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hmm, thats a thinker(help with rough running engine)

2K views 60 replies 14 participants last post by  dathers 
#1 ·
right stick with me on this as need some opinoins

right tonight ive been trying to figure out what wrong with the car and whats causing it to missfire, i did the following by a process of elimination.

right first up, pull out plugs, 1-2-3 were all black and sooty, no4 was completely clean, almost as if it hasnt fired since i put the engine back in, so then looked down at the crowns, 1-2-3 were a bit sooty, no 4 was completly clean.

Ok next, i pulled out the injectors, and while still on the rail i pointed the upwards and cranked over the engine, every one was spraying fuel, but i had a spare set and swapped the over and they were the same too, all firing together, next i put the plugs back in and got it running, pulled the wiring clip of injector no4, no change on engine running, put it back and then did no 3, engine promtly died, so swapped the wires round on 3&4 and it started fine, and it was the same again, pulled of 4, no change, pulled off 3 engine died.

next, got engine running again pulled the HT of no 4 from the dispack no engine change but the was a spark jumping from the pack to the lead, put it back on the pack then did the same to the plug end, pulled it off, and the spark was jumping to the plug and the bore untill i removed it, then got it close to the engine again and it was sparking away, pulled of lead no 3 and the engine died, i had a spare lead in the garage so used this on no 4 and it was still the same.

ok, running out of ideas, so i have a hunt for an old plug, pull out no4 and put the plug in the end, crank over and its sparking, so i put this pulg in the engine and it sound to run everso slightly better, hmm, odd pul off the lead on no4 and it sound a little bit different and then put the the origonal plug in the lead and earth it out and it sparks.

now im completely stumped, it sparks out of the engine but when its in its not firing atall, could it be tha it breaking down and firing when it feels like it, or is it that the compression has been upped and is blowing out the spark(they are all gapped at 0.8mm).

or could it be the dispack that is faulty, i dont know the history of it as i got it second hand.

also i used an exhuat gas analyzer and it reading between 1.5%-1.8% CO2 at idle.

help please
 
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#30 ·
i cant get my head round this. so if 3 and 4 are firing at the same time, that means when 3 is firing for the power stroke, cylinder 4 is recieving its wasted spark shot at the bottom of its induction stroke, verging on its compression stroke. yikes. where normally the wasted spark is administered to the cylinder on its exhaust stroke = no problems
 
#33 ·
jamie_f said:
ok ill give that a go, what will this prove then? shagged dispac?

at the mo i have it so 1&2 are are on 1 'bank' and 3&4 are on the other 'bank'

not its not running solids, why you ask?
Reason I ask about the solids was that mine is running on solids and I was scared for a moment that it was a little noisy in comparison to yours... I'm one of these "oh 5hit, whats that noise coming from my fkin expensive engine" types I'm afraid!! Driving is a total nightmare for me!!

As you say, this will help determine whether the dispac is at fault. Not sure what dispac you have - if you look at the moulding underneath, it will be easy to tell that there are two coils/two banks. Cylinders 1 and 4 are connected to one group and cylinders 2 and 3 are connected to another group.

I presume you've touched the no 4 exhaust manifold after running the engine up for a short while, as another confidence check that its not firing this pipe will obviously stay cold.

Good luck with it!!
 
#42 ·
having said that, compared to the little nicks in the stock XE pistons, even the exhaust coutouts on the omegas make them look like a paper cut. i dont reckon cams like yours (that i was gonna get) will even get close to them. they only need 2mm more than stock cutouts, and theyve got like a foot.

hey you never know, it might be the mod of the future, backwards omegas :rolleyes:

its been one of those days
 
#43 ·
i wouldnt bother if i were you, while mine were out, i offered an inlet valve up to the piston and the exhaust cutout on the piston was bigger that the inlet valve area, even steve said you can run stupid lift on the omegas and still have stacks of room, even more so with a thicked gasket too
 
#50 ·
Jamie, Jamie, Jamie lmao lmao lmao

Who on earth would do a thing like that :rolleyes:

(Hopes 0ddball doesn't remember when I did exactly the same thing lmao)

I'm surprised it was running as well as it was TBH, I got the flames lapping the fuel lines on the bulkhead :D.
 
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