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Discussion Starter #1
Hi guys

could do with some ideas please!

In neutral, the revs lethargically creap to a maximum of 3,500. Turn the engine off and back on again ....try again and its absolutely fine and will reach the red line at the usual pace.

I gave the car a good tune up on the motorway yesterday and it was perfect, able to red line it and no issues.

This issue has happened a lot recently. I'm confused by it being perfect, then not, then perfect. Its not egr related as that is physically blanked. There are no unusual noises.

Is it likely to be a sensor on its way out or a turbo related issue, or something else??

Thoughts appreciated.
 

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I would guess electrical because of the intermittent nature. If it's going into limp then there will be a code to read. If there's no code but the cars running bad then it indicates the cars map is receiving bad data. MAF and MAP could be start of investigation.
Or
Throttle position sensor.
 

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Discussion Starter #3
Cheers. I'll check for codes tomorrow.


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Discussion Starter #5
I do clean the map sensor reasonably often, but the maf is quite old. Could be a job for the weekend.


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I wouldn't go near the maf with carb cleaner..

Carb cleaner can be oily, and the very last thing you want is to leave an oily residue on the hot-wire element of the MAF...

Safer option is electrical contact cleaner on the MAF element, as it will dry without leaving any film/residue behind..

Even safe option is to unplug the electrical connector to the MAF sensor and take it for a drive... If it drives better, you've got a duff MAF.. If it drives worse, your MAF is likely fine.
 

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rev cycling at idle and low revs points very strongly to MAF as its at lower RPM that the amount of fuel injected is calculated by the MAF readings, once you get into higher revs the ECU will ''assume'' there is enough air and revert to pre stored parameters

TPS isn't a bad shout either but would show up across the range as failure is not liked to engine rpm but is either positional or Random as the potentiometer goes bad, the car may also stall, again randomly.

Map sensor is also a possible but could also show up with rough running whilst accelerating and decelerating as well as at Idle.

they could all affect fuel economy but the fact you describe it being mostly at idle and then what sounds like limp mode and then fine after a re-start points to MAF, I had this recently and read codes on torque app pro, got P010F, changed MAF all good.

shame your not nearer as I have a good MAF and MAP in the garage..I am keeping but would have been happy to lend you them for diagnostic purposes.
 

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Discussion Starter #9
Thanks guys! I'll get some electrical cleaner this afternoon, to be on the safe side. Bosch mafs are a bit pricey if i screw it up!

Cheers for the offer joey.

I shall report back later.


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Discussion Starter #10
Looking to get the maf sensor out ...but it looks like a sealed unit! ...and needs the cylindrical bit to come out too!

Am i correct or missing something?

(Pic in next post)

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Yea that's the sealed unit, the sensor won't come out of the housing so no point trying!

Two bolts hold it to the airbox, then one hose/snap clamp clip thingy that holds the rubber hose on the other side...

Same as the one on mine, the whole MAF and housing needs to come out I'm afraid, and you don't get as good access to clean the element.. and it's not interchangeable with the other unit where the senor is removable...
 

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Discussion Starter #13
Thanks Ed. I thought that was the case Grrrrrrrr!

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They are sealed..

TBH never cleaned one. They are cleanable because loads of people do it,have HAD one cleaned and it worked for a bit but really its just a stop gap.

in some diesels maf is considered a 50k service item so if you are pushing 100k or more I would just bite the bullet and change it out.

I got both maf and map from ecp for £120 after some negotiation..Bosch genuine on both.

Facet are equally ok and a bit cheaper.

Shop4parts do them.

I have a spare as I accidently ordered two...both were £90 inc VAT...but as said I am keeping as I am on the lookout for a GT with a banjaxed turbo for peanuts as I have a spare turbo as well...

My cousin wants one and I fancy buying really cheap and doing wishbones ,clutch ,DMF, refurb the turbo somewhere and then fit ourselves and use all the pre modded parts from my car and then down to AL for EGR delete and remap.

Reckon I can do the whole project for £1500 IF I find the right car he is a good lad and deserves a nice car only ever having had fiesta's Corsa's and the like.
 

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Discussion Starter #15
If I clean and it solves the problem, then I will get a new one. Its a case of problem solving first.

I can't get my ratchet and socket, to one of those nuts, the ratchet is too thick. The airbox is in the way and not enough angular movement for a spanner. I need one of those combination ratchet spanners or just a thinner socket wrench. Hopefully I can get one tomorrow.

Why is nothing ever nice and easy lol
 

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If I clean and it solves the problem, then I will get a new one. Its a case of problem solving first.

I can't get my ratchet and socket, to one of those nuts, the ratchet is too thick. The airbox is in the way and not enough angular movement for a spanner. I need one of those combination ratchet spanners or just a thinner socket wrench. Hopefully I can get one tomorrow.

Why is nothing ever nice and easy lol
I know exactly which nut you speak of.. It's that f**ker at the bottom isn't it...

Hidden from above by airbox/MAF etc... Blocked by the VNT solenoid from below...

I found that if I unsnapped the hose clip on the other side of the MAF, that free'd things up enough to bend and flex things about so I could get a socket on the end of an extension bar on the nut, then swing the ratchet in the space where the rubber hose was...

I think the first time I backed that nut off by 1/8 turn at a time, and took 30+ minutes doing it... wasn't until putting back together I found I could get a socket on it with some creative wrist work...
 

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God ,when compared to working on my E36's or even the Wife's old honda things like oil and filter and air filter are just a PITA.

That said bleeding the radiator on the beemer after a coolant change or any coolant system related work could be horrendous!

They all have their specific idiosyncricies..!
 
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