My DSM is sick. Can you help?

I'm looking for a DSM expert here. I need a little bit of help with my Talon. If you can help, you'll become my hero. I want to try this site before I take her in for a diagnosis. Here's my story:

I've got a '91 Talon TSi 2.0 Turbo FWD. Recently, she's been acting pretty funny. She'll usually start up all right, but she idles 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.

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. 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 anyone can help, I promise to take them out for a beer when I make it to your part of the country.

Thanks for looking and thanks even more for replying.

Jon
jhieb1@hotmail.com

you can test the isc two ways

1. with an ohmeter get the resitantance or each coil it should be about 30 ohms each. there are four coils test between terminals 1-2, 2-3, 4-5, 5-6

the plug looks like this
________
| 1 2 3 |
| 4 5 6 |
---------- not done very well but u get the idea

or test it the easy but not always accurate way take it out of the car but keep the electrical connector connected then have a friend turn the key to acc then to on it should move in and out when the key changes

you can test the isc two ways

1. with an ohmeter get the resitantance or each coil it should be about 30 ohms each. there are four coils test between terminals 1-2, 2-3, 4-5, 5-6

the plug looks like this
________
| 1 2 3 |
| 4 5 6 |
---------- not done very well but u get the idea

or test it the easy but not always accurate way take it out of the car but keep the electrical connector connected then have a friend turn the key to acc then to on it should move in and out when the key changes

about the beer sorry ya can't take me for one im only 17 :( but u could buy my talon from me so that i can get a turbo :)

I neglected to add one bit of information that may have a bearing on this particular situation. The reason I bring this up is because it prompts another question from me. The car was involved in a front end collision that shoved the radiator into the turbo assembly. Before this accident occured, this problem wasn't there. I've searched everything I could think of, but all components seem to be intact. When the radiator support was pushed back, it was pushed violently against the air cleaner canister. Now, the air inlet that sucks air through the hole behind the headlight that's riveted onto the canister is bent and there is an obvious space between it and the canister. I doubt that that has any bearing, but it could be possible. Is there any particular component down near the turbo that could be causing the boost leak? Again, any help you could give would be greatly appreciated.

Thanks.
Jon

Also, do I need to check the upper and lower hoses coming off of the intercooler for leaks? I hate to sound dumb, but I haven't learned all that much about turbo charged systems yet.

Thanks again.
Jon

Quick update for anyone who cares. I think I've gotten to the bottom of the hard start problem. Pulled a plug and it was ridiculously black and sooty. Looks like the black smoke and unburnt fuel spitting out the tailpipe was caused by the car running too rich. Fouled the plugs out. I replaced them, and it fired up, no problem. But, it's still running crappy, so I still need to diagnose the turbo problem. I'm going to try and look for a boost leak tomorrow.

Question: Does a boost leak cause the computer to alter the fuel/air ratio? Would a leak cause it to run to rich? If not, how about the MAF sensor? It took a hell of a hit in the accident. If anyone can help with that, I'd appreciate it.

Thanks again.
Jon

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

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

you also have to plug the intake pipe into the throttle body

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

I'm not going to be updating this post any longer. It's rather old, and some people are getting upset about the presence of multiple posts about what is essentially the same problem. I am, however, going to keep three identical posts for the three types of cars that are essentially the same, those being the Laser, the Eclipse, and the Talon. So, if you have any questions for me or want to offer any help, can you post it to one or all of the following posts:

Laser: http://www.automotiveforums.com/vbulletin/showthread.php?t=231451
Eclipse: http://www.automotiveforums.com/vbulletin/showthread.php?t=231452
Talon: http://www.automotiveforums.com/vbulletin/showthread.php?t=231450

I appreciate you checking this post, though. If you've got any help for me, write it up on one of those other posts. I'll get it that way.

Thanks again for helping me.
Jon

Okay, we can close the book on my problems, once and for all. I've finally gotten my Talon back in working order. Turns out my problems were twofold. I ended up having a bad turbo and a bad ECU. Replaced the turbo first, and that got rid of the jerking. It was still running rich, though. Then, over the course of the last few days, I came to the conclusion that my ECU was shot. So, yesterday I pulled one out of another car and put it in. She started right up. So, I'm rolling again, and it's in no small part to all you guys that helped me out on this website. Thanks for everything. You guys saved me.

Jon