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Car misfiring
RoadkillUK - 2/4/16 at 07:37 PM

It's that time of the year again when the car gets put back on the road, however, I'm having issues.

2.0 Zetec
CBR 600 Carbs
Megajolt

The car runs fine idling, but when I accelerate it runs like a dog, misfiring all over, spitting fuel out of the carbs and almost dying. It doesn't do it all the time either, but it does do it most of the time.

Things I've done so far ...




After I removed the plugs and set the gaps, it ran quite well for about 5 minutes, I took the car out and it was fine on acceleration, after stopping at lights etc. but as I got close to home, I had to stop at the lights and when I set off, it could hardly move, the car was spluttering and there was fuel coming out of the carbs (I had no bonnet or filters on) but once I did get it to speed the car was fine, off the accelerator for a couple of seconds and it's spluttering all over again.

The only time it seems to run fine is high revs and idling.

Any suggestions as to what to check next and also maybe the best way to do these checks?

Thanks, Lee.

plutos3 - 2/4/16 at 08:01 PM

could it be stail fuel

RoadkillUK - 2/4/16 at 08:03 PM

Thanks for the input, but sadly no, the tank was low and I put a tenner in and the car has been running for some time.

02GF74 - 2/4/16 at 08:45 PM

Fuel out of carbs kinda point to too high fuel pressure..... although it dont explain why its ok at idle.

What fuel pump you using?

RoadkillUK - 2/4/16 at 09:29 PM

The pump is for a Honda CBR600 from ebay.

rusty nuts - 3/4/16 at 08:13 AM

Try new plugs set to 1mm

RoadkillUK - 3/4/16 at 09:54 AM

I'll get some today and try it. Thanks.

coozer - 3/4/16 at 10:10 AM

Carb breathers open and not blocked with spiders/insects??

britishtrident - 3/4/16 at 11:21 AM

From the descripion it doesn't sound like a plug issue. A plug or ignition HT issue will normally show pulling hard from low medium RPM and disappear at lower throttle positions.

Has the oil been changed?, using the wrong oil in a Zetec Silverrtop will cause tappet jacking.

It could be be a loose connection somewhere in the ignition wiring.
Another possible is contaminated fuel.

My first

RoadkillUK - 3/4/16 at 02:54 PM

So far today I have taken the car out for a spin, it seemed fine on the 10 minute trip to get some plugs.

So I've changed the plugs and the car still occasionally splutters, when it does and if I can accelerate through it, it goes for a while. It seems to be more frequent after the car has been idling or coasting at lowish revs.

I'm just finding some leads to swap over again.

britishtrident - 3/4/16 at 04:24 PM

quote:
Originally posted by RoadkillUK
So far today I have taken the car out for a spin, it seemed fine on the 10 minute trip to get some plugs.

So I've changed the plugs and the car still occasionally splutters, when it does and if I can accelerate through it, it goes for a while. It seems to be more frequent after the car has been idling or coasting at lowish revs.

I'm just finding some leads to swap over again.


That is pointing towards excess fuel pressure.

RoadkillUK - 3/4/16 at 05:26 PM

I've taken it out again, had a good 20 minute run, not a lot went wrong this time, a couple of times it was a little spluttery but I can accelerate out of it and it's fine again.

I'm done for today, so I'm planning to change the fuel filters and the plug leads. Probably could do with them anyway.

britishtrident - 3/4/16 at 06:22 PM

Spark plug lead resistance testing to check for breakes in the conductor ---NGK official method https://www.ngk.de/en/technology-in-detail/ignition-cables/diagnosis/testing-of-ignition-cables/

Checking the leads for shorts is also easy you just need a pices of wire connected to a ground I use a normal 12v test lamp (not LED type) because it has good insulation and a crocodile clip at the other end. With the engine running give the leads a gentle spray of water and run the pointed end of the test probe along the plug lead looking for leaking sparks.