Diesel Idle Speed Up And Down

[cprob]

Hi Guys,

 

The idle speed on my 1.9tdi AHU 90 is alternating between 882 and 924 rpm (according to Vag Com). I can also hear the engine 'hunting' up and down.

 

I have the following fault codes which I've had for a while and are linked to the car going into limp mode which I think is a seperate problem.

 

65535 - Internal Controller Error

37-10 - Memory Error

 

00575 - Intake Manifold Pressure

17-10 - Control Difference - Intermittent

 

Any ideas what could be making the idle speed go up and down?

 

Cheers,

Robin.

[Phil]

I would change all the vacuum lines, this is usually linked with both hunting and with turbo causing limp mode. also EVERY time i have seen 65535 - Internal Controller Error this has been caused by just aged vacuum line INSIDE the ECU, its only a length about 10-15 cm long, replace all your vacuum lines with silicon pipe instead as it lasts longer and is cheap, and does not split and crack with age.

 

 

Wbr

 

Phil

[cprob]

I would change all the vacuum lines, this is usually linked with both hunting and with turbo causing limp mode. also EVERY time i have seen 65535 - Internal Controller Error this has been caused by just aged vacuum line INSIDE the ECU, its only a length about 10-15 cm long, replace all your vacuum lines with silicon pipe instead as it lasts longer and is cheap, and does not split and crack with age.

 

 

Wbr

 

Phil

 

Thanks Phil for the advice. I replaced all the vacuum pipes with silicon a few weeks ago ... except the pipe to, and inside the ecu! Looks like I need to change these too asap!

 

Cheers,

Robin.

[cprob]

I've now changed every single vacuum hose including the small one inside the ECU. All my fault codes have gone but I can still hear the engine revs hunting up and down slightly. The rev counter doesn't move but I can hear the revs changing slightly. Vag Com tells me the revs are going up and down by about 20rpm. It's not much I know but does anyone have any idea what could be causing it please?

 

Cheers,

Robin.

[chrispb123456]

I've now changed every single vacuum hose including the small one inside the ECU. All my fault codes have gone but I can still hear the engine revs hunting up and down slightly. The rev counter doesn't move but I can hear the revs changing slightly. Vag Com tells me the revs are going up and down by about 20rpm. It's not much I know but does anyone have any idea what could be causing it please?

 

Cheers,

Robin.

That happened to me when I put one of those cheap MAF sensors on from Ebay, ended up getting a genuine Bosch one, been OK ever since

[cprob]

My MAF came from a breakers yard and it looked like it had been to the moon and back! I might try another one, don't really want to spend

[chrispb123456]

My MAF came from a breakers yard and it looked like it had been to the moon and back! I might try another one, don't really want to spend

[cprob]

My MAF came from a breakers yard and it looked like it had been to the moon and back! I might try another one, don't really want to spend

[jonbob]

one other possibility which happened with mine was the water temp sensor

 

Jon

[cprob]

one other possibility which happened with mine was the water temp sensor

 

Jon

 

Thanks Jon, although I did put a new water temp sensor on it a couple of months ago (not a Ford one though). I'll check the connections just in case.

 

Cheers,

Robin.

[ghr]

I cleaned the MAF with isopropanol and although the injector loom was duff it at least it ran consistently after this. I know this might be nothing to do with it but since I changed that bloody injector loom it doesn't have the sluggishness it developed over the years; runs and accelerates like it did when it was new. (...probably the kiss of death).

[cprob]

I've cured my problem of my engine revs hunting up and down.

 

The alternator packed up so I bought a new one, fitted it and hey presto ..... no more hunting!

 

I haven't a clue why the alternator would have caused this but it's fixed .... so who am I to question why?????

 

Cheers,

Robin.