Intermittent Misfire/hesitation/stuttering

[ScoobyJawa 23]

Hi all

 

my car developed an intermittent "misfire". Its like its missing and holding back, you can feel the car stuttering.

 

Rev counter remains solid as a rock so it points me away from an electrical issue.

 

Anthony sent me a Ignition Amp and coil which he tried on his fine, I've tried both now and still have exactly the same problem.

 

Had the plugs out they all look normal, they were replaced about 7-10 years ago but the car has done max 10k miles in that time. The ht leads were also done at the same time as was a new dizzy and rotar arm (which also look fine). I also did the fuel filter around the same time.

 

I'm pretty sure the AFM is a recon on I also put on around the same time as the above but can't remember 100%. I've taken that off and cleaned it all up with carb cleaner.

 

It seems worse when the car is hot, idle is very lumpy at this point. Seems worst effected between 1.5k-4k rpm after that its fine. And it doesn't do it all the time, its very frequent, but sometimes revs cleanly.

 

Having looked at other posts its one of the following:

 

AFM

Plugs

HT Leads

Coil

Dizzy/Rotar

Ignition Amp

Fuel Pump

Fuel Filter

 

Anything I'm missing?

 

So it looks like I could still have a faulty AFM possibly? I'm not convinced its the plugs/leads/dizzy as they haven't done many miles and all looked ok. Ig Amp and Coil are known good as tried on Anthony's car.

 

Is it possible this sort of thing could be caused by the fuel pump or fuel filter?

 

Thanks

Neil

 

 

 

 

[jackherer 543]

Old HT leads are likely to cause problems, it doesn't matter if they've been used or not really.

[TheReaperWaits 6 1 Cars]

Had a similar issue with mine. Swapped essentially everything you have. Soon as I put fresh plugs in, it stopped. If you are near me you can borrow an AFM to test.

[Obey_R 23]

I had very similar problems on my 1600. Chunky aftermarket HT leads helped but was eventually sorted by running an additional earth to the coil. Worth a try!

[Anthony 1,003]

Unlikely in my opinion to be fuel pump or filter, as typically issues with these will show up primarily at high revs/load (i.e. at peak fuel demand)

 

I would agree with the comments above about not ruling out the ignition consumables just because they've only done 10k miles - being upto 10 years old is quite a lot and it's quite feasible that they're beginning to break down despite the low number of miles. All of the bits really are cheap enough to replace if you're in any doubt - from memory, last time I bought plugs, cap, arm, and leads it was about £30 or so for the lot.

 

AFM's can cause hestitation, although it would be unusual for it to do so over such a wide rpm range (and presumably at varying loads)

 

Coil and amp did an 80 mile round trip on mine without issue before posting, the majority of that in the rev range you're having problems with, so if the issues are identical to your existing coil/amp then you can probably safely rule them out as the cause. Generally speaking, a failing ignition amp will either give a constant misfire or is likely to give an almost rev-limit like symptom at higher revs (normally around 4k ish), whereas a failing coil will normally be OK at idle and low load, but miss - usually badly - under heavy load.

[ScoobyJawa 23]

Thanks for the comments chaps - Ok then next up lets go for plugs, leads, dizzy and arm and see what that does to things......

[ScoobyJawa 23]

Any thoughts on make - Bosch/Bremi/Beru or are they all much of a muchness?

[Anthony 1,003]

Plugs get standard NGK's - they're cheap and they work reliably.

 

Dizzy cap and arm I'm not sure there's much difference tbh - currently I'm running Halfords ones with no issues as I have done previously, just because they're cheap as chips on trade and they're always on the shelf.

 

HT leads I would personally avoid Bosch, as whilst they work. I've had no end of issues with the ends pulling off in the past on various sets. Bougicord were the OE leads and would thus be my prefered option, but not sure where you can get these from now - GSF used to do them a while back though. Just avoid the really cheap and nasty no-names stuff and chances are anything branded will likely be OK

[ScoobyJawa 23]

Smart - all ordered, got a fuel filter for the sake of it too! Will replace one thing at a time to find what was at fault!

[ScoobyJawa 23]

Well I think I've cracked it. It would appear German crap went wrong on my poor French car!

 

I've changed the plugs and leads and one of the Bosch HT leads was difficult to get off the Dizzy.

 

Here's why:

 

 

All the others were ok, this was the longest lead. So hopefully all should be well again, did a small test drive - couldn't get it to misfire.

Edited August 4, 2013 by ScoobyJawa

[Anthony 1,003]

Yup, looks about par for the course and what's happened on about every set of Bosch HT leads I've had, hence my warning above.

 

Hopefully that's fixed it

[DanteICE 72]

Nice find with that one!

 

When I'm in first rolling along (clutch out) and I press the accelerator fully down the car bogs down for half a second before it starts to accelerate at normal pace. It's a Jetronic 1.9 btw.

 

I know the car isn't properly tuned and I pay to have a full September month working on it, but the bogging down seems unrelated to idling issues and the like.

 

Any ideas?

 

Geoff