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#1060602 - 02/02/19 11:08 PM Having ECM issues  
Joined: Aug 2010
Posts: 168
RDKLXPRS Offline
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RDKLXPRS  Offline
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Joined: Aug 2010
Posts: 168
Lexington, NC; Daytona Beach, ...
1986 SS
stock ECM, dist, CCC
350/T56
Dakota Digital HDX
Separate AFR gauge
Full exhaust with ECU O2 sensor in driver side header and AFR gauge O2 in pax side header. I don't know that that makes any difference but i'm trying to give as much info (sorry if i'm a rambling man)
I put the T56 and HDX in last winter.
Car is not leaning out at cruise and i'm losing about 50 miles per tank. Was getting 300+ over the summer and after i got back form my honeymoon in September it has been lucky to get 250 miles.
I have been chasing this a while and have no clues. no vacuum leak. My check engine light does not send out a signal even though I know there has been one sitting there for years (TPS circuit voltage high); I cant get a signal with the test light either at the computer or at the instrument panel harness. I do think that the HDX may have something to do with the CEL .

Here's some questions I have:
1. What exactly happens when you bridge A and B terminals to go in diagnostic mode. I can hear the cut down and the AFR goes to 16+. i thought it was supposed to go rich. What else should i be seeing.
2. How can I get my CEL working again, did i break the circuit somewhere since it doesn't use the instrument circuit board now. Its a WHT/ DK GRN wire out of the ECM but 2 Yellow wires going to the IP harness..

Ill add more as I think of it, if you read this thank you and if you have some ideas you'd like to share thank you in advance.


[Linked Image]
1986 MONTE CARLO SS 5.7L 420,000 mi.
https://www.facebook.com/Bakersprsprt
#1060609 - 02/03/19 12:49 AM Re: Having ECM issues [Re: RDKLXPRS]  
Joined: May 2007
Posts: 4,658
Buick Runner Offline
10+ Year
Buick Runner  Offline
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Joined: May 2007
Posts: 4,658
Dharma station 1 the Hydra
Did the issue happen before or after your HDX / T56 install? The mixture failing to lean out usually the result of a vacuum leak, which can be very hard to find. Check your carb gaskets and intake gaskets.

Last edited by Buick Runner; 02/03/19 12:50 AM.

SBC powered 1987 Regal with TES headers, ZZ4 intake, ZZ4 PROM chip, mini starter, THM2004R, 2500 stall converter, 2040 cam, CCC system, and 3.73 posi rear.

2008 ex NPS P71 Crown Victoria, cop motor, cop shocks, cop brakes.

Never argue with an idiot.
They will just drag you down to their level and beat you with experience.
#1060611 - 02/03/19 02:27 AM Re: Having ECM issues [Re: RDKLXPRS]  
Joined: Aug 2010
Posts: 168
RDKLXPRS Offline
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RDKLXPRS  Offline
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Posts: 168
Lexington, NC; Daytona Beach, ...
About 6 months after the install. I don't think I have a vacuum leak. I have a gauge as well and its holding 19-20 at idle. I created a small vacuum leak and it dropped to 5. Earlier in the summer the afr ran perfect. 14.7 at cruise and 12.5 at WOT.


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1986 MONTE CARLO SS 5.7L 420,000 mi.
https://www.facebook.com/Bakersprsprt
#1060612 - 02/03/19 06:16 AM Re: Having ECM issues [Re: RDKLXPRS]  
Joined: Jan 2000
Posts: 4,202
mmc427ss Offline
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mmc427ss  Offline
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Pottstown, Pa
Do you have the Helm's Electrical Supp for your car? Schematics, that is the first thing needed to trace the necessary circuits.
Found this which will help in a pinch, scroll down, SES diagram for your car is there.
https://www.justanswer.com/chevy/3d...e-engine-light-doesnt-work-no-power.html

Couple questions:
Have you located the "Light Driver" for the SES?
You checked the bulb?
Been a long time since having a CCC, but think the SES light came on when the IGN was turned to ON.
You still have VSS connection to the ECM?
You have the Gear Selector switch in the open position, this effects the ECM program. In Park and Neural the switch is closed, Drive is open. Stick shift cars with CCC need to to be Open. Just thought I'd throw that out there.
Being you have stuck with the CCC, and maybe using it for the future a scanner would be a good thing to own. Something like a Brainmaster can be invaluable.
Have you checked the base ign timing lately, dist have been know to move.
Assuming not a big cam, engine vac on the high side unless a really mild cam.
Staying with the 86 ECM? Not likely bad but upgrade to a 079 ECM if you need to replace it.
Terminal B WHT/BLK wire, terminal D Yellow wire on the ALDL are the two terminals to jump to activate the SES light.
Reliable AFR meter? Is it one that needs to be recalibrated every now and then?
Correct TPS voltage at idle necessary, they go bad. You had that code before?
Listen to what the MC solenoid is doing as the engine warms up to operating temp and goes from open to closed loop. The AFR gauge, the vac gauge and MC can can indicate mixture problems while revving the engine.

