Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[GaryBC]

1) Very slightly rough idle but otherwise performs perfectly. Pulls as hard as it always has and runs sweet as a nut. Recent (a few weeks ago) MoT emissions were perfect. No mayo under oil filler cap. (She consumes a little oil - a cupful a month - but she is over 200k miles old!) I fitted new plugs when I did the rocker cover gaskets six months ago - this 'fault' has only surfaced in the last week or so though.

2) Normal driving (gentle, hard, 'stolen!') temp gauge pretty stable in the mid-eighties. Not enough variation in the reading to catch my eye. Sitting in traffic the temp rises to the low nineties until the aux fan cuts in to pull it back down again - it will then drift up to c92 until the fan brings it back to c87 and will continue to cycle up and down until I get moving again. After 10-15 minutes driving it will settle back do to mid-eighties and stay there.

I don't know if these two sets of symptoms are related and point to anything specific or if they are two completely separate issues, but I'd like to put them both right if I can!

Any ideas?

Cheers,
Gaz

[PMitchell]

Gary,

re: point 2 - sounds normal to me, my 2.6 does just the same and has always done so, settles at 85 on a cold day whatever speed it is run at, and drifts up to the fan cut in temp and then goes up and down until running fast ish again with more air flowing over the radiator. On a hot day just runs slightly nearer 90.

Re point 1 - rough idle, hmmm.... many possibilities, mucky / sticky egr, bad leads / DIS pack, blocked air filter, lazy injector, etc. Not sure but start with the stuff that can be cleaned - egr etc.
I take it that you used genuine GM rocker gaskets and black sealant when you changed them, 'cos if not pattern ones have a nasty habit of only lasting 4-6 months and then filling the plug wells up. Pull the leads and check if there is any oil in the plug wells.

Does it lose any water?

The only other thing that might be worth checking is the lamba sensors, mine went (but not failed) at 135K miles and renewed they have given the engine back 10% more fuel economy and a better running temperature and smoother idle.  These hadn't failed on mine, just got sluggish and so the mixture was cycling to try and keep up.

Cheers

Paul

[JasonH]

I would say almost definitely that one of the fans on the front of the radiator has failed. With the aircon on auto these should both run together (I can't remember if that's all the time or just when required). With aircon on auto the car should regulate its temperature really well. If one fan has stopped then the temperature cycles a bit in traffic and when a bit hot the idle gets a little lumpy.

[GaryBC]

Hmm... Food for thought - cheers guys.

The aircon packed up last year. I might get it fixed but have other (better?) things to spend a few (?!) hundred quid on! Take your point about the fans though. Is there a way of checking they're all working ok? Although my guess would be that, even if it's failed, it's not causing the lumpy idle as the idle is lumpy before the engine 'overheats'.

Up until only a month or so ago the engine temp never varied by more than a needle's width at around 82 - 84 deg. Rain or shine, hot or cold, thrashing the nuts off it or idling for hours. And this new instability seems to correlate with the slightly lumpy idle.

Sounds like my best course is, as Paul suggests, to start with the simple/cheap options and work outwards! I used kosher GM gasket/goo and the entire area is bone dry so it's not that. Air filter & EGR is probably first! Does the EGR come apart for cleaning? Or is it a replacement job? Leads, DIS pack and injector are obviously 'replacement only' fixes so they'll come last! (Plus, of course, I'd have to replace all 6 injectors as I'd never work out which - if any - was the dodgy one. I guess I could always run a can of injector cleaner through the tank?)

The Lambda readings were straight down the middle at it's MoT less than three weeks ago so I'll probably discount that as the source of the problem.

Thanks. y'all!!

Gaz