2G Bad TPS....AGAIN?

[ChrisFlo]

I have a 98 gst.

After months of problems I finally gave in and took my car to an auto shop. They told me I had a bad TPS sensor, so I gave the go ahead to replace it.

However, the car has once again begun acting up on me. I'm getting idle surge, with the car jumping between 1k and 2.5k. I first thought it was the result of a bad MAS, but after closer inspection I'm starting to think that once again, I somehow ended up with another bad TPS. Below are fixes I've tried, as well as symptoms after various tests.

Fixes tried

New spark plugs and wires
"New" TPS (from shop)
Two ISC's tested
Two MAP sensors tested
Biss screw adjustment
Vacuum/boost leak test
Two batteries tried
fuel pump inspection

Symptoms and tests

1. With the car running, and just the TPS unplugged, the car holds a steady idle but that idle sits at the 2k range.

2. When plugging the TPS back in, the car begins surging between 1 and 2.5k rpms

3. With the TPS plugged in, I tried unhooking the ISC. No change. Still surging.

4. With the TPS plugged in, I tried unhooking the MAS. The car almost dies, as it should.


I'm pretty convinced that another TPS is needed following these results. Any advice that can help me get this car up and going will be greatly appreciated.

 

[steve]

Just because an ECU looks good, doesn't mean it's good. Mine looked MINT and still had a blown capacitor.

The reason why AJ's TPS was doing what it did was due to a blown sensor ground inside the ECU and not really the capacitors. They were leaking and would have killed the ECU given time but at some point he had a wiring issue shorting the sensor ground to 12v and that vaporized a circuit trace on the board.

 

[o0GuitarKid0o]

Just to post for future peeps I had a similar experience with an ecu I rebuilt I missed a little dot that was corroded (transfers on side of the pcb to the other) and it was the ground from the 100 uf capacitor and caused my tps to be pegged at 99% at idle and idle surge when throttle was pressed I also touched up a solder joint but thinking it was the one near the 100 uf cap


On a side note blew an isc driver today isc is not in spec and wouldn't even move . Was chasing this high idle for a few days when hot noticed it wouldn't go below 60 on the data logger . Now what na ecu to turn into a parts ecu hmmm. I have 4 6255 ecus

 

[AllanL]

Now what na ecu to turn into a parts ecu hmmm. I have 4 6255 ecus

any are EPROM?

 

[o0GuitarKid0o]

any are EPROM?

No eproms those are super hard to find , I tried finding one a while back so I could burn an nt chip for my car when it was n/a. Think the image is still on the Yahoo DSM-ECU group

 

[steve]

I missed a little dot that was corroded (transfers on side of the pcb to the other) and it was the ground from the 100uf capacitor

FYI, The little dots from one side to the other are called via's.

On the DSM ECU's corrosion can cause the trace leading up to the via to separate from the via at a microscopic level causing circuit opens. It's a pain to test continuity of each one.

 

[o0GuitarKid0o]

FYI, The little dots from one side to the other are called via's.

On the DSM ECU's corrosion can cause the trace leading up to the via to separate from the via at a microscopic level causing circuit opens. It's a pain to test continuity of each one.

Good to know what there called Haha I woundnt mind making a tech article dedicated to ecu repair (like the maintenance guide ) for diyers with more information than anyone could ever need , your posts have come in handy to many times be good to have an all in one guide here on tuners