2.4 JTD Hesitating (but clears with power) - Alfa Romeo Forum
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(Post Link) post #1 of 7 Old 28-11-10 Thread Starter
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2.4 JTD Hesitating (but clears with power)

Yes I know another hesitating question but mine clears with a bootfull of power and does not seem to fit with what I found using the search!

Its a 2001 156 2.4 JTD that apart from the hesitation runs normally and does around 42 mpg. If I have been driving the car hard before finishing my journey it doesn't seem to hesitate at part throttle on re-start even from cold. If I have previously been doing a normal journey it will tend to hesitate straight away on start. If I rev the car hard (having allowed it to warm up) I get a fairly large cloud of black smoke and the hesitation clears. If I then continue to drive the car hard the hesitation won't return. If I drive the car on low throttle (20 mins or so) i.e. motorway driving or stuck in traffic it will again hesitate again until I boot it.

Any Ideas? I can live with it but if it is an easy (i.e. cheap!) fix then that would be great.

Cheers

Andy
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It could be a 'sticky' EGR valve

Has the car been fitted with a tuning box or remapped?
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Its not fitted with a tuning box and has not been remapped to my knowledge.
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My experience with faults on assorted JTD engines has led me to the conclusion (others may feel differently) that there are two principal culprits for unusual running issues which cannot be easily traced :

1. The EGR - solution: strip it & clean it/replace it/blank it off.
2. The MAF - solution: replace it (ouch)/clean it. To be honest, cleaning the sensor is a pain.

You could try disconnecting the MAF sensor completely (just unplug it), that should make the car run on a default setting in the ECU. If it's altogether more 'perky' and you suffer no hesitation at all etc etc then you know there's a very good chance that the MAF is goosed.

Other questions I would ask:
Presumably the car is regularly serviced?
How many miles has it done?
Have you tried running any injector cleaners and/or additives through the fuel system?

The turbos are generally really reliable to pretty high mileage, but it is remotely possible that a fault could be present, the actuator valve gubbins usually goes first.......

Ocht
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Many thanks.

I did a mini service myself in May. I changed the oil (with Forte flush), oil filter, air filter & fuel filter and also added Forte fuel system cleaner at the same time. There is far less smoke than before. In addition it supposedly had a new MAF fitted by the Alfa Dealer just before I bought it.

It has done 101,00 miles. So maybe the EGR then?

Cheers

Andy
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I'd look at the EGR, but check the MAF just in case
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(Post Link) post #7 of 7 Old 05-02-11 Thread Starter
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Sorry to drag this back up. However, the car now seems much better and the reason seems a little odd unless someone more mechanically minded can enlighten me. Basically the car was starting fairly poorly and on changing the battery I discovered that a 'tight fisted' previous owner had used a battery more suited to a 1 ltr car. Simply by changing to the proper battery the car is now far less hesitant. There is still a little bit of hesitation but it is far better overall. Any ideas why? I could understand it if it was just better after a start, as the alternator is working harder to re-charge the battery, but it is better all the time? Any thoughts?

Sorry, having read one of the top sticky threads it seems that it could well be the battery.

Last edited by rolandpull; 05-02-11 at 21:34.
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