Turbo and idling woes.

[JohnnyWadd]

Got serious 1G DSM troubles, and I was wondering if anyone smarter than me could help me out. Here's what I've got; it's a '91 Talon TSi 2.0 Turbo FWD. A little while back, I was involved in a front end collision, and the front end got pushed back into the engine. She's only been acting funny since I crashed, which would lead me to believe the problem is related to that. She'll usually start up all right if she's been sitting for a day or two, but sometimes, she'll idle eratically. I mean VERY eratically. When I start driving her, she runs fine, as long as I don't lay heavily into the accelerator. If I lay into it, she bogs down badly. The key here is that this happens whenever the turbo guage gets above zero pounds of boost. Whenever it gets above manifold pressure, the car starts to jerk really bad. The best comparison I can make is the way a car jerks when you've got an inexperienced driver trying to learn to drive stick. As long as I keep the turbo guage below zero, I can accelerate as high as I want with relative smoothness. The second the turbo guage jumps above zero, the jerking starts again. Every once in a while, the symptoms will change. It's not that common, but sometimes instead of jerking and lunging when the turbo kicks in, the turbo won't even kick in at all. Well, barely, anyway. When I accelerate, the turbo guage stops at about 2 or 3 pounds of boost and will go no higher. When I'm driving, she runs fine, just no boost.

Whether it's jerking and lunging or not kicking in at all, after the car warms up, idling becomes a bigger problem. When I've been driving for a while and I come to a stop (like at a traffic light), my car won't stay running. Additionally, it's hard to start when I try to restart her, often times not firing until I push on the gas pedal.

One final thing of note and I'll stop this book. Sometimes when I've had her running for a while, but shut her down for an extended period of time (like maybe an hour or more), I'll try to start her and she doesn't want to run at all. She'll fire, but die instantaneously. Nothing helps this, except persistence. Feathering the gas doesn't make her run. If I keep the starter engaged, which I know is a horrible thing to do to a starter, she'll run, but dies as soon as I disengage it. In addition, she spits black smoke and some sort of nasty black liquid (I'm guessing unburnt fuel) out of the tailpipe onto the ground. After being persistent and restarting her dozens and dozens of times, eventually, she'll run, but then she runs like shit, doing what I told you about above.

Guess I'd better add one more thing that may or may not have bearing. In what is probably an unrelated problem, I recently replace the ISC motor. It was chattering like a chipmunk to me, and since I've got a parts car, I just swapped it over. The problem I'm having was there before I swapped parts, and it's still there after. So, I doubt the ISC is the problem. I guess it's possible that the one on the parts car was bad, but I'm doubting that that's the problem.

If anyones got any ideas for me, I'd be forever in your debt. Any help you can give will be greatly appreciated.

Thanks a ton.
Jon

P.S. By the way, I've already posted a thread before about these symptoms back in March. If by chance you already replied to that one, you can ignore this one unless you've got some more ideas for me.

[JohnnyWadd]

Here's another update. I did a lead check on the turbo system last night. Haven't checked the MAF sensor as of yet. That's my next order of business. Wanted to ask a question before I move on. I wasn't able to check all of the lines in the turbo system for leaks. Reason for this was because I couldn't get the system to pressure up long enough. I've never done any of this, so I'm not sure what's supposed to happen. Whenever I'd pressure the system using my air bubble, I'd hear a hiss from the valve train for about five seconds. Then, all of the pressure would be gone. If I took off the oil filler cap, the noise would get louder.

Now, I'm not sure what this means. I'm guessing that what I'm hearing is the air leaking into the cylinders through whichever valves are remaining open when I shut the car off. Is it supposed to do this? If not, what can I do to stop this?

Thanks again to all who read this. Any help I get is greatly appreciated.