A healthy antique CCC system is not a bad system. At the least the SES has to work so codes can be pulled. Fix that first then chase the mileage issue.
Bob

#1060618 - 02/03/19 05:50 PM Re: Having ECM issues [Re: RDKLXPRS]  
Joined: Aug 2010
Posts: 168
RDKLXPRS Offline
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RDKLXPRS  Offline
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Joined: Aug 2010
Posts: 168
Lexington, NC; Daytona Beach, ...
Couple questions:
Have you located the "Light Driver" for the SES?
I have not, this is the first ive heard of it, so thank you for that info.

You checked the bulb?
The bulb is no longer in since the whole circut board behind the cluster is gone. Everything is run by the dakota digital. BUT I do not have the CEL hooked up to the HDX.

Been a long time since having a CCC, but think the SES light came on when the IGN was turned to ON.
You still have VSS connection to the ECM?
I do not have a VSS connection to the ECM only to the HDX control box, I did try to connect it and get the cruise to work after the swap but i was not successful.

You have the Gear Selector switch in the open position, this effects the ECM program. In Park and Neural the switch is closed, Drive is open. Stick shift cars with CCC need to to be Open. Just thought I'd throw that out there.
Yes, i did have that hiccup soon after the swap, that and I replaced the wrong water temp sensor so the ECM didnt see the engine warm up, but after I fixed those 2 issue the car ran perfect for 6 months.

Being you have stuck with the CCC, and maybe using it for the future a scanner would be a good thing to own. Something like a Brainmaster can be invaluable.
I have a ALDL>USB cord that i was messing with yesterday, but i cannot get the dang thing to show up in the WinALDL program. not sure what im doing wrong with all that.

Have you checked the base ign timing lately, dist have been know to move.
I have not recently.i need to, I have serious vibration at 2500-3000, been there since the swap, not sure if its engine mounts or the clutch/flywheel not balanced correctly. But maybe the vibration has shifted the distributor.

Assuming not a big cam, engine vac on the high side unless a really mild cam.
Stock cam that came with the 350. GMs basic replacement 350.

Staying with the 86 ECM? Not likely bad but upgrade to a 079 ECM if you need to replace it.
Is that the 87-88 ECM? had one of these lined up but fell through, though i want all the kinks worked out so im not chasing gremlins.

Terminal B WHT/BLK wire, terminal D Yellow wire on the ALDL are the two terminals to jump to activate the SES light.
Ill check that. I thought it was A/B

Reliable AFR meter? Is it one that needs to be recalibrated every now and then?
Should be reliable. Autometer never had trouble with it and never had a reason to think it was off.

Correct TPS voltage at idle necessary, they go bad. You had that code before?
Yeah, unfortunalty I had the carb rebuilt a few years ago by a shop 500 miles away, and the code popped up shortly after i got it back. Lifetime warranty on the rebuild but i haven't had the chance to send it back. Car is my DD. It never affected how the car performed before.

Listen to what the MC solenoid is doing as the engine warms up to operating temp and goes from open to closed loop. The AFR gauge, the vac gauge and MC can can indicate mixture problems while revving the engine.
I heard the MCS yesterday clicking on a off with the grounding of the diagnostic terminal, after the car had been warmed up, engine off.


[Linked Image]
1986 MONTE CARLO SS 5.7L 420,000 mi.
https://www.facebook.com/Bakersprsprt
#1060627 - 02/04/19 08:18 AM Re: Having ECM issues [Re: RDKLXPRS]  
Joined: May 2007
Posts: 4,658
Buick Runner Offline
10+ Year
Buick Runner  Offline
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Posts: 4,658
Dharma station 1 the Hydra
The ECM requires a VSS signal to operate correctly, it needs all the sensors, no deletes.

You also need to reinstall the SES light system.

There may not be anything wrong with the TPS other than it needs final adjusting on the engine. Shops can only guess some of the adjustments. Several of the adjustments must be fine tuned once tbe carb is on the engine itself, especially a non stock engine.


SBC powered 1987 Regal with TES headers, ZZ4 intake, ZZ4 PROM chip, mini starter, THM2004R, 2500 stall converter, 2040 cam, CCC system, and 3.73 posi rear.

