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        General >> Problems >> Misfire under load
        
(Message started by: Paulus on Jan 23^rd, 2006, 9:09am)

Title: Misfire under load
Post by Paulus on Jan 23^rd, 2006, 9:09am

12V Ultima Estate.

Why does my car misfire when under load? It's fine when cruising, but when I put my foot down, oh dear.

Paul.

Title: Re: Misfire under load
Post by Dave on Jan 23^rd, 2006, 9:56am

Check spark plugs, ignition leads, distributor cap and rotor arm for starters. Might find they just need a clean up!

Title: Re: Misfire under load
Post by David_South_West on Jan 23^rd, 2006, 10:33am

Had same problem with 24v ..new set of plugs sorted out problem.
Good luck

Title: Re: Misfire under load
Post by Paulus on Jan 23^rd, 2006, 12:31pm

Well, it got new plugs at the weekend - still no better.

After a run, I did notice that the two spark plugs furthest away rom the front of the car had got oily, the rest were fine. Could that be relevant?

Paul.

Title: Re: Misfire under load
Post by Dave on Jan 23^rd, 2006, 1:40pm

Could be, sounds like they got oily quite quick. How are your cam cover gaskets looking? Mine leak a bit and that gets down the spark plug holes.

Title: Re: Misfire under load
Post by David_South_West on Jan 23^rd, 2006, 2:41pm

Could be plug leads...trying checking under bonnet when it's dark....any shorts are easier to see.

Title: Re: Misfire under load
Post by Paulus on Jan 27^th, 2006, 11:33pm

No shorts (from what I could see). I went to Halfords to get some new leads anyway, but the don't have them listed in their book. >:(

I'm off to my local Ford spares department in Stafford tomorrow. }{

The misfire is getting worse. Any other suggestions? ???

Title: Re: Misfire under load
Post by Paulus on Jan 29^th, 2006, 2:40pm

Right then.

New leads fitted (and air filter). There is a definite improvement, but still there is something going on under full throttle.

No leaks from the rocker to contaminate the plugs/leads. Sparkies look a little sooty.

Any more suggestions? I've got to commute 165 miles to work on Tuesday. I would rather do it without this problem.

Title: Re: Misfire under load
Post by Dave on Jan 29^th, 2006, 3:04pm

Have a look at the distributor cap and rotor arm, they may well be in need of a good clean!

Title: Re: Misfire under load
Post by Paulus on Jan 29^th, 2006, 3:09pm

Rotor arm and distributor are all nice, clean and in good condition. I might replace them anyway. Ya never know ???

I have just checked the sparkies again (first time since the new leads) and they are all looking great.

So then. Next job is to try a new rotor arm and cap.

Title: Re: Misfire under load
Post by howiedintheplace on Jan 29^th, 2006, 5:50pm

Check the timing sometimes it's out a bit & can cause a misfire under load also a cracked distrubter cap or worn rotor will do the same.

Title: Re: Misfire under load
Post by Paulus on Jan 30^th, 2006, 6:17pm

I wasn't aware that the timing could be adjusted. Can it?

Title: Re: Misfire under load
Post by howiedintheplace on Jan 30^th, 2006, 7:40pm

Yeah it can, if someone has messed with the engine then it's usally out espically if they don't know what they are doing.
You should do it in service mode or unplug the throttle sensor ;)

Title: Re: Misfire under load
Post by martin_rowe on Jan 31^st, 2006, 8:39am

'oily quite quick' perhaps you should start with basics, carry out a conpression / cylinder loss test.

Title: Re: Misfire under load
Post by Paulus on Feb 5^th, 2006, 5:00pm

Another update.
No more oily plugs. They are looking good.
I have replaced plugs, leads, rotor arm, distributor cap and air filter.
I have taken a look at the injectors - nice and clean.
I can't find any cracked hoses that would give an induction/vacuum leak somewhere.
Compression tester on order.

How do I go about checking the timing? I don't think that it is the problem because the the car has been OK up until the last few weeks.

Also, the tacho dances a merry dance when it is misfiring. Coil perhaps?

If I had any hair to pull out, I'd be doing that!!!

What else could it be?

Title: Re: Misfire under load
Post by ricky on Feb 5^th, 2006, 7:20pm

missfire under load is nearly allways caused by the electrical system , ie plugs ,leads, coil, wiring, ect

Title: Re: Misfire under load
Post by Paulus on Feb 7^th, 2006, 11:20am

Right then. My Compression tester has arrived. What should I be getting. I know that they should all be within about 10psi or so, but in what range?

Also, can anyone point me in the right direction for checking the timing?

Title: Re: Misfire under load
Post by ferretmobile on Feb 7^th, 2006, 6:05pm

I have got this problem as well :(
Just as you say, under load or on kick down. I had 4rds put in two new ignition coils and since then ...hmmmm

Ferret

Title: Re: Misfire under load
Post by howiedintheplace on Feb 7^th, 2006, 6:17pm

Well it don't sound like the timing has been afected but you can check it with a strobe conected to plug one & the TPS disconected to put it in service mode.
I think it's 15 degree @ tick over for a CAT 12V but do check that.

Title: Re: Misfire under load
Post by ferretmobile on Feb 10^th, 2006, 2:01pm

I have now bunged in some STP fuel treatment and the problem isnt so bad but when the engine is cold it misfires if I floor it. :( Most of my daily driving is on motorway and when the engine is nice and warm the problem seems to go away...hmmm
Maybe a case of scorpiosis }{
But I am suspecting a dodgy plug at the mo, I diddnt have this problem untill recently, FORDSput in two new ignition coils cos one failed on me, spose at 86,000 they have reached the end of their life and to replace both makes sense. BUT, a day or two after I got the car back,
this misfire thing started. wether it is due to a better source of ignition finding a weak spot in the system is open to conjecture. I dont think it is timing because it ticks over and drives fine..... }{most of the time LOL
any comments or help would be most apreciated.
I have had an RAC man look at it and he reckons it is a fuel problem but I am not so sure.
Oh yeh, and the front discs have gone wobbly...............................AGAIN!!! >:( >:( I am on the third set since having the scorp. This in only three years and I dont use the brakes hard or sit on them in traffic. what were 4rds thinking when they designed the 2.3 with unventilated discs or was it a friday evening..."oi nobby, wotcha dooin...its nokin orf tym!! or some such conversation :-/
errr rant over...Ferret

Title: Re: Misfire under load
Post by mr._floppy on Feb 10^th, 2006, 5:17pm

Are you sure it's the discs that is causing steering wheel shake on brake application ?

Could be the suspension bushes/ balljoints or track rod ends, Etc.

Title: Re: Misfire under load
Post by ferretmobile on Feb 14^th, 2006, 11:20am

Hi Flop, the blessed thing has just passed its MOT at a FORD dealer so I know that everything else is OK :-X
..................or is it ???
ferret

Title: Re: Misfire under load
Post by Geoff_W on Feb 14^th, 2006, 12:22pm

Ferret

I had similar vibration under braking for about twelve months, had several sets of front disks replaced under warranty had new bushes and problem went away.

Geoff