So, it idles on 3 cylinders - why?
 

This actually started quite some months ago and I never bothered to look into it. This is one of my winter projects and I'm looking for input.

Car starts and idles on 3 cylinders. Cold worse than hot, but still. I noticed this due to shaking engine and less vacuum.

Seems back to normal above 3000rpm-ish. Power is there: 235rwhp.

Cylinder 3 is not doing much. I can pull the plug wire and it idles the same. Not so on other cylinders.

Swapped injector, same.

Swapped coil between 2 & 3 (same pack), same.

Plug wire sparks violently on block if I let it. Less on other plugs actually so plenty of spark.

So - what are the options we have left?
- faulty or leaking HLA
- ?

I will have compression and leak down tested soon, but want ideas now.

how's the no. 3 plug itself looking?

Fine, like all the others. Swapped for new - same result.

marginal injector that wont open below a certain pulsewidth?

No:I swapped injector 3 and 4. Still 3 is missing the show.
These are new flow tested RC 550s from BEGI.

Cylinder 3 is just lazy, only possible explanation.

I say look into the valvetrin, really the only other thing left since you have ruled out fuel and spark. Probably pointless even if you haven't already done it BUT..try swapping plug wires..? Good luck.

EDIT: nothing wrong with the injector's harness (car side not injector side) on #3 is there?

cylinder health?

.

Another vote for valvetrain... ok

Wires swapped, no difference.

The car is supposedly running fine in the higher rpm range, so, could it? Also I run MSPNP so the entire harness is OEM, nothing ever changes there. I doubt this is it.

Probably not, but you never know, could be a fray in a wire or something and when the engine is at higher rpms it makes better contact **shrug** w/o testing the valve train that's the only thing left that comes to mind

Does spraying unburned fuel out of the exhaust when cold rule this out? :)
It seems injection is happening, spark is there but no compression under 3krpm.

I doubt it's the block itself as it's still putting down 235rwhp on a stock 94 head. But I will have that checked.

I think you've got your problem all but figured out, get those compression/leak down #'s and you'll have your answer.

I still made 230rwhp as I blew my motor on the dyno itself. Ever since May I had smoke in boost and bad blow by. I had good compression across the board but horrible consumption. When I finally swapped the shortblock I only drained 3/4qt of oil, maybe 300 miles on it since the last change. lolz.

Oil consumption on track is minimal. No smoke. I don't need your drama in my thread :vash:. Go scare someone else :) You had a stock engine. Also, 235rwhp is on a Superflow, not DynoJet.

Hot leakdown ~80% in cyl #3 through valves.
Others are ~2%.
Ripping open valve cover this weak. Probably HLA.

had the same problem in cyl 3 awhile back - runs like crap until you get above 2000 or 2500 rpm, then normal - water was getting past my headgasket (ouch)

That could also be the case as I did have cooling issues before...

Intake valves are 'sagged'. Pulling head to see what's up (valve seats or?).
Probable cause is the overheating issues I had in the early days.

perfect opportunity to source a '99 head though...