Intermittent cut out with check engine light

Thanks guys.
Great advice, I really appreciate all the help.

I don't get much time to work on it so I'll get info back to you in bits n pieces.

I watched the TPS on the Scanmaster today on the way home from work. The car drove in fine in the morning, but on the way home after about 10 miles, I had the issue under light acceleration, and low boost as usual so I just watched the TPS. It stayed stable so I'll rule out the TPS.

I also checked TPS with just the ign in on position (engine off) and it sweeps steady from 0.42 to 4.40 with no jumps.

I also watched the alternator volts. Stayed between 13.1 and 13.4.
Any other ScanMaster readings to monitor?

The symptoms hung around for a mile or so through a few stop lights and re-accelerations.

Then as quickly as the issue came back....it went away.... and the GN ran fine the rest of the way home.

I looked at the harnesses running behind the engine and the harnesses look OK, but I did not open them up to look at wires yet.

I inspected the pins on the ECM orange wire at the battery and the male side looks like it might have some oxidation, but it's hard to tell.

Last week I had checked the plug on the ign module and it seemd OK. I did not inspect wires yet, but I cleaned the pins with electronics cleaner.

I'll find time in the next couple days to really look things over including the battery cable and the wiring running behind and under the engine as well as at the ECM.

Thanks again,
Tim
 
FWIW... the scanmaster definately won't refresh fast enough to catch the issue if it is like I had.... with the battery cable..... it only took 2-3 frames of data (using DirectScan) at a rate of 18 frames per second...... since the scanmaster is several seconds per frame....... not gonna see it with it........ keep plugging away.... you'll find it....
 
Blazer406 said:
FWIW... the scanmaster definately won't refresh fast enough to catch the issue if it is like I had.... with the battery cable..... it only took 2-3 frames of data (using DirectScan) at a rate of 18 frames per second...... since the scanmaster is several seconds per frame....... not gonna see it with it........ keep plugging away.... you'll find it....
Click to expand...

Point taken.;)
Maybe I need to charge up the laptop battery, hook it up to the DirectScan and see what I can grab while it's hiccuping.
 
I also want to emphasize that these symptoms ...quick cut-out/hesitation with check engine light...only happen when the car is warmed up and during the warmer part of the day.

I drive the same distance to work in the AM and have never had the issue...car runs great in the AM.

But in the afternoon/early evening when the outside temps are higher than they were in the AM, the issue happens after 10-20 miles of driving and only under light boost acceleration.

One other detail...a few weeks back when it first did it, I changed the spark plugs (they had over 10K miles of hard core kill mode driving on them) and it seemed to make the problem go away...so I thought that maybe a couple of the spark plugs that looked a tad abused were the problem. They weren't oil fouled or anything like that, but they were definitely expired....:p

The problem stayed away for a few weeks until it came back last week.

Whatever it is, is definitley heat related...that's why I suspect something like the ignition module or ECM (both original parts with 22 years on them) is getting hot and then pitching a fit under load transitions....

Any thoughts?
 
don't do anything else until you check the positive battery cable. it takes about 5 seconds to see if it's rubbing on the downpipe or header. if it's rubbing and burned through the insulation then you've identified the problem. don't overthink the issue and go right for the laptop. check the easy stuff first.

i bet your scanmaster goes "- - -" when the car hesitates and the engine light flashes. if so, it's definately the battery cable. mine did the same thing. and for whatever reason, only when the car was up to temp.

if it's not the bat cable then break out the laptop and focus on the ignition.
 
ryan319 said:
don't do anything else until you check the positive battery cable. it takes about 5 seconds to see if it's rubbing on the downpipe or header. if it's rubbing and burned through the insulation then you've identified the problem.

i bet your scanmaster goes "- - -" when the car hesitates and the engine light flashes. if so, it's definately the battery cable. mine did the same thing. and for whatever reason, only when the car was up to temp.

if it's not the bat cable then break out the laptop and focus on the ignition.
Click to expand...

I looked at the + bat cable last night at the spot where it rides the frame rail just under the header and it didn't look hurt. The factory black plastic sheeth is still in tact with no burns, etc. I still want to pull the sheeth back and inspect it and the rest of the starter wiring from under the car tho'

ScanMaster actually does not do the --- thing. It functions as normal. It probably would --- if there was a complete power interuption, but I'm not getting that.
 
