jimmomo

As soon as I start my car (1989 GTA) my check engine light comes on. I have no codes other than 12
How do I stop the light from coming on? Other than when I first start the car and it run rough the car runs fine.
Once warmed up I seem to be good to go. I am worried something is going wrong and don't want to sit along the road some day.

Vader

Actually, the "12" is an error code.

Missing distributor reference pulses is not a problem when the engine is not running, and is expected. If it happens during an engine run cycle it IS a problem, however.

When the ignition is turned ON without starting the engine, what does the CHECK ENGINE light do?

jimmomo

When you turn the key to the on position the light comes on. When you start the car the light is off for maybe 5 second and then come on. The car seems to run OK but I did have it die once last year and got flat bedded home. I thought my distributor was bad as I had bought it on e-bay and learned a lot of people have had issues with check quality distributors off e-bay so changed it to a quality on from Jegs and the car fired right up. Maybe it was not the distributor?

Komet

I think your ecm is actually throwing a code when the engine is running, if the light comes on. A datalogger can capture it and tell you which one.

jimmomo

Thanks, I am not sure how a datalogger works

Vader

Check that "SES" lamp operation more closely. When the ignition is first turned on without starting the engine, the lamp should turn on for about half a second, turn off for about half a second, then turn on again and remain on until the ignition is turned off or the engine is started.

If that sequence does not happen, there is a problem.

jimmomo

Will do. It is funny I have owned this car 20 years and never paid any attention to that. I contacted the guy who burned the chip and he asked me to check a few things as well. He has burned 4 different chips over the years and they all have been fine but it does not hurt to check that too. Years back you gave me some advice and I have always respected your thoughts. I believe we are about the same age and I know you understand these cars, thanks.

jimmomo

Vader I just checked what's happening when I turn the key to the on position. The engine light comes on and does not blink. I tried it three times and the light comes on and stays on.
I also swapped the EMC out for one I had on the shelf and one difference. Could it be a bad chip?

Vader

If you have a stock MEMCAL you could plug that in and try the ignition.

The "SES bounce" is a feature that was active on GMs well into the 2000's .

jimmomo

I don't have the stock unit. I tried both other chips I have and only one will do what you said but the car won't start with that chip. However I do have a code 15 as well as 12. What is ses bounce I have never heard that term before. I don't think I can run a stock set up anymore. My car has no air pump, egr, cats, it has all that stuff off and that is why I have a custom chip. I am running all slp stuff on the car. The headers have been plugged where the air tube went. Slp runners have been matched to the intake. I am running aluminum heads off a corvette and 24 lb injectors , ZZ4 cam. It is a 383 now as well. I am near retirement and this is a big boy toy I have built up over the years. I plan on driving it more now so I am working out all the small bugs. Don't get me wrong this car runs strong but there are a few thing just not right.
I don't like having the engine light on all the time.

jimmomo

Ok, latest update, I spent a few hours trying to find anything that would cause a bad code. I took a bunch of the plugs off and cleaned them with electrical cleaner. Well the check engine light is off. Now when I turn the key on as Vader says the light comes on blinks once and stays on until the engine starts. When I drive it things are fine other than once in a while when it shifts to 4th gear it cuts out for a split second. The engine light flashes quickly but goes right out. Is the transmission tied to the engine electrical in any way that would cause this? I am gaining thanks to having this site for information.

Vader

This might explain the SES lamp function at power-up. It's similar to the POST (Power On Self-Test) of almost every PC on the planet.

https://www.thirdgen.org/forums/tpi/...ml#post5727053


A more thorough, but still general, explanation of the system operation is here:

https://www.thirdgen.org/forums/tech...tml#post138582


The rapid flashing of the SES while driving can indicate several things. Most commonly it is a fault in the MEMCAL. That could be as simple as a connection of the MEMCAL to the mainboard socket of the ECM, a connection of the PROM in the MEMCAL to its socket, damaged resistor networks in the MEMCAL (for backup fuel/spark), or a problem with the PROM itself in either the Checksum or a mismatch in PROM switching speed. All bets are off with an aftermarket or custom PROM, and unless you can read/erase/write the old UV PROMs, about all that can be done is to check connections. If you can open the MEMCAL and read the device labeling on the PROM itself (NOT the sticker over the UV erase window) you can decode the size and speed of the device.

Any of those socketed connections can be cleaned with De-Ox-it to assure that the pins and sockets are clean and conductive.

Vader

If you can read the PROM, the label should be something like "27C128-100" or similar. The "100" is the read access time, and should be 100nS or less.

Also, the ECM does have a connection to the transmission (automatic) in that there is a fourth gear switch which reports to the ECM to permit TCC lockup function. If the 4th gear indication switch input is missing and/or the TCC lockup solenoid is not connected, a fault will be generated.

jimmomo

I read both of the posts you sent links to. Very good info for sure, makes me realize how little I really know about these cars. I wish you lived next door

I think I will try both a new MEMCAL and PROM

I will let you know what happens

Vader

But I DO live next door. Probably not to you, however.

