1G ECU going bad?

[wranglerunner22]

Alright heres the deal.

Recently rebuilt my motor (just got the car), has 600 miles on it. Every once in a while I will go to start my car, it turns over and fires up just fine, no weird sounds, then when I let the key go to the on position it just shuts off? Also, after that happens, It is like it thinks its still on, you can somtimes hear the injectors injecting with the car off...
(I have only noticed this when it has been hot and humid, maybe has happened 3 times)

Also, I have been having some really bad idle surges Idle may vary between 750 and 1500 or more. I have done a blt, and blocked off the egr trying to narrow it down. My thought is that if I try a different ECU the surges will maybe go away?

What do you guys think?

 

[XiKeiyaZI]

Uh.. that's....odd.

 

[yoyo13131]

Alright heres the deal.

Recently rebuilt my motor (just got the car), has 600 miles on it. Every once in a while I will go to start my car, it turns over and fires up just fine, no weird sounds, then when I let the key go to the on position it just shuts off? Also, after that happens, It is like it thinks its still on, you can somtimes hear the injectors injecting with the car off...
(I have only noticed this when it has been hot and humid, maybe has happened 3 times)

Also, I have been having some really bad idle surges Idle may vary between 750 and 1500 or more. I have done a blt, and blocked off the egr trying to narrow it down. My thought is that if I try a different ECU the surges will maybe go away?

What do you guys think?

the ECU might be the problem with the weird injector problem, or bad wiring? (I'd take it out and open it up just to take a look), also when is your car surging? When it's dead cold, or warmed up? try squeezing all of your vacuum/emission hoses to see if one of them fix the problem. If it fixes the surging only while your clamping the hoses it might be your FIAV not adjusted properly/bad emission hose. or ISC motor not working properly/bad BISS screw o-ring/dirty throttle body or your timings off.

What kind of DSM?

 

[wranglerunner22]

the ECU might be the problem with the weird injector problem, or bad wiring? (I'd take it out and open it up just to take a look), also when is your car surging? When it's dead cold, or warmed up? try squeezing all of your vacuum/emission hoses to see if one of them fix the problem. If it fixes the surging only while your clamping the hoses it might be your FIAV not adjusted properly/bad emission hose. or ISC motor not working properly/bad BISS screw o-ring/dirty throttle body or your timings off.

What kind of DSM?

Should have been more detailed.

It is a 94 tsi fwd. 5spd.

Has vac delete too.

Tonight I will take the TB off and clean it, check the caps on the ecu ect..

Also, it surges when all the way warmed up. When its cold it seems to want to die if I hit the pedal to fast (I have to ease on the throttle.)

Uh.. that's....odd.

Yes trust me I was amazed the first time It happened.


Well I re-adjusted the throttle cable with the motor warm and that seemed to help(at the time). Then I ran around town in the Talon, came home and let it sit to cool down and try to start it again. Started it up, drove it to get it warmed up, same thing.

Then I went and replaced the plug wires, which did help quite a bit. Now the surge goes between 900-1200. I let the car idle for 20 mins and the idle kicked down to 500 once then popped back up.

The fishy part:

After all that I took out the ECU to check the caps, and none of the tops burst or turned colors or anything. But it looks like the cap closesd to the female connectors has leaked quite a bit. There is two dime sized spots on the board with the black crispy looking film on the board.

Think that is the next issue I should addresss?

 

[steve]

The fishy part:

After all that I took out the ECU to check the caps, and none of the tops burst or turned colors or anything. But it looks like the cap closesd to the female connectors has leaked quite a bit. There is two dime sized spots on the board with the black crispy looking film on the board.

Think that is the next issue I should addresss?

Get the ECU fixed or replaced, check that your IPS works since people tend to take off the TB ground strap, disabling the IPS, and check the coil resistances on the ISC.

 

[wranglerunner22]

Get the ECU fixed or replaced, check that your IPS works since people tend to take off the TB ground strap, disabling the IPS, and check the coil resistances on the ISC.

Where would there be a ground strap on the tb? Im at work so I cant really go see.

 

[Calan]

Where would there be a ground strap on the tb? Im at work so I cant really go see.

There should be a small metal strap that bolts to the top front IM stud and wraps over to the top of the TB. There should also be a ground wire from the back of the IM to the firewall.

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[XiKeiyaZI]

Yeah.. your engine bay is NOT a good example of where that strap is.

I mean... Look at it. It looks Zero-Vaccum ready...

 

[yoyo13131]

Should have been more detailed.

It is a 94 tsi fwd. 5spd.

Has vac delete too.

Tonight I will take the TB off and clean it, check the caps on the ecu ect..

Also, it surges when all the way warmed up. When its cold it seems to want to die if I hit the pedal to fast (I have to ease on the throttle.)



Yes trust me I was amazed the first time It happened.


Well I re-adjusted the throttle cable with the motor warm and that seemed to help(at the time). Then I ran around town in the Talon, came home and let it sit to cool down and try to start it again. Started it up, drove it to get it warmed up, same thing.

Then I went and replaced the plug wires, which did help quite a bit. Now the surge goes between 900-1200. I let the car idle for 20 mins and the idle kicked down to 500 once then popped back up.

The fishy part:

After all that I took out the ECU to check the caps, and none of the tops burst or turned colors or anything. But it looks like the cap closesd to the female connectors has leaked quite a bit. There is two dime sized spots on the board with the black crispy looking film on the board.

Think that is the next issue I should addresss?

Vac delete? Your surging still could be your FIAV not closing all the way when hot couldn't it? Making the AFM to rich at warm idle. I would get your board fixed also, might be causing the weird injector problem.

Also the ground strap on my car is behind the intake manifold connecting to the metal firewall in between clutch reservoir and throttle cable box.

