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General 1.9 MJET Terrible MPG less than 30!

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General 1.9 MJET Terrible MPG less than 30!

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bobbycarver

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Hi, bought the 1.9 MJET sporting a few weeks back, so im still getting to terms with the car however i think something is quite not right. i will list the problems im having.

- low mpg, my mpg is sitting on 29.3. before anyone says its from short journeys its not, I travel 15 miles each way to university down the m6, gives it a good run between 70-80. the mpg will go up to around 31 but as soon as i exit the motorway its back down again. this surely isn't right? i've changed fuel, using v power nitro diesel and no difference. im doing just over 200 miles a week


- first gear has no power/ boost. puling off is shocking, i can go up to 3.5k revs and my old 1.2 corsa would pull off faster. go into second gear however and it pulls hard after 2.5k revs but dies down again.

- when in traffic in 1st gear at a crawl the car will jutter

- sometimes takes long to start up, first time start up takes ages, ill wait for the lights to go out, twist the key and it will try and start but takes atleast 10 seconds for it to get going, once it does get going white smoke comes shooting out the back. this doesnt happen all the time though. infact most of the time it starts without any problems even on cold morning.


all i can think of is the EGR, would there be anything else?
 
Could be your MAF sensor, the one thats right after the airbox. I had similar symptoms with the poor MPG and that was the culprit, new MAF fitted and shot back up to 50mpg.

A test a lot of people do is going for a drive with the MAF disconnected so see if it improves performance, it didnt for me personally but then the new part did so you could try it but it might not rule it out.

Do you have access to a fault code reader, this will confirm if its the MAF or not?

It could possibly be EGR, its worth giving it a clean if you dont mind getting your hands dirty, there is a good guide in the guides section which outlines everything you need to know to do that and while your at it you should (very carefully) remove and clean the MAP sensor just to rule that out too.

Other than that if those two things are replaced and you still have problems its time to look at the Boost hoses, there is a common fault of the 90 elbow hose straight after the turbo, its well documented on here. If there are no leaks after the turbo you should look at the vacuum pipes before the turbo, turbo actuator etc... Its easy to find stuff about it on here and also on the alfa forum if you search JTDM *your issue* as opposed to mjet.

But take it a step at a time, sounds like it could be the MAF due to the poor MPG, as was with mine but best way to know if it is is to get a diagnostics done, better still if you have your own fault code reader but its not expensive to get the codes read at a garage.
 
tjscotton said:
Could be your MAF sensor, the one thats right after the airbox. I had similar symptoms with the poor MPG and that was the culprit, new MAF fitted and shot back up to 50mpg.

A test a lot of people do is going for a drive with the MAF disconnected so see if it improves performance, it didnt for me personally but then the new part did so you could try it but it might not rule it out.

Do you have access to a fault code reader, this will confirm if its the MAF or not?

It could possibly be EGR, its worth giving it a clean if you dont mind getting your hands dirty, there is a good guide in the guides section which outlines everything you need to know to do that and while your at it you should (very carefully) remove and clean the MAP sensor just to rule that out too.

Other than that if those two things are replaced and you still have problems its time to look at the Boost hoses, there is a common fault of the 90 elbow hose straight after the turbo, its well documented on here. If there are no leaks after the turbo you should look at the vacuum pipes before the turbo, turbo actuator etc... Its easy to find stuff about it on here and also on the alfa forum if you search JTDM *your issue* as opposed to mjet.

But take it a step at a time, sounds like it could be the MAF due to the poor MPG, as was with mine but best way to know if it is is to get a diagnostics done, better still if you have your own fault code reader but its not expensive to get the codes read at a garage.
Click to expand...

thanks for the information! i've got my own diagnostic kit along with the paid version of multiecuscan so ill give that a go and ill post back soon. thanks
 
ok so a few errors have come up not nothing on the maf, see attachments
 

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Hmm okay then, give running without your MAF connected a go and just see what that does. It might make running a bit worse in which case you know its not that but if its better then you know its the MAF causing your problems. Sometimes things won't throw up an error until its royally knackered such as the EGR. If MAF is a dead end and doesnt make a difference id give cleaning the EGR a go, its not too difficult just need to be patient and careful not to strip the threads when retightening as they go into metal that doesnt seem to be that different from the strength of cheese.
 
