Hello I have recently acquired a 1988 formula with a 305tpi. I am currently having a big problem that I can not figure out. As of now I keep the tan/black wire unhooked that goes to the ecm. It is located in the wire harness and the point were you can unhook it is located near the blower motor. It is the only wire that can be unhooked in the plastic cover that contains all of the wires for the ecm. A mechanic did this and told me the car wasn't running with it hooked up. I have changed the computer, doesnt help. There are no trouble codes. I think this wire goes to the distributor but I dont know. Could someone please help me with this I am so confused on what to do at this point. Thanks, Aaron

 

That wire, when disconnected, disables the electronic spark control. If the car just will not run with it hooked up and you already replaced the ECM, try replacing the ESC module.

 

Am I correct in saying that the ignition module and the electronic spark control module are different? Parts stores seem to be confused.

 

If you can find my post a few months ago It'll guide you through every thing i did....after replacing everything esc module, ecm, maf burnoff module, power module, dist cap and bug, ....it finally turned out to be the distributor itself...ah, there were a few wires that were frayed and leaking a spark, and the connectors had to all be cleaned. I rebuilt one connnector...it was a mess but I'd hold her up to a vette now and i still haven't done anything to the prom....Hang in there....alldata or some other diagnostic tree will surely help guide you

Stan

 

well it wasn't the spark control module. I guess I will try the distributor. I guess I really want to know what that tan/black wire goes too.(refer to my initial question) Why is it the only wire that you can unplug inside of the plastic cover of wires that go to the ecm? I guess I am also confused to how I can unplug it and the car runs decent but if I plug it together the car sputters and will stall? Thank you so much for everyones help. Aaron

 

That wire disables the electronic spark control, it is meant to be disconnected when setting the timing (like disconnecting the vacuum advance hose on older cars), That is why it is the only wire going to the ECM that you can disconnect.

 

well if you had to put money on it what do you think the problem is? Thanks, Aaron

 

Well, you have eliminated the ESC, but have you checked the plugs, wires, coil and spark module? If they are all good then I'd have to go with a distributor rebuild, and don't worry, all the parts mentioned above would need to be replaced in a rebuild anyway.

 

Nobody has asked what his base timing is. Get a timing light and with the wire disconnected see where it is set. Maybe it's as simple as the distributor being loose. If it's already 20 deg advanced the ESC when hooked up will drive it nuts.

 

Actually I was thinking that the timing might be off. I noticed in my chiltons manual that it said to set the timing for 82-87 firebirds to disconect the tan/black wire and for 88-92 that you do not do that. My formula is an 88. To fill in some history I just bought the car and a mechanic did this to make the car run.

 

My formula is a 90 and the sticker on my radiator says to disconnect the tan/black wire. When I replaced my distributor I did this to set my timing and I haven't had any problems.

 

Well I tried to adjust the timing and well it works fine but then when I try and restart the car it starts like crap. I am so confused on what to do now. How to I check to see what vin my formula is. I have a 88 305 tpi automatic. Im not sure if it is a, e, f, g or an h.

 

Its an F, its the 9th "digit" in the vin.

 

well i got a 34 code on my computer. The mass air flow sensor was replaced not too long ago. Could it mean that the maf sensor power relay needs to be replaced?

 

Aaron, don't always pay attention to Chilton. There are many mistakes. If you have an ESC wire and plug use THAT to set base timing. 6-8 deg is usually ok for 305-350 engines. Establish that before anything else. MAF actually has 2 relays, one for power and one for burnoff. If you are going to change one, change both. Gm part #14089936 for both relays. If there is a MAF problem typical symptom is inability to idle, stalling and generally poor performance.

 

Here is one for you. When looking at the motor from the front I noticed that the left pcv filter was leaking some oil. When I took it off I noticed that it was completely empty inside. So I put a new one in. Now I notice that some smoke is coming from my the dipstick. What do you think the problem is? Thanks, Aaron

 

That thing on the passenger side isn't a PCV valve, it is a breather and should not be plugged up, thats why you have vapor coming from the dipstick.

 

Do you know the breather might be leaking then? It leaks right around where it meets up with the cylinder head. Thanks, Aaron

 

The grommet in the passenger side valve cover should be a 90 deg one that has a short piece of pipe, another 90 deg elbow, a longer piece of pipe going along the intake manifold to a short hose that plugs into the throttlebody.

There could be a few reasons why it leaks at the valve cover.

1) using valve covers without oil baffels in them

2) too high crank case pressure

3) improperly routed breather tube

4) loose rubber grommet on the valve cover