Sincerely,
Jon

[JohnnyWadd]

Sorry, guys. Should've clarified just how I tried to pressure test the turbo system. I took off the outlet hose (the one between the turbo and the intercooler) from the turbo system and put a PVC cap in the hose. I drilled a hole in it and put a valve stem in it. I used an air tank to pressurize the system. I wasn't able to check the hoses, intercooler, BOV, and the like for leaks because I couldn't get the system to stay pressurized. Within seconds, I'd lose whatever pressure I put into the system through the valve train. I could hear the hiss for a few seconds from under the valve cover, and it got louder when I removed the oil filler cap. Not sure why this happened. I'm guessing that I lost the pressure through the valves that were open when I shut off the car. But, is this supposed to happen? Like I said, I'm new to this and I've never done anything like this before.

Thanks again, fellas!
Jon

[kjewer1]

It should hold pressure for some time, long enough to spray soapy water around. If it doesnt you have a leak. I suppose the motor could have stopped where one cylinder was in the overlap phase and all 4 valves were slightly open, but thats unlikely. Turn the motor over some and try again. If you still think its leaking past a valve (could be the sounds playing tricks on your ear too, I can never tell where the sound is coming from in the engine bay), do a compression test.

I'm sticking with intake leaks on this though... Good luck.

[JohnnyWadd]

Okay, guys, time for a further update. I came to a revelation last night. So, today, I'm putting the boost leak check on hold. Remember when I said that after I changed the plugs, I got her to run, just not very well? Well, last night, I started her and tried to take her for a spin. I couldn't get her to go anywhere. She would not stay running. So, I took the suggestion of more than a few people and I disconnected the Mass Airflow Meter (the one in the air cleaner cannister). While I was at it, I disconnected the battery for a few minutes to reset the computer, thinking maybe that would reset the fuel/air mixture. When I reconnected the battery and started the car, it ran. Not very well, but it ran. So, I'm thinking, "Cool. I just reset the fuel air mixture", and took her for a spin, albeit a very rough spin. I drive a few blocks, then pulled over to reconnect the MAF Meter. I popped the hood and reconnected the plug, then tried to restart her. I was right back where I started. She wouldn't stay running at all. She'd fire and die instantly. So, I disconnected the MAF Meter, and drove her back home.

Here's another oddity of that situation. I replaced the Idle Speed Control a couple of months ago because it was chattering at me like a chipmunk when the key was on but the car wasn't running. I was thinking that was the reason that she was running so crappy. That didn't fix the problem, though. The new one I put on still chatters. Well, I hadn't noticed at the time, but last night when I disconnected the MAF Meter, the ISC stopped chattering. When I plugged it back in, I noticed that the chattering had been gone and came back when I plugged the MAF Meter back in. So, after a series of disconnects and reconnects of the MAF Meter, sure enough, whenever it was unplugged, the ISC was quiet. Whenever it was plugged in, the ISC went crazy.

So, what does that sound like to you? MAF Meter's bad, right? Couldn't just be caused by a vacuum leak, could it? I'm going to alleviate any possibility of that tomorrow. I'm going to go buy a spool of vacuum line and replace all of them. Not just because it's running bad. After 13 years, I'm sure it'll do the car some good. I'm going to go to my donor car today and grab the MAF Meter off of it. Not sure if that'll fix it, though. The reason I say that is because the outer housing of the air cleaner cannister on the donor car is missing. So, that MAF Meter has been blowing in the wind for God knows how long. I'm sure that one's bad. But, for free, it can't hurt to give it a go. If anybody has any other ideas for me or wants to confirm my suspicions, I welcome any comments. I'll keep you posted as to what I come up with.

Thanks for everybody's help.
Jon

[JohnnyWadd]

Okay, in part, I feel like I'm right back at square one. Remember what I wrote about thinking that maybe the MAF Sensor was bad? Well, I changed it up with the one on my donor car, and not a thing changed. So, I'm wondering if that's even the problem. I'm not ruling it out yet, though. Who knows if the one I replaced it with is even working. See, as I said before, the outer housing of the air cannister was missing, so who knows if that other one got knocked around or not. It might be bad as well.

