trouble shooting motor don't accelerate

**BRUNO 57** · 27-04-08, 18:21

have a problem which occupied me, all the weekend, and I turn(shoot) to you: HELP!
- my Q4 start bad and when it start it does not rise above 2500 rpm and arrived has this regime of rotation stop. I did not make modifications and before that it arrives at me when I was in acceleration I had cuts but the engine continued has to rise in regime.
- you have a solution

**wrinx** · 27-04-08, 19:39

At a guess....the idle valve.

If that's not the problem there's a pipe that can cause trouble. Think it's at the rear of the engine, Jack had problems with it so he will be able to help more than me.

wrinx

**BRUNO 57** · 27-04-08, 19:58

Thank's WRINX for the idle valve no problems i test it and the voltage at the 3 pins it's ok!
-I wait now information from JACK!!!!!!!!!!!!!!!!!

**AlfaJack** · 28-04-08, 16:55

Yes this could be a split in the MAP sensor pipe. When it splits the engine will run terribly and over fuel a lot! - It is a difficult one to check as its hidden underneath the front of the inlet manifold in the middle. I will try and get a photo later!

**Juan AR155Q4** · 28-04-08, 19:24

Originally Posted by BRUNO 57

Thank's WRINX for the idle valve no problems i test it and the voltage at the 3 pins it's ok!
-I wait now information from JACK!!!!!!!!!!!!!!!!!

No mater you read the voltage, it could be stuck due to dirty in it.
But it should only bother the idle. I?ll look at MAP sensor as they said above.

**BRUNO 57** · 28-04-08, 20:40

This day i change my gasoline filter end when i start the engine the problem is the same the motor stop after few minute at low revolution .
-I decide to control one more time the sparkplug ,i remove them when i turn the" ON" position the 4 sparkplugs make sparks,and when i turn the key in start position the engine turn bat no sparks .I HOPE SO I'M NEAR THE PROBLEM.
-some body know this problem ?I ride the differentes check on the tech part of this site and i don't see the solution because the technical ignition part is for twin spark and 6 cylinders "bosch " and not " weber magneti marelli"

**Steve Webb** · 28-04-08, 21:26

Have you checked the fuel pressure? Maybe your fuel pump is failing. When you took the spark plugs (bougies) out what colour were they? Very light coloured or Black?

Steve

**Brul(tm)** · 28-04-08, 23:58

Originally Posted by Steve Webb

Maybe your fuel pump is failing.

Can also be a failing wastegate. When pressure builds, you will get fuel cuts! I think you should check hoses first and take it from there.
Good luck trouble shooting.

Greetings,
Marc

**Stuntz** · 29-04-08, 06:46

I have similar problem the engine eats up 25 l/100 km if i drive normaly it smokes black on ideling It didnt hold minimal rpm but user AXA changed TPS and set it right now it holds Idle .Boost is sometimes 1.1 and then again 0.8 ( i have a chip opened to 1.35 bar). I will bi changeing injectors WG and now this pipe to MAP sensor. Hopefuly i sort it out

**AlfaJack** · 29-04-08, 09:53

This is the MAP sensor pipe if it helps:

**AlfaJack** · 29-04-08, 09:54

Originally Posted by Brul(tm)

Can also be a failing wastegate. When pressure builds, you will get fuel cuts!

Huge cuts at 1.5 Bar I remember - you really know about it when it happens!

**BRUNO 57** · 29-04-08, 16:20

thank's all of you i hope so it's ignition failure i haven't sparks when i try to start engine "spark plugs removed "but i have spark one time at the 4 sparksplugs when i turnt the key in "on " position

**Stuntz** · 29-04-08, 17:08

Heh mister replace your crank shaft sensor or set it right using manual.

**BRUNO 57** · 29-04-08, 20:07

Thank's a lot for your help!!
I FIX IT!!!!I disconnect and clean connections of :R.P.M and TDC sensor
and Timing sensor
AND NOW THE ENGINE RUN !
THANK'S GUYS!!!
-Cordialy BRUNO