Polo rough idle on cold start, idle stumble, etc

[s4mmie]

Thanks Jmac, yeah its definitely crap when the SAIs working. Revs up fine but when it drops back down coughs and splutters and farts, happens if I drive it too fast after startup too. If its the SAI it won't be giving me any problems when it's gone! Hopefully I'll get it sorted before Pog Wars...

[Jmac]

Thanks Jmac, yeah its definitely crap when the SAIs working. Revs up fine but when it drops back down coughs and splutters and farts, happens if I drive it too fast after startup too. If its the SAI it won't be giving me any problems when it's gone! Hopefully I'll get it sorted before Pog Wars...

Yep too true, see you there mate
Jmac

[s4mmie]

Thought I'd post this here, save a new thread and all...

The little pog has developed a new annoying symptom... it idles at about 750rpm, nothing wrong with that, but it seems to be pulsating up and down ~20-30 rpm. Almost like it's hunting.. like a vacuum leak. It still has it's big hiccup where it will drop down to about 450rpm for a second and then bounce back up, but that's been there for a while :/

I'm going to spend the day tomorrow giving it the once over as it's due a service.
I'm going to:
Change out the plugs and re-gap them to 0.030" instead of 0.040"
Check all the vacuum lines and fit the TIP if I have time,
Check all my intercooler hoses,
Check the DP to turbo connection (turbo bolts seem tight)
and... what else should I have a look at? Any ideas?

I've slowly been losing coolant as well.. in the last 10000kms it's gone down about half an inch :/ In the old days I would suspect a head gasket with the symptoms, but I don't know, I really hope not.

So as I was saying, any other things I should check out while it's in bits?

[Jmac]

Hardly be head gasket mate, I would be checking the radiator or the fan switch area on the rad, very very common and covered heaps on here. Id be gapping the plugs to 28 thou, just saying. I had one stumble like that before way back, it ended up being a batch of crap fuel in it, im sure if you scanned it there would be no faults. If you were drawing secondary air you would know about it
Cheers
Jmac

[Redliner]

Could it be a misaligned throttle body?

[Jmac]

Generally would only be the case with a gummed up one, or a flat battery or one that's been disconnected, but not a bad call Redliner.
Cheers
Jmac

[kaanage]

Sort the plug gap before anything else - with a big gap like that, the plugs can actually start sparking across the insulator rather than the gap if there is enough carbon on the insulator.

[s4mmie]

Can I reset the throttle body myself? I don't have a VCDS cable. Ill take the throttle hose off and give it a clean with some throttle body cleaner. Has anyone used that engine cleaner foam you spray into the intake manifold? A mechanic friend swears by it and says its standard procedure for Subarus at service time to clean the crud out.

Yeah I want to get the plugs sorted. Thinking of going back to standard coppers over the iridiums. Standard are BKR6E's?

[kaanage]

If the iridiums are in good condition, then there's no reason to ditch them unless they're the wrong temp range

[noone]

I've used the throttle body cleaner (Subaru stuff), but never had any real issues with buildup. Pretty easy, to use, just do it outdoors away from people.

[Jmac]

to do it properly it needs to be aligned with software. The Subaru cleaner is great but if you read the can not recommended on DBW throttles. . The plug gap would be killin it for sure, its a fair gap for the spark to jump. And like I say I had one a while back and all it was bad fuel, a fresh tank and a shot of one shot in the tank and the car has been fine ever since, I seen it for a couple of years after that with no complaints. And if you scanned it there would more than likely be no faults.
These engines idle pretty stable so im sure you will have it right pretty quickly

Cheers
Jmac

[noone]

if you try new plugs, 7E's are a common choice for Tuned Polo's

[s4mmie]

I managed to get a little time to go over it on the weekend.
Re-gapped the plugs to 0.028",
Cleaned the MAF, IAT and MAP sensors,
Checked any IC clamps I could get too, I didn't have time to take the bumper off.
Did a basic reset of the throttle position. Read somewhere that you turn the ignition on and wait for it the high pitched sound from the throttle body to stop. With the throttle hose off, it did appear to be doing something..
Also gave it a good clean with TB cleaner.

It seems to have helped the problem, it's still there though. I'm going to get a bottle of tank cleaner on the off chance it was a crap batch of fuel.. I've checked it over for anything sinister and can't find anything (no codes either). I think I'll wait for it's big 90k service and take it in.

[kaanage]

Have you tried an Italian tune up since the maintenance work?

[s4mmie]

I haven't had a chance yet unfortunately... I want to chuck some tank/injector cleaner in and then take it for a good thrash