So, my next order of business was to change all of the vacuum lines. Well, most of them, anyway. I replaced most of the small ones, but not any of the larger ones yet. I replaced all of the ones that run from the two little vacuum motors near the master cylinder to the throttle body, temperature switch / sensor, and whatever that vacuum cannister is below the battery. Haven't yet replaced the ones on and around the air cleaner housing and the turbo system, either. Pretty sure those are holding up, though. I'll tell you why I think that in a second.

Came to a question while I was changing the lines, though. There are splitters on the vacuum lines coming from those two vacuum motors near the master cylinder. I'm not sure if I hooked up the lines after the splits in the same spots that they were in before. Does it matter if you flip-flop the lines that run to that vacuum cannister below the battery and the throttle body?

So, anyway, I haven't tried to start her since I replaced the vacuum lines. Instead, I decided to commence on another attempt at a turbo system leak test. Went about it a little differently this time, though. I went and got more hose and built the attachment to put on the turbo inlet. I took the entire air cleaner cannister assembly out, so the lines that hook up to the big hose between the MAF sensor and the turbo are all open, those coming from the valve cover, intake manifold, and BOV. That doesn't hurt anything, does it? Shouldn't, since I also disconnected the hose that hooks to the throttle body and blocked that with a PVC cap. Finally, I also blocked the vacuum hose that hooks to the little vacuum motor on the air cleaner cannister. That's why I said before that I think that they're holding up. They didn't leak when I gave the system a shot of air. Now that I was ready, I pressurized the system.

It was recommended that I put as much pressure in the system as it runs normally, and to determine this by watching the guage. Well, I didn't have someone who could watch the guage for me, so I had to do it on my own. I'd pressurize the system just to the point where the BOV would release the pressure. If I went to the car to check the guage, I was never able to make the guage move. Not sure where the guage reads it's pressure from, so I'm not sure why that was. The guage works normally, it just didn't seem to be when I'd fill the system with my air tank.

I did hear a leak, though. Problem is, I can't find it. It was a steady hiss, and it let the pressure out rather fast. I wouldn't go so far as to call it a "woosh", just a noticible hiss. Once the BOV would vent and I'd stop adding pressure, it would take about 10-15 seconds for the hiss to stop. I tried the soapy water trick, but still couldn't pinpoint the leak. It seems to be coming from the back side of the turbo, somewhere below the exhaust manifold. This would stand to reason, since everything got shoved into the turbo in the accident. I can hear hear the leak, just can't see it. Can anyone give me any ideas as to what, if anything, would leak from the back side of the turbo? How about point me to a diagram of the inner workings of my particular turbo so that I can get an idea just where to look?

By the way, I'm thinking that the air I was losing into the valve cover from my first attempt at leak testing was coming in through the PCV valve. I've never replaced it in the the time I've owned the car.

Here's another thing that might be of issue. Remember when I mentioned that the ISC motor was chattering? Well, every once in a while, I hear some other sort of chattering noise as well. This time, it comes from the two little vacuum motors near the master cylinder. One or both of them gets pretty cranky every now and then and isn't afraid to let me know it. I'm sure all of this is related. Any idea what would cause that?

Finally, is there any way to check the little vacuum motor that sits on the top of the air cleaner cannister? I broke one of the vacuum tabs off of it when I was taking the car apart after the accident. So, I put a used one on it. Doubt that's causing any trouble, but it'd be nice to eliminate it as an option.

So, what do you guys think? I'm still thinking that the hiss I found while leak checking would be the problem. I also realize that even though I put a different MAF sensor and ISC motor, but since both were used, it's a distinct possibility that one of them is still not right. Let me know what ideas you have. I'd love to hear them.

Thanks again for any help you can give.
Jon

P.S. I've been asked as to whether or not I have any modifications on my car. That answer would be "no". She's all stock.

P.P.S. Sorry to be so long winded. Didn't want to leave anything out, though.

[JohnnyWadd]

One more stupid question... What does it mean to LOG your car? I'm sure I'll feel stupid once I find out the answer to this question, but I can't figure it out on my own. So, if anyone can answer this, go ahead and make me feel dumb!!

