Random Sudden Loss of Power

[XECLIPZEX]

Pretty much as the title states, I am having a random sudden loss of power. First though, a little background info.

The car is a 91 TSI FWD. I bought it from the original owner non running with 80k original miles. The car is 100% stock except for the free mods and the emissions being removed. Since I have had it I have replaced the following:
Upper and lower injector seals
New fuel tank (because the old one was FULL of rust)
Fuel filter
Evo IX fuel pump
Spark plugs
Water Pump
Timing and Balance shaft belts
All fluids
The ECU was bad when i got it so i pulled it out and replaced the caps in it, then it ran fine.

My problem started with just a little blip in power as I was driving. Other than that it ran fine. It would do this at random times. Then one day as I was coming back to work from lunch I started the car and noticed that the idle was really rough. (I have been battling idle surge with this car ever since I had it running with no luck in resolving it. The ISC checks out good, the fiav has beem disabled and there are zero boost leaks. Thats a problem in itself though.) Anyway, after I noticed the idle I decided to drive it back anyway expecting it to straighten out. It usually does. I start to pull out on the main highway and then the power just drops to nothing. RPMs fall to about 800-1000. I put the pedal to the floor and it revs to about 2500 and stops like its hitting the rev limiter. After setting for a minute it was fine so we continued on back to work with it. Took a few backroads to get back to the building and on one of them it happens again. This time im driving at about 50, I feel the car start to slow down and see that the RPMs are dropping again. Again I put the pedal on the floor and nothing happens. Then I start downshifting. Again nothing. It comes to a complete stop and the car is idling at about 800-1000 just like before. Press the pedal again and it acts like its on the rev limiter at about 2500.

Fast forward to recently. After towing the car home I let it sit for a couple months out of disgust. Then I gradually started driving it around closer to home. I have checked for boost leaks, there are none. I even swapped in a new ecu. It idled better and the problem didnt happen. I drove the car around for a while and it seemed to fix it, then I thought I would put the original ECU back in to see if I could replicate the problem with that one, nope. It hasn't had that same problem again but its started to have the blip in power like I stated earlier, before the full out loss of power happens. Like its building up to it again.

One last thing, before i put in new caps in the ECU it would do pretty much the same thing ecxept it wouldnt drive at all. It would just sit there and rev to about 2500 and stop like it was on the rev limiter. Other than this random problem the car drives great, and has great power to be in stock form. There are times I prefer driving it rather than driving my Evo but this little problem is ruining this car for me. Im sick of it and consider selling it all the time.

 

[Soccerguy136]

That sucks that it is such an intermittent problem.

Halfway through reading this I was actually about to suggest that you swap in another ecu and see if that fixes it. At least it sounds like it has a little.

Anyway, it sure sounds like an electrical issue is plaguing your car. The main suspect I would point to, after you have confirmed for sure that it is not the ECU, is the MAF. It could have a random short in it or one of it's wires and cause the car to go into limp mode and short out. Does the check engine light ever come one?

I'm just guessing, based on the rust problems that plagued your fuel pump and tank, that the car probably sat for a while. Unfortunately you may have to go through the engine/car and look for any suspect wires. Especially ground wires to the ECU/MAF/Main Grounds. Those are what I would go over to ensure that they are working.

Hopefully that new ECU has fixed your issue, but I would definitely still go over the grounds when I had a chance, and look for any loose or missing connections for that matter.

 

[XECLIPZEX]

I just swapped that ecu in there temporarily. It's back on the stock one now. I'm currently searching for a good one to swap in there though. If it doesn't fix my problem it will at least fix the idle.

 

[Soccerguy136]

Good luck!

It sure sounds like the New ECU is your solution though since none of the issue are present and the idle is fixed .

Why don't you leave it in the car instead of swapping the old one back in?

One last random thought. Does the car have cruise control? I was reminded of some ahem...Toyota...cough...issues when I re-read the first post. If you don't then disregard, but if you do, maybe the cruise control circuit in the ecu went bad randomly or something.

 

[XECLIPZEX]

The other ecu wasn't mine and yes the car does have cruise control. It wasn't active at the time the problems happened.

 

[Soccerguy136]

Yeah, I didn't really think the cruise control on these cars was able to override anything like that, but it was just a thought.

I was also referring to the specific circuit in the ECU going faulty, which again would necessitate a new ECU.

