donbartlett

Hey all;

If any of you remember, I had an issue with the car wanting to either start then die right after shut off at temp; and/or it would fire but would be fat and rich for a minute or so requiring part throttle to clean it up......

Well, I owe a thanks to the folks that pointed to the cold start pipe; I simply disconnected that wiring harness to the injector and Violla' no more issue (SO FAR!!!) Now for a block off and re mapping of chip to 89 and up specs...........

Thanks a lot for that one guys! I REALLY appreciate it.

Now for the new one to test Y'All's on:

Driving down highway 60-70 MPH, Service engine soon light comes on, Power drops off, and sometimes completely quits for a half second- to a second , and twice now the Up shift light illuminates on the Tach side of the dash pod.........

Very intermittent, Has happened four times now in 6-8 drives, typically around 170 degrees and up......

I have purchased a code scanner (AutoXray Tech Scan 7000) .., No codes scanned, or registered, and appears the variable info on the live feed are within the desired parameters per my GM Helm Manual...... (Best I can tell)

Recent work:

1. New plugs .035.
2. New cap
3. New rotor
4. All parts such as coil, insulating rubber disk, ground wire/strap replaced, all three wire sets connected to driver's side of Distributor under cap.

On visual inspection I have not found any obvious wires that may have grounded.......

any ideas or guesses that might put me in a direction??

......????????..........

Have any of you connected your scanner while actually driving down the road and pulled over to read the scanner, or check for a DTC when the anomaly happened??

Argh.

Thanks ahead of time!!!!!

Don

tehcarguy

You shouldn't start the engine when it's in diagnostic mode...Check your fuel pressure and all the other basic stuff...

sailorsteve

This is true, however, with the op's scanner, he can get real-time readouts while the engine is running, this does not involve diagnostic mode. This is the difference between a scanner and a code reader.

donbartlett

I may have answered part of my own question;

Having the scanner in live feed mode the engine is already running; So actually driving while it is on may be the only way to find the possible issue (with the help of a passenger to read as I drive, or vice-versa) Since it does not (as of yet) leave a DTC I may have to actually be "In the condition" to see if there is anything out of the ordinary.....

Anyway, I am still hoping somebody may recognize this issue of mine as being close to something that happened to them....or maybe even the same?.........

Thanks a guys........

sailorsteve

Just for the heck of it, go through the engine compartment and check all the connectors you can see for tightness, as well as any grounds. A loose connection is the source of many transient issues like this, as the voltages involved are quite low.

donbartlett

BUMP!

I am just trying to re liven this topic as I would love to track down this issue.

I have tried to check all the electrical connections I could find, and they all appear to be in good shape with tight connection and good weather seals.

I have no codes showing at all on the ECM, and I have run the live data feed with nothing appearing to be out of the ordinary as far as the expected norms on idle, fuel mix, voltages and the like......

Has not something like this happened to any of you????????

I would love to get rid of this gremlin.......

Thanks,

Don

cgantner5150

How about ECM connections under the dash and check the fusible links by the battery. The one feeding the ECM was literally hanging by a thread on mine. Caused all kinda of craziness when I first got my 86.

donbartlett

I'll definitely give that a check......... thx.........

donbartlett

Today I made access to the ECM and disconnected it. It had some minor white corrosion and two small rust spots on some of the contacts.

I cleaned them all off with electrical contact cleaner and a small file to be sure I had fresh metal to metal contact.

That gives me some piece of mind....I'll check the fusible's tomorrow........

Thanks...

donbartlett

Never mind the above....That was not the ECM, It was the light dimmer/timer I believe. Heck! It looked like an 80's computer to me!!!!! LOL

I have found the ECM however and plan to check it out next.

All of the fusible links by the battery appear to be fine.

If I had some minor corrosion on the connecter for the dimmer / timer than it stands to reason I may on the ECM as well huh??......

Today I drove the car for about 1.5 hours and it only cut out for a VERY brief second then after that I could not duplicate the issue. What I did notice however is that it cleared my control center and after that it would;d no longer read or reset while the car ran. It worked fine after I shut the car down.

That does tell me I lost all electrical power for a very short time..........

I also had the Code scanner attached throughout the drive on live feed and nothing appeared out of the ordinary. (Best that I could tell)

More to come.......

and also;

If any of this is familiar to you or close please let me know what was up with yours.......

OkieC4

If you lost all electrical power for a very short time, it would make sense that either the positive or negative battery cables broke contact momentarily. Have you pulled everything off the junction block for the positive or at the G106 ground on the engine?

The only other thing that comes to mind is the ign switch is failing or has a burnt contact.

cgantner5150

FWIW, don't know if it is the same, but when I have the laptop with Datamaster scanning realtime, my info center, specifically fuel mileage, will not readout correctly or reset. When I disconnect the ALDL it goes back to normal.
Just so you possibly won't go chasing a wrong lead/symptom.

donbartlett

Well, I got out the ECM. It was not too hard to do, but a bit rugged on the back!!!

