misfire/hesitation problem

[BHDave]

I've had a look at past threads on misfires and only found one that relates to my problem but there was no solution given so here goes.

My car is currently having a bit of an issue between 2000 and 3000 rpm with medium load where it has a bit of a hesitation, kind of like one cylinder isn't firing properly but it's not actually missing. As a result the acceleration isn't smooth between 2 and 3k but surges slightly. It also does it on deceleration at the same point.

To date i have:

swapped ignitor

swapped injectors for cleaned and flowed set

swapped plugs and gapped them down to .9

swapped two coils that had a bit of cracking for known good ones (i will be swapping another 2 out once the car cools down for the two cracked ones to see if it makes a difference and then doing the same again later this arvo if it's still there)

Prior to this it would occasionally drop a cylinder during light load (freeway) driving by fouling the plug. If i floored it and built a bit of boost it would start to run on that cylinder again. This was what got me changing the injectors as i thought i had a seized one and i did the plugs while i was there. Now it doesn't drop a cylinder but still runs a bit rough in the 2-3k range.

Any suggestions would be appreciated gents.

Thanks

Dave

[BHDave]

So now i have swapped out all the coils, no change.

Cleaned afm, no change.

Will be swapping for a working ecu on the weekend and hopefully getting ahold of a afm

[cameron]

Do a compression test,

Check your vacume lines as their might be a leak,

And check your crank angel sensor plug.

[pstanbis]

If you know anyone with a nissan dianostics computer, get them to check the mapping (assuming you still have the stock ECU) matte of mine had the exact same problem in his honda (mutiple plug per cylinder thing - weird) but basicaly only messed about at light/med load, just kinda waffled a bit...

[BHDave]

Thanks for the advice guys.

Yep, compression test was on the list of things to do though i've dumped it in the unlikely basket due to the problem being inconsistant, sometimes it's shocking and sometimes you barely notice it.

Swapped in another ecu last night and it seemed to run perfectly but then this morning it was back to the same problem.

I'm waiting on an adapter for my new laptop so i can check what the emanage is seeing. I really want to see what the airflow meter signal is like when it is having issues as it will allow me to rule it out as a possiblity.

I've had the plug off the cas a few times in the past and actually had it off on the weekend when i swapped the injectors. It still clips in fine and doesn't seem to be damaged at all. Is there anything in particular to look for?

Vacuum leak is on the list of probables as the car is getting on now so i expect there are a few pipes past their prime around the intake manifold though there is nothing really obvious that i could see on the weekend, just a few slightly hard pipes.

Thanks again, I guess i'll just keep trying til i run out of patience then torch the car and claim insurance.

[BHDave]

Now i'm really getting the shits with it.

Have now swapped the cas and had a look at the plug. Plug seems fine, what am i supposed to be looking for? Continuity test between the plug and ecu pin ins? Also did a diagnostic and it is giving me 11, 21 and 34 which is CAS (which really shits me), Ignition signal ( what about it, that doesn't really tell me much, got me stumped unless it's due to the cas playing up) and Knock sensor (I'll play with that once i get the cas and ignition issues sorted).

I have a feeling the ignition sig is due to the emanage being in the way but i pulled the ignition loom out yesterday and it made no difference to the car.

Checked vacuum lines they are all ok.

Checked compression, all cylinders in the 130-132 range (not great but even) so it isn't a dropped ring/ring land.

Any ideas people. I might re wire the cas if i can be bothered, any idea where i can find a plug? Or how to pull my existing plug apart?

Thanks guys

[BHDave]

Checked for continuity between the cas plug and the ecu plug, all good. Checked the cas ground and it's good. Has power too which is nice.

Unplugged the knock sensors from the loom. Gave the car a nice midrange kick but it is probably pinging its ass off. Didn't fix the prob anyway so that'll be getting plugged back in staight away though i'll be keeping an eye on it in the future as a possible power sucker.

So that leaves the ignition issue so i'm stumped. Might try swapping the ignition loom cos mines a bit crispy and do some continuity checks and the like when i have a bit of time.

Anyone else have a prposal

[BHDave]

Reset the the ecu and went for a drive. now only getting 21 and 34 so that rules out the cas completely now. So looks like it's in the wiring. I hate chasing wires....

So now to try another ignition loom. and then check for continuity back to ecu plug if that doesn't fix anything. Atleast i'm making some headway in what the problem isn't.

[BenA31]

i've got the same problem dude when cold, although just yesterday my idle has now increased heaps to like 1500 - 2000, i've got a feeling its a leak in the intake or a intake gasket leak.....

[boj01]

Change over the AFM for a known good one!

[BHDave]

Already tried afm

tried consult, threw up a few errors but nothing serious

played with the fuel and rewired ignition and sorted a dud earth to tps and temp sensor, no fix.

I'm going to chuck the engine, it's getting a little long in the tooth now anyway (about 180k) and replace with a lower k engine and replace the loom while i'm at it. Also got a new exhaust manifold to install which is high mount so will require all new intake piping.