unstable tps reading

[AHALLA05]

Well i decided to get back into dsm`s hoping to have better luck the last time but within a week of buying my new talon im having problems already. Bad throwout bearing, boost leaks everywhere,.....and now the dreadful idle surge/ not idling at all. Ive searched the forms many times looking at the possible causes and tried fixing each one. everything checked out ok yet it still idles like crap.I decided to hook up my logger and log a run the other day to notice that the tps was jumping all over the place at wot. I tried again and again even using two feet on the gas to get it at a steady reading. but nothing worked. i checked it with the car off and putting my foot to floor, held the throttle open by hand and it still jumps all over the place.. I replaced the tps with a spare i had laying around and still nothing... both test ok from pin 2 to 4 at .9k ohms but pin 1 to 4 reads 4.22kohms on one sensor and 5.3 on the other where is says that they should read 5. I dont know whats going on with the car. other current problems include the ISC buzzing with the ignition in the on position and the car buckes and jumps at wot. Please some one help me

 

[DSM90AWD]

Well i decided to get back into dsm`s hoping to have better luck the last time but within a week of buying my new talon im having problems already

DSMs are automotive heroine. Having one quickly moves you toward financial ruin but those infrequent "highs" you get when the car actually runs gives you the illusion it was worth it. Then you hit bottom (catastophic failure, wife/GF threatens to leave as spend more time with car than her, can't make minimum pmts on the credit card). Go thru rehab (buy a Honda or other dullish non-modified econobox), only to fall off the proverbial wagon in the near future falling victim to the sweet stench of burning oil once again

I replaced the tps with a spare i had laying around and still nothing... both test ok from pin 2 to 4 at .9k ohms but pin 1 to 4 reads 4.22kohms on one sensor and 5.3 on the other where is says that they should read 5. I dont know whats going on with the car. other current problems include the ISC buzzing with the ignition in the on position and the car buckes and jumps at wot. Please some one help me

Just to be clear you've:
- Checked/corrected any boost leaks
- Checked/Set Base Idle speed
- Checked/Set base timing
- Removed ISC from TB and thoroughly cleaned out the valve seat/passage

My ISC "resets" each time I turn the car to ON which sounds much like buzzing sound you refer to. The above will ensure that the ISC is within it's adjustment range when additional demands are put on the engine (A/C, fans, PS..etc)

 

[AHALLA05]

DSMs are automotive heroine.
^
I deffinately know what your talking about but about the car
I checked boost leaks and im down to one which is the TB shaft seals but it is a very small leak that i will still be fixing
The Biss screw ive turned till it bottomed out and it still idles high/surged untill it finally calmed down after a few mins.
Base timing I have yet to check the motor has been recently rebuilt and im sure it was set(on race gas) but I just bought the car and i dont have a timing light the logger says 5* while the car is off and the ignition in on position
i switched the ISC with an old one i had laying around and it idles great for a few mins. I later went back to drive it and it idled like crap again. both ISC`s tested good. They dont just buzz for a sec or two they do it the entire time the key is in the on pos.
I cleaned the TB with it was on the car just a quick wipe and it wasnt that bad

The surge just came out of no where one day it ran great, i shut it off then started it back up and it surged like crazy then started bucking at wot. I tried to log it but the tps wouldnt stay consistant which made it pointless. I started leaning tward the tps but I have no idea. thanks for the help. A.J.

 

[doggo]

Get a palm with MMCD so you can see what signals the TPS is sending in real-time. MMCD is free, Palm will run used on eBay about $20.

Oh, I forgot you need a special cable too, to connect to diagnostic port under dash- again about $20 on ebay.

 

[DarthBulk]

I would check the voltage going to the TPS (and other sensors). I had a lot of problems with sensor readings jumping around like crazy, and it turned out to be a low voltage in the sensor power circuit.

 

[AHALLA05]

Ok first off thanks for all of the fast replys. Next "Doggo" I am currently logging everything on mmcd on my laptop. I have switched tps sensors with a spare i had laying around and one i just borrowed off of my buddy. All 3 tps sensors have tested good but while watching mmcd with the car off and key on the tps ready continues to bounce all over the place which leads me to believe that it isnt my tps sensor but rather something in my wiring or ecu? i have a spare ecu laying around which i will switch it with and go from there.
"I would check the voltage going to the TPS (and other sensors). I had a lot of problems with sensor readings jumping around like crazy, and it turned out to be a low voltage in the sensor power circuit."DarthBulk
^
My isc reading on my palm is also bouncing around while the car is off and the key is on. I dont understand what u mean buy the sensor power curcuit. but yea both reading are jumping around. Like i said im gonna switch ecu`s and see what happens but thanks again for all the fast replys, keep em comming . A.J.

 

[DarthBulk]

Most all of the sensors on your engine are fed by a common power circuit. The ECU turns on the MPI relay (at least on a 1G), which then sends power to all of these sensors. I had a problem with low voltage coming out of the MPI relay, so all of my sensors were seeing from 5-9 Volts. This made their readings jump around like crazy, with the car off and the key set to the "run" position. You can check this voltage either at the MPI relay, or at any of the sensors (like the CAS, the power transistor, the MAF, etc.) I checked mine at the red wire on the CAS, because that was easy to get to.

 

[AHALLA05]

Well i feel like a complete idiot. I switched ecu`s with a spare that I had and what do ya no no more jumping tps. Then i remembered last week when i took out my ecu to check if it was an eprom or not. I forgot to unhook the battery. i never drove it that day and i think the next day was probably when it started surging and it got work from there to the point where is wouldnt even run. So i guess thats it. I guess ill never do that again(the caps are good by the way?)is my ecu still fixable. Im getting an eprom anyway but its always nice to have a spare ecu. thanks for all the help though. By the way my tps now ready 96.4% at wot and 12% closed is that ok ? thanks A.J.

 

[steve]

While you might not be able to see anything wrong with the caps I'd be really surprised if they hadn't leaked. Did you happen to nitice if any of the other analog sensors were bouncing around like the ECT or IAT?

The sensors get both 5v and ground from the ECU so they or the pins in the ECU connector could be bad as was as the ADC circuit in the ECU.

Yes, there is a good chance your ECU can be fixed.

Steve