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Weird missfire problem...Please help


garetheves

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Can excess heat cause the coil packs to break down quicker, its just this prob all started after the very spirited drive round the lakes, ending in a very fast run up and down to Hartside Cafe. This was the first time id really tested the car after fitting a FMIC so im guessing engine temps were a little bit on the high side after the drive, especially as there was a lot of engine braking.

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As Pig said, try simply refurbing your coil pack connectors. They can get loose (the actual metal pins and sleeves) which can really drop the power going through the packs. If your connector disintegrates on attempting to take them to bits, it's new connector time anyway :)

 

Edit to say - I've had some REALLY buggered coil packs before where about 0.2bar of boost caused a massive misfire - and yet it idled and ran off boost perfectly. It does sound more like a connection problem than the packs themselves. But absxxxx can test them if you can do without them for a while?

 

-Ian

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As Pig said, try simply refurbing your coil pack connectors. They can get loose (the actual metal pins and sleeves) which can really drop the power going through the packs. If your connector disintegrates on attempting to take them to bits, it's new connector time anyway :)

 

Edit to say - I've had some REALLY buggered coil packs before where about 0.2bar of boost caused a massive misfire - and yet it idled and ran off boost perfectly. It does sound more like a connection problem than the packs themselves. But absxxxx can test them if you can do without them for a while?

 

-Ian

 

Its the connectors which are loose. When fitting them back, with the clips in place, i could pull the connectors of the front 2 packs right out of the clips easily. Then it was a major hastle to get them to sit "straight" while i clipped them onto the pack again. That prob makes no sense actually. Might buy some new cables and clips first, rather than the packs themselves.

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Ok, got some new connector clips fom Martin so fitted them this morning. Didnt get to check whether i was still getting the missfire while driving because now it has got an intermittant miss on idle, which becomes more rythmic when revs increased. Below is a list of things ive tried already, any ideas??

 

1. Complete change of plugs (although i didnt gap any of them, just plugged straight in)

 

2. Brand new coil pack connectors.

 

3. Reset ECU (Just in case)

 

Could it be the gaps arent quite right?? I was under the impression that a slight difference in gap size would only be apparent at high boost. to be honest the car feels, at idle, like one of them has gone completely and its only running on 5 cylinders. It is missing sufficiently enough that it cut out a few times after reving the engine sat on the drive.

 

Oh and one more thing which may help, the miss seems to get worse the warmer the engine gets.

 

Any help please???

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Gaz have you tried disconnectin each coil pack 1 at a time and running the Car to see if it makes any difference - just to eliminate one of the coil packs being faulty.

May also be worth swapping in an other igniter to rule that out. Other causes could be dirty/bad injector clips or even injectors but unlikely. Personally, As a last resort i would do a compression test on the engine.

 

Marty

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Gaz have you tried disconnectin each coil pack 1 at a time and running the Car to see if it makes any difference - just to eliminate one of the coil packs being faulty.

May also be worth swapping in an other igniter to rule that out. Other causes could be dirty/bad injector clips or even injectors but unlikely. Personally, As a last resort i would do a compression test on the engine.

 

Marty

 

Cheers mate. Will try disconnecting the packs tomorrow if i get chance.

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Ok, just tested each of the coil packs individually. Did this by disconnecting each one, one oat a time, while the car was running. Each one caused a noticeable incease in the missfire, to the extent that the car cut out more often than not. This, to me, rules out the coil packs as surely if one was faulty then while i unplugged that particular plug, the performance of the engine would not change. Also, since doing these tests the car now wont start unless i rev the engine for 20 secs after startup. If i dont it cuts out.

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Try swapping in an Igniter, then check the cam and crank sensor connections - this should hopefully eliminate a problem with the ignition system unless it is one of the sensors mentioned.

 

I would also look at the fueling side, starting with the fuel filter, then checking the condition of the plugs, and also removing all coil packs and firing over to check each plug is damp with fuel.

 

With a problem like this though, there are a lot of maybe's and could be's..can you not get it left in to somebody???

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Try swapping in an Igniter, then check the cam and crank sensor connections - this should hopefully eliminate a problem with the ignition system unless it is one of the sensors mentioned.

 

I would also look at the fueling side, starting with the fuel filter, then checking the condition of the plugs, and also removing all coil packs and firing over to check each plug is damp with fuel.

 

With a problem like this though, there are a lot of maybe's and could be's..can you not get it left in to somebody???

 

Not really driveable in the state its in. Having said that though i havent got a clue how i would check the ignitor, cam and crank sensor, fueling etc. So it looks like i may have to try to get it to someone.

