Trouble codes and another odd issue

[Rex2342]

I'm having a bit of an odd issue. Last week I swapped out my 90 TB for the 91-94 style. While I was at it I eliminated the fiav and ISC. Before I did the swap I set the TPS with a multi meter and everything worked out well. I cut the harness off of my 90 tps and matched the wire colors to the pigtail I had for the 91-94 TPS. I soldered all the connections, used heat shrink, and all that. I'm not having any running issues but every once in a while my CEL will flash and go back off. Its done it twice since the swap but doesn't stay on. The logger reads like 16% at idle and 99.8% at full throttle which I think is normal?
My logger tells me I have two stored codes. They are 14 and 31 which are TPS and knock sensor codes respectively. A few weeks ago my knock sensor crapped out on me and threw the CEL but I changed it and it hasn't come back on. However, for some reason I when I clear the codes with the logger they both come right back and I don't know why.

A separate issue that just started today is that my oil light came on when I started the car. It did it twice today after sitting for a bit at the doctors office then again when i left my buddies house. The stock gauge doesn't move for a few seconds and then it does and the light goes out. Its ating like the pressure is just taking longer to build. I haven't checked the wire for the sender yet but it's never done this before today. The oil level is good and the pressure while running seems normal. I drive it every day so i know where the gauge usually reads while I'm driving.

 

[steve]

The 90 ECU software is missing the command to clear the fault codes, you have to unplug them or disconnect the battery to clear.

At idle the TPS should read 10%, what it reads at WOT doesn't really matter as long as the butterfly opens 100% and the TPS values change smoothly across the entire range and the WOT output isn't something stupid like 70% or less.

 

[Rex2342]

I followed this when I adjusted it at first TPS Adjustment
Like I said everything came together fine. The logger shows a smooth signal across the full range. I'll double check the adjustments now that its on the car and try to get it to read 10% at idle. Could this be the reason the CEL flashes? It doesn't stay on and it seems to do it when coming to a stop and the rpms drop but it's only done it twice.

 

[Rex2342]

I'm still having this issue. I checked the TPS voltage and adjusted it using the all data at work. My voltage was like .763v and now it's right around .5v and the logger is reading 10.2% at idle. I checked the resistance between the pins and it was within the spec all data gave and I went back and checked my wiring again. Since I adjusted it the light is coming on more frequently. I seems to come on when I'm hardly on the gas and goes out as soon as I hit the throttle. I disconnected the battery to clear the codes and the code 14 (tps) is whats coming back. Is there anything else that would cause this? If the closed throttle switch isn't adjusted right would it cause this? The car is running fine but the light is annoying.

 

[steve]

The basic tests for a TPS fault are:

TPS voltage higher than 40% and the IPS is closed
TPS voltage lower than 4%

I believe there are tests to see if the output voltages is spiking or dropping out but I can't find them right now.

What I've seen happen is the TPS wears out, it's a mechanical wiper on a resistance element and over time it wears though the element causing dropouts in the voltage as the throttle moves. Since you spend more time driving around in the lower throttle openings it the part just above idle that wears out first.