 

[Calan]

Yeah.. your engine bay is NOT a good example of where that strap is.

I mean... Look at it. It looks Zero-Vaccum ready...

What does that mean?

 

[wranglerunner22]

I guess I should probibly mention I have a N/T throttle body. But I would guess it was still have the grounding strap huh?

 

[steve]

Yes, it should. The ground strap just connected the TB to the IM. The IM has to also be grounded to the firewall. If you don't have either ground you can just ground the TB to the firewall directly.

 

[yoyo13131]

I guess I should probibly mention I have a N/T throttle body. But I would guess it was still have the grounding strap huh?

Yes, I have a non turbo also and the strap is located here...
<br>
<img src="http://i85.photobucket.com/albums/k64/yoyo13131_88/DSCF1262.jpg" width="550" height="413"></a>

 

[wranglerunner22]

Alright so I just came in from messing with it.

I did not have a strap I guess.

First I put it on the IM and it didnt seem to help anything. Then I remembered the post I read here said you could just go from the TB to the firewall. I tried that, and It seemed to show some very good results. Still is running pretty rich, (burns your eyes when you stick your head by the muffler.)

I will find out what happens when I let it cool and run it again. I think my ECU is on its way to the shitter. This weekend I am borrowing one from a friend to see if that will help.

p.s. What am I going to do with all my free time once I get this figured out?!

 

[steve]

Yes, I have a non turbo also and the strap is located here...
<br>
<img src="http://i85.photobucket.com/albums/k64/yoyo13131_88/DSCF1262.jpg" width="550" height="413"></a>

That's the Intake Manifold ground but not the specific TB ground strap we've been discussing.
I don't see a place to attach it on a NT TB, it screws into the top of the Turbo TB but on the NT the bolts and stud nuts contact the TB directly and they should provide the ground if the IM is grounded.

On a turbo the TB is between two gaskets, and the bolts tighten on the intake manifold stay and the studs on the elbow so the strap is the only way it gets grounded.

 

[wranglerunner22]

I let it fully cool down and tried it again. It does seem a bit better. Do you think ignition timing could have gotten fugged up due to there not being a grounding strap?

Also, when I quickly press on the gas pedal it seems to want to bog down and die. When its cold in some cases it will die. Could this be from the timing being retarded?

 

[steve]

I let it fully cool down and tried it again. It does seem a bit better. Do you think ignition timing could have gotten fugged up due to there not being a grounding strap?

No. Your BISS adjustment could be but not your timing.
If you have any questions about the ignition timing, check it.

 

[pj91gsx]

you can somtimes hear the injectors injecting with the car off...

What do you guys think?

That sounds impossible because the injectors are triggered to fire when the cam angle sensor is spun. Could it be your IAC making a noise it sounds like a rattle.

 

[steve]

Normally, with a good ECU, the MPI relay turns off about 10 seconds after you turn the ignition off.
The injectors are powered from the MPI relay so they should also be off and without power they can't fire.

Check to make sure your MPI relay does turn off.

 

[wranglerunner22]

Alright I have good/confusing news!

I was just out in the garage messing with a bunch of stuff. The only way I could keep the car running and not die out was to turn the BISS out quite a bit.

Now, with the car able to idle(more like stay on without dieing) I started to unplug sensors to see if anything would help/worsen the idle.

Finally I decided to unplug the MAF? (The sensor plug on the aircan.)

And bam! Smoothe idle no misfire, I was able to turn the BISS down to where it is supposed to be, and it idled like a kitten. Also, I was able to step on the gas pedal and the motor would not bog down at all before the RPM's went up. Also, the check engine light came on! ( I wasnt sure if it worked or not )

So, I shut the car off and tried to restart the motor with the Maf unplugged, and it would not start. But if I pluged it in and screwed the BISS out alot I could get it to start. And then repeat from the top.

I have not replaced my ECU yet since I am still trying to get ahold of the guy. My theory is that the potentially bad ECU is sending a bad signal to the MAF(But not triggler the CEL??) Or the Maf is bad.

What do you guys think?

 

[yoyo13131]

With the MAF unplugged the ECU reverts to a programed default setting...it could be either your bad ECU causing this or your MAF isn't working properly.

Test your MAF by...
<img src="http://i85.photobucket.com/albums/k64/yoyo13131_88/Air.jpg?t=1278035343" width="700" height="506"></a>

 

[wranglerunner22]

With the MAF unplugged the ECU reverts to a programed default setting...it could be either your bad ECU causing this or your MAF isn't working properly.

Test your MAF by...
<img src="http://i85.photobucket.com/albums/k64/yoyo13131_88/Air.jpg?t=1278035343" width="700" height="506"></a>

So assuming the MAF is the sensor on the Air Can, would I check the resistance of the actual sensor on the aircan or on the engine harness?

I guess my only other question would be what sensor do I heat up? It doesnt really specify.

 

[BLINKY619]

There should be a small metal strap that bolts to the top front IM stud and wraps over to the top of the TB. There should also be a ground wire from the back of the IM to the firewall.

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i dont have any of those and my car runs fine..... i didnt know there should be a wire on the intake manifold...!!!

 

[wranglerunner22]

So assuming the MAF is the sensor on the Air Can, would I check the resistance of the actual sensor on the aircan or on the engine harness?

I guess my only other question would be what sensor do I heat up? It doesnt really specify.

Ok so I figured out what to do.

the magic number for cold is 1.39 and according to that wonderful illustration it should be much higher then that.

 

[wranglerunner22]

Update:

I kind of found out what makes my weird idle surge. (With the bad ECU) At idle, The ISC reading is 0. Then when I unplug the MAF the ISC reading goes to 58. Then Plug in MAF and goes back to zero. And somtimes with MAF plugged in the ISC will kick in. So the ECU must be mixing up the two signals.