D's-maro

Hi All,
Here is a little history of or project. I bought a 1990 Iroc project car for my son turns out that the previous owner had cut out the engine wiring harness and ALDL connector and took the ECM too. Ended up buying a 305 tpi motor with trans, it was supposed to be a go running motor but we found out that it had a broken piston from a Tork bit tip broke off and went down in the motor when we were going to replace all the gaskets so we rebuilt the motor then I found a wiring harness & ECM from somebody on EBay, turns out they cut the starting and charging wires out of the harness. So I rewired everything that was messed up based on GM service manual. After all that we finally got the motor running. Now we have a few issues that we can’t seem to figure out yet so need a little help to finish this project.
Here are the issues we are having trouble with


1. High idle problem. 1175rpm at idle I’ve tried all the procedure’s listed on the net to set this with no luck (check length, ohm’d the IAC, reset procedure, checked for vacuum leaks with propane pulled EGR and cleaned it, checked TB to see if blades are closed) my next step is to pull the intake tubes and double check the gasket and look for warpage. Also checked park/ neutral switch on scanner. The only thing I haven’t figured out yet is both fans always kick in when the temp is at 180, have AC off and compressor unplugged?


2. Lack of power. If you drive it like and old lady it runs fine but if you try accelerate it feels flat and misses. Scan tool says it’s lean when you give it gas. Checked fuel pressure 35-40psi at idle, Check pressure while driving and you accelerate it would flutter from 25psi to 45psi so change fuel filter and still no power haven’t checked fuel pressure after fuel filter change. Ohm’d injectors the checked out OK. Think I’m going to have them cleaned when I pull the intake again.


3. Speedo will slowly quit working after 5miles of driving. The scan tool and the speedo show the same thing; would this be an ECM problem? (This has the VSS in the Trans)


4. Last thing I not sure what this ECM/memcal came out off (305 TPI or 350 TPI) what kind of problems would I see if this was for a 350. Any way of telling without the burn software

Thanks for the help

rusty vango

welcome to the mis matched hell of things. IMHO youre gonna havta take it back to the way it was when new. then you can wire it as it was intended. THEN trouble shoot all your problems. many of us have had your particular situation . many have resorted to a half gallon of gas and a lighter as a permanent fix.

alan91z28

don't get discouraged, these are great cars and make great projects for father and son... i have same type project going on with my son and a 87 formula

anyways on your issue, one of the first things i would do is confirm what memcal you actually have

if you take the computer out and take the cover plate off, on the memcal "window" you should see a sticker with some lettering on it... find out what the 4 digit code is on it, it will be 4 letters in caps... if you post that i will look it up for you and let you know what engine, tranny, gear ratio, etc

alan91z28

also on your fuel pressure issue, i am going through a similar issue on my 89 vert, it drives pretty well and is good to about 4000 rpm but when i go WOT the O2 sensor goes lean even though can clearly see from the datamaster log the ECM is still in PE and commanding the expected rich condition in the 11 AFR range

i suspect it is with the fuel pump area as i have already done filter and fuel system on engine (FPR, injectors) and the car has 100K miles on it so it needs it anyways. i am talking the tank down this weekend with my son and will be putting a new Walboro pump in with new sender assembly while we are at it...

D's-maro

Yeah it’s been a pretty good learning experience for him hopefully he will relies all the hard work we put into it and not beat the crap out of it!! Not to mention I’ve learned quite a bit about the TPI system on these cars too.

Well I ohm’d the injectors again the other day and I had 4 of them show bad now so I ordered some bosch injectors from Southbay injectors.

So we installed them along with new TPI manifold gaskets and it started to idle lower till it warmed up then we took it for a spin and still no power a little better but still flat. Then we pulled the ECM and googled the Memcal number and it comes back as a 350 TPI auto chip ( AUJP ) Then I removed the covers of the ECM and I have a diode burned up on the board. Looks like I’m going to get a different Memcal burned to match what we have and find a different ECM. Then see what happens.