a stock V6 now, if that is any good Engine is solid as a rock 135-138PSI compression.

Thanks to Tunedperformance for the tips.. Plans are now to drive for the summer and look to do a 730 swap in the winter when I park it. Learn to tune the 730 then fab up a turbo system for it. The block is good for 400hp, (so I read somewhere) rear end well that would have to be changed out too.

730 J bodies are a dime a dozen around here, and we have a self service wrecking yard with over 2000 vehicles in stock any given day..

Heres to lots of reading over the summer

Tuned Performance

iTrader: (92)

pick six shooters brain he is a wealth of knowledge on tuning and mods on six bangers

Fordvette

yep He helped diagnose the lean condition for me.