It seems to look fine; connections are good (Visually) and the area around it; wires, etc look fine. I did notice that when I took it out it was pretty warm; I did have the heater on during my drive, mostly in the lower area "Heat" setting not vent or defrost.......... Do these generate any heat of their own??

See pics:









I was also just reading that it is not uncommon for these to just simply start going bad maybe due to solder issues, loose connections inside etc. and cause non traceable intermittent issues.....any of you know of this???? And; what are the chances that could be my issue??

Remembering:

Engine goes completely dead just for an instant; sometimes once, other a few times, Service engine light comes on, power drops off (appears to be limp home mode) and sometimes the Upshift light illuminates in the tach.

Does it not seem peculiar that all these different areas show symptoms at once?? Trans,(up shift) over all power, service, etc.... and no codes can be found either!!!!!!!!!!

Arghhhhh..........

I will get this eventually ....(I hope!)

Thanks for all the help, past and future!!!!!!!!

donbartlett

I think it was reading out fine until I (the car) had the episode, then it went on the fritz.



I think.....LOL...Ill have to check on that.....Thks.....

OkieC4

It may be.. As you said, these junction blocks go bad and the stacking of all the major amp draw circuits (power distribution) on the post have led to problem over time with soldier joints, corrosion, and pitting, etc on the circuit terminal lugs. Several folks have fabricated covers to protect the junction block are from the elements of vehicle washing, etc.

donbartlett

OMG;

this is really a bugger to find!

Here is what I know thus far:

I keep getting the scenario of cutting out briefly followed by wjhat I am going to assume is limp home mode, The dash lights with Service engine soon, occasionally the Upshift lamp comes on at the tachometer gauge..... and today it just died going around a turn. Luckily I was aware, put it into neutral restarted and averted disaster!! LOL

I have used my AutoXray scanner on it NUMEROUS times now and find NOTHING. Argh. No codes, no anomalies, Just nothing; it just reads system pass no problems.

This has happened at 180 degrees, 200 degrees etc; no rhyme or reason there. It has happened while driving and today while parked and revved up to 2000 rpms.

Very frustrating. Why do you guys think there are NO codes being kept? Why do you think it will not read a code even when the issue is happening and I try to read a code??

The closest I have come thus far to an anomaly is when I have the scanner hooked up, and the issue happens I have it set to read DTC's and it will say attempting to communicate with vehicle through GM dual baud, then after a moment of saying working please wait, it comes back with improper connection try again?........if no issue happening, then I can do the same and it works fine, only now it says no issues, system pass.

I really need a direction to go here guys.......

donbartlett

OMG;

this is really a bugger to find!

Here is what I know thus far:

I keep getting the scenario of cutting out briefly followed by what I am going to assume is limp home mode, The dash lights with Service engine soon, occasionally the Upshift lamp comes on at the tachometer gauge..... and today it just died going around a turn. Luckily I was aware, put it into neutral restarted and averted disaster!! LOL

I have used my AutoXray scanner on it NUMEROUS times now and find NOTHING. Argh. No codes, no anomalies, Just nothing; it just reads system pass no problems.

This has happened at 180 degrees, 200 degrees etc; no rhyme or reason there. It has happened while driving and today while parked and revved up to 2000 rpms.

Very frustrating. Why do you guys think there are NO codes being kept? Why do you think it will not read a code even when the issue is happening and I try to read a code??

The closest I have come thus far to an anomaly is when I have the scanner hooked up, and the issue happens I have it set to read DTC's and it will say attempting to communicate with vehicle through GM dual baud, then after a moment of saying working please wait, it comes back with improper connection try again?........if no issue happening, then I can do the same and it works fine, only now it says no issues, system pass.

I really need a direction to go here guys.......

Best I can tell, no loose grounds, no issues with wiring, vacuum lines seem fine, MAF sensor appears clean and clear, new plugs, new cap and rotor, oil change, air filter..............

I can understand if something either goes bad all at once which is a typical characteristic of some type of electrical/electronic failure, or even a component wearing out..........but this Hit and miss stuff is really tough to find, especially with no codes or direction to go..............Am I the only one with this scenario??????

I have to Admit, my 1968 Camaro in addition to being WAAAAAAAAYYYYYY faster than this cool car is WAAAAAAAAAAYYY easier to work on.......... Eye Jee wa-wa.

I know; DOUBLE POST. My bad.

OkieC4

I may be wrong, but I'm still thinking the ignition switch has burnt contacts.... There is a old thread over on the C5 forum with pix of a disassembled switch... Please excuse me for posting an old thread link, but the pictures tell the story.....

http://forums.corvetteforum.com/c5-t...ch-repair.html

If you do an internet search of GM ignition switch problems, you will get many results, across all car lines of problems resoved by the ignition switch...

Just my thoughts.......

donbartlett

Needless to say I'll check into that as well as soon as I finish typing this.......I really appreciate you trying to help out Okie.

donbartlett

I checked this out today; and the result was that running the car with it connected had no effect on my readouts.......UNTIL, that is until the issue popped up........

So I can not blame the scanner for it..........

Thanks for the idea to check that out.

Don