2008 ex NPS P71 Crown Victoria, cop motor, cop shocks, cop brakes.

Never argue with an idiot.
They will just drag you down to their level and beat you with experience.
#1060628 - 02/04/19 12:13 PM Re: Having ECM issues [Re: RDKLXPRS]  
Joined: Mar 2012
Posts: 695
MC96 Offline
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Posts: 695
St. Johns MI
I tried sending a message but you are over your PM limit.

I have an ECM out of my car if you want to swap it and see what that does.

25 shipped.


86 SS
400SBC, 4l80e, MSD Atomic injection/trans controller, Tilt glass clip, all tubular arms, corvette brakes, 9" rear
In progress
#1060637 - 02/04/19 09:55 PM Re: Having ECM issues [Re: Buick Runner]  
Joined: Aug 2010
Posts: 168
RDKLXPRS Offline
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RDKLXPRS  Offline
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Joined: Aug 2010
Posts: 168
Lexington, NC; Daytona Beach, ...
Originally Posted by Buick Runner
The ECM requires a VSS signal to operate correctly, it needs all the sensors, no deletes.
Not doubting you there, but it ran perfect over the summer, something else changed.

You also need to reinstall the SES light system.
What do you mean, how would you suggest? the only thing I have done is unhook the connector at the circuit board behind the cluster anad tapped into the necessary wires for the HDX control box. Is there some type circuit that's now broken with out that board? My logic was that was just to light the bulb, I notice there are 2 wires going into the same pin for the SES on that harness. Edit: I think I just answered my own question, there is a ground on that connector that is no longer connected so the circuit is broken, maybe I just need to actually hookup the SES light to the HDX, I haven't yet because of the other code and I didn't want the light on all the time. Thanks.

There may not be anything wrong with the TPS other than it needs final adjusting on the engine. Shops can only guess some of the adjustments. Several of the adjustments must be fine tuned once tbe carb is on the engine itself, especially a non stock engine.
I have to look more into this.


Answered your questions, thanks for your responses.

Last edited by RDKLXPRS; 02/04/19 10:11 PM.

[Linked Image]
1986 MONTE CARLO SS 5.7L 420,000 mi.
https://www.facebook.com/Bakersprsprt
#1060668 - 02/07/19 05:49 AM Re: Having ECM issues [Re: RDKLXPRS]  
Joined: Jan 2000
Posts: 4,202
mmc427ss Offline
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mmc427ss  Offline
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Pottstown, Pa
Tyler, make any progress on you problem?

As far as the VSS goes it's needed for cruise, and the ECM needs it for torque converter lockup. I can't say specifically whether the ECM needs it to manage the fuel and ignition timing but I think not. I do think a stick shift car doesn't need VSS.

Not familiar with the HDX box and tying the SES light into it. Would think that the ECM output for the SES is 5 vdc like all the other outputs from the ECM.
Bob

#1060673 - 02/07/19 06:15 PM Re: Having ECM issues [Re: RDKLXPRS]  
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Bitflipper Offline
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Las Vegas, NV
Looking at the ECM code, the only place I see it using VSS is for deciding whether or not to use a fixed spark advance for Park/Neutral. I do not see any spark adders for non-zero speed, nor do I see VSS influencing fuel management.

Mostly VSS appears to be used for shifting and lockup.


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#1060675 - 02/07/19 11:22 PM Re: Having ECM issues [Re: RDKLXPRS]  
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mmc427ss Offline
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mmc427ss  Offline
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Pottstown, Pa
Thanks Dylan!
Bob

#1060707 - 02/10/19 09:17 PM Re: Having ECM issues [Re: mmc427ss]  
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RDKLXPRS Offline
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RDKLXPRS  Offline
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Lexington, NC; Daytona Beach, ...
Originally Posted by mmc427ss
Tyler, make any progress on you problem?

As far as the VSS goes it's needed for cruise, and the ECM needs it for torque converter lockup. I can't say specifically whether the ECM needs it to manage the fuel and ignition timing but I think not. I do think a stick shift car doesn't need VSS.

Not familiar with the HDX box and tying the SES light into it. Would think that the ECM output for the SES is 5 vdc like all the other outputs from the ECM.
Bob


Hey Bob,

Haven't made too much progress yet. I did check my timing and it is still spot on, so much for an easy fix...My wife and I are closing on a house on the 21st so it may have to wait but ill finally have a garage to work in. My next step is to get the SES light hooked up and actually get the codes off and go from there. Thanks for the check up.


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1986 MONTE CARLO SS 5.7L 420,000 mi.
https://www.facebook.com/Bakersprsprt

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