Jon

[JohnnyWadd]

Okay, I'm going to resume my crusade to find the source of my turbo lead test hiss. Hopefully I'll find it. I'm thinking that the turbo housing itself is the culprit, but won't know for sure until I keep digging.

I have a few questions, though, and I was wondering if anyone could help me out. Here they are:

Can the turbo itself be pressure checked by removing it from the car?

If the turbo turns out to be the problem, can somebody recommend a good place to either get a turbo reconditioned (I'll rebuild the one on the donor car) or to purchase one that's already reconditioned?

Is turbo overhaul a difficult task? Would it be something that a guy who has above average knowledge about cars in general but well below average knowledge about turbo systems (that'd be me)?

Thanks for your help, guys!
Jon

[kjewer1]

99% of the time the turbo is fine. To rule it out, simply install your tester right after the turbo. Just get creative with the tester and associated couplers. If the test results are the same, the turbo is fine.

To be honest, there is WAY too much there to read. I hope you make some progress with the leak test

[JohnnyWadd]

Okay, I think I've drawn my final conclusion as to what is ailing my car. What I want is to present this conclusion to you all and see if you agree with my assessment. If you think what I'm saying is feasible, tell me. If you're thinking I'm off my rocker, tell me that, too. I'm about to commence on some semi-intensive labor, and I'd like to do so with confidence. So, let me know what you think.

First off, let me see if I understand things correctly about the inner workings of a turbo charged Talon. As I understand it, there are two sides to the turbo charger of my car. There's the exhaust side and the intake side. I also understand that there is a shaft inside of the turbo that extends from the intake side to the exhaust side with an impeller on either side. The impeller on the exhaust side is turned by the exhaust gases, which turns the impeller inside the intake portion of the turbo. This forces air through the turbo components into the throttle body.

Now, as for the Idle Speed Control and the Mass Airflow Meter, they work together with the car's computer to supply the correct fuel / air mixture to the engine. The MAF Meter reads the amount of air going into the turbo and relays this information to the ECU. The ECU takes this information and decides how much fuel to supply the engine with. The ECU then tells the ISC motor how much fuel to let through, and the plunger on the ISC motor moves accordingly.

Now, throw a boost leak into the scenario. The way I understand it, if there is a boost leak, that changes the amount of air in the system. The MAF doesn't know that air is being lost downstream, so it's telling the computer how much air is coming through and how much it thinks is in the system. But, this is incorrect information. So, the computer is now dumping a certain amount of fuel into the mix based on bum scoop from the MAF Meter. So, since air is being lost, too much fuel is present in the fuel / air mix. This makes the car run horribly bad and now the computer doesn't know what in the hell to do to make it run better. So, now it starts scrambling to try and fix what's wrong. That's why my ISC started going crazy - because the computer didn't know what else to do.

So, I'm thinking that I have a boost leak. That's what most people have been telling me all along. So, I did my leak test as I told you before. My turbo system won't hold any pressure, and I can hear a hiss for about ten seconds from somewhere around the turbo housing. I tried to soapy water test and found nothing. My original thought was that the leak was on the back of the turbo, and try as I might, I just couldn't see it.

I've got a new theory, though. I'm wondering if maybe the reason that I can't see the leak is because it can't be seen from the outside. That shaft inside the turbo has got to be sealed somewhere. I'm thinking that maybe that seal is shot and the leak that I hear is the pressure from the intake side leaking through that seal into the exhaust side inside of the exhaust system. Of course I wouldn't be able to see that.

So, here's what I want to know. If I pressurize my turbo system from the inlet of the turbo and cap off the system at the end of the hose that runs to the inlet of the throttle body, should it stay pressurized until I let the pressure out? Well, within reason, I mean. I realize that it wouldn't stay pressurized forever. I'm not supposed to lose air anywhere, right? At least not as rapidly as I am. So, I ask you this: does it sound like the seal inside of my turbo is shot, and that's what's letting out the pressure from the turbo system? Does it sound like I need to pull the turbo out of my car and put in a new one? Can I pull it out and pressure test it on a work bench and test that theory? If anyone can answer these questions for me, I'd be forever in your debt.

