sonnyking

I have this wonderful low mileage TA - white 86' 30k miles, but the darn thing doesn't want to work right. I haven't driven it in 3 years due to a reoccurring problem.

about 40% of the time it will start, tach goes to 2k then it gets jumpy and quits. Service engine soon light comes on too. I have had the computer replaced roughly 8 times, works fine for a while then BAM! No go.


It's a 5.0 auto, any thoughts. I love the car and would really like to be able to drive it.

Thanks very much for any comments.

Sk

Vader

SK,

Welcome Aboard!

You'll frequently read from me that many ECMs are replaced that are more often than not completely good, just because the diagnosis isn't complete. ECMs rarely fail. A seat-of-the-pants guess is that about 85-95% of ECMs replaced are working properly. They have great levels of isolation and protection built into them, and are actually contructed rather ruggedly.

Generally the problems that cause people to errantly blame a "faulty" ECM are connections or failed I/O hardware. In your case, you should have already proven to yourself that the ECM is not at fault - eight times now.

Start looking into the HEI module, tach filter, and ESC control and all the associated connections for those circuits. Don't overlook the grounding at the ECM and the engine, since a reliable ground reference is critical.

Is your car an LB9 or L69?

sonnyking

It is a LB9 made in Van Nuys. Yeah I figured it wasn't the ECM, everytime I took it to the dealer or a garage that's all they would do. The funny thing is it would work fine for a couple months then start all over again. First the engine service light would come on a few times a week, then it would start the idle problem which would progressively get worse until you couldn't even get it down the block. I'm in the process of towing the car to a new storage location which should happen next week some time. That's got me refocused on the problem.

I'm going to get this thing fixed if it takes me another 10 years! I would hate to have to put a crate motor in such a low mileage car. Any thoughts on that?


Thank you very much for your help!!

Sonny King

87WS6

iTrader: (1)

There are a lot of threads on here about fluttering RPMs and idle issues. You should search for those and read up on them. It could be your distributor, rotor, spark plugs, ignition, TPS sensor. It's a tough problem to deal with or at least it can be. It has been on mine. It still isn't fixed yet. Although I have ruled out a few issues.

Vader

Sonny,

Get a paper clip, note pad, and your favorite writing instrument (all they allow me to have is crayons). Scan the ECM for error codes, make a list, and post it here. We should be able to walk you through solving them or at least theorize the problem to its final demise.

If you haven't scanned for error codes (DTCs) before, it will take you about five minutes. Here's the process:

First, you'll need to acquire a GM OBD I ECM Diagnostic Trouble Code Retrieval Tool (commonly known as a paper clip to TGO members). You'll also need to have a Diagnostic Trouble Code recorder. I use a 3¼ x 5 ruled index card and genuine Crayola Carmine Red crayon, but I suppose any note pad and writing instrument will work for a first-timer.

With the engine and ignition turned off, locate the ALDL connector under the dash, just to the right of the steering wheel in the driver's foot well area. There should be a small rectangular cover over the access hole in the lower dash trim.



Insert a tool as described above (paper clip) into the 'A' and 'B' terminals on the ALDL connector:



WITHOUT STARTING the engine, turn the ignition to the "RUN" position. Watch the Malfunction Indicator Lamp (MIL) and it will begin to flash. This is also commonly called the "Service Engine Soon" or "SES" lamp. The first code will flash three times, and will usually be a code '12'. This is encoded by one flash of the lamp, a brief pause, then two successive flashes of the lamp. Each code will repeat three times, so you should see a "Code 12" flash three times. Any other error codes will follow in numerical order, and each code should flash three times. After all codes have been displayed three times, the "Code 12" will again flash three times, then all other codes will follow as described earlier. This cycle will continue until the jumper is removed or the ignition is turned off.

After you have made a note of all error codes, turn off the ignition and remove the jumper immediately. If you forget to remove the jumper and attempt to start the engine with it in place, you could damage the ECM. For this reason you should remove it immediately.

Once you have a note of all error codes, check this file for the decoding:

GM Error Codes.pdf.

You'll need Adobe Acrobat Reader to open/print the file.

sonnyking

Thank you very much!,

I won't have access to the car again until next weekend when it is moved / towed to a new storage unit. This will be the first thing I do, then I'll post the results. Once again thank you very much, this board is what I needed say in about 1986, it has had this problem in mildly different forms since the day it was delivered! But for some reason I absolutely love the car. I'm thinking about getting another one on ebay just to see if works? It's cool that you get these things for pretty cheap now, one day I'm sure that won't be the case.

-Sonny king

sonnyking

Thank you very much!,

I won't have access to the car again until next weekend when it is moved / towed to a new storage unit. This will be the first thing I do, then I'll post the results. Once again thank you very much, this board is what I needed say in about 1986, it has had this problem in mildly different forms since the day it was delivered! But for some reason I absolutely love the car. I'm thinking about getting another one on ebay just to see if works? It's cool that you get these things for pretty cheap now, one day I'm sure that won't be the case.

-Sonny king

Vader

You may not be aware of it, but there was a factory TSB (Technical Service Bulletin) regarding the EPROMs in 1986 TPI engines. It seems the factory discovered some calibration issues after the production year ended, and released an upgraded EPROM in October of 1986. I installed one in my car about 6 years ago, and it made a noticable difference in performance. The replacement is a dealer item, and cost me $53.00. It was worth every cent. Unfortunately, since the cars would still run and meet emissions standards, there was no recall, and thus no "free" replacement parts.

I'd advise at least checking into it. It may not solve all your problems, but should improve some of them.

Guest

There is also a TSB about the distributor wires rubbing the engine hoist bracket, which is near the passenger side rear of the engine. Might want to check those wires, see if they are ok or have been rubbed bare and are touching metal.