86 ecu diagnosis
 

I have an 86 coupe that just developed this problem. The car will start and idle for 2 or 3 seconds and then die. I tried to recover codes but jumping the link dosen't work and the check engine light stays on continuous. Also the cooling fan runs as soon as the key is turned on. Any thoughts?

Thanks

Dave

Well I have the ecu out now and it looks like someone before me put a Hypertech chip in it. Are there any common failures with these?

Thanks,

Dave

Ok well I went through the shop manual and followed the steps that direct you to unplug the ecm and check the check engine light which did go off. Then it says to plug everything back in and back probe the circuit. When I did that my test light didnt light up but the car now starts and runs. I still have a check engine light and I am not able to access the diagnostic mode.

Dave

I feel like I am writing in a journal. I now have a new ecm and will install it tonight. I will let myself and anyone else know if it works.

No joy. Well shop manual says if you still have a problem after changing the ecm then change the memcal. We shall see.

Ok so I ordered a Jet Chip as a replacement for the Hypertech chip that seems to be bad. I get the chip and the instructions say to mount orginal chip onto new Hypertech Chip. Well I don't have the original chip and I can't see anyway you could put the Hypertech onto the new Jet Chip. I call Jet and the guy actually says "dude you need the old chip". Ok so I respond by saying where in the advertising literature does it say that? He says it would cost way more if it was all in one. So now that I am out $145 I figure why not try the Jet Chip as is. It looks like the Hypertech chip which didn't have anything piggy backed on it so why not try. Lo and behold the electric fan does not come on when I turn the key on and I can now read the codes. So I start the car and it runs! Runs like crap but it runs. It has thrown a code 41 which leads me to believe that it does need some type of piggy back to function properly. I am now purchasing a stock memcal and have high hopes that will end this problem.

Ok I guess this will be my last entry. I installed a stock GM chip I purchased and the car is alive once again. The chip I received was for an auto transmission with cast iron heads, which is what I wanted. However I have a 2.59 rear axle and the chip was for a 3.07 axle car. It seems like the shift points are a little different but not positive otherwise the car runs fine. Thanks for everyone's help. Hopefully my problems will help somebody else.

Dave:)

Wish I could have helped as you struggled with the problem ,but you were way beyond my level! Thanks a bunch for all the posts,especially what finally cured the problem. I still don't know much,but I know more than I did thanks to you!
Ron

Update..

The car runs fine and idles much lower than with the stupid Hypertech chip. Idles at 600 in drive which is where it should be. As for how the car runs with the original GM chip versus the Hypertech chip it is night and day, I have owned this car for ten years now and only knew what it was like with the Hypertech chip. Now that I have the stock chip in it I can honestly say it is a different car. It is so much smoother on and off the throttle. It had a small stumble off idle that is now gone and as noted the idle is back where it should be. As for wide open throttle performance I feel no difference. I can still smoke the tires right off it. I am still getting used to the different shift points which I assume are caused by the chip looking for the 3.07 rear end versus my 2.59. I can't speak for the new generation of computers and the many options to reprogram them but I can say with certainty that anyone that spent $275 for this chip threw their money away.

Dave