Idling/ stalling, no pedal response, weird ecu readings

[ike84]

Originally Posted by ecp

I ran a hardwire from the MAF ground to chassis. Throttle body initialized, car fired right up. Smooth sailing from here? I’ll have to attach it properly but this seems promising. Breathed a sigh of relief when it started.

NICE!

Damn mice....

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[blue62]

If you go back to my first post to you.....
a possibility of a common ground issue was mentioned..
These cars have different 14 ground points...
I see you got it fired up by running a jumper ground to the MAF.
I think the MAF grounds via the ECU but I am not positive.
The MAF is also two sensors in one.....
One measures air temp. the other measure air mass.
I do not know if they both ground via a common ground or not.
A wiring diagram would show you.
If the MAF does ground via the ECU you have and ECU ground issue.
If you have a ground point issue chances are your going to have further issues with the car.
You need to go through your ground points and the ECU ground point to avoid that possibility.

[ecp]

Originally Posted by blue62

If you go back to my first post to you.....
a possibility of a common ground issue was mentioned..
These cars have different 14 ground points...
I see you got it fired up by running a jumper ground to the MAF.
I think the MAF grounds via the ECU but I am not positive.
The MAF is also two sensors in one.....
One measures air temp. the other measure air mass.
I do not know if they both ground via a common ground or not.
A wiring diagram would show you.
If the MAF does ground via the ECU you have and ECU ground issue.
If you have a ground point issue chances are your going to have further issues with the car.
You need to go through your ground points and the ECU ground point to avoid that possibility.

The diagram shows one ground wire from the MAF so I’d assume they both share that ground. It also shows it grounds via ecu. I’m not sure if the ecu has a ground that goes to to chassis in which all are connected or what. I do have continuity from ecu harness and maf ground but I will check the resistance and try tracing the wire to make sure it is fully in tact tomorrow. It may be a bandaid fix but if it can make it to the body shop I will be thrilled. Could still be totaled out by insurance….. got my work cutout for me tomorrow.

[blue62]

Originally Posted by ecp

The diagram shows one ground wire from the MAF so I’d assume they both share that ground. It also shows it grounds via ecu. I’m not sure if the ecu has a ground that goes to to chassis in which all are connected or what. I do have continuity from ecu harness and maf ground but I will check the resistance and try tracing the wire to make sure it is fully in tact tomorrow. It may be a bandaid fix but if it can make it to the body shop I will be thrilled. Could still be totaled out by insurance….. got my work cutout for me tomorrow.

I forgot all about your insurance.... totaled or not totaled out situation.
So your bandaid fix makes more sense at this point.
If there are circuits that get their ground via the ECU then the ECU has to be grounded to the chassis in some way.
ECU ground issues are not that uncommon.
If you go to youtube and look up scannerdanner he has some video's on diagnosing the issue.
He is a very good source of diagnostic information.

[ecp]

Originally Posted by blue62

I forgot all about your insurance.... totaled or not totaled out situation.
So your bandaid fix makes more sense at this point.
If there are circuits that get their ground via the ECU then the ECU has to be grounded to the chassis in some way.
ECU ground issues are not that uncommon.
If you go to youtube and look up scannerdanner he has some video's on diagnosing the issue.
He is a very good source of diagnostic information.

Thank you, I got a ground cable working, some weird stuff is going on. Looks like only part of the MAF is working properly. I get airflow and intake temp readings but on my durametric hot film MAF reads 0v and there’s a stored code inside.

[blue62]

I am unsure why the Durametric shows Hot film type MAF data when hooked up to our cars.
Our cars use A Hot wire type MAF. not Hot film type
So 0v on the Hot film data "may be" what you want to see.
Just depends on how the Duramatic software is set up
I have always disregarded the hot film data and just looked at the other MAF data.
If your getting air temp. data and Mass Air flow data then both parts of the MAF are working.

[ecp]

Originally Posted by blue62

I am unsure why the Durametric shows Hot film type MAF data when hooked up to our cars.
Our cars use A Hot wire type MAF. not Hot film type
So 0v on the Hot film data "may be" what you want to see.
Just depends on how the Duramatic software is set up
I have always disregarded the hot film data and just looked at the other MAF data.
If your getting air temp. data and Mass Air flow data then both parts of the MAF are working.

Got everything buttoned up and she drives great!!!! New pedal is so much smoother and feels like it has much more travel. Feels great. I checked everything after filling up and driving around for a bit and the ecu is adapting and adjusting fuel trims properly. Everything looks normal and functioning well.

One note about the wire, I initially tried grounding the wire to one of the ground points on the front of the engine block, however, I noticed it wouldn’t run smooth on that ground, and there were stored codes still. I changed the ground point to the chassis. There’s a bolt hole in the body right near the MAF so I grounded it there using a bolt. Reset everything and calibrated throttle and it started up and ran flawlessly.

