I need help bad, electrical issues making my hair gray!

[Wayfarer696]

1988 grand prix, 2.8 multi-port:
OK let me start out with what my symtoms are, when i turn the ignition to the on position, my service engine soon light and coolant light come on like they should, but then they each flash seperately and continue to do so. Then i turn the motor over and it wont fire, but once in a great while. Now i've had a mechanic look at it twice and put it on a computer. first he cleaned the throttle body, and reset the ecm, and taught it how to idle again, it was good for two days then same problem. so i replace the computer, then i got no ses light or coolant light in the "on position", took it in again and he reprogrammed and replace two wires feeding the new computer. after that it got two blocks away from the shop and now im back to the ses and coolant light flashing, i've replaced starter, checked the coil pack, all fuses, and electrical connections for corrosion, nuthing helps. but by chance yesturday after double checking fuses and what not, i turned the ignition to the run or "on" position, and i notices the two lights stay on. so i cranked it over and it fired right up and ran like a champ, i drove it in variable conditions for about 20 minutes, thought maybe i got lucky, but then this morning i went go for a sunday drive, and from the time i parked it "and it was working great then", and this morning the problem came back. I'm so confused at this point, any tips of inexspensive things to try now? im almost to the point where the car isnt worth what i've put into it over the last month, I appreciate any help or suggestions!

[Wayfarer696]

please dont be shy, i'm open to any suggestions!

[e2helper]

Sounds similar to a problem I had with 1989 Grand Prix

But that was about 10 years ago!!

So it is going to take me a while to remember. I am sure we also had the PCM replaced. I'll be back if I come up with anything.

Edit

Too funny, I still had repair orders - thx for reminding me all the problems I had with that vehicle. I bought vehicle new.

I first took it in 41,000 miles with complaint about stall when hot and may restart if you let it sit. They replaced PCM

A year later took back it acts like wants to stall out when comes to a stop when warm. they replaced the Idle Air Control with update

2 years after that took back because it surged when hot. They relearned minimum idle

I sold the car a year or so later and leased a 1996 Grand Am. Much better luck with that vehicle, but I'm in a leasing mode now and so don't keep cars as long as that 1989 Grand Prix any more.

I believe the first complaint also had some issue with coolant light although it didn't say anything about this in the repair order.

I will follow-up if I come up with a suggestion that might actually help you..

[kilroypr]

At this age could be anything. Since it worked yesterday and today is not working could be a bad or loose wire. Determining which one could take a while and the wiring diagrams.

[Wayfarer696]

I appreciate the tips, do you think it would be worth my time taking it to a different mech. dont they have diognostic computers that would point them in the right direction as far as a bad or faulty wire? supposively the last mech. replaced two that should have had a constant 12 volt charge to the computer. and it still didnt correct the problem, but anythings worth a shot now. has anyone every encountered a bad sensor of some sort that sounds like this problem?



Keep it commin guys
and thanks again.

[kilroypr]

On my Z34 I replaced 3 EGR valves before checking the wiring. At the 3rd one I discovered a loose connection. The only way to get a loose connection is using a continuity tester and playing with the cables. Could be that both cables are grounding at some point. That is the tricky part. Checking the cables integrity

[Wayfarer696]

Anyone have any idea on which wires to check? any in [articular that would cause the ses and coolant light to flash like that?

[michelq]

AT the left side next to battary there a battary post make sure is clean and tight

[Wayfarer696]

Will do, i tried checking some wires the other night, but it was running great again! wierd, but when i started it, it idled really high, like around 3000 rmps. i took out the TPS and cleaned it up, it didnt seem to spring out as far as i would think it should when i shut the key off, when i turned the key on it sucked in, is this normal?

[Murphyg]

Originally Posted by Wayfarer696

I appreciate the tips, do you think it would be worth my time taking it to a different mech. dont they have diognostic computers that would point them in the right direction as far as a bad or faulty wire?

Yes they do. Depending on the year you can also access the OBD right from the dash. The first thing the mech should do is hook up to the OBD (On Board Computer) and see what codes come up then cross refrence them from a manual or library of some sort.
When there is a fault the computer will store that info in the form of a code so as to be able to diagnose the problem.

Doing an idle learn is ok and all but not being able to access the codes kinda makes it useless.
The idle learn is "a diagnostic test to see if initial throttle position sensor learn, and idle learn values have been stored in the PCM (Power Control Modulator)".
Seeing as youve messed with your thrittle body you should have done another idle learn procedure. Its preety well mandatory.

There's a whole bunch of other stuff as to the codes and such but what I have isnt for a grand prix. Its all basicly the same idea though. I also drive a GM.

Hope my blather might have helped you.
Good luck

[kilroypr]

Well if you are certain that they do not have the diagnostic equipment then take it where they do. And of course they know what to do with it

[Wayfarer696]

Thanks for the tips again, i know they had the diognostic computers, but i dont think he put much effort into it, and i cant get it to display any codes other than a twelve, which means everythings working good, i've been looking at wires in the harness, havent found anything yet, but im hoping to find something soon, the thing i cant seem to get an awnser to or figure out myself is, why the svc. engine soon light and coolant light flash alternately " one then the other" when it wont start, then the next day they wont flash and it will run good. I and know one else seems to have any idea what that would be. And the comperter has no codes to display. I seems to weird that if it was a short or broken wire, why is it that it can sit for a while, and it will work, then with out touching anything or moving the vehicle, the next day the lights act up again, and it wont fire. Could it be something in the ignition switch or something?

[Murphyg]

My Mother inlaw apparently had almost the same problem with her 99 GTP. Only diff was she only had the coolant light coming on.
They told her it was nothing to worry about. Said that eveything was fine. Some glitch that made the light come on even though everything was fine. Dont worry about it they said.
Well she freaked out. "How will I know if there is a problem then ! Will the light go out!" !!
She had warannty and all so they had no choice but to fix it.
Will try to remember to ask her if she knows what they did. She keeps all paper work so there is a good chance. Just a matter If I remember or not.

[Wayfarer696]

Still Havent had any luck finding any bad wires, does anyone know if i should be getting a tone when i remove the battery and take a reading between the positive and negative battery cables? cause i do. I get get a beep when i check between the positive terminal and and any ground " i.e. the engine block, alternator housing". is it supposed to do that? or do i have a short?

[Wayfarer696]

And keep in mind guys, it wont do anything but fire once in a great while when i turn it over, unless the svc eng. soon light and coolant light arent flashing alternately when the key is in the run position.