Thanks again for reading my stuff. I couldn't have gotten this far without you guys.
Jon

[kjewer1]

The ISC controls how much air bypasses the TB, and has nothing to do with fuel. It allows the ECU to have control over idle speed by changining how much air gets by the TB.

It is also common for the turbo seals to leak a bit when the car is off. When the car is running and yo have ~80 psi of oil pressure behind the seal, 20 psi air pressure isnt going to get by If you want, try rigging up the tester on the lower intercooler pipe, rather then the compressor inlet. See how that works.

[JoeWagon]

Exactly what Kevin said.

The ISC lets air into the intake manifold for idle, because the TB is closed. If it wasn't there, the car wouldn't idle. The motor is what controls how much air goes through, just like your throttle cable controls the TB. If the motor is bad, too much or too little air goes into the engine, or in any combination/sequence of both, and causes a high/weird/wrong idle.

If you think your turbo seal is bad, connect the same pressure tester to the lower intercooler piping to eliminate the turbo altogether. If you STILL have a leak, it's most likely not the turbo. If there is no leak, it is the turbo (I doubt this will be the case). Good luck

[JohnnyWadd]

Well, guys, for any of you who care, I think I can stamp the official seal on my assessment that my car has a leaky turbo. Got lots of feedback from people over these past couple of weeks telling me what I should and should not check. The most popular consensus was a boost leak. So, I finally got the system to pressurize, and that's when I started to hear a hissing noise from somewhere near my turbo housing. Heard lots of naysaying about that, though. Apparently, it's not very common for turbo housings to leak. So, I eliminated all other possibilities. I constructed the leak tester with the PVC cap, valve stem, and section of hose and hooked that to the turbo inlet. Then, I constructed another one, minus the valve stem, and blocked the turbo outlet. I'd pressure her up, and the hiss was so obvious. Nothing else it could be except a leak on the turbo somewhere. I'm 99.9% positive that the hoses I made aren't the problem, so the turbo seems to be my only option.

So, here's my plan of attack: Unless someone tells me in the next 24 hours that this is a stupid idea, I'm going to pull the turbo. Don't see any other option. Even if it doesn't need to be replaced, something needs to be fixed. I don't see any other option than to pull the turbo off of the car. If anyone else has any ideas for me, don't be afraid to tell me. Also, if you think that I'm doing the right thing, words of encouragement help as much as the contrary.

So, here's my question, now: If I were to install a different one, how stupid would it be to get one off of another car, like at a salvage yard or off of someone's parts car? Replacement turbos are pricey, are they not? I'm not exactly sure, as I've never priced one before. Only going off of what others have told me. If a used one would be suicide, can anyone recommend a good place to go to find a good stock-replacement turbo. I'm not looking for any aftermarket performance turbo. This car isn't my toy. I've got a '68 Camaro for that. This one is my cool sporty car that's an everyday driver for me. I don't need to hop it up. Not yet, anyway. If you know a place to get a good, stock-replacement turbo for a reasonable price, let me know. I'm open to all suggestions.

Thanks again for all of your input, guys. I appreciate it like you wouldn't believe.

Jon

P.S. Is it possible to test a turbo while it's off of the car? If I get a used one, I want to know if it works.

[kjewer1]

I Cant even remmeber what year car you have. If its a 2g you can pick up used T25s from 75-150 bucks, and for 1g you can get good 14Bs for 150 bucks. Buying from a DSMer that has upgraded before his turbo crapped out is often the best way to go. I have a local club that had a good supply of used T25s for me for good money. A junkyard turbo can certainly be risky... Buying off the trader can be risky too though...

[JohnnyWadd]

1991 Talon Tsi FWD

That's be a 14B Turbo, right?