Need help with GSR idling issue, keeps dropping revs like its not sparking properly

[goingforadds]

Hi everyone,

my GSR seems to be having an idling issue, it only started a day ago, but it's frustrating the hell out of me

Symptoms:

It sounds like a miss-fire, it hovers around 700rpm, then drops intermittently, it sometimes feels like it's going to stall, like its struggling to hold revs/ or a slight misfire in the timing sequence


What i've looked for so far:

- So i've done a service, changed all the spark plugs and gotten new leads

- I've checked for air leaks in all the vacuum lines from the Throttle body and everywhere else

- Cleaned out the throttle body

- And looked for any loose plugs that could be causing me a poor idle

I can keep a decent idle with the air-con running, however, as soon as i turn it off or let go of the pedal its starts to loose idle again, it isn't stalling though and power is fine through the revs as i'm putting my foot down, however, you can still hear the stumble

I'm yet to try the idle speed motor yet or unplugging it, so i'll be doing that soon

But i wanted to ask if anyone had any other thoughts on what it could be?

Thanks Meta

 

[4piknup]

Could be a misadjusted tps, sounds like your isc is working ok.
Maybe biss is out as well causing the isc to bottom out and loose idle control.
There are vfaq on adjustment for tps and biss but they are pretty rough.
I adjust mine through the ecmlink and laptop

 

[khubner1]

don't touch the biss!.

check you power tr unit and coil packs. afm and tps before anything else.
your isc seems to be fine as without a working tps when the aircon kicks in you would stall.

 

[goingforadds]

thanks for the replies guys, I've looked up the Biss guide, but like Khubner1 has suggested i might hold off until i've done everything else, will give the TPS a good look over though, could fuel play a problem with idling? perhaps a faulty pump or clogged filter?

 

[4piknup]

I think that it not pump or filter related as this would mess with full throttle before idle. Idle is hard on ignition parts.
Isc controls aircon not tps. Tps tells ecu when it should be idleing. Tps may be misadjusted so ecu doesn't know it should be idling

 

[EVO-00X]

You're off to a good start by replacing those bits and checking the items you've listed thus far. A vacuum leak would have been an easy solution for you
Its pretty hard to diagnose over the internet as it could be any number of issues depending if its only an idle problem or different.
a) You didnt mention whether you hear any 'missing' if say you kept your foot on the accelerator pedal at 2000-3000rpm? You need to determine if its an idle only problem or whether there's an underlying problem that happens throughout the rev-range.
B) Do me a favour and see if the Crank Angle Sensor is loose and can be turned? the bolts could have came loose and put the timing out. If not, DO NOT touch it or adjust timing yet. Instead, check if the timing belt is loose after several rotations. If the CAS bolts are tight and the belt is nice and tight, dont adjust anything to do with timing at all. Our main aim here is to determine a simple solution as a timing related problem to ensure that the engine is not at risk of serious failure before moving onto other checks.
c) Try to get someone to help you test if there is spark getting through each lead. Get them to turn the ignition key whilst you have one spark plug lead unplugged from the spark plug and about 5mm from an earthing point somewhere on the engine. During cranking look for a nice blue spark that sparks the same rythm over and over. A bit like beats to the music... watch for missing beats during cranking. Check each lead one at a time, each time plugging it back onto the corresponding spark plug before moving onto the next lead to test. You'll be looking to see if each lead gets a consistent spark, therefore eliminating the leads, ignitor and coil packs as the problem. It may also not rule out the CAS entirely, as it could still possibly be the cause if there is a loose or freyed wire in the plug and earthing out or moving about losing contact whilst the engine is running. Also re-check each spark plug to make sure one of the new ones isnt now coated with oil suggesting that you may have an issue with compression in one of your cylinders and will need to get a leak down test performed.
d) Can you see if the Check Engine light is on in the dash? Sometimes a malfunctioning alternator and a weak battery can give similar symptoms. Check the earthing points for the battery terminal and the chassis - easy check. Whilst at it, check the rest of the wires on the same loom as the Crank Angle Sensor harness. There should be about 3 wires used for different temperature pickups for water etc. Make sure one of these isnt freyed and shorting out and that all are connected properly.
e) Dont touch the biss screw on the throttle body. Do not adjust idle on the throttle body idle screw either unless if feels finger loose to you. It could have backed out a little during time, but if its rock solid and not moving with the retainer nut tightly holding it in place, dont touch the mechanical items on throttle body unit at all. It would best be to check the idle stepper motor unit and TPS. There's a good tech sticky in this section somewhere on each of those units. The ISC is usually the main cause of idle problems, but it appears to be working when the aircon is turned on. Still, its worth a check.
f) Another issue could be dirty or damaged or faulty AFM, or a faulty ECU due to any number of reasons. You'll need to look up tech articles on fault-finding each of them.
g) Last of all, if it aint electronic or mechanical, its probably fuel related. Although its hardly ever the case, your symptoms might be due to something as simple as a clogged fuel filter, clogged injectors, or damaged injector plug/wire and/or resister pack, split fuel pressure reg vacuum hose or faulty FPR, or maybe a bad fuel pump or bad fuel. These things would be a long shot with idle problems, but if you get missfire throughout the rev range, then they are definitely worth investigating.
Hope this gives you a few things to check in the meantime lol :lol:

 

[EVOCPE]

or when the car is started pull the injector plugs out, 1 at a time and then plug it back in, if they make a change when u unplug it then they are working and its getting spark

Also try unpluggin the AFM while the car is on and see if that makes any difference

It could even be a crack in the cooler, give it a rev and get someone to stand in front and see if they can hear any leaks

 

[goingforadds]

Thanks for the replies guys,

I've tried some more trouble shooting today with a mechanic friend of mine whilst at work,

Still have the problem, however, we're getting closer to narrowing it down lol

So today we:

- Took apart the throttle body and cleaned out completely

- Took out the Idle steeper motor and cleaned it, checked it, it was very dirty lol

- We also searched for air leaks, we've found one, it's coming from the butterfly valve in the throttle body, I believe it's due to a worn out bushing, so we believe this is part of the problem, however, it still doesn't explain why it was such an abrupt change in the motors characteristic

- I've also changed the fuel, going back to BP ultimate, as opposed to caltex Vortex 98

- Run some injector cleaner again

- Checked the fuel pump and pressure/return lines, its feeding fine under pressue, I've got a replacement filter which i'll fit just incase

- We played around with the BISS screw, adjusting idle for the time being, its helped to keep the rev's up a bit better, however the issue is still obviously there, just not as bad

- Also reset the comp by disconnecting the battery and pumping the brakes

Now to the other issues I'm yet to check lol :

- There's no error light as such, everything is normal

- I haven't looked at the CAS yet, however, after driving it today and placing it under different load conditions, I didn't find any loss of power upon putting my foot down, in saying that i mean, it wasn't struggling, stalling or stuttering, though it does feel slight sluggish when doing so, like a slight delay, i can still feel also a slight miss-fire or uneasiness as I put my foot down, not in a hesitant way, more so that it's not pulling cleaning

Now for the offer issues that have come up lol!!!!....just keeps getting worst lol

- I"ve noticed that that it doesn't crank over immediately now, as in you turn the key and it just stalls sort of thing, like its been harshly kicked over, but doesn't actually start

- I've also lost 4-5 psi, it'll only boost to 10psi now?????

Thanks for all your help guys

Meta

 

[goingforadds]

Alright, just checked all the plugs, no oil there

Checked the CAS no movement, everything is still tight and solid there

Checked the injectors, they're all firing away

Unplugged the AFM, its working lol

Now onto the fault codes!!!!

(I"M hoping this was just bad fuel lol!!!)

 

[EVO-00X]

Hmm... it does sound more and more like a couple of things now:
1. An air leak somewhere between the turbo->icoola->intercooler piping->Bov->throttle body->intake manifold. The MAP sensor might be registering so much air but the amount of air and fuel mixing in the combustion chamber is fukd up. Have you noticed a more than usual rich fuel smell?
2. A dodgey O2 sensor (or wiring/plug) giving off false readings to your ECU and stuffing up your air/fuel mixtures. You would definitely notice that at idle and the noticable lag when trying to come on power when driving.

 

[goingforadds]

yeah, its becoming more hassle than its worth lol, i'm getting to the point where it might be kinder on my sanity if i just purchase another complete running 4g93t lol

Thanks for your help though mate, i'll keep trying and looking for more leaks or possible issues, the list is slowly getting smaller lol

 

[khubner1]

check the butterfly closed position screw

 

[Sevenlmns]

I had the same idle issues you seem to have just after i bought my gsr. And after doing roughly what youve been told to do managed to get the idle pretty stable, but after reading your "It just keeps getting worse post" i had to post as this is what happened to mine.

Also seems to harshly kick over when you start it as you said.
Running a 12pound wastegate spring with no other boost control and getting 7-8 pounds as well

I however do have a fuel smell and am 90% sure the problem is coming from an air leak, in my opinion this is where your problem will be, may just be an awkard one to find as there are no 'obvious" ones on my car either.

Lemon

 

[Michael Grackoski]

Sounds like a problem I had, I found out it was one of the cables going into the plug that goes onto the tr unit