Technical Cold Backfire no acceleration

[TuX]

When the car is cold it just wont rev, any touch on the throttle brings the jrevs down then it backfires. If i crawl around for 5 mins / 1/2 mile it eventuially wakes up a bit.

Any idea what could be causing this???? its a 155 hgt.

Full accelerator doesnt do anything when warm either, it seems to be at maximum hp half way down the accelerator, im thinking a sensor or fueling or ecu problems.

Anyone had this its driving me mad:bang:

 

[Ffoxy]

I havent had this in any new car but waaaay back, cars that backfired had either the ignition timing out (too advanced) or poor fuel / air mixture (usually too lean IIRC). Can also be an exhaust valve leaking but as yours is better when warmed up I cant see it being that.
These days it could be the timing belt out by a tooth or two, has it had, or does it need a cambelt replacement? Failing that it might be an engine management problem causing issues with spark / fuelling timing or even the throttle position sensor.

Are you sure its backfiring and not just running rough? Rough running can be a lot of things but it might be worth a look at the coolant temperature sensor maybe?

 

[TuX]

Its more of a pop than a bang, just wierd that the throttle increase causes the revs to go down,

What about a spark plug not working, would that cause samey issues?

might have to take it to a fiat mechanic although im not looking forward to that:yuck:

 

[Ffoxy]

Its more of a pop than a bang, just wierd that the throttle increase causes the revs to go down,

What about a spark plug not working, would that cause samey issues?

might have to take it to a fiat mechanic although im not looking forward to that:yuck:

Mixture sounds way too lean for some reason, no small pipes off the induction / airbox side are there? Is the car standard in all respects?

 

[airey hgt]

sounds like its overfueling mate does it smell of petrol id take a plug out see if its runnin rich before u take it anywere

 

[Ffoxy]

sounds like its overfueling mate does it smell of petrol id take a plug out see if its runnin rich before u take it anywere

Air leak will actually lean the mixture and the ECU will overcompensate, symptoms will be similar IMO. Needs a good look over on the fuel and air sides.

 

[TuX]

Had the engine problem still there,looking for airbox stuff, found a couple of loose wires but i think their for ecu checking, and a random box attached to the airbox, circled, what is that, never seen like it before.

After a couple of minutes the engine sound changes noticeably so i checked and the problem was gone. Wonder what causes this for a couple of minutes, the sound difference was audible.

Do injection cars still have a choke somewhere automatic??

 

[TuX]

Yes, smells a lot like petrol when it hiccups and i swear its drinking more than before, thanks btw

 

[TuX]

Thanks all for your input, have the guy from the garage picking it up from cold and taking it to the garage,

he will c the problems and hopefully give a solution.

Bonus is he doesn't charge until he finds what's wrong, and he's honest

I will keep u all informed in case anyone else has the same problem

 

[TuX]

Just an update, keep u guys informed to help the future generation,
apparently the problem was £500 of issues, MAF sensor and Lambda sensor making it up as they went along, completely random outputs, no doubt ecu was bricking it.
£150 maf sensor
£70 Lambda sensor
£200 for an ecu/electronic expert to insert his computer etc
+vat

harsh, but its like a new car, at least 40 more hp and double the rev range, still smiling driving it now, and parents paid lucky

 

[TuX]

I remember this old thread. Cant believe i blown that money

I fixed it now, hope this post will help someone;

1 x MAF sensor, 5 seconds to change, 2x 25torx security screws
Roughly £60 eurocarparts, drives like new