Technical JTD hesitation/ misfire at 2000rpm

[john55]

My JTD 115hp has developed a hesitation at around 2000 rpm, but only under light acceleration. If when I press the accelerator down a bit when it does it, it goes away immediately and the car accelerated, or if I lift off the accelerator a bit, it also goes away. It does not always do it and is more noticeable before the engine is fully warmed up.

It is starting to annoy me a bit though and seems to be doing it more as the weather cools down. Also, I now get a plume of smoke on cold starts, but I think that is glow plugs although there is no warning message.

Anyone had this before?

I have had a recent new turbo, intercooler pipe (the one that splits), Cleaned EGR valve, changed overboost valve (although it was one from a breakers yard), new MAF and cleaned MAP sensor.

 

[Argonought]

I'd do the EGR mod as mentioned elsewhere - should only cost you a tenner.

EGR shouldn't kick in anyway until the engine's warm but still worth doing I'd say

 

[PNL]

Give the throttle body a spring clean its a jtd and probably full of crap..like stilosportings was..:yuck:

 

[john55]

Give the throttle body a spring clean its a jtd and probably full of crap..like stilosportings was..:yuck:

It is a diesel, so no throttle body to clean.

I will try putting my beer can EGR blanking plate back in. I put it in a while ago, before I had this fault and it made no difference so I took it out again.

 

[OzMoSiS]

i think it was ABZSTILO who had this and he had a huge thread talking about it.

here ya go

 

[D4nny8oy]

It is a diesel, so no throttle body to clean.

PNL's right, there is a "throttle body". Although it operates on a different principle, it's still there.

Personally I'd fit the modified EGR gaskets, they were produced to cure this shuddering/hesitation problem at 1800-2500rpm on part-throttle.

 

[stilosporting]

if you search on my threads i had a real nightmare with this problem and there was no real answer at the time. i really hope for our sake you have better luck finding a solution.

although the new gasket could be the miracle cure???

 

[stilosporting]

https://www.fiatforum.com/stilo/131549-bad-flutter-light-throttle.html

above is the original thread. hope it helps some.

 

[PNL]

PNL's right, there is a "throttle body". Although it operates on a different principle, it's still there.

Personally I'd fit the modified EGR gaskets, they were produced to cure this shuddering/hesitation problem at 1800-2500rpm on part-throttle.

There certainly is a TB as young Danny has pointed out..thank you Danny for this useful post....lol

 

[john55]

There certainly is a TB as young Danny has pointed out..thank you Danny for this useful post....lol

I know what you are referring to. It is not a throttle body. No diesel has one. It is the stop valve (Fiat may have a different name for it). It is only used to cut off the air flow when the engine stops, in order to make it slow down more quickly and prevent any run on. When the engine is running, it stays fully open all the time and only closes for a few seconds when you turn the key off.

 

[Argonought]

I know what you are referring to. It is not a throttle body. No diesel has one. It is the stop valve (Fiat may have a different name for it). It is only used to cut off the air flow when the engine stops, in order to make it slow down more quickly and prevent any run on. When the engine is running, it stays fully open all the time and only closes for a few seconds when you turn the key off.

I fully agree with your description but in all Fiat documentation it is referred to as a throttle body (well it does throttle the air stream in a rather extreme way )

To save further argument on this I think it would be best if it is accepted that on a JTD at least

throttle body = stop valve​

 

[john55]

I fully agree with your description but in all Fiat documentation it is referred to as a throttle body (well it does throttle the air stream in a rather extreme way )

To save further argument on this I think it would be best if it is accepted that on a JTD at least

throttle body = stop valve​

OK, I didn't know Fiat refers to it as a throttle body. The point I mainly want to make is to differentiate it from the function of a throttle body on a petrol engine, which is a critical piece of the inlet system and where dirty throttle bodies can cause all manner of problems. The JTD would quite happily run with it not there, non operational or badly gunked up with soot / oil sluge like mine was. I cleaned it a while ago as it was very badly sooted up (I estimate about 20% reduction in the size of the air passage) and it made absolutely no difference to the way the engine ran, where as cleaning a very thin film of dirt from arould the butterfly of a petrol Renault Megane throttle body makes a huge difference in the way the car runs.

 

[stilosporting]

i disagree with a dirty throttle body/stop valve making no difference on a diesel. when i cleaned mine (estimate 35% reduction) i had 90% smoke reduction and quicker pick-up/response in acceloration.

although granted they work differently on a petrol as they increase/ reduce airflow accordingly. whereas on a diesel is is on/off.

the name 'stop valve' makes more and more sense though

 

[john55]

i disagree with a dirty throttle body/stop valve making no difference on a diesel. when i cleaned mine (estimate 35% reduction) i had 90% smoke reduction and quicker pick-up/response in acceloration.

although granted they work differently on a petrol as they increase/ reduce airflow accordingly. whereas on a diesel is is on/off.

the name 'stop valve' makes more and more sense though

Did you notice any reduction in idle vibration afterwards? This is one thing I hate about the JTD.
Also did you clean the whole manifold or just the TB? I am debating whether to take my inlet manifold off and clean it or not.

Also, I have now blocked the EGR which seems to have stopped the original stutter problem.

Thanks.

 

[OzMoSiS]

john, does your car lose power completely like in my scenario or is it just a slight "flutter"?

 

[john55]

john, does your car lose power completely like in my scenario or is it just a slight "flutter"?

Just a misfire. If when it does it, I press the accelerator more it goes away. Yours maybe the same problem though. Basically if the EGR valve sticks open you get no boost from the turbo, so very little power.

 

[Argonought]

Did you notice any reduction in idle vibration afterwards? This is one thing I hate about the JTD.

Also, I have now blocked the EGR which seems to have stopped the original stutter problem.

I told you - you should have done that mod

My experience is that an active EGR system makes the engine vibrate less. In fact, if anything I'd say mine vibrates more since I've done the EGR mod although it's entirely possible I've just imagined it as a whole stack of things seem to affect how smooth the JTD idles (like weather, temp, condition of sky-roof and stuff in door pockets etc )

Have you considered checking/adjusting tappet clearances?

 

[john55]

Have you considered checking/adjusting tappet clearances?

Mine is the same, both with or without the EGR blanked. I thought you said yours changed when you unplugged the EGR, rather than blanking it off, which is understandable.

I have checked the tappets. They are all within spec, but 2 are close to the limit. Adjusting involves buying a set of shimms and a special tool, then changing/ adding shimms to get the correct clearance - not a simple job.

I am mainly interested in knowing if I should bother removing the whole manifold to clean it, or if this is a waste of time.

 

[Argonought]

"Mine is the same, both with or without the EGR blanked. I thought you said yours changed when you unplugged the EGR, rather than blanking it off, which is understandable."
I did but struck me as doing much the same thing

"I have checked the tappets. They are all within spec, but 2 are close to the limit. Adjusting involves buying a set of shimms and a special tool, then changing/ adding shimms to get the correct clearance - not a simple job"
Tell me about it - which it why I've not bothered checking mine

"I am mainly interested in knowing if I should bother removing the whole manifold to clean it, or if this is a waste of time."
Yes, I'd like the answer to that too although recently when the garage looked at mine they reported the soot in the throttle valve was less then in many diesels they've worked on - so on that basis I'm not hopeful it's worth doing.

 

[stilosporting]

based on the soot in my tb im sure the manifold could do with a clean and wil be done before the/an engine is refitted.

with the flutter i noticed it go when i unplugged the egr but that brought up its own problems. and even after fitting a new egr the problems were there. one of the reasons this issue was driving me insane.