MU71L4710N

was driving home from a friends house today and my car started acting stupid and it has me stumped. its fine if i keep it below about 1/3-1/2 throttle, but as soon as i go past about the 50% mark, its literally like i just took my foot off the gas. it will buck about once every 5 seconds but basically it goes limp at WOT in any gear at any RPM. my battery light is on and flickers when i'm at WOT with no power, but the battery light has been on for a couple years now (diodes in alternator are bad but its never caused a problem before so ive ignored it).

makes me think its the TPS sensor but i dunno, i havent seen anyone post this same problem before.

uberstang1

It is more than likely NOT the TPS sensor. The tps sensor is basically a mechanical senster with a coiled spring inside. When they go bad its because the spring becomes weak and the sensor sends incorrect data to the ECU. When the tps sensor is bad you will have idle issues most of the time and alot of RPM hang. The easiest way to check the TPS is when these issues are present simply disconnect the connection to the TPS itself and see if the idles normal. I would not recomend going WOT with the tps sensor unplugged though. You're issue sounds more like a fuel/spark issue.

Z28KLR

You can also check the TPS with a mutimeter- as you turn it through it's range the resistance reading should increase or decrease in a smooth, linear fashion. It should not jump all over the place.

02TrueBlueGT

Sounds like an issue I had with my TPS. Didn't matter what rpms I went through, it was just plain out rough. I would think it's that but uber makes it sound like it's not that. Only a $20 part, and they can go bad mysteriously.

MU71L4710N

yeah i'm gonna check the tps out after class today i couldnt find my DMM last night. i can't do your method uber, like i said the car is perfectly fine idle and driving until i go over 1/2 throttle.

according to my google search this morning people have had SIMILAR (not nearly this extreme though) problems and one person had a dirty maf (i doubt this one, i've had a dirty maf before and symptoms were not like this), and one persons alternator went completely bad and the car was running off battery.

i just dont understand how it could be fuel or spark when the car is perfect below 50% throttle. no misfires, no loss of power, etc... the minute i hit the gas pedal it basically starts idling even though its at WOT.

uberstang1

As RPM increases so does fuel delivery and spark delivery. So as you give the pedal more push you are putting more demands on the ignition system along with the fuel system. A mass airflow could be a problem as well but they generally throw the CEL when faulty. If you are having a problem with you're alternator or ignition system this very well can be the culprit you are after, when alternators good bad on late model cars it can do all kinds of funky things, a good example is the 2003 Mercury Sable my step father owns, when the alternator was on the way out the entire car would randomy cut out, from the engine down to the radio, and all of a sudden fire back up withing 5 seconds.

MU71L4710N

Well my IAC is ohming out good (10.3~ ohms, i know its not at all a likely source since i am not having any idle problems but i was already in there with a DMM so i figured why not)

TPS looked ok. went fairly smooth from like .5 up to 3.5-4 (ohms, Mohms, Kohms, whatever it is i didnt check). seemed like it was hitting open for a split second around half throttle but it was probably just been the multimeter not bieng able to keep up.

i tried your thing with disconnecting the TPS and my car immiedately died. is this normal or should it have continued to idle? also, you mentioned RPM hang. when i rev it my RPMs drop much quicker than they used to. its almost like i have the IAC rev mod done but i don't. used to hang for a couple seconds then falls slow, now it drops pretty quick after i let off the gas.

took my air filter off and sprayed it down. sprayed electrical cleaner on my maf. they are drying now.

i disconnected the battery, still has the problem but i assume the car would die out if the alternator was toast and no battery hooked up. going to go to oreillys tomorrow and have my batt and alt tested (assuming i can hold RPMS for the machine. batt should be fine i just replaced it about a month ago) i should have done that before i sprayed my filter and maf down but i wasnt thinking.

uberstang1

Did you disconnect it before you started it or while it was running? I usually end up putting a new TPS on my car every other year cause I keep buying autozone ones. I disconnect my TPS then start the car and it runs fine, even taking it around the block.

cliffyk

The first thing you need to do is have a complete high load/stability test performed on the charging system and battery--unless that system is performing as intended all sorts of issues can arise in the engine control electronics.

If the generator is dropping out at higher speeds, or the system voltage is swinging below 10.5V or above 15.5V, the PCM would sense a BIG problem and fall back to "limp" mode--actually called HLOS (Hardware Limited Operation Strategy) mode.

HLOS is triggered if the the PCM stops. In HLOS mode the spark timing and fuel injector pulse are controlled directly by the crankshaft position sensor, the fuel pump relay is energised, and the IAC is functional--that's it.


There is also a mode called FMEM (Failure Mode Effects Management) in which the PCM is running however one or more sensors has failed. In this mode the PCM will substitute a fixed value for the failed sensor and then monitor the bad sensor--if it begins working properly the PCM will return to normal operation.

FMEM operation does not always cause continuous memory DTCs, however the Ford IDS (Integrated Diagnostic System) can record the sequence error messages.

What you describe sounds like the HLOS kicking in...

deviousgt

TPS? how often should the battery be changed?