misfire/hesitation

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puma sam
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misfire/hesitation

Post by puma sam » Sat Jul 10, 2010 5:36 pm

Hi, I have a 2001 1.7 puma and it has developed a misfire at low revs. It had new leads, plugs and coil pack fitted a couple of months ago when a different fault developed and another new set of plugs today which have made no difference. The car drives fine, but when you allow the revs to drop under 2K revs then apply the throttle to accelerate again then the car will stutter and hesitate as if mis-firing and occasionaly will even backfire. This only happens for a few seconds and then is fine again and also if you change down to keep the revs above 2k then it never happens. The car starts fine and drives fine apart from this one issue and a friend plugged it into his diagnostic box today and it came up with no faults.

Help Please!!!! Sam.
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john gordon
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Re: misfire/hesitation

Post by john gordon » Sat Jul 10, 2010 6:44 pm

what did the plugs look like when you pulled them out? Was there a lot of oil in the plug holes? I have a similar kinda problem, I think its caused by my rocker cover gasket. As its weaping quite badly into the plug holes. Mines getting changed next week when i do the cambelt so i will let you know if it helps.
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pumapilot
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Re: misfire/hesitation

Post by pumapilot » Sat Jul 10, 2010 9:19 pm

Wynns injector cleaner, and a tankful of petrol station unleaded, wont cure it straight away, but it will help.
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nutty
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Re: misfire/hesitation

Post by nutty » Fri Jul 16, 2010 7:27 pm

HI

Try the crank position sensor

Paul
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PumaNoob
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Re: misfire/hesitation

Post by PumaNoob » Fri Jul 16, 2010 11:37 pm

If its back firing mate, its overfuelling, so id bet your lambda is going/gone. Those are exact symptoms of a faulty lambda/hego sensor. It cant measure the correct o2 in the exhaust gasses, so it runs rich. Your ecu cant pick up that its overfuelling, because its the lambda that reads if its overfuelling, so no mil/engine check light. You can tell because you get a build up of soot in your tail pipe, and when you clean it, it seems to come back pretty quickly!
If its not that, a possibility is cam sensor, but that would bring up an ecu fault, but then if you have a tape ecu, it wont light up on the dash! But id put money on lambda. If you have a newer car with 2 lambdas, then ecu will pick up the problem, but older pumas wont. Hope this helps
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qot
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misfire/hesitation

Post by qot » Sun Dec 02, 2018 7:33 pm

I know it's an old thread, but this:
"The car drives fine, but when you allow the revs to drop under 2K revs then apply the throttle to accelerate again then the car will stutter and hesitate as if mis-firing and occasionaly will even backfire. This only happens for a few seconds and then is fine again and also if you change down to keep the revs above 2k then it never happens. The car starts fine and drives fine apart from this one issue and a friend plugged it into his diagnostic box today and it came up with no faults."
is exactly what I'm getting........has anybody over the last 8 years bottomed it out?
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DOH
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misfire/hesitation

Post by DOH » Mon Dec 03, 2018 12:13 pm

Here's a few pointers , assuming the plugs are fairly recent i.e less than 40K , not oiled up & gap'd correctly.

The puma had 2 types of coil packs fitted, the earlier type the gap should be 1.3mm & the later 1.0mm.

Start by checking for oil around the spark plugs from a leaking rocker cover.

If that's ok, then check the resistance values of the Spark plug leads with a digital /Analogue meter that measures in K ohms. 5-8 K ohms is ok anything with a higher reading than that, then that lead needs to be replaced.

They often get damaged because the lead pulls out of the part that fits onto the top of the spark plug. This is because the heat & extended plug change intervals of approx 50 k miles causes them to stick.

Never pull directly on the lead itself , remove by using pliers pulling on the rubber part fitted to the plug only.

I have found adjustable wire strippers with the 90 degree part fitted just below the rubber part of the plug lead and initially twist them first before trying to pull from the spark plug :thumbs: .
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