1G RPM and TPS problems after new 1990 build

[clang1114]

I've just finished rebuilding and modifying my 90 GSX. I converted my car from a 90 CAS to a 91-94 CAS. Also converted from a 90 throttle body to a 91-94 throttle body with an ISC/FIAV blockoff plate on it.

After taking it for its first ride I am getting a TPS circuit malfunction code and my tachometer gauge isn't working. I wired both sensors like this thread below says. It seems multiple have done this and had no issues.

91 t-body and CAS in a 90 >>>>http://www.dsmtuners.com/forums/bolt-tech/213438-91-t-body-cas-90-a.html

I found a thread saying it is common for the 90 rpm gauge to stop working because of the noise filter. I bypassed it by jumping wires in the connector like the thread below says, tachometer still not working. Someone was saying the transistor could be bad or the rpm capacitor? And I should add that the rpm does read on DSMLink just not the gauge. So the ECU is receiving the signal.

http://www.dsmtuners.com/forums/articles-electrical-wiring/414636-how-fix-1990-dsm-tach.html

Tach not working after rebuild - DSM Forums: Mitsubishi Eclipse, Plymouth Laser, and Eagle Talon Forum: DSMtalk.com

As for my TPS malfunction code. The wiring is properly done and hooked up. In DSMlink it responds perfectly fine. Goes 0-100% normally with no issues. So I don't know why I'm getting that code. The car has very low power, So low I had trouble accelerating in 2nd gear to 30mph. Hoping this is caused by the TPS malfunction.

Any ideas anyone? My DSM friend and I have been pondering this together. We think the problem could evolve around the fact that I don't have an ISC. Maybe the ISC and TPS share a ground?

I did some ecu pin out testing. Pin 109 (tach input for ecu)was soldered before and didn't look like a good connection so I re soldered it. Didn't help but good insurance.

Pin 23 (5 volt power baro sensor and tps) didn't have any voltage with key on engine off. I am pretty sure that wire is suppose to be a constant supply voltage but not sure. Like I said the TPS reads properly on dsmlink.


Maybe I should have posted this thread in the tech section.....

 

[clang1114]

My car is a 1990. Ive had the infamous issues of the non working 90 tach. I purchased an aftermarket tach. I got the rpm signal from the ecu(white wire). This seemed to work for the first 5 min of driving but then It started to get wacky and my car started to misfire and run weird. I am assuming the ecu is getting confused or something because it is being shared with the gauge.

Where else can I tap in for the signal? It could be a waste of time trying to get it form the transistor or coilpack considering that is why I got an aftermarket gauge in the first place.

 

[lilevo]

The tach signal goes from the coil pack through tach adapter, tach filter, then directly to cluster.

The cluster doesn't get a tach signal from the ECU on a 90.

Or at least it doesn't need to.

 

[clang1114]

I Know it doesn't get its signal from the ecu. I am installing an aftermarket tach because my 90 tach doesn't work like I said above. I am assuming the coilpack signal won't be of any use considering that is why I am here in the first place.

 

[cammons]

i believe it gets its signal from the cam sensor

 

[lilevo]

91+ get tach signal from the transistor.

 

[clang1114]

I'm having weird random misfire issue that I've never seen before. The car drives good but randomly my tach will start to get jumpy while cruising. Then the next time I come to a stop the car will stall. No puttering or stumbling, idle just drops to nothing. The car is a 90 and I had to resort to an aftermarket tach after months of trying to figure out a non working stock tach.

I initially thought it was the wiring fir the aftermarket tach but I uninstalled It and the car did the same thing. If anyone has input it would be really helpful.

 

[hubz91talontsi]

Does it have a 90 ecu?

 

[WES_393]

Check your PTU (power transistor unit).

http://www.dsmtuners.com/forums/articles-electrical-wiring/229419-how-test-power-transistors.html

 

[dtmoke]

What year ECU do you have? You might need to do this...

http://www.dsmtuners.com/forums/art...4-ecu-swap-into-1990-dsm-ignition-wiring.html

 

[Chris25]

Mine was doing the same thing ECU was starting to take a crap on me. Replaced it and everything was back to normal just make sure you get a 90 ECU.

 

[Diamond Star Werks]

Check your PTU (power transistor unit).

http://www.dsmtuners.com/forums/articles-electrical-wiring/229419-how-test-power-transistors.html

+1 on this

 

[camas90gsx]

I had this happen in the past and it was a set of plug wires I had bought. The tach would jump at idle and cruising and my knock gauge would go crazy when I would accelerate (at random times, no rhyme or reason).

Long story short, I tried everything from PTU to electric connections. But when I pulled them off and threw my old NGK wires back on and it went away, both the knock and tach issue.

Also check your plugs and the plug gap as well.

I know there are issues with the tach when you use a 91-94 ECU in a 90, but I thought it just wouldnt work period unless you did a ECU mod. I'm pretty sure I remember its as easy as running 1 wire from point a to point b, but I could be wrong on that.

 

[goldeninja20]

Check your ICM (power transistor unit).

http://www.dsmtuners.com/forums/articles-electrical-wiring/229419-how-test-power-transistors.html

+2 check to make sure the plug is all the way in. Alot of the clips break that hold the plug on.

 

[clang1114]

My car has a 91-94 ECU in it. I was told by the previous owner that he sent it out to Jeff at dsmchips to get it socketed and there was some issues, long story short he sent back a 91-94 ecu with a tach adapter inside it to make the 90 tach work.

I've given up on getting the stock tach, that's why I uninstalled it and put an aftermarket one in its place. I noticed my PTU doesn't have the clip on the connector to keep it strongly plugged into the PTU. But it seems like its on there pretty good without it.

Currently my NGK wires only have about 1k miles on them. I haven't changed my spark plugs since my rebuild. I guess I should start there. They could be junk from the whole break in process.

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