Poor idle on cold and midrange misfires!

[Ross]

I've not driven the RS2 for over 5 weeks... before the sympathy comes I spend a good chunk of that time in Florida

...anyway my brother (not Sonic) borrowed the RS2 and had great fun terrorising people up in the midlands, until the car started misbehaving. Issues are:

For 1-2min on cold idle you have to give it some revs or it just dies. After a minute or so it's fine, and won't reoccur until the car is cold.

There's hesitation and misfiring between 3-4k only when it comes on song with WOT. However if drive it with mid throttle, or if you mash the throttle to the floor. However if you progressively apply throttle to WOT it boosts fine.

After hesitation it sometimes goes into limp mode.

I've asked my bro to check clips and plugs around the ISV and along the intake, because the hesitation and occasional limp screamed 'boost leak' to me. He says it all feels tight. The idle is wierd in that it's only that early start of warm-up, like when the lambda is heating up... I changed the ISV the night before I left to solve my 'creeping revs' issue on lift-off.

Anyone got any pointers I can check when I get up to see the car? I'm going prepped to find a major boost leak but the idle is wierd - lots of 'bad idle when hot' threads but not the other way round, it's really throwing me off...

[driftin jo]

MAF connector

[diogocartier]

my car is with the same issue and I don't know what is the root cause.

Your car is loosing power after 30 min of operation?

[UrS4boy]

Ross: Could be the G70 MAF connector (pin issues) as suggested OR it could be a bad G39 O2 (lambda) sensor or even a bad G62 Coolant temp sensor. Possible POS issue as well. (??) You need to pull the MIL codes (if you can). More info on the G70, G39 and G62 available by clicking on the labels in this diagram:

http://members.shaw.ca/speedtek/UrS%20Engine%20Bay%20Device%20Map.html

[prj]

Leak test it, probably something loose.

Also, it is possible that the MAF, well... let's say...

[Ross]

I did think MAF but seeing as it is new and the plug recently cleaned so I figured it'll be fine... But good point, I ought to check it still has a wire

I'm still struggling to get and see the car myself, but codes will be the first thing I check, followed by hoses. Ignition crossed my mind but all POS and coils were replaced in the last 5 years, so hoping not. I have a spare lambda I'll take.

Will update this when I get to the car, no time at the mo, next weekend hopefully I can get up to Shropshire and sort it out

Thanks for the tips

[Ross]

Nail on the head Dmitri... the car has consumed it's 2,000 mile / 6 month old MAF

Pulled codes, 2324 (MAF signal outside of range). Here's a close-up of the damage. Is it possible to use the housing and wire of my old MAF, and swap the sensor and connector from the new one? That would give an effectively reconditioned MAF. I've just put my old one back on, car feels normal now, revs cleanly through the midrange as it should. Didn't want to do anything crazy with a slightly out of spec MAF but a quick WOT in 3rd from 40-80 suggests things are funcitoning correctly.

Hot Film MAF conversion is next on the cards I think

Just to add.. this happened (according to my brother) when he lifted off quickly to abord an overtake. A rather violent lift, sudden misfires and instant hesitant running. I'm thinking turbulence in the intake boot, probably from the sudden release from the DV, was the cause here.