Engine revs to 3000rpm on cold start

[Simon78]

Hi I'm new here.

I have just bought a march/2003 registered 2.2 diesel X-trail 164k miles in need of a service. However I'm still very very! impressed with it all the same.

But when I start first thing from cold the engine revs to about 3000 rpm without me touching the pedal. After about a minute it drops to a normal tick over.

After this it starts ok for the rest of the day.

I've seen threads suggesting cleaning the MAF sensor, replacing the fuels rail pressure sensor and/or the fuel pump sensor.   

I'm doing the service anyway but can anyone lay bets on which of the above part changes to try first to solve the above problem or suggest another action. 

Cheers

Simon 

[Simon78]

Hi, I've done the air, diesel,oil filter and oil change. No change to the revving problem as I thought would be the case. I did find some thin (3 or 4 mm dia.) steel pipes at the top of the engine around the injectors which are open ended with no rubber pipes attached and I'm guessing this is correct? but what are they for?

I also found a rubber pipe (10mm dia) rising from the transmission or transfer box and this was also open ended, could this be a vent pipe?

 About to clean the MAF sensor.  

[Simon78]

Hi Just cleaned the MAF sensor with electrical contact cleaner ----- No difference. Obviously it could still be down to a faulty sensor but not a dirty sensor element.

Any ideas?  Throttle position sensor maybe?

Simon

[Trevor]

Have you checked the system through the OBD socket to look for fault codes or live data....I have had problems with the throttle position sensor (on the pedal) and if not set correctly, then this can cause the fault you are describing.

[Simon78]

Hi Trevor No I haven't which is a bit mad as I've got a code reader. Just thought that  there was no engine warning light on so there would not be any codes. I'll do it tonight. cheers.

Thanks 

[Trevor]

you should be looking for a voltage range from pedal rest and changes as you slowly open and close throttle. A lot easier if you have a scope function on your scanner.

It's then a case of loosening the securing screws and slightly moving the sensor until you get the correct readings.

Measure with ignition on & engine stopped - Pedal released 0.8V-1.3V fully pressed >3.5V.

[Simon78]

HI no scope sorry. in fact my Pro Scan V580 scanner couldn't connect either! The ODB port is just to the right and below the steering column Yes? There aren't two are there?

I have got a multi meter though which should work?

Thanks

Simon 

[Trevor]

Multimeter is fine but a bit fiddly.

I would accurately mark up the original sensor position in case you have to return it back to that point.

Loosen the sensor securing bolts/nuts. Leave the sensor plugged in and switch the ignition on.

Measure one of the wires and earth (sorry cannot remember which wires) and see what the reading is at idle position.

This should then progressively change and at wide open setting it should be within the range specified above.

Tighten the bolts/nuts to secure the sensor.

Note:  the wiring going to the connectors is usually really crap on the connector so if necessary bias it over to something solid and cable tie the loom in position.

[Simon78]

Hi Trevor

You were right about the wiring being difficult. No space for probes, so I couldn't get my probes in to be sure I was getting a good contact. Ended up putting it into limp mode. LOL Disconnected the battery for 20 mins and it came back ok but still with the original problem. There are 8 wires to potentially check and I couldn't find which one was the correct  one to probe. Do you know where I can get the colour code of the wire I should be measuring voltage at? The only voltages I did find weren't conclusive either, as they varied every time I re measured them which only made me think I'd got a bad earth or wasn't making good contact to the wire with the probe. 

Cheers

Simon

 

[Trevor]

Unfortunately, that is the problem...if you could borrow a scanner to dial it in with it would be a lot easier. Alternatively, if you loosen the securing bolts and gradually adjust it to a position where the engine revs at idle are okay and it doesn't go into limp mode then you've cracked it but you only need to move it a minute fraction at a time in either direction until you find the exact point.  Good luck

[Simon78]

Hi Trevor I'll as around to borrow a scanner and/or try adjusting it. I'll let you know.

Cheers

Simon

[Simon78]

Hi

I haven't managed to get a scanner. I tried adjusting the pedal both ways and one way made the revs increase. There wasn't much adjustment left to move the pedal unit the other way and the little it did move didn't seem to have any effect on the revs.

Its like the ECU is detecting a problem and compensating for it all the time as well at start up.  Because some times when i'm driving without moving my foot the car shuts of power a little then moments later opens back up to where it was before. 

Is there a sensor at the throttle body end?

Simon

 

[Trevor]

I would almost guarantee it is the pedal sensor and once set up correctly it should be fine. The only other issue is the loom connecting to the sensor has a weak connection so I cable tied mine so that when it was set up it couldn't move on the connector/terminals...it worked fine then. (typical Nissan/Renault electrics)

[Simon78]

OK Thanks Trevor,

Just to be clear........ you're saying from what I've told you, you think I should replace my existing sensor (and then I will need to set up correctly)  or should I carry on adjusting the existing sensor because you think it's only the position that is wrong and I should continue adjusting slightly each time until it comes right? 

The Nissan agent did say they sold a lot of replacement throttle pedal units.

Like you say I'm also suspicious about the wiring connector because the last time I was adjusting the position of the sensor, I would have been pressing on/moving the wires/connector as there's very little room to work.  It went into limp home mode but know I didn't disconnect the connector. So there might be a joint or baynet contact in the block which isn't making a consistent good contact. So when/if I get it sorted I'll zip tie them in position.

Thanks again, I'll let you know how it ends. Simon

[Trevor]

I would try to set it up properly first and the only real way of doing that is to dial it in with a scanner. Once it is set in the correct position then cable tie the loom and double check the voltage readings then road test. Almost guarantee it is the loom and connector making it go limp home...did it on my x-trail until I sussed it out. 

Also, one other thing I forgot about, sometimes the sensor can become contaminated with debris (moisture, carbon, etc) I took mine apart and cleaned it carefully before reassembing....but yours may not need that doing.

If you do try to adjust it manually then be aware it is the minutest movement required to make a huge difference.

[Simon78]

OK thanks Trevor

I'll try harder to find a scanner.

thanks again i'll update you with the result.

Simon