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Gaz after resetting the ECU it usually takes a few miles for the re-learn process to adapt including the Idle control. Some cars can take up to 20 miles of driving

 

http://supras-ireland.net/manuals/Workshop%20Manuals/Supra%20MK4/02%20-%20Maintenance%20&%20Servicing/Computer%20re-learn%20procedures.pdf

 

 

as for the Igniter, if you can get a loan of one from a member if they have one going spare? takes 2mins to change it.

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Gaz after resetting the ECU it usually takes a few miles for the re-learn process to adapt including the Idle control. Some cars can take up to 20 miles of driving

 

http://supras-ireland.net/manuals/Workshop%20Manuals/Supra%20MK4/02%20-%20Maintenance%20&%20Servicing/Computer%20re-learn%20procedures.pdf

 

 

as for the Igniter, if you can get a loan of one from a member if they have one going spare? takes 2mins to change it.

 

Cheers mate, gonna try running it for longer tonight to help relearn the ECU. In your opinion is it unlikely that the miss is caused by a poor gap in the plugs?? Like i said i changed the plugs the other week but left the gap as it came out of the box.

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Cheers mate, gonna try running it for longer tonight to help relearn the ECU. In your opinion is it unlikely that the miss is caused by a poor gap in the plugs?? Like i said i changed the plugs the other week but left the gap as it came out of the box.

 

Gaz, usually the only time the stock plug gap effects running is under heavy load/boost when we would usually gap Smaller. under idle and normal running conditions, ik22, ik24 etc etc preset gaps should'nt cause any running problems.

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Gaz, usually the only time the stock plug gap effects running is under heavy load/boost when we would usually gap Smaller. under idle and normal running conditions, ik22, ik24 etc etc preset gaps should'nt cause any running problems.

 

They arent IK's they are copper though. It should still only affect it under boost though so prob not this.

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i'm pretty sure this is the exact same problem i've got. i had just renewed plugs, cranks seals and turbo seals. this problem just started rearing its head.

im now 4-5 months down the line, renewed - MAP sensor (turbo sensor), o2 sensor, cleaned the butterfly, the vacuum pipes, everything i can think of.

its really bad when i drive calm keeping my accelerator steady. it got so bad the other day that i couldn't get the car started without the accelerator, then not idling at all.

i found that the only thing that stops it is turning her off and letting her cool down for 1/2 hour. then works fine for a while.

got a new TS bonnet coming, hope that it'll cool the engine a bit better....

 

(also im sure the guy before me changed the coil packs after a slight misfire problem.)

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i'm pretty sure this is the exact same problem i've got. i had just renewed plugs, cranks seals and turbo seals. this problem just started rearing its head.

im now 4-5 months down the line, renewed - MAP sensor (turbo sensor), o2 sensor, cleaned the butterfly, the vacuum pipes, everything i can think of.

its really bad when i drive calm keeping my accelerator steady. it got so bad the other day that i couldn't get the car started without the accelerator, then not idling at all.

i found that the only thing that stops it is turning her off and letting her cool down for 1/2 hour. then works fine for a while.

got a new TS bonnet coming, hope that it'll cool the engine a bit better....

 

(also im sure the guy before me changed the coil packs after a slight misfire problem.)

 

 

Yup, that sounds exactly the same as mine. Keep me posted on how you get on please, and ill do the same. Any chance of a list of other things you have tried so far so that i can try a few other things.

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yeah sure,

 

i also checked the resistances on the coil packs - both hot and cold, changed the fuel filter..

 

haven't done the igniter, still looks ok but not really sure how to test, also thinking about the injectors.

 

its all still standard and not really looked into replacement costs.

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Could someone post a pic of where the ignitor is and what it looks like so i could check this.

 

It's the little black box on the Passenger side Suspension Turret. Looms on one end.

 

I have a spare one which I need to test and if it works I can send you that early next week to try out?

 

PM me mate

 

Ro

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It's the little black box on the Passenger side Suspension Turret. Looms on one end.

 

I have a spare one which I need to test and if it works I can send you that early next week to try out?

 

PM me mate

 

Ro

 

ahh so thats what little box is. always wondered that. That would be awesome if you could send it me mate, obviously id cover your postage if you want. My address is:

 

Gareth Eves

20 Old Pepper Lane

Standish

Wigan

WN6 0PH.

 

Cheers mate its a massive help.

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i'm pretty sure this is the exact same problem i've got. i had just renewed plugs, cranks seals and turbo seals. this problem just started rearing its head.

 

was the Crank position plate at the back of the Crank pulley in good condition? it wouldnt have taken a knock or anything? did you give the crank sensor a clean??

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