Those random set of faults (assuming they're not current) probably means your battery / alternator / earthing points may be not up to scratch. This in turn would cause your battery be be constantly charging and put extra load on alternator. Probably not to the extend your getting but it's worth getting the battery checked.
 
tjscotton said:
Hmm okay then, give running without your MAF connected a go and just see what that does. It might make running a bit worse in which case you know its not that but if its better then you know its the MAF causing your problems. Sometimes things won't throw up an error until its royally knackered such as the EGR. If MAF is a dead end and doesnt make a difference id give cleaning the EGR a go, its not too difficult just need to be patient and careful not to strip the threads when retightening as they go into metal that doesnt seem to be that different from the strength of cheese.
Click to expand...

thanks. ill disconnected the MAF, when you say disconnect do you mean just pull out the electrical connector or remove the maf completely
 
ChrisUK said:
Those random set of faults (assuming they're not current) probably means your battery / alternator / earthing points may be not up to scratch. This in turn would cause your battery be be constantly charging and put extra load on alternator. Probably not to the extend your getting but it's worth getting the battery checked.
Click to expand...

thanks for the help, ill get the battery checked over :)
 
tjscotton said:
Just the little connector itself, sits right after the airbox.
Click to expand...


ok so i disconnected the maf, turned on the engine and waited for it to get up to temp. drove 10 miles mix of country roads and some stop and start, and there is no change apart from a slight whistle noise
 
Right ok, still doesnt 100% rule out the MAF but i'd look at other things first. Good port of call would be to clean the EGR valve out to rule that out. Like i said earlier if you look in the guides > grande punto section you'll find it in there its pretty easy to do just take your time.

Do you get any black smoke when your on boost? Or just more smoke than usual? Could point towards a boost leak if its whistling. Have a look at the post KBonnie put in a similar thread i posted a few weeks ago regarding boost leaks;

https://www.fiatforum.com/grande-punto/418029-m-jet-laggy-when-up-temp.html

If you clean the EGR give the MAP sensor a clean while youve got the EGR off, its the sensor that goes into the inlet on the drivers side of the engine - its held in by just a single torx bolt, just be careful when you clean it as the sensor itself is fragile so I used a normal tooth brush as opposed to a wire brush that you should be using on the EGR.
 
tjscotton said:
Right ok, still doesnt 100% rule out the MAF but i'd look at other things first. Good port of call would be to clean the EGR valve out to rule that out. Like i said earlier if you look in the guides > grande punto section you'll find it in there its pretty easy to do just take your time.

Do you get any black smoke when your on boost? Or just more smoke than usual? Could point towards a boost leak if its whistling. Have a look at the post KBonnie put in a similar thread i posted a few weeks ago regarding boost leaks;

https://www.fiatforum.com/grande-punto/418029-m-jet-laggy-when-up-temp.html

If you clean the EGR give the MAP sensor a clean while youve got the EGR off, its the sensor that goes into the inlet on the drivers side of the engine - its held in by just a single torx bolt, just be careful when you clean it as the sensor itself is fragile so I used a normal tooth brush as opposed to a wire brush that you should be using on the EGR.
Click to expand...

thanks, ill give that ago tomrrow when i have more time.
 
Last edited:
That alternator d+ error is a classic
Clear it and make sure it's not coming back while you drive or if you let the engine idle after rev.

You may see it again on startups nothing serious.
All is happening is that alternator is not energizing on startup and needs a lil rev-sometimes.

Read voltage to make sure it's fine.
 
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