Popping Noise From Exhaust

[Scratch]

I've got a r32 GTR (93) and its making popping noises from the exhaust while idle. The car has just had a timing belt and water pump changed including service just two days ago (new plugs, oil filter, motul oil, etc). I've always been getting horrible fuel consumption and i can see that i'm running rich from the carbon build up on the exhaust. I was sure the belt change and tune up would fix it, but alas it still plagues me.

The car has a twin HKS pods, N1 water pump, brand new battery and a thrust catback exhaust; stock standard otherwise including stock boost.

there is no fixed sequence of pops and happens every 10-15 seconds randomly. car was idle-ing for about 15 mins. Did a search on the forums and most people state sparkplugs is the cause but again, i have brand new spark plugs.

anyone have any thoughts on what might be causing it?

[QRI05E]

Have you noticed the idle fluctuating at all?? sounds it could be AFM or injector related... my R33 had slight poping on idle, after i cleaned the AFM its fixed the problem... a mate of mine had the same issue on his R33 GTR and his injectors needed a clean...

Cheers

[Scratch]

Have you noticed the idle fluctuating at all?? sounds it could be AFM or injector related... my R33 had slight poping on idle, after i cleaned the AFM its fixed the problem... a mate of mine had the same issue on his R33 GTR and his injectors needed a clean...

Cheers

hey QRI05E,

Checked the idle and it isnt fluctuating. Will try the AFM cleaning as suggested, might be worthwhile. As far as injector cleaning goes, whats the best way of doing this? getting some Injector cleaner additives? or professionally cleaned?

[Modena]

Most definately AFM or atmo BOV. Check AFM soldering inside (need to open it up)... or swap it with a good AFM to test prior doing this task.

[mad082]

could just be the rich mapping of the stock ecu. but try cleaning the AFM and see if that helps. just use some electrical contact cleaner.

[SXR]

what gap is the plugs? i do notice on some GTRs when there gapped to low it pops during idle and fine through the rev range.

also might wanna check the O2 sensor

[Zas)-(]

what gap is the plugs? i do notice on some GTRs when there gapped to low it pops during idle and fine through the rev range.

also might wanna check the O2 sensor

yeah mine pops after changing da plugs to .66 same as what described yet all good at normal rev range..

... its most likely plugs dude if u just got em changed..

so clean afm , check plugs and some spitfire injector clean.. all gooodddddd

[Scratch]

The car is running like absolute croc shit... heavy HEAVY fuel consumption, feels like its lost power and pop's while driving now. got some CRC C02 electronic contact cleaner. only had time to do one intake last night. sprayed in the same direction as the air flow direction. Will try and do the other today night.. improved slightly but still pop's during driving.

I'm begining to wonder if the AFM's are really the cause of this.. a new battery was installed the day after i got the timing belt , water pump and service done. the battery was out for roughly 3-5 mins only. did not press the brake lights or anything so i doubt the ECU has reset itself and is currently learning. But does anyone know if this is likely?

[QRI05E]

An ECU reset will not cause the car to behave this way unless its an aftermarket ECU... it sounds like an AFM issue... got any mates with an R32 GTR? try their AFM and see how you go... you can also test the AFM by disconnecting it on idle and seeing if the car has any reaction... if the car splutters/stalls then it may not me the AFm.. but if the idle stays the same then you have found the problem.. good luck and keep us posted...

Cheers

[Scratch]

Blasted the 2nd AFM sensor (turbo A's sensor) with contact cleaner (the slightly harder one to remove) this evening when i got home from work. The cleaner that dripped out was black so it was pretty crudded up in there. Will have to pick up some new HKS filter pads (sigh.. more money!) anyway I gave it a fair clean.

let the AFM dry up, connected the piping back and let the car warm up a little bit. No audible pops yet on idle.. very good sign (note: the engine was cold). Drove the car around for a little while till it warmed up to normal range. Then drove a little spiritedly around the block, floored it to check my boost, and suprisingly it went up to around 0.7-.8 bar! (is this normal anyone?)backed off at that point because I was coming to an intersection.

Drove around to cool down and parked the car, set the turbo timer on 2 mins. Had a listen to the exhaust, to my dismay it started popping again on idle (note: this time the engine was warmed up after all the driving).

I'm going to get a spark plug gap gauge from super cheap auto to check the gap on my spark plugs (0.8mil i believe its supposed to be?). From there I'll find out what plugs were used when my car was serviced last week. Will post the results.

I've read that you can check coil packs by measuring resistance between the terminals. more resistance = good (is this true?). Anyone know if its worthwhile checking the coilpacks at this stage?

Edited September 26, 2006 by Scratch

[Scratch]

you can also test the AFM by disconnecting it on idle and seeing if the car has any reaction... if the car splutters/stalls then it may not me the AFm.. but if the idle stays the same then you have found the problem..

sounds like a good idea, i'll follow your instructions and do this tommorow. cheers mate.

[QRI05E]

No probs... i highly doubt the poping on idle would be caused by the spark plugs... im pretty sure its AFM related...

