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Volkswagen Jetta, Golf, GTI: 1985-1992 (A2) Possible ECM problems, looking for confirmation.


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Last Post: Jul 10, 2010 5:28 PM Last Post By: JGr
rogueson

Posts: 4
Registered: 07/09/10
Possible ECM problems, looking for confirmation.
Posted: Jul 9, 2010 1:27 AM
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I have a 91 Jetta 1.8L Digi.

Car makes an attempt to start, hits near idle speed and dies, This all happens in about 2 seconds or so. We checked fuel from the pumps to the rail, all good.
Checked ISV, mass air, O2 and temp, replaced all except ISV with new, and that we have a working one sitting around we can test with. (it is on the car right now, but belongs to another, if mine isn't broken I don't need the expense)

We are getting fire to the plugs with no anomalies that we can find.

We checked Injectors and this is what lead us to look at the ECM. The injectors spray, the problem is they never stop spraying. I have no experience with this myself but it is my understanding that this can happen with a bad ground that takes out the ECM. We pulled the plugs after a round of trying to start it, sure enough, all fuel fouled. We have air, we have fire, we have far too much fuel.

Am I on the right track? Thank you in advance for the replies.
JGr

Posts: 67
Registered: 05/20/10
Re: Possible ECM problems, looking for confirmation.
Posted: Jul 9, 2010 11:20 AM   in response to: rogueson in response to: rogueson
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Do the following. I had same problem. Also once the car gets flooded from repeated attempts to start it will have to sit for a few hours.

This is how I solved this same problem

remove air filter housing and make sure its completly clean inside. Use garden hose to clean out. then make sure air filter is installed with no air leaking. Install air filter with housing out of the car. If air filter doesnt fit, get new one. make sure the hose coming from the manifold to the air filter housing has no leaks. check the fuel injectors and see if fuel is leaking on the intake manifold under the injectors. take out fuel injectors and clean or replace. check for vacuum leaks in all the hoses around the big rubber hose (from the air filter, the main hose) in back of the intake manifold. check the rubber hose on the idle air stablizer. The one with the elbows. check throttle body gasket. if there are leaks the car will haave starting problems. I never replaced the computer. disconnect and reconnect all electrical connections in the engine compartment. also same with relays inside car My car starts and idles perfect now.

Edited by: JGreene on Jul 9, 2010 11:47 AM

Edited by: JGreene on Jul 9, 2010 12:03 PM

Edited by: JGreene on Jul 9, 2010 12:09 PMI

Edited by: JGreene on Jul 9, 2010 7:37 PM
JGr

Posts: 67
Registered: 05/20/10
Re: Possible ECM problems, looking for confirmation.
Posted: Jul 9, 2010 11:42 AM   in response to: rogueson in response to: rogueson
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Also remove throttle body and clean out all dirt and residue from the round things that open and close. this prevents them closing easily. . also see if the fuel lines under the car by the fuel pump are tight. take out the fuel pump and clean the filter and spray screen and inside with carb cleaner. There is a fuel pump inside the tank with a screen also. remove the wire connector on the fuel pump and replace a couple times to make good connection. Also inside the trunk under the carpet is where the other fuel pump connector is, do the same. The book exlaines in more detail on this. I still have the same fuel pumps also.
rogueson

Posts: 4
Registered: 07/09/10
Re: Possible ECM problems, looking for confirmation.
Posted: Jul 9, 2010 5:23 PM   in response to: rogueson in response to: rogueson
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We have pulled both fuel pumps, checked them and the filters/screen. All clear.

The air filter is new and sits in the box well. Giving a general check of the area we have found no air leaks but I will take a look at all of the vacuum lines again just to make sure.

Everything from the filter box to the butterflies is clean, we made sure of this.

I also know that the car needs to sit after it has been flooded. We have been working on it for about a week now so have had quite a few attempts at starting it.

Thank you for the reply, I look forward to hearing more. I am hoping that we have missed something here, replacing the ECM is a bit pricey.
JGr

Posts: 67
Registered: 05/20/10
Re: Possible ECM problems, looking for confirmation.
Posted: Jul 9, 2010 5:42 PM   in response to: rogueson in response to: rogueson
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I also had to replace the coil several years ago. Also some of the hose leaks are hard to detect just by looking at them. The hose with the elbows were cracked and only leaked sometimes Have you taken out the fuel injectors? I had one bad injector and once I replaced this in addition to everything else solved problem. I never fooled with timing only replaced coolant sensor blue. Try replacing blue coolant sensor
rogueson

Posts: 4
Registered: 07/09/10
Re: Possible ECM problems, looking for confirmation.
Posted: Jul 9, 2010 6:53 PM   in response to: JGr in response to: JGr
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Yeah, we pulled the fuel rail to test the injectors. The first thing we did was set it up to watch how it sprays. You turn the key on and the computer never stops giving the signal to spray. Trying to start it they never stop spraying. In short, they never turn off once you turn the key on.

