Engine wont rev!!!

Post Tue Apr 26, 2005 12:28 am

hi there,

got a kinda e30 type query....

been looking at an e34 525i on fleabay, with a view to buying for my dad

anyways, got the 2.5 m20 in it and will start but will not rev!
...

cuts out as soon as you plant the boot

i'm thinking its either

1)the AFM not lettting in enough air (the engine then floods) or

2)the ECU is overfuelling the car. (leads to flooding also)

do any of you guys have any other suggestions or possible solutions?

thanks

320Touring

Post Tue Apr 26, 2005 12:33 am

perished intake hoses

Post Tue Apr 26, 2005 12:35 am

liking your thinking jhonno!
will need to take plenty of gaff tape if I win it then

anything else strike you as a possibility?!

Post Tue Apr 26, 2005 12:37 am

erm Idle control valve...

Post Tue Apr 26, 2005 8:34 am

don't these engines/ecu's etc rely on sensors all over the place to control everything? If it's anything like the earlier motronic cars, they have a sensor (2 actuall) that take pulses from the bellhousing and send info to the ecu, if one of these fail, it either stops it from starting or revving over 1000rpm! This happened to my e23, and I replaced both sensors, and it is now OK.

Just a thought.

AG

Post Tue Apr 26, 2005 10:17 am

)

AndyG wrote:don't these engines/ecu's etc rely on sensors all over the place to control everything? If it's anything like the earlier motronic cars, they have a sensor (2 actuall) that take pulses from the bellhousing and send info to the ecu, if one of these fail, it either stops it from starting or revving over 1000rpm! This happened to my e23, and I replaced both sensors, and it is now OK.

Just a thought.

AG

thanks for that-may be worth cleaning the sensors etc, its a later m20 iirc as its on an F plate, so may not be same as e23/28 etc.

will find out soon (if I win

)

Post Tue Apr 26, 2005 1:13 pm

Could be dodgy fuel pump relay (swap it with one of the headlight ones, I think they are the same). Check the AFM is moving ok, take the airbox off and start it, see if the flap is moving ok.

I think the sensors are inductive pickup rather than optical, therefore dirt shouldn't actually affect them that much.

Earlier models have 2 sensors on the bellhousing, speed and position, the later models have a single pulse sensor located next to the valve cover at the front of the engine for the 5 series, and next to the diagnostic connector on the 3 series.

From Haynes Manual:

For Early Models

The grey connector is for the position sensor, and the white connector is for the speed sensor.
Using an ohmmeter, check the resistance between terminal 1 (yellow wire) and terminal 2 (black wire) on the sensor side of each connector. The resistance should be 860 to 1,060 ohms.
3 Also check the resistance between terminal 3 and either terminal 1 or terminal 2. The resistance should be approximately 100 000 ohms.
4 If the reading(s) are incorrect, renew the sensor(s).

For Later Models

7 Locate the two electrical connectors for the sensor. Disconnect the electrical connector from the front.
8 Using an ohmmeter, check resistance between terminal 1 (yellow wire) and terminal 2 (black wire) on the sensor side of each connector. The resistance should be 500 to 600 ohms.
9 If the reading is incorrect, renew the sensor.

I am about to go and take my sensors off:)

Post Tue Apr 26, 2005 1:18 pm

thanks for all the respones people..

looks like I got me some checking to do...

just gotta win the auction first!

watch this space....

Cheers

320Touring

Post Fri Apr 29, 2005 10:02 am

Right Me and the Bro have won the e34, and at a bargain price too!

going to collect it on sunday, so just a last shout for any other causes of the engine not revving. so far these have been suggested....

1)AFM

2)ECU

3)ICV

4)Intake Hoses perished

5)Fuel Pump Relay

6)Sensor on bellhousing/valve cover at the front

thanks dudes!

Post Mon May 02, 2005 8:18 am

and the winner is....

4) intake hose perished! Jhonno take a bow!

big tear in the hose from airbox to the TB so we taped it up with duct tape and it revved away lovely!

I had forgotten how good the e34's were to drive

for an indepth sob story, see this thread!

http://www.e30zone.co.uk/modules.php?na ... highlight=

just feels like a bigger more solid e30, and the 2.5 m20 is awesome-this one has 160k on it and makes my 2.0 (with 88k)sound like a bag of nails.

so gotta do tappets, oil and coolant on mine next weekend!

think my dad will like the e34-it

thanks for all your input-u guys (and gals) are the best!