misfire really annoying now!

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EssexAaron

Member
ever since i picked my pulsar up ive had a missfire on idle,while reving and more noticeably on boost where it cough even at standard boost!

now ive done the ignition timing, changed the plugs (iridiums) leads, cap and rotorm arm are all new genuine nissan, its got a walbro 255lph fuel pump. checked for any air leaks from vacum pipes ect, blocked off the breather to inlet pipes.

the fault code check comes back clear!

also the engine idles at around 1150

so what do i change now?

im gona rip the engine out soon and rebuilt the inlet soon as its frustrating me.:doh:
 
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pulsarboby

Guest
yes as above,
is the car popping from exhaust or maybe spitting back through airfilter?
if so you may have a burnt out valve, this will cause a regular misfire, consistent with engine speed!
 
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EssexAaron

Member
no poping or spitting back, i will do one though so i aint wasting my time with the other bits..

ive got a compression tester but not with pulsar fitment ed so ill have to find somehwere to get one
 
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EssexAaron

Member
just an upate on this. still got the missfire, only on idle! when standing behind the exhaust you can hear it hicup, now ive changed the maff re-gapped the plugs, set my TPS up and done a compession test which came back 150psi on all 4 cylinders so the engines very healthy. one thing i noticed thoughwas no 4 plug was burning more fuel then 1-3 could it be a faulty injector causing this?
 
antgtir

antgtir

New Member
Did you change the MAF for a known good working one? Id check the voltage on the earth to as this can be a problem also.

Try soapy water around the inlet gaskets to make sure the gaskets are not blown and sucking in air.

Have you tried the vacuum test, i know you said youve checked for this but wondered if you had tried the technique discussed in another thread using a compressor, tyre valve, end cap and piping?

Ant.
 
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youngsyp

New Member
If this 'missfire' is only happening at idle, you may be looking for something that's not there.

You'll never have a perfectly stable and constant idle. The odd change in note every now and then is just a characteristic of the car.... well, at least my one. If you have something like an AVCR or SAFC that shows RPM in numeric form, you'll see these little 'hiccups' as you call them. The RPM speed may change by 5 or 10 cycles momentarily, and then settle again. You'll hear a 'bump' ( I know, very technical) sound from the exhaust at the same time.
There's a lot of very old and worn components on these cars, even those that have been rebuilt. Generally, the throttle bodies won't be touched and things like the auxilliary air control valve etc.. won't have been touched either. These will all effect quality of idle.

Just a thought.

Paul

P.s. I didn 't notice if you'd changed your fuel filter or not ?!
 
projectgtir

projectgtir

Member
missfire

I have the same problem Aaron slight miss on idle .my car smokes like a bi*ch on idle as well though so all my plugs are sooty black. I have changed all the parts you have except the tps and vacuum test.
 
projectgtir

projectgtir

Member
mines really high when cold about 1700 then goes down to 1000 once hot. with every miss my car drops 100 revs to 900 then back up to 1000 once its stopped .sometimes it ok for acouple of mins then starts to pop n bang .have you tried a fault code check.
 
antgtir

antgtir

New Member
Have the throttle bodies been off in the past? If so maybe the old gasket was used and was damaged during re installation, i had this on an old cavalier lol, the inlet manifold had a leaky gasket and caused the car to over rev as it was drawing in more air.

What colour are the spark plugs after a run out in the car?

Ant.
 
mattytappy

mattytappy

New Member
have you still got all your throttle body caps in place....and the ones that cover the idle srews??
And do you know what your ignition timing is set at and with what fuel are you running it on as ive found differnt fuels make my car pop alot more than others do...also as soon as i got rid of the pcv valve my idle settled down nicely and it hardly pops at all now compared to when it was in place still.....?
 
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