It is a random issue to be sure. Some of the soldering inside the circuits of the ECU could have gone bad, or some other random circuitry issue. I would definitely suspect that is your problem.

One last thought though, is a faulty wire somewhere, but unless you hit some bumps or something, I don't see why it wouldn't have happened again.

I, personally, would bank on that ECU. You should be able to find one pretty cheap on Ebay, the Classifieds, or a Donor car somewhere. Provided you didn't want an EPROM .

Good Luck and hope you get this figured out. Would be a shame to sell one with such low miles.

 

[XECLIPZEX]

Update:

I got a newer ecu and swapped it in there. It idles great and runs pretty good, however, in the upper RPMs it is cutting out. Almost like fuel cut, or a boost leak test. I did a boost leak test on it and found that the throttle body shafts seals are leaking. Everything else is fine though, no leaks. One thing I did notice though was that when I was performing the test I noticed that after a second or two the BOV came open and dumped air through the recirculation tube. This is the stock BOV and with the throttle plate opened. Could the BOV be the culprit? I have an extra SSQV that I could swap on there and see i guess.

 

[XECLIPZEX]

Another update. I never changed the bov, I left the stock one on there. I did change the fuel filter and spark plug wires. I also re gapped the spark plugs to the correct gap. The problem is happening right at partial throttle. It starts cutting out and sputtering. Anything above that and it runs strong. It will do this up to about 3500 or 4000. After that it acts like it hits fuel cut but like I said in an earlier post there is no boost leak except the tbss. Also there is no check engine light.

 

[mutters2Gspyder]

I'm Having The Same Problem. Idles Fine, No Boost Leaks, As Soon As I Give Her Gas, Like Barely Touch The Peddle Its Like Fuel Cut, But If I Push Through That And Give Her A Little More Gas She Just Wants To Take Off. And Right After I Let Off The Gas She Dies. 91 Gst Btw. No Idle Surge, Plugs And Wires Are All Good. I'm Lost.

 

[jared_gibbs]

You might consider pulling your injectors and cleaning them manually. If your tank was full of rust it's likely the injectors are clogged. Don't use injector cleaner that you would dump in your gas tank, it will not work. Pull your injectors and clean them. Use the 1.5v current from a AA battery to keep them open then flush them with carb cleaner. It only takes an hour TOPS to do all four; just as well rule them out. Be careful when installing to not ruin the plastic caps on the end. lmk if you need more info on this I'd be happy to help. It cheered my Talon right up. If you're tank was rusted I suspect this is the culprit. It explains crappy performance yet know CEL's.

 

[mutters2Gspyder]

I'm Guessing Your Talking To Both Of Us Jared? If So, I'll Get Right On IIt Cleaning The Injectors. I'm Willing To Try Anything

 

[XECLIPZEX]

You might consider pulling your injectors and cleaning them manually. If your tank was full of rust it's likely the injectors are clogged. Don't use injector cleaner that you would dump in your gas tank, it will not work. Pull your injectors and clean them. Use the 1.5v current from a AA battery to keep them open then flush them with carb cleaner. It only takes an hour TOPS to do all four; just as well rule them out. Be careful when installing to not ruin the plastic caps on the end. lmk if you need more info on this I'd be happy to help. It cheered my Talon right up. If you're tank was rusted I suspect this is the culprit. It explains crappy performance yet know CEL's.

You know that very well could be the problem. The gas tank was horrible. This is what the pump looked like after knocking some of it off.

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[Awd-laser]

EEEWWWW thats looks really bad.

 

[lasershark]

just a thought, but a laser that I had had either the same problem or one close have you checked you maf? mine was junk it idled like crap and on the highway it had the same issues

 

[mutters2Gspyder]

When I Purchased My Gst Not A Month Ago The Filter Around The Maf Was Not On It And In The Trunk. The Maf Was Touching The Frame Of The Car. Would That Short The Maf Out? I Don't Think It Was Making Any Contact With Any Of The Wires On It. ??

 

[lasershark]

When I Purchased My Gst Not A Month Ago The Filter Around The Maf Was Not On It And In The Trunk. The Maf Was Touching The Frame Of The Car. Would That Short The Maf Out? I Don't Think It Was Making Any Contact With Any Of The Wires On It. ??

No that will not short out the maf was the harness hacked? or is the harness still intact?

