Throttle Position Sensor. My Fix. Problems Gone.

[rs73]

My car idling a bit high around 900rpm even when warm (air con off).

When aircon on, every time the compressor kicks in to cool air, the rpm will drop to 500rpm, almost stalled the car, then somehow the engine or the ecu managed to keep it up to around 700-800 rpm again....

Is this caused by the same TPS or something else? My car has automatic ECU (was an automatic now converted to manual). Should I change to manual ECU?

[Cubes]

What I also noticed especially when the car was cold is that when the car was in the flat spot area of acceleration it would spool the turbo up really easily, the boost guage would sit on 0psi, the car would be slightly hessitating and feeling like some thing is holding it back then all of a sudden it would take off.

So possibly it was running lean on light throttle?

It drives like a totally different car now. I think it feels a little more responsive on light throttle and feels so smooth.

[Brody]

I still have no idea where it is...

I don't have my car atm, though the only thing i can think of, is the metal wire that u pull to rev the engine.

Fill me in

[CanberraR33]

well I know what I'm doing tommorow!

I get exactly the same thing. The flat spot at about 2k revs, just before coming on boost! Plus my car is a bitch to start on a cold morning.

Would this fix the occasional staling in reverse as well?

Yay, I so can't wait to do this! I thought the flat spot was just cause it was cold and the engine is getting a bit old! I had the same thing with a pulsar I had many years ogo. Plus one of my mates gets the same thing on his CC lancer. I don't think it will work on the lancer though 'cause it has a carby.

Cheers Joel!!

Just one thing: if so many ppl have this, does anyone know if it's done for a reason. I.e. to reduce engine wear when cold? Or is it just wear & tear that causes it to wind up like this?

[steve_R32]

My R32 gtst does EXACTLY what kabab describes his does in the morning. I put it down to the cold start sensor thing that joel had a thread about ages ago, where he cleaned it out etc.... because exactly as soon as my temp guage gets to half way (as in the car has warmed up) the hesitation, no light throttle feeling goes away with a splurge. It will have no light throttle, then vroom, all is normal. My car is standard, apart from the apexi air filter. I dunno, but its still going, so I'm happy

Steve (aka toy_R32, aka steve_R32)

[Cubes]

Steve ... Its the TPS. Believe me..

Unless the TPS adjustment is just patching up an underlying problem..

[kjb_r33]

There is iactually 2 seperate TPS's on the skylines. The oone for engine management indicates closed throttle and 3/4 throttle only. The other one is for an automatic transmission, and this one is a variable resister/potentiometer. Both are in the same housing.

Another thing that can cause a sputter on first opening the throttle is a minor air leak, such as from a PVC valve.

[Cubes]

Interesting, I might have a quick check over mine.

I did notice when I pulled the PCV Valve thing that goes to the Turbo Inlet that there was like some sort of wire bottle brush filter looking thing in the piping?!?! Is that normal?

[Gumby]

Yeh, I had a similar thing when a tiny vaccum hose come off the fuel rail or somewhere around there. Idle went up, car hesitated, and the on, off throttle was terrible banging the slack in the transmission. Pulled the AFM out and cleaned it, pulled the plugs, all good, checked the Throttle Posi Switch, I was stumped and frustrated. Then whilst looking over the bay, noticed the little hose not quite sitting securely on the little pipe off the fuel rail, put it back and car was perfect again.

BTW, anyone know what the little canister normally mounted on the RH strut tower is for (the one with the boost restrictor) my car doesn't have one at all, must be bypassed.

[kjb_r33]

Gumby...

your problem would not only have been an air leak, but also high fuel pressure down low. That hose takes manifold pressure to the fuel regulator, high vacumm (idle) means lower pressure.

[Moschops]

Joel - U got any pics of the offending TPS??

[Cubes]

When I'm up my parents on the weekend i'll take a pic with their digital camera.

All still seems good. No flat spots so far and no backfires pops.

[dAVE]

My 33 has exactly what kebab described too, Looks like im off to go fix it now then

[dAVE]

had a quick play. amazing how that thing can change so much. seems to have removed my flat spot, but now idling at 1,100rpm.. hmm

[Cubes]

You have adjusted it to high then daVE.

I had the screws with slight tension on them and tapped the TPS with the screw driver slowly until I heard the rev's drop to normal idle then i tightened it up.

It may take a couple of goes but you will get the feel of it.

[WazR32GTSt]

does the TPS actually come off or do you just turn it???

i took off the screws and could not get it off. didn't want to force it so i just had a play but flat spot still there.

pelase explain in more detail what it is you are doing...

[Cubes]

You don't pull it off. Re-read the description of what I did.

There isn't really much more detail that I can explain it in. Have a re-read.. Even read it and then write it in your own words if it will help you understand it.

[WazR32GTSt]

thanks bud i had another read and makes sense. i must have read it half asleep!

[ix9]

Guys,

would this situation be applicable to a noticable flat spot around 3.2kRPM - 4.5krpm.... or would that be more related to an overfuelling issue ?

[Cubes]

I had another fiddle with mine to try to get it just that little bit better. I noticed when I tried to fiddle with it when the car was warm it was extremly difficult to get it right. When the car was cold it is a lot easier.

Strich9.. I would notice a flat spot anywhere in the rev range if i would really really really slowly feed the throttle on from nothing. Then all of a sudden it would take off. I would also notice the boost guage looking like it was making boost but I wasn't actually going anywhere.