While you're in there, check/clean the socket connections as well.

jimmomo

Well the issues continue but I think I am going forward, at least I hope so. Here is where I am now. I bought a new mem cal on line and had a new prom made to the specs of the car. Tonight I installed them and tried the car out. Good news is it starts right up and sits there and idles great. It also has no engine light on and the engine light does bounce as Vander calls it. Now the problem as I drive it it still cuts out a second and then runs fine. I do get an engine light flash when it does it. I checked and I have code 33 so I searched the forums and read what I could on code 33. Looks like a bear to figure out . However I do know it happens almost always when the engine rpms are right about 2000. If I drive in 3rd gear no issues at all and it runs like a champ. Even in a lower gear at 2000 or so it will happen sometimes. So I guess I could use some direction on what to look at. MAF seems to be a possible issue from what I have read. I do have an adjustable MAF which I have read by many are junk. Should I try the stock one? I have also read that the coolant sensor could be an issue as well? I read one post saying the MAF relay on the fire wall which is some I have no clue about, what is it? VADER any thoughts?
Thanks

Vader

Hopefully, whoever burned the PROM used the appropriate MAF tables for your setup. Using a 305-based .bin on a 350 will set a "33" code. Don't ask how I know.

It may also be a good idea to verify the TPS voltage at closed-throttle and set it no lower than 0.54 VDC, and preferably a little higher.

jimmomo

i have decided to take off the Granatellli MAF as I have read many reports that they cause issue. I will put the stock MAF back on and start from there. I also was looking at the plug close and see it looks a bit dirty to me. I will also be putting on a new plug.
Thanks for you thoughts.

Jim

Vader

I didn't realize you had the aftermarket adjustable MAF.

jimmomo

Well here is where I am at now. I kept getting code 33 when I would drive the car. So I took the car to a local guy who does a lot of hot rodding as well as working on family cars. I trust him and everyone in town does. He looked everything over and came to the conclusion that air was getting into the throttle body after the MAF . This is because I cut the factory rubber to install the air filter Hawks makes for the air ram hood I bought from them and that is what they said to do. I have tried sealing this many ways over the years and thought it was sealed. So this time I shopped around on line and found an adapter from 3" to 4" off a turbo charger. That fits tight and clamps down snug. The other thing he thought was possibly the TPS was bad even though it is brand new, so I bought another one. I put it on and set it at .540 right on. So it was late last night and I did not try it. I decided to drive it to work this morning and it started right up sat there and idled fine at 900 RPM. I let things warm up and started for work. Same thing happens, at just about 1900rpms when driving steady the car stumbles and the check engine light comes on. If I speed up or slow down 400 rpms the light goes off and the car runs fine. If I drive at 1500rpms in 4th gear it is fine. Speed up to 1900rpms and it stumbles. If I drive in third gear the car runs like a champ. I am not sure it is the rpms or position of the gas peddle that does this. When I stop at an intersection and slowly make the turn the same thing happens sometimes then clears up. Last night I cleared the codes and when I got here I have code 33 again. It is 33 miles to get here and all open road driving. I do have a Granatelli MAF on the car. I tried to adjust the small screw on top and it does not make a huge difference from what I can see. This is really bugging me. I also changed the MEM CAL and Prom as well just in case. I also did a smoke test on the car and no leaks, everything came out the tail pipes and throttle body so no vacuum leaks. I am at the point I am done with ideas? Any thoughts on this?

jimmomo

Well , here is the latest update. I have tried swapping out the MAF to a stock one and there is a bit of a difference but nothing major. I also changed the relays and did not see much of a difference there ether. However last night I decided to check the burn off of the MAF so I took off the air ram box (made by Hawks) so I could look at the MAF right after I turned the car off and the wire does glow orange for a second shortly after you shut the engine off so that is working correctly. How ever I did notice something a bit funny. I cover half the MAF with my hand and the engine smoothed right out and idled better. I have always noticed you can hear a great deal of air going into the air box at idle and always thought that was good. More air more power in my mind. I am wondering if going down the road if that air ram is putting too much air into the MAF at times. Under wide open it really runs great and you can really the air rushing into the engine like the old 4 barrels did. But at a steady highway speed the engine will stumble sometimes. Give it a bit more or less gas and it gets better. Code 33 .I put a new throttle TPS on it as well and have the volts set at 540 as everyone says. Do you think the amount of air is too much at times and leans the car out? My next attempt will be putting a stock air intake back on and trying that. With the stock set up the MAF is ways away from the throttle body and with the air ram box the MAF is 3" from the throttle body. Any thoughts on this?

jimmomo

Well it has been a long learning experience and here what I have learned. With all the no codes blinking engine lights and all. After changing parts back and forth and all the bottom line is the Hawks air ram box was the issue. I learned this in a funny way. During our trip to the Hershey car show one night we went down to the parking lot to visit with some flat head Ford racers. While visiting with them my tuneport came up. One of the guys in his seventies said I worked on them for years before my flathead days. I told him everything I could that I could think of. He sat there a minute and said get rid of the air ram box. When I asked why his answer was the Maf has to be at least 10 inches from the throttle body. With the air ram it is only about 3 inches. I had nothing to lose and I put an after market cold air intake on with the air filter down by the passenger side fender. No other changes other then unhooking the battery and no blinking check engine light, no flat or dead spots while driving. Runs great and no difference in power that I can see.
If you have one of these set up with the air ram hood I would dump the air filter. It could be causing issues you don't even realize. In mymind the whole set up is junk! Thank God the old flat head guy came along.
I still like tune ports better !