 

[jared_gibbs]

Dude I can guarantee it's your injectors. Your storyline went just like mine did. Pulled out on the highway and it bogged down like crazy. You were pushing a lot of fuel to accelerate to highway speeds thus accelerating the rate of debris lodging in the injectors. You may have jammed up your new fuel filter so be ready to replace that.

Now's a good time to replace your fuel pump. I got a Walbro 190 from thedsmgraveyard for $100ish, don't really remember. Make sure to use flare wrenches or you'll #### it up real quick. You could get a 255l if you intend to build a monster but I'm pretty sure you'll need a fuel pressure regulator. Also consider a fuel pump rewire. That should help to continue blasting all that crud out of there.

Clean your injectors weekly for a few months until you flush all that crap out of there. Probably not a bad idea to replace the fuel filter again at that point. Again, don't forget flare wrenches. I had a guy at Autozone tell me to use a butane torch to help loosen it up. If I have to tell you what a shitty idea that is you should sell me your DSM.

Good luck man!

 

[chris00326]

just a thought, but a laser that I had had either the same problem or one close have you checked you maf? mine was junk it idled like crap and on the highway it had the same issues

I have to say i agree. When the maf goes it can do alot of wierd stuff and make you think inhectors or a fuel problem. I suggest swapping it out for a known good one.

 

[XECLIPZEX]

Dude I can guarantee it's your injectors. Your storyline went just like mine did. Pulled out on the highway and it bogged down like crazy. You were pushing a lot of fuel to accelerate to highway speeds thus accelerating the rate of debris lodging in the injectors. You may have jammed up your new fuel filter so be ready to replace that.

Now's a good time to replace your fuel pump. I got a Walbro 190 from thedsmgraveyard for $100ish, don't really remember. Make sure to use flare wrenches or you'll #### it up real quick. You could get a 255l if you intend to build a monster but I'm pretty sure you'll need a fuel pressure regulator. Also consider a fuel pump rewire. That should help to continue blasting all that crud out of there.

Clean your injectors weekly for a few months until you flush all that crap out of there. Probably not a bad idea to replace the fuel filter again at that point. Again, don't forget flare wrenches. I had a guy at Autozone tell me to use a butane torch to help loosen it up. If I have to tell you what a shitty idea that is you should sell me your DSM.

Good luck man!

I've already changed the fuel pump. The stocker was dead so I cleaned the tank and used an old 190 I had. Obviously I didn't clean it good enough because it caused my 190 to scream like it was starving for fuel. So I swapped tanks, then put in an evo ix pump, then changed the filter. I also just recently changed the filter again. I guess last in line would be the injectors so I am going to clean them and see what happens.

I have to say i agree. When the maf goes it can do alot of wierd stuff and make you think inhectors or a fuel problem. I suggest swapping it out for a known good one.

If it was a problem with the maf wouldn't there be a check engine code? If it turns out to be a bad maf instead of the injectors clogged then I'm going to set my evo up for speed density and use the maf off of it. Also get new injectors and use the stock evo ones on the talon.

 

[mutters2Gspyder]

No that will not short out the maf was the harness hacked? or is the harness still intact?

No, The Harness Was Fine. Everything Was Intact. Only Thing Missing WA The Can Around The Filter.

 

[chris00326]

If it was a problem with the maf wouldn't there be a check engine code? If it turns out to be a bad maf instead of the injectors clogged then I'm going to set my evo up for speed density and use the maf off of it. Also get new injectors and use the stock evo ones on the talon.

No not always. when mine went out i had no cel. it was having a lot of the same issues as yours and i was thinking it had to be injectors or fuel pump but only after checking and finding nothing wrong with them i swapped my maf for a buddies good one and it fixed it instantly.

 

[lasershark]

If it was a problem with the maf wouldn't there be a check engine code? If it turns out to be a bad maf instead of the injectors clogged then I'm going to set my evo up for speed density and use the maf off of it. Also get new injectors and use the stock evo ones on the talon.

mine threw no codes or CEL either if I unplugged the harness from the maf the CEL would come on but it would idle a little better it would run low rpms without doing the sudden power loss as well, it didn't run good by any means but the sudden power loss stopped, definitely not a fix but a good thing to try around the block

 

[XECLIPZEX]

Another update. I cleaned the injectors finally. The problem still exists.