I don’t know if I’ll end up with this car, I sure love it to death. Considering it’s got 140k miles I might just leave the bandaid fix until it blows, or maybe it’ll go for another 50k miles who knows. Either way, I’m glad I could sort the issue in time, and can drop it off and enjoy my trip. A lot of blood sweat and money in this thing.

[ecp]

surely not everyones cup of tea, but man was I proud. full colored ppf wrap done myself. only had it for a month before the car got hit. Do you guys think it's worth trying to keep? so many new parts all new suspension, lots of engine work, relatively new clutch, 987 custom seats full power and heated, cruise control and Bose sound with upgraded amp and speakers, new transmission, big sway bars, borla exhaust. I just wouldn't be able to replace it for whatever insurance would pay I'm sure. or I could save my pennies for a 996.....

[Gilles]

Only you know how much money and effort has been put on this car, I don't know the extent of the damage but perhaps is best to let the insurance company write off the car, and then buy it back from them..

With the money left, you can start saving for a 987BS, after driving the 986 you would not like the 996.. yes it's bigger but that's it..

[ecp]

Originally Posted by Gilles

Only you know how much money and effort has been put on this car, I don't know the extent of the damage but perhaps is best to let the insurance company write off the car, and then buy it back from them..

With the money left, you can start saving for a 987BS, after driving the 986 you would not like the 996.. yes it's bigger but that's it..

It’s minor damage. Need new hood and bumper cover. A lady backed up into me in a drive through. The trailer hitch hit the front of the hood and it buckled. It’s all bowed up. Pushed the frunk in about a quarter inch where the hood latch is. The work on the tub is what I think will total it. Ballpark 6k repair bill. Since I’m not at fault and have a police report I’d like them to handle it. However if they’re not going to give me anything for the many thousands in parts I have on the car then I will fight as much as I can. I know book value is about half of a decent 986 these days without the kind of work I’ve done to mine. A the end of the day fixed or not it’s a rolling total, but man it sure does drive perfect. Except for when it breaks.

[ike84]

Dude, I remember your car now... You posted pics after the wrap and a bunch of ****************************s gave you **************** about the matte black, right?

I think it's a sweet car myself. Not factory, but very sharp and very unique. That's what custom stuff is all about!

I would take the insurance money, patch her up (you're clearly skilled), and see how much longer she will go. Yes, things will continue to break. Id be curious about a compression test - 140k miles is a lot for any gasser.

Blue is right about the ecu grounding comments - the ecu itself is grounded but it monitors the voltage on the ground to serve as a reference for the grounds that feed into it. That way, sensitive electronics (maf sensors included) that have small variations in their signal voltages due to electrical fluctuations can be "sorted out" by the ecu. It's kind of like running a ****************ty pic through a filter.

However, for the maf sensor, it really doesn't matter too much. In open loop fueling the dme ignores the maf altogether, and in closed loop fueling the narrowband o2 sensors trump the maf input. Sure, the maf readings do matter, but only so that the ecu can ballpark the conditions onto the fueling maps. If it's completely out of whack then it will cause issues, and that is why you saw trouble when you were grounded to the block - there is way too much electrical interference there. But grounding to the chassis is more than likely good enough for just driving and enjoying the car.

Never forget... The enemy of good is better

Sent from my SM-N975U using Tapatalk

[ecp]

Originally Posted by ike84

Dude, I remember your car now... You posted pics after the wrap and a bunch of ****************************s gave you **************** about the matte black, right?

I think it's a sweet car myself. Not factory, but very sharp and very unique. That's what custom stuff is all about!

I would take the insurance money, patch her up (you're clearly skilled), and see how much longer she will go. Yes, things will continue to break. Id be curious about a compression test - 140k miles is a lot for any gasser.

Blue is right about the ecu grounding comments - the ecu itself is grounded but it monitors the voltage on the ground to serve as a reference for the grounds that feed into it. That way, sensitive electronics (maf sensors included) that have small variations in their signal voltages due to electrical fluctuations can be "sorted out" by the ecu. It's kind of like running a ****************ty pic through a filter.

However, for the maf sensor, it really doesn't matter too much. In open loop fueling the dme ignores the maf altogether, and in closed loop fueling the narrowband o2 sensors trump the maf input. Sure, the maf readings do matter, but only so that the ecu can ballpark the conditions onto the fueling maps. If it's completely out of whack then it will cause issues, and that is why you saw trouble when you were grounded to the block - there is way too much electrical interference there. But grounding to the chassis is more than likely good enough for just driving and enjoying the car.

Never forget... The enemy of good is better

Sent from my SM-N975U using Tapatalk

Haha fortunately I’ve never posted my car and had any smack talk about it. Seems like the car will be able to be fixed and not totaled out. Bill is $6300 but covered by insurance. I’m planning on just driving it like I have been, it’s been a good car with a few hiccups here and there. Needs some rear wheel bearings and the rims have been bent which has been bugging me so I’ll want to sort that out. Maybe some 18 inch turbo twists would look cool.
I did a compression test like two years ago and if I remember correctly it was 160-165 psi all the way around with the throttle plate closed which from whatever I was reading at the time looked good.