High RPM Idle

Richand · 21 Dec 2011 at 10:28

Hi All,

I'm new to motors as I drive a rubbish citroen....picasso!

but, I read this forum section a lot and know there are some clever people in here so I'm after some advice.

Last night coming back from town my car was rev'ing on its own, out of gear and it would just free rev, I cut the engine and let it sit for a few minutes and on starting it backup the engine was pulsing +50RPM and back to idle.

30minutes later I took it for a 5minute spin and it was ok so thought maybe a stuck accelarator cable, wd40'd this morning before leaving for a 15mile drive to work.

on getting to around mile 10 the high idle RPM problem returned and didn't go away all the way into the office, I then went in and did some work and returned to check on the car, problem had gone so I would say it only seems to high idle when its warm but the pulsing problem remained.

Topped up water as maybe overheating? it sounds like a diesel, very rough engine sound and a noticeable whine from somewhere.

I have it booked in tomorrow before this problem came up for a new cam belt, aux belt and water pump.

Will the work I have it in for tomorrow solve the issue? I fitted a new exhaust and have done a service on the car before its MOT earlier in the month, related?

Any help much appreciated....

Gibbo · 21 Dec 2011 at 10:59

Hi there

No doubt something such as:-
Vacuum leak - Check fuel trims with a scanner to check or do a smoke test.
Throttlebody - Maybe throttlebody or butterfly sticking, might just need a clean.
Idle Control valve - If it has one, again may need a clean.
EGR Valve - Not sure about this one.
If the car uses a throttle cable? Is it really that old then clean all around its area until you get smooth operation, which is back to the throttle body.
Finally you could also try resetting your cars ECU, disconnect battery negative terminal, re-connect it 30 minutes later, then leave the car to idle for 5 mins and then go for a 30 minute drive so the ECU can re-learn. (Make sure you have your radio code handy, you will need it).

I'd check the fuel trims, if they are within +/- 5% should be fine, normally an emmissions light will come on when they cross a certain threshold in the -/+ 20-25% region.

Then remove air intake, get some MAF and Throttlebody cleaner, give MAF/Sensors a spray, then give the throttlebody and idle control valve a good spraying with throttlebody cleaner. Then make sure you put it all back together and nice and air tight.

Other thing you could try is maybe injector cleaner (forte), though I doubt this is it.

Your work tomorrow won't fix this, unless they have to remove air intake to do it at which point they may spot a vacuum leak or perished pipe etc.

Service again doubt it unless something was not put back right.

You say it sounds like a diesel, I guess its a petrol then?
If so then you may have a more severe engine problem or it could just be tappets or VVT rattling (if it has VVT). You say its been serviced recently, maybe wrong grade of oil or never changed. Id be dropping in a bottle of Forte engine flush, run car for 45 mins, drop the oil hot, fit new filter, correct grade decent oil and top up with Forte top-end engine treatment of whatever its called now to see if that quietens it down.

Locky · 21 Dec 2011 at 11:22

dunno if I'm being blind but is the car a petrol or derv?

Richand · 21 Dec 2011 at 11:58

locky, its a petrol

Gibbo, all very good advice, its a quite day at the office so I have just been and took the throttlebody apart and cleaned it, while doing this there is a rubber bung that holds the throttle cable in place and fits inside a small metal O ring, this had come loose, fitted this back in its ring and cleaned/lubricated the cable and housing.

while at it I stripped the injectors and cleaned these also topped up coolant and lubricated the various cogs powered by the auxiliary belt (AC, PS, Alternator).

powered her back up and she didn't hunt, pulse and sounds much cleaner and smoother... if nothing else it will make the garages life easier tomorrow being all clean and lubricated.

will see how it behaves after the drive home this evening!

Gibbo · 21 Dec 2011 at 14:50

Richand said:
locky, its a petrol

Gibbo, all very good advice, its a quite day at the office so I have just been and took the throttlebody apart and cleaned it, while doing this there is a rubber bung that holds the throttle cable in place and fits inside a small metal O ