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Discussion Starter #1
so this has got me stumped now, bloody thing.

its a 1.9 jtd m-jet 16v.

I'm missing low end power, you hit about 2.5k and it takes off like a mad badger, but low down nothing at all.

I suspected the MAF, so unplugged it, went for a drive and it pulls brilliantly without the MAF plugged in. great, new MAF job done.

now I have tried a MAF from my local garage, albeit second hand, made no difference, so wrote that off as a dead MAF. Ordered a new MAF, fitted it, still no low end power. leave it unplugged and it goes brilliantly.

not sure where to go next? I've gone over the VNT system with a fine tooth comb, it all works just fine, any actuator test, vacuum seems great and it clearly works as I have great power with MAF unplugged.

I've checked, cleaned and refitted the EGR and cleaned out the MAP sensor whilst I was at it and I am now completely stumped.

Can it honestly be that 3 dead MAFs, wouldnt be suprised if mine is dead but the second hand unit I got the garage I was told was good and I do trust them and the one I got brand new is genuine BOSCH direct from a BOSCH service centre.

what do we all think?
 

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Has it been mapped? Is it smokey under power?
 

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to me it seems your variable turbo vanes are stuck

get someone to start your car and switch off you should see rod moving on turbo
 

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to me it seems your variable turbo vanes are stuck

get someone to start your car and switch off you should see rod moving on turbo
I thought that but it doesn't explain it boosting up as it should with no MAF plugged in. :confused:
 

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I thought that but it doesn't explain it boosting up as it should with no MAF plugged in. :confused:
running off default
exhaust gases are driving inlet turbine slower than normal because the lack of inertia and once exhaust gas speed is high enough it comes into sweet spot thus normal power up rev range .....so i would check for splits in small bore pipe work from turbo actuator to control valve and then through to engine



EDIT .... when good MAF is fitted its learning correct values
 

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Discussion Starter #8
I thought that but it doesn't explain it boosting up as it should with no MAF plugged in. :confused:
agreed, thats what stumps me.

I can run actuator test on FES and VNT solenoid / actuator performs perfectly.

Should also add that it has front mount intercooler and all hard piping, so its not even like one of the pipes could have split.

Not mapped mate no and no real smoke to speak of either, certainly nothing more than usual its a fairly light smoker for a derv.

I have within the last 18 months also replaced MAP sensor, VNT solenoid and all associated vacuum piping and like I said, with MAF unplugged it all runs perfectly!
 

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Can you do a log of fuel quantity injected vs rpms on a full load run, 1 with MAF unplugged and 1 with MAF plugged in? Also a log of MAF output on the run with it plugged in would be good..
 

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Can you do a log of fuel quantity injected vs rpms on a full load run, 1 with MAF unplugged and 1 with MAF plugged in? Also a log of MAF output on the run with it plugged in would be good..
i would add boost control solenoid to that as well:thumbs:
 

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Discussion Starter #11
Yeh certainly, will have to do tomorrow if I can as its a bit too dark to see to unplug maf right now. Cheers gents
 

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Have you checked your VNT pipe?

Isn't MAF normally upper rev range where it shows symptoms.
 

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Discussion Starter #13
what is this vent pipe? embarased to say not sure what your on about there lol
 

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see above
 

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I have exactly the same problem on the same engine (but in a Fiat Sedici 4x4).

I ran it without the MAF plugged in because, as you say, it ran fine, but then the same problem crept in and about 10 miles later it ground to a halt.

One DPF later (£450 plus £300 diagnostics and fitting(rip off)) and it's working again but still has the low down power loss problem.

Desperate for some insight from any of you guys.... plus some spare change would be great!

CM
 

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I have exactly the same problem on the same engine (but in a Fiat Sedici 4x4).

I ran it without the MAF plugged in because, as you say, it ran fine, but then the same problem crept in and about 10 miles later it ground to a halt.

One DPF later (£450 plus £300 diagnostics and fitting(rip off)) and it's working again but still has the low down power loss problem.

Desperate for some insight from any of you guys.... plus some spare change would be great!

CM
so its not fixed then.........i personnally think its swirl valves sticking on inlet manifold
 

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so this has got me stumped now, bloody thing.

its a 1.9 jtd m-jet 16v.

I'm missing low end power, you hit about 2.5k and it takes off like a mad badger, but low down nothing at all.

I suspected the MAF, so unplugged it, went for a drive and it pulls brilliantly without the MAF plugged in. great, new MAF job done.

now I have tried a MAF from my local garage, albeit second hand, made no difference, so wrote that off as a dead MAF. Ordered a new MAF, fitted it, still no low end power. leave it unplugged and it goes brilliantly.

not sure where to go next? I've gone over the VNT system with a fine tooth comb, it all works just fine, any actuator test, vacuum seems great and it clearly works as I have great power with MAF unplugged.

I've checked, cleaned and refitted the EGR and cleaned out the MAP sensor whilst I was at it and I am now completely stumped.

Can it honestly be that 3 dead MAFs, wouldnt be suprised if mine is dead but the second hand unit I got the garage I was told was good and I do trust them and the one I got brand new is genuine BOSCH direct from a BOSCH service centre.

what do we all think?
Look here:
http://www.alfaowner.com/Forum/alfa-147-156-and-gt/232563-jtd-jtdm-mcsf-and-other-problems-fix.html

I'd say cracked vacuum hose, or faulty Pierburg valve, so VGT regulation doesn't work.
 

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I've just done a temporary block on the EGR valve using an aluminium can and tested it. Driving perfectly now.

So my EGR valve is faulty. It's letting exhaust gas into the engine at low RPM, causing a lack of power. It's also making the DPF clog up faster than it can regenerate.

I'll either be fitting a new EGR or blocking it off more permanently.

Here's the original thread on the FIAT forum i'm on.
Technical: Air Flow Sensor - The FIAT Forum

I'm thinking about getting a GT JTDm which has exactly the same engine as my FIAT Sedici. Less incentive now though as my car is back up and running!
 
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