The importance of a properly set TPS!

[slipnfall]

Hi folks, I get lots of help here, so I see it as only fair that I report when a problem is fixed! I'v been having drivability issues with my '92 DE since I got it back on the road. The problem I was having was with low-gear shifting(stop->1st, 1st->2nd) and hessitations. When I would start out, I'd have to slip the clutch to keep the car from bogging. It wouldn't bog enough to stall, but even if I rev-matched exactly my car would buck ever so slighly. Even after the clutch was fully engaged the car wouldn't pull hard untill 500-1k rpm later. I attributed all this to driving a completely different/'new' car(coming from 1.5yrs on a new Accord 5spd), and that I was still getting used to it.

Anyways, here are things that I was sure on:-Completely stock, only removed air resonators & AIV-1100mi on rebuilt DE, 175+ compression-New clutch/pp/slave, removed damper-Good engine vacuum-New OEM o2 sensor, coolant temp sensor-timing/idle OK, checked MAFS-Dealer said A/F test was OK-two transmission shops verified m/t was OK

Well I finally checked the throttle position sensor, and low-and-behold, it was off. I'm 1/2 embarassed I waited this long to check it. Readings were 0.7V at idle, should be 0.4V. After 'calibrating' it properly, all the above problems went away. I have a feeling my gas mileage will improve also, we'll see. Was getting 19Mpg previously on '87.

After adjusting the TPS, my car feels like a whole different animal! It pulls *soooo* much more smoothly and consistent after clutch engagement. Oddly enough the clutch engagement seemed to have moved further 'up' on the pedal, but I guess it's just the throttle that has changed. It's so different I feel like I'm relearning how to drive this car!

Later I bumped my timing ahead to around 22-23BTDC(have since switched to '93). No knock, and the car has now finally satisfied my expectations; I knew, even though the DE isn't a huge powerhouse, that it should feel peppier than what it did. Engine is noticably louder after 3.5k than before, but this may be due to no resonators(still louder than before).

BTW, TPS calibration should be put in the 'idle/poor drivability' sticky if it's not already!

I'm guess that the ECU was adding more fuel, thinking the throttle was partially open, then the O2 sensor detected the 'truth', and adjusted from there. I attribute my stumbling to this 'response' time, but I may be wrong.

Cheers, hope this may help someone down the road.-Jamie
Modified by slipnfall at 3:09 PM 4/23/2005

[slipnfall]

Oh and one thing to note: if you decide to check your own TPS, make sure you go by the voltage output on the signal wire, not just the potentiometer's resistance. As long as you have 5V on the power wire, then all that matters is that you get a full sweep from .4-5Vdc on the signal. If you don't, *then* you'll want to check the resistance reading on the 'pot.

::edit:: fat finger typo ::edit::