Its not often i post in here asking for help lol, but sometimes a problem shared and all that.

 

Here goes: car ran fine, then recently started chugging on tickover, which i thought i had pinned down to the temp sensor, the clip was missing and wasnt seated tightly, sorted that issue and all seemed fine. Then this week kept stalling on me and hunting, gave the throttle a blip and stayed up for a while, but tickover was lumpy, power down until past 3k or so revs and eventually pulled well.

 

So i decided to do a process of elimination and some connector checks. All the injector plug terminals had some green corrosion, even though i had used dialectic grease on them previously ( year or so) so cleaned up and refitted and same, if not worse than when i started lol.

 

Same issue with the TPS and AIV connectors, so cleaned them up, couldnt even settle the idle with the idle screw, which can indicate an air issue or maf so i continued to inspect the maf and cas, visually connector wise looked fine.

 

Took off each coil pack connector to see if there was a change and it appears that cyl 5 has no difference, so i guess running on five cylinders will give me the lack of power and rough running.

So will change plugs and coil pack as a first measure to eliminate it at least.

 

Unfortunately i cant get my OBD scantech working yet, no port found, so another job to sort lol

 

Im going to continue working through the usual suspects, but in case i have missed something i thought i would post up to see if an eagle eye or anyone who has had a similar issue might be able to shed some more light:thumbup:

 

Cheers

Maf? Mine was similar I chased a misfire and even idle all round the houses. It it islet was fine over 3k but awful under it. New maf problem solved like night and day.

Definately MAF !

Ref your coilpack issue, move the suspect coilpack to another bank and do the same test. If the fault remains on that cylinder then the coilpack is not at fault, if it moves to the bank you switched it to, you know it was at fault.

 

Agreed the whole 3k issue sounds suspect maf, can you borrow a known good one to troubleshoot?

I have a similar problem, back fires ever time you let of the throttle. Juddering at low speed,fine after 3000 rpm:-(

electrically unplug the MAF and see what it does. The ECU will take it out the equation and substitute a value in 'limp mode'. it will not solve the problem, but describing what happens will help with the fault finding.

if it still runs on 5 then there is deffinately an issue on that cylinder. MAF fault would not cause one cylinder to drop out. if you think it was worse after you checked all the plugs and connectors then that would suggest there is still an issue with corrosion or a broken wire somewhere.

if you can get a scanner on there to see some live values this will help a lot.

im with Joely.

Check the injector to see if it is ticking/firing mine was doing a similar thing a couple of years ago and the wire in the injector plug casing had snapped

Cheers for the suggestions, here is wha ive found so far today, I did a voltage check on the coilpacks and all read 1.o ohm, so are in spec, however after checking the injectors, all read 14v apart from cylinder 3 which was 17v, now according to info i have read anything majorly outside 10-14v means a duff injector.

This would sort of make sense as there has been a smell of fuel recently, especially when booting a bit, so if its knackered it will be overfuelling and also the cause of the slight smoke when floored.

It must have been on its way out over a period of time rather than just dying as occasionally it would be very slightly lumpy on idle and i mean hardly noticeable unless you have your hand on the plenum and you could feel it.

 

Maf was always my first port of call and i visually checked it and will check the voltage tomorrow, the revs can go past 3k, which is why i initially ignored the fact it might be the maf, but until i can get the scantech connected and see the voltage i cant be certain.

 

So tomorrow will be changing the injector ( not looking forward to it lol) unless it comes out nice and easily and will change the plugs and coil pack on cyl5 and see what happens next.

 

Cheers again and will keep you updated, hope the weather holds out for a few hours:thumbup1:

Update, changed the injector, not too bad a job as i thought, still running the same, i disconnected the MAF and apart from idling higher it did seem to stabilise the engine and worse when connected so will have to change the maf.

Still no difference when removing the coil pack connector on cyl5, will change that tomorrow when i do the plugs.

 

So Maf it is at the moment, although engine still slightly lumpy, hopefully new plugs and change of coil pack will resolve that.

Got the laptop connected eventually and it looks like the maf 1,24v, but aiv at 90% needs to be 15% at idle and will not adjust, so definitely MAF for the main part lol

Glad you found the problem Graham - and good luck with the fix:wink:

Getting there mate, process of elimination and frustration, but so glad ive got the com ports sorted on the laptop, you can see the problem glaring at you then :biggrin:

aiv at 90% needs to be 15% at idle and will not adjust, so definitely MAF for the main part lol

 

i wouldnt worry about that until you change the MAF. with it being faulty the idle is lower than it would be normally so the AIV tries to ramp open more to reach the idle setpoint. 90% isnt the feedback from the AIV, its the demand placed on it which is why adjusting it makes no difference. If you imagine pulling a coil pack and puting more load on the engine the AIV has to open more to stop it stalling.

 

since you twiddled this earlier, once the new MAF is in go through the base idle procedure in the manual where you disconnect the idle valve and set the screw to get the correct RPM.

Yep, will have to reset the idle :thumbup1: now ive got diagnostics back, will make the job easier. I only had a replacement MAF a couple of years ago, which is why i didnt suspect it in the first place, it was one of those "cant be" moments :biggrin:

I have a similar problem, back fires ever time you let of the throttle. Juddering at low speed,fine after 3000 rpm:-(

 

I thought it had been sorted? :confused1:

Update, i got another MAF loaned courtesy of Bri (Znut) and the car runs better, however i have cyl5 down, so still running slightly lumpy and definitely down on power compared to before, so i had a multitude of issues aside from the MAF.

 

voltage reading on both MAF's on scantech is 1.24v, yet my MAF makes it run like a pig, so must be another component in the MAF that has died.

Will now re check the coil pack on 5, injector and ptu plugs and terminals and hope that it is an electrical issue and not a cylinder down :scared:

Silly question, you have reset the ecu right?

I have reset the codes on scantech and the learning, but will disconnect the battery while im looking at the ptu harness.

Worth a go isn't it, it may gave taught itself some bad habits.

Ive just disconnected the battery as there is no ecu reset on scantech and no option in the free consult :thumbdown:

 

Fingers crossed :biggrin:

UPDATE: ok after changing the maf and running better, i had to sort out the lumpy running issue, found to be cylinder 5, i have spark, so i know its not that, so i got the needle files out and cleaned the terminals on the injector and the plug and Hey presto, no lumpiness now :thumbup:

 

The only issue now is getting the idle to stay down, ive got the idle air at 15% but idle is 950rpm, so tomorrow will check all the hoses and clean the throttle bodies and as much of the plenum as possible as there is oily residue i can see through the balance bar holes.

Edited October 29, 201312 yr by groover