TPS effect on closed loop operation

[FTA1995]

Hey again guys,
I brought up a misfire issue I was having before in closed loop; after rewriting the PCM again to remain in open loop (for garage testing and tuning). I have been slowly getting rid of problems from the last owner of the car with a reasonable success
I noticed on a log my tps had a good deal of flat spots throughout the sensor range. I replaced it today since to get rid of the flat spots, and my misfire problem completely disappeared.
My question is, what effect does the tps have on closed loop operation?
I know that it controls your off idle closed throttle timing, but how is that factored in with the MAP vacuum values?

Thanks again guys

[bobdec]

In theory TPS is used in the injector PW calculation, but I have no experience if it would cause noticeably bad missing or not. According to "How To Tune & Modify Engine Management Systems" - Jeff Hartman the TPS is used to " factor in transient enrichment offsets from throttle position changes". More to the point.. How bad were your flat spots ? If TPS voltage dropped significantly the PCM/ECM could drop into an incorrect idle or deceleration BLM cell (16,17,18), or with correct RPM/MAP conditions it could possibly go into DFCO and kill the injectors.

[FTA1995]

They were pretty nasty, any where between 15 and about 50 % throttle was nearly the same in voltage, always read around .75-.85 volts. After 50% it took off to where it was supposed to be. I have been having soo much trouble geting this thing to have solid balanced blms between off-idle and about 2800 rpm (idle is balanced, smooths out really quick above 2800)

[Rob B (shoebox)]

In simple terms, you gotta figure if the TPS is incorrectly indicating the actual throttle position, engine running parameters are going to be all screwed up.

[FTA1995]

Got a new tps, it did show me some different resistance/degrees in comparison to the old sensor, along with the lack of flat spots of course . engine is running much happier now. It did seem like there was a great deal of effect from tps input. Now I'm having issues with my idle returning back to the stopped value, e.g. it is sitting at 1200 rpm sometimes coming to a stop. My first suspect is the IAC valve, especially since the steps are going down along with that 5 degrees of spark retard for idle overspeed correction. I think that is more likely than an intermittent vacuum leak or something silly like that.