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Hunting on Start up and Throttle response sluggish

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2.3K views 9 replies 4 participants last post by  damiencannell1  
#1 ·
Hi All

Due to new Jag diesel the Mondy's (2.0l Petrol) been sitting on the driveway and only getting occasional usage of late. I just haven't got around to sorting these bits out but not sure where to start.

So....

When starting from cold the engine hunts at idle. This settles down and doesn't do it when the engine is warm. Anyone have any ideas? I seen other hunting issues on the forum but not really the same as mine!

Next up is sluggish throttle response (this is where my wallet starts to itch!). Acceleration in 2nd and 4th seems really sluggish and almost like no power. I suspect one of three problems but im afraid im very much an amateur:

- One or several of the dreaded flaps clogging up the manifold.
- Fuel issue/filter
- Throttle body

If anyone has any comments or suggestions of where to start with these issues It would be most appreciated.

Cheers
D.
 
#2 ·
first of all, i'd take it for a good run, drive it hard, "clean put the cobwebs" if it's not getting much use, if no improvement, i'd go down the service route first, a couple of filters, a gallon of oil and some new plugs can work wonders.

Rough running could be spark related, might be the coilpack? doubt it would be the throttle body, as for the flaps, are you sure its not had the upgrade? Several who have posted in the i/m flaps thread have removed them completely, and just bunged the holes that are open up, saves the expense of new flaps, and if it hasn't got them, it can't eat them.
 
#3 ·
I second Siruncle advice, an Italian tune up (thrashing on the motorway) and a service (cheap and nice selling sweetner)

Failing that the most common problem would be the coilpack, doubt the throttlebody and the flaps would of caused a lot more damage by now and evident with a rattle sound from the bits bouncing around, its possible the flap actuator could of poped off its arm in the closed position so worth checking, there are threads around showing the arm/ball joint.
 
#4 ·
#5 ·
Hi Guys

Thanks for the replies, Much appreciated.

It was MOT'd last week and has had new track rod ends and brand new spark plugs. Its had a thrash up and down the A3 for the last few days for work as the Jag has a split intercooler hose! So its deffo had a run out to clear the pipes etc. I will change the oil, air and fuel filter to see of that make a difference to the performance.

The idle/hunting issue has been about for a while and is still happening after the plug change. Do you think the coil pack could also be the source of this or is it more likely to only affect the performance side of things?

Cheers
D.
 
#6 ·
imagine your rev gauge, well the coilpack has 4 sparks (1 spark per sparkplug) to make for every 1 rpm. at idle, say 750rpm thats 3000 sparks. at high speed, say at 5000rpm thats 20000 sparks.

in the higher rev range, a few missed sparks might not be noticed, whereas at lower revs one might make the car judder a little, a few closer together could affect your acceleration, cause a low spot or a judder.

a coilpack will set you back between ÂŁ30 and ÂŁ65 (prices sourced from eurocarparts) but you will get 25% off if you use code above, (maybe go for a slightly better than cheap one, bosch?) you can do this easily yourself, possibly in 10 minutes if you have the right tools. If it doesn't work, at least you'll then know you're getting a good spark.

plug leads could be a possible cause to eliminate, but again, its difficult to check them without specialist kit, or a new or known good set which will probably cost more than a coilpack.
 
#7 · (Edited by Moderator)
#8 ·
was gonna suggest the bay, but if can get oem, that'd be a bonus.
 
#9 ·
When starting from cold the engine hunts at idle. This settles down and doesn't do it when the engine is warm. Anyone have any ideas? I seen other hunting issues on the forum but not really the same as mine!
Is this just when sat ticking over or when on the move and using the revs as well? If it's just when it's sat and ticking over when cold it could be the idle control valve or the throttle sensor (TPS).
 
#10 ·
Hey, its only sitting at idle on first start up, not a problem when driving. Can the Idle control valve be cleaned/checked? also where is the throttle position sensor and i will give them a check over and replace if necessary.

Cheers
D.