Coil, Hall sender, ICM, plugs and wires are all fine. We are getting spark just like we should be.

I have a roll of vacuum hose, we will replace all the small lines, then we will pressure check all the other lines for holes/cracks.

Oh, all the fuel injectors are good. They have good spray and when tested outside of the car they open and close just fine. This is why we started looking at the ECM. The injectors work, just what is controlling them is telling them to stay open all the time. So that should mean that either the ECM is fried or something is making the ECM want to keep them open.

Coolant sensor is new.

Thank you again.
JGr

Posts: 67
Registered: 05/20/10
Re: Possible ECM problems, looking for confirmation.
Posted: Jul 9, 2010 7:16 PM   in response to: rogueson in response to: rogueson
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What about the throttle position pontimeter or fuel relay. I read in the bookthat this throttle position pontimeter controls fuel output or something. maybe fuel relay bad
Not sure but maybe bad hoses. The rear smaller hose where it enters the big hose coming from the air filter housing and the hose with the elbows. Also had a fuel injector leaking fuel on top of the engine. cleaned the air filter housing with a garden hose

Edited by: JGreene on Jul 9, 2010 7:41 PM
JGr

Posts: 67
Registered: 05/20/10
Re: Possible ECM problems, looking for confirmation.
Posted: Jul 9, 2010 7:35 PM   in response to: rogueson in response to: rogueson
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what was the car was working then one day wouldnt start or stalled.
rogueson

Posts: 4
Registered: 07/09/10
Re: Possible ECM problems, looking for confirmation.
Posted: Jul 9, 2010 8:17 PM   in response to: JGr in response to: JGr
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Feul relay is good, pumps work as they should, all good on that end.

The mass airflow unit is new, just replaced two days ago.

Going to check all the vacuum lines when I have time to mess with the car, today suddenly got busy on me. With that ill check pretty much everything else between the air intake and the head for any leaks or bad lines.

The car was being used by an in-law, last I saw it was running fine. Now he calls me up and this is how it is. Switched him to the ol beater truck and when I get this running again I think ill drive it for work. It got decent gas mileage and I can let the lady of the house use the newer car full time.

Thanks again.
tcovenant2000

Posts: 1,802
Registered: 12/09/03
Re: Possible ECM problems, looking for confirmation.
Posted: Jul 10, 2010 10:52 AM   in response to: rogueson in response to: rogueson
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The easy answer is that the ECM is turning on the fuel injectors and leaving them on. Vacuum lines and such are items that need attention but they aren't related to this problem.
I'm no expert, but to my knowledge there isn't a mode in which they stay on all the time. They're pulsed. So it seems likely to me that the ECM either has a faulty ground or it's bad. These cars are designed to run even when things are broken. The three main devices that determine fuel flow are the MFC, the TPS and the O2 sensor. If one is broken the ECM will use the other two to try to keep the car running. I'm speaking generically here, not specific to VW.
You should grab the Bentley and do the electrical tests for the ECM.

Thomas
JGr

Posts: 67
Registered: 05/20/10
Re: Possible ECM problems, looking for confirmation.
Posted: Jul 10, 2010 5:18 PM   in response to: rogueson in response to: rogueson
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If I rember correctly when I set mine up when turning on the key to acc they put out a couple spirts then turned off. Does the fuel pump and relay stay on as well it must if your getting continious. something is thinking your going full throttle. Anyway would still start just idle fast.
throttle position must tell computer your accelerating. maybe throttle cable.
JGr

Posts: 67
Registered: 05/20/10
Re: Possible ECM problems, looking for confirmation.
Posted: Jul 10, 2010 5:28 PM   in response to: rogueson in response to: rogueson
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Bad momentary relay, bad wire at the computer, In the book talks about what controlls fuel. Do the computers go bad. Try connecting and reconnecting wires. I reconnect all connections including computer. A lot of water gets around maybe bad connection.

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