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The mkiv Supra Owners Club

Missfire is back.


Kirk

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Right guys i had a slight missfire not long ago which seemed to cure itself but when it occurred i pulled every possible thing to see if it was anything obvious, which there wasnt. Granted the plugs were a little sutty but nothing serious. I even checked the compression to see if it was internal related. 5 out of 6 were consistent and good and number 6 was a little low but nothing serious. Now I had changed everything prior to that, new plugs, rotor arm, dizzy cap, leads were totaly fine.

 

As of this morning it appears to have returned, its more problematic when the engines cold but once its warmed up it seems fine. Also when coasting to the lights or stopped at the lights the idle jumps erraticly from 900 to almost 0 and oddly when i shut the door the bang seems to drop the idle for a moment. I havent checked anything as of yet but its something i would like to get sorted asap as it is annoying especially when its popping and farting on tick over.

 

Idea's other than the basic's would be much appreciated :)

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Just some thoughts.

 

Try ECU reset

Battery terminals tight?

Earthing points clean and tight?

All pipes in engine bay connected?

Double check distributor cap and rotor arm are fitted properly.

Recheck spark plugs.

O2 sensors last changed?

Fuel filter last changed?

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Just some thoughts.

 

Try ECU reset

Battery terminals tight?

Earthing points clean and tight?

All pipes in engine bay connected?

Double check distributor cap and rotor arm are fitted properly.

Recheck spark plugs.

O2 sensors last changed?

Fuel filter last changed?

 

ECU reset twice already.

Battery terminals have been recently overhauled and are tight.

All pipes connected that im sure of.

Fuel filter is brand new

 

O2 sensors havent been changed although i suppose its probly a good idea. May do the lemon juice method for now.

 

Ill check the dizzy and rotor arm etc later on.

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O2 sensors havent been changed although i suppose its probly a good idea. May do the lemon juice method for now.

 

Knackered O2 sensors wouldn't cause a misfire, but it would run rich which can make it feel a bit lumpy at idle and low revs.

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No i didnt think so but last time it happened the plugs were rather sutty. Just wonder if the plugs need a good cleaning.

 

See the thing is when the missfire isnt there it idle's perfectly and smoothly which is realy baffling me as its rather intermittent. :think:

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the engine almost cutting out at stops......

 

I had that problem when my air filter was down in the bumper it was almost as if the engine wasnt getting the air up in it seems weird....... air filter in engine bay no problems if i put it back down in the bumper it causes it to sometimes stall out or almost stall

 

the only misfire mines had was last winter early morning i started it and it was real ruff diff exhaust note switched it of reset the ecu then it was fine (obv youve tried this and it didnt work)

 

have you checked the grounds? im sure one of them on mine was the cause for a dodgy idle it was covered in oil from the rocker cover gasket leaking cleaned it up and it was perfect again

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Ok ive checked the ecu for error codes after the ecu reset and triggering the 'missfire' again and it has come back with a code 41 which is TPS signal. Now im guessing if the TPS is dodgy then it can cause the engine to 'jerk' on acceleration which is what it does. Im just wondering if its a jerk rather than a missfire.

 

Does anyone have the correct adjustment spec's for adjusting the TPS?

Edited by Kirk (see edit history)
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