Caspers' coil pack tester. Best money you will ever spend for your Turbo Buick.
Especially if you are rolling with OEM C3I components on the car.
Unless water has gotten into the ECM, I would suspect ignition module first. As you said, it only happens when it heats up. I'm sure the insulation goop has probably broken down/melted out and allowed moisture to get in.
Just a thought.

Patrick
 
Now this might be interesting....
Today on the way home....symptoms returned....getting much more repeatable....
This time I kept an eye on the volts. What I noticed is cruising along or at idle, the volts hover around 13.5-13.8.

As I dip into the throttle casually to accelerate from a stop or even while rolling, the volts drop as low as 12.8 but normally hover 13.1 to 13.4.

Once I pushed through the symptoms and knew it was safe to do so, I went WOT and the volts jump to the low 14's.

FYI I am running a HOBS style volt booster switch off the back of the alternator so a .75-1volt jump at WOT is expected, but the voltage drop during the throttle transition is suspicious to me.

Maybe my alternator is fritzing (it's pretty old...might even be original....)....or something else is loading the system as I start to give it gas.

Makes sense that this voltage drop would make a difference when everything is hot since system electrical resistance increases with heat, and voltage drops related to the resistance through the system occurr naturally.....so with a larger voltage drop than normal from the alternator....my ignition may be lacking enough fire power until the HOBS switch kicks in.....

any thoughts?
 
I've had issues where voltage below 13v was not enough to light the coils. Much less fire the injectors and fuel pump. I had an alternator once, that was acting up on my old Grey car. Voltage would drop below 13v and the car would start hesitating, bucking and even popping under boost. For the life of me, I couldn't figure it out. Then I had a Buick guru (thanks Joe) tell me to watch my voltage and see if it starts fluctuating when it acts up. Sure enough it would drop below 13v when it acted up. Battery would test perfectly and hold a charge. So I had the alternator run on a tester (off the car of course at Autozone) and it failed the load test.
Replaced it with one of their replacements and voltage was back to normal and cured all issues. This was with a Volt Blaster as well.

It's my opinion, that these cars need at least 13v to run right. Especially when you consider the demands of the C3I system and fuel system. Throw in your headlights and dash lights and now we have even more demand. You're good to go with your volt booster, but I can tell you, if that is an original 23 year old survivor alternator, the volt booster has probably taken it's tole on it and created your issues. Good job on watching voltage when the gremlin happened. A flashing Scanmaster reading, would definitely indicate an interruption of power. Grounding out power wire and such. But your symptoms to me sound like alternator getting ready to go poof.

With all of your, (shall we say) representing ;) you have been doing lately, I would replace the alternator as preventive maintenance anyway. We can't have you blowing a head gasket while puttin the hurt on that pesky Cobra now can we?
Just my O2's worth.

Patrick
 
RUQWKNF said:
I've had issues where voltage below 13v was not enough to light the coils. Much less fire the injectors and fuel pump. I had an alternator once, that was acting up on my old Grey car. Voltage would drop below 13v and the car would start hesitating, bucking and even popping under boost. For the life of me, I couldn't figure it out. Then I had a Buick guru (thanks Joe) tell me to watch my voltage and see if it starts fluctuating when it acts up. Sure enough it would drop below 13v when it acted up. Battery would test perfectly and hold a charge. So I had the alternator run on a tester (off the car of course at Autozone) and it failed the load test.
Replaced it with one of their replacements and voltage was back to normal and cured all issues. This was with a Volt Blaster as well.

It's my opinion, that these cars need at least 13v to run right. Especially when you consider the demands of the C3I system and fuel system. Throw in your headlights and dash lights and now we have even more demand. You're good to go with your volt booster, but I can tell you, if that is an original 23 year old survivor alternator, the volt booster has probably taken it's tole on it and created your issues. Good job on watching voltage when the gremlin happened. A flashing Scanmaster reading, would definitely indicate an interruption of power. Grounding out power wire and such. But your symptoms to me sound like alternator getting ready to go poof.

With all of your, (shall we say) representing ;) you have been doing lately, I would replace the alternator as preventive maintenance anyway. We can't have you blowing a head gasket while puttin the hurt on that pesky Cobra now can we?
Just my O2's worth.

