TPS/MAP sensor issues?

[jfujita]

Hi all,


I'm having some problems with my 01 ACR. About 6 months ago the check engine light came on and I noticed the idle rpm bouncing between 1000 and 1500 rpm after I'd come to a stop at an intersection. This abnormal idling never occurred during the engine-start and warm-up period.

I borrowed a friend's OBD scanner and according to the shop manual the error was that the throttle position sensor (TPS) reading didn't match the MAP sensor reading. I disconnected the electrical plug from the TPS, cleaned it up and reconnected it firmly. The problem seemed to go away and the check engine light turned off.

Yesterday I turn the car on and the check engine light is instantly lit but it starts fine and the idle rpm is normal (500 rpm) and steady as I let it warm-up for a minute or so. I get it on the streets and I notice a problem with the throttle response... The throttle response is proportional from idle (500) to about 1700 rpm where it then sticks at around 1700 rpm even as you keep applying more throttle. If you modulate your gas pedal position between 1700 rpm and about 2700 rpm the actual engine rpm's will still stay at 1700. If you apply even more throttle then the rpms violently hop up to your current throttle position.

This makes pulling away from a stop light or intersection dangerous as you apply throttle and the car lugs at 1700 rpm... apply more throttle and then BAM instant power.

Also when I'm coming to a stop sign/light and put the car in neutral to coast the engine rpm's will plummet to 0 and about 3 out of 4 times the engine will stall... (Not the shuddering stall like killing the engine, but rather the engine just goes silent like it's being starved of fuel or ignition.) I've noticed that gently downshifting to the stop will sometimes keep the engine from stalling in these circumstances.

I can reproduce this throttle problem with the car parked and can confirm that there doesn't seem to be any mechanical problem with the throttle cable and/or throttle body/valves.

I suspect this new problem is symptomatic of a worsening condition related to my original TPS or MAP sensor issues.

I'm wondering if anybody has encountered these issues and if so what they're symptomatic of... TPS? or MAP?



Best,


Justin

 

[dave6666]

Try cleaning your IAC.

 

[fqberful]

Sounds like a TPS failing. Also make sure the throttle linkage is all together and not broken.

--FQB

 

[Steve-Indy]

voltage readings??

 

[cruser]

Sounds similar to an issue I had when my battery was going out.

 

[jfujita]

An update:

I checked the battery, and it's reading fine above 12.

I removed the IAC and played with the pintle. I got no movement on the IAC when I turned the ignition to "accessories". I pushed the pintle down into the IAC and turned the key and nothing happened. I pulled the Pintle out fully extended and turned the key and nothing happened. It's looking like this thing is dead. It is my understanding that when I turn the key there should be some sort of self-calibration movement, right?


-Justin

 

[BOTTLEFED]

Yes, the pintle should shutter a little when the ignition is turned on as it quickly self-adjusts.

I would also ohm check your TPS just to make sure it is not worn out. You want a steady, linear reading with no jumps. The exact procedure and specs should be in the FSM.

 

[Jack B]

Try cleaning your IAC.

That is a second, what hash mark to you believe is 500 rpm? The car idles at 670 (+/-20 rpm).

 

[bvk]

re-ground the TPS - its a crappy ground from the factory. I had the exact same rev issue as you, VERY annoying. Cleaned the heck out of the IAC, reset the computer, did the whole 'TPS learning' thing etc, it helped occasionally for a short time or not at all, and the car was back to idling at 1500 rpm or so.

read on here about re-grounding the TPS, tapped into it (black wire) and ran another wire to a better ground, problem solved, idles perfectly, that was 18 months ago, still idles perfect.