Idle surging with check engine light

[MrFiveSpeed]

Howdy all. I really wanted to just post and say "Hey, I'm new here, this is my car" and introduce myself without having to ask for any help, but we all know those kinds of things never work out, haha.

I just got my first DSM, a '91 Talon TSi AWD 5 speed, on Saturday. This morning I went to go to work and the car started and idled at 2000rpm, which was odd. I set off to work and about half a mile down the road, the check engine light came on. When I pulled up to a light, I saw that the engine was surging between 1200 and 1500rpm.

I read about the idle speed controller causing this problem, but that doesn't set a check engine light. I pulled the codes (using the multimeter method, since my datalogger doesn't work) and got 12 and 14...intake air temperature sensor and throttle position sensor. I pulled the plugs on the idle speed controller and throttle position sensor to see if it stopped the surging, but they had no effect. So I pulled the plug on what I think is the intake air temp sensor and that stops the surging, but the car is still idling at 1500rpms and smells like its running really rich.

I don't know if you guys need to know the engine mods done to the car to diagnose the problem...but the car has a JDM 6 bolt block with the balance shafts removed, an EPROM ecu with a Kyle T chip, 16g turbo, a Buscher Racing MBC (which I haven't touched) turboback exhaust with high flow cat and ported 2g exhaust manifold, and an Apexi SAFC, which I also haven't adjusted.

Really, I just can't wait to have the thing running right again...I've never driven anything like it. I planned to spend the day trying to figure this out on my own, but got called in to work. Any help you guys can offer would be greatly appreciated. Thanks a lot.

 

[Spln_Hrd]

i am pretty sure the 1st gens have the intake air temp sensor in the mafs.

put your multimeter in your tps and "sweep it" and make sure it gives you a smooth reading.

 

[ddavisaf]

If you have a CEL, shouldn't you go find out what it is first before you start ripping into the motor?

 

[VBGSX]

Welcome to the DSM community.
My first suggestion:
If you don't have it, go out and buy a Haynes manual for your year/make/model.
It will be worth it's weight in gold when you start looking into problems and such.

It sounds like you're handy with a multimeter. That's great because for your issues, it will come in handy.

I'll start with the ISC. Unplugging it will not alway affect or resolve your problem. The coils could short open or closed.
This is how you check it:
http://dmtalon.v8eaters.com/ISC.html

Now with your codes:
TPS check
http://www.plymouthlaser.com/tps.htm

I do not know how to check your intake temp sensor
I'll have to research that one myself
One thing you can do is swap your mass air sensor out with a known good one(Do you have a friend with a 1g).


***edit***
My haynes manual does show how to check the intake air temp. Mine is a 2g so the pinouts will be different. Go grab yourself a Haynes manual

Or if someone reading this has a 1g haynes manual, please help him out and put it on here.

...put your multimeter in your tps and "sweep it" and make sure it gives you a smooth reading.

Like ^^^ said, with the testing of the TPS, you'll be looking for for a smooth change on the Ohm meter as the throttle valve is moved. Make sure it's within it's limits also.
Good luck

 

[MrFiveSpeed]

I ended up cleaning the connectors on the TPS, ISC, and IAT, then unhooking the battery to clear out the codes, hoping that it would set the code again and I'd check to see if that there was only one. Instead, the car didn't set any codes and is running fine right now. Electrical stuff is weird like that...but I will still check the TPS and ISC to make sure they're good.

I would have ended up replacing one of them, but none of my local parts stores had any of them, and a Dodge dealer wanted $260 for the TPS, which they may or may not have been able to bring in from Boston the next day.

As far as a manual goes, I actually got the factory service manual with the car, though it would appear to be missing a book. Is the factory manual 2 or 3 books? I have 1 and 2.

The advice is greatly appreciated though. Thanks a lot.