Patrick
Click to expand...

Testify!
:biggrin:
Gotsta represent!!!!

I have an appointment at Lou Czarnota's this afternoon. (he's 10 minutes from my house....very convenient to be that close to one of the best)
He's going to check the alternator, battery and coil/ign module for me to see which might be punking out.
 
I went to Lou's today.
Alt and Battery checked out OK, but we did find that my coil had a weak middle coil using his caspers tool, so we swapped the coil and ign module for known good pair he had there in the shop. Smoothed out a rough idle issue that I didn't even realize was an issue...I just thought it was a Buick thang...:tongue:

Also verified the chip is installed OK with good pins.

He does not think the coil pack was my cutin' out engine light issue tho'
He let me borrow his test MAF to see if that helps....jury is out.

My old ign module seemed to function OK, but when we removed the coil we found the ign module was full of this sticky taffy like blue goo....stuff was nasty....gets everywhere....poor Lou got his fingers stuck together trying to work around it :biggrin:(sorry Lou).
It's an original ign module....had the markings and everything....but Lou didn't know what the blue goo was all about....

I'll be changing my drivers side header (cracked), changing oil tomorrow so while I do that, I'll continue to inspect wiring.

I don't know if the problem is fixed or not, yet...
 
So far so good.....

I also added a ground strap between the ign module base and the firewall today just for fun.
 
MEANCHICKEN:

Try this. Disconnect the Directscan. Completely. Don't just shut it off - you need to remove the edge connector off the ECM board.

The issue with directscan is your whole ECM databus gets put on that ribbon cable, and is hanging out there to absorb all sorts of EMF. It took me 4+ years to diagnose this issue. I did everything you did. Burnt bat cables, modules, coils, grounds - Phooey!

Check my thread on this issue. You even chimed in. Eric Marshall and Bmackinnon finally pointed me the right way.

http://www.turbobuick.com/forums/ge...battery-voltage-dropout-radio-interferen.html
 
Reply

meanchicken said:
I went to Lou's today.
Alt and Battery checked out OK, but we did find that my coil had a weak middle coil using his caspers tool, so we swapped the coil and ign module for known good pair he had there in the shop. Smoothed out a rough idle issue that I didn't even realize was an issue...I just thought it was a Buick thang...:tongue:

Also verified the chip is installed OK with good pins.

He does not think the coil pack was my cutin' out engine light issue tho'
He let me borrow his test MAF to see if that helps....jury is out.

My old ign module seemed to function OK, but when we removed the coil we found the ign module was full of this sticky taffy like blue goo....stuff was nasty....gets everywhere....poor Lou got his fingers stuck together trying to work around it :biggrin:(sorry Lou).
It's an original ign module....had the markings and everything....but Lou didn't know what the blue goo was all about....

I'll be changing my drivers side header (cracked), changing oil tomorrow so while I do that, I'll continue to inspect wiring.

I don't know if the problem is fixed or not, yet...
Click to expand...
So much for your $40.00 bargain coil pack. An ohm meter test would of never found that problem. Whats suspicious is the check engine light issue & no codes. A year ago when I installed the engine I always use extreme caution with grounds & wiring. But Like the one member suggested make sure the positive batt cable is away from the header & not touching. Put a wrench on the ground cables just to verify tightness. Every now & then someone decides to use the orange computer feed wire for a convenient place to wire in things like kill switches,power antennas,electric exhaust cutouts etc. not a good idea. Put a wrench on the battery ground cable bolt at the block to make sure its tight. The bolts & nuts that secure the module to the engine must be tight & grounded. I'm sure all that's mentioned is correct but I'm mentioning this as to what I have run into that can drive one nuts related to this sort of complaint..
 
Hey DMan.

Thanks.
That was actually one of the first things I tried a few weeks back when the problem first started. I pulled the ECM out and removed the DirectScan...but....didn't help.
 
Yes.
It went away after I replaced the coil pack and ECM with known good units form Lou.

The coil pack was definitely bad as stated in my previous post and verified with a Caspers tester by Pappa Lou Czarnota, and the ECM was suspect since the goupe under the coil pack was all runny.
 
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