jumpy idle at start up

deian · Unread post by **deian** » 05 Jul 2006, 18:05

Hi guys, (2.1td 1998)

I started my car leaving from work today (16:30, hot day, car not been used since 10am) and the idle kept bouncing from exactly 1000 to exactly 1500, blipped the throttle and it was the same when i came off it, i reversed out and it was fine when i got changing directions, but no engine light as this was happening... any ideas what this was about, i guess it was a one off as it didn't happen when i tried the car just now, but would still like to know just in case it could lead to something more serious.

Thanks

JohnD · Unread post by **JohnD** » 05 Jul 2006, 18:12

Could be a little bit of air in the fuel line. If the trouble persists on startup, give the primer bulb a few squeezes before starting. If the trouble then goes away, sure enough, it's air.

deian · Unread post by **deian** » 05 Jul 2006, 18:43

air? i think the revs were too calculated to be caused by air, can't think how air got into the system though, unless it's the hot weather and high pressure weather?

AndersDK · Unread post by **AndersDK** » 05 Jul 2006, 20:27

Deian I agree with John -

Air in the fuel is the most common teaser when diesel engines do odd things. The air is coming from any ever so small leak in the fuel lines - a pin hole from rust - a hairline crack on perished rubber lines - any tiny imperfection at fuel filter seals. The fuel oeverun return lines are suspective as well.

The reason is that the way the governor works in the rotary fuel distributor pump makes it unstable if air is allowed to get into to pump. Thus the fuel quantity varies a small amount constantly - with the engine revs hunting as a consequence.

I have a similar problem on my BX TD : when the fuel is low in the tank - the engine revs becomes highly unstable - sometimes it even tends to run on like a ghost is controlling the throttle pedal. Not so very funny when leaving the Highway and approaching a roundabout

Start diagnosing as pr JohnD

deian · Unread post by **deian** » 05 Jul 2006, 20:44

ok, i will check for visible leakage, i've been running on 3/4 to 1/2 a tank all week though, so it's not empty at all, maybe this weather is causing my baby to have some fits

thanks again

BonceChops · Unread post by **BonceChops** » 07 Jul 2006, 00:09

Don't forget the 2.1TD Xantia has a fly by wire electronic pump. They are known to have erratic idling problems. Early EPIC pumps had a problem with the pump body causing pump failure. I hope it is not a taste of the future for you my friend.

deian · Unread post by **deian** » 07 Jul 2006, 16:15

Mine was one of the last 2.1's did they update the EPIC pumps during the 2.1 phase, or was up dated or replaced when the Hdi's took over.

I doubt i'd have many problems, it's done 190k without a hickup, although there is a certain point during a car's lifetime where everything will fail one after another, so maybe my car has gone through that stage with the previous owner, or at least this is what I hope.

Mind you, I prefer electrical/puzzling problems rather than (say) a clutch failure, or head gasket, at least there is something to work and learn as you solve the problem where as with a clutch you know, it's gonna be long day (or two), but there is no learning as it's quite straightforward in general, and the car is immobile when it breaks. Get me!?

BonceChops · Unread post by **BonceChops** » 08 Jul 2006, 19:53

deian wrote:Mind you, I prefer electrical/puzzling problems

Have you seen the price for a replacement EPIC pump?

deian · Unread post by **deian** » 08 Jul 2006, 19:58

This is bad news yea.... anyway, it hasn't happened since, so i will let sleeping dogs lie now.

Let me guess.... about £375? Higher or lower?