[Scratch]

Okay, another update:

Didnt manage to get to supercheap or any other store before 5.30, so i wasnt able to get the gap gauge. Did an ECU reset by removing one of the battery terminals and then holding down the brake for a min. Restarted car, when it did misfire a few times. Remembered the test QR105E mentioned to check if the AFM's are working, pulled both out one by one and the car spluttered and died after each one was pulled out. It crossed my mind that I've just reset the ECU and it might have been remapping as i disconnected the AFM's. Just to make sure i didnt stuff up my mapping, I did the ECU reset again. The car drives better now (prolly the AFM clean), but still pops on idle.

Just incase someone is wondering what i mean by BAD fuel consumption. I filled up 54 liters of BP98RON, i'm at 3/4 tank and i've only done 184km!!!!

my bonnet sticker says plug gaps is supposed to be 1.05mm, this sounds a bit much to me, anyone know what the recommended plug gap would be? I'm going to be using NGK-R's this saturday when i can get some.

[QRI05E]

0.8mm would be the smallest gap i would run my plugs...

In what wat did you notice the car to drive better after the ECU reset?

[Zas)-(]

repco has the tool to check the spark plug gappage to ....

i think its easy to make a 25 cent call to the mechanic to ask him what he did realli.... n ask him wat the plugs were gapped at, from there you can go on.

i put .8m plugs it wouldnt pop...( but couldnt run 17psi ) after putting .66 my car flies yet makes sometimes popping at idle so concluded popping is related to the smaller gap

?

best thing is call up mechanic just ask em before u spend more cash

hope it helps man ... realli interested what the conclusion will be

[Az_StrYdeR]

I hope you haven't gone and bought those new filters pads, because I think its a waste of your money...

The HKS filters are rubbish, and when you can afford it, I suggest that you buy yourself a couple of A’Pexi Power Intakes

I recently read this article:

http://mkiv.com/techarticles/filters_test/2/

Then straight away went and bought an A’Pexi from bigsully84. The crap inside the HKS filter and adaptor was amazing when I took it off, and I hate to think what it does to engines…

If you sell off the HKS filters you should be able to recoup most of the money.

Anyway, give it some serious thought!

[Scratch]

I hope you haven't gone and bought those new filters pads, because I think its a waste of your money...

The HKS filters are rubbish, and when you can afford it, I suggest that you buy yourself a couple of A’Pexi Power Intakes

I recently read this article:

http://mkiv.com/techarticles/filters_test/2/

Then straight away went and bought an A’Pexi from bigsully84. The crap inside the HKS filter and adaptor was amazing when I took it off, and I hate to think what it does to engines…

If you sell off the HKS filters you should be able to recoup most of the money.

Anyway, give it some serious thought!

I read the article, SHOCKING... ABSOLUTELY SHOCKING! I do agree with it, I noticed the HKS filters are not very good at filtering small particles. Personally i thought the blitz one would be worse.. Okay now i have to spend MORE money again!

Taking the GTR down to a mates workshop to check out my coilpacks and plug gaps. I'll post updates then.

Cheers

[Scratch]

0.8mm would be the smallest gap i would run my plugs...

In what wat did you notice the car to drive better after the ECU reset?

throttle response improved, the car rev's freely before it seemed it bit laboured. the missfires during idle happens more when the ECU is reset. you could actually smell the fuel, these to me seem like characteristics of running too rich... it almost seems like it starts off really rich then leans out.

I'll prolly get about 200k's ish out of the 54liters i put in.. thats really worrying me.

[brad_gtr]

I had a R31 that only got 200 klms out of a tank full , turned out to be a dirty connector to the tempature sender !!.

Good luck Brad

[Scratch]

Damn, a dirty connector did all of that?! shows what can go wrong with little things. thanks brad, i'll check that as well. Another update:

Took the car down to hyperdrive to get ken to have a squiggle. They were pretty busy down there but being the good bloke he is, he still took the time to check out the car quickly. The car was misfiring all the way to hell, almost thought I lost a turbo with the way it was poffing,popping and spluttering. during the test drive ken said the car was way underpowered and its definately running rich as fk, and feels like there is a block somewhere. I have to book it in for further investigation, see what that turns up.

Took the car back to the garage and pulled out both afm's and blasted them with contact cleaner with a vengence, suspect it could be screwed even though it looked fine. 30 mins later, i pulled out the plugs and coilpacks. The coilpacks looked ok, no surface cracks or hairline splits besides the normal joins. The shocking part were the plugs! They were so caked with carbon it was jet black with no metal exposed. the plugs are only 2 weeks old. I'll post a picture of them when i have time. all 6 plugs were carbonized to hell. The gapping on them was something like .8 mil by the looks of it. Changed them to NGK-R plugs and re-assembled everything. The car did not behave like it did at hyperdrive yet, but i'll have to wait two weeks to see any real facts as the previous plugs were on for 2 weeks before it got reallly bad. fuel consumption is still around the 200K per tank mark, just filled up and I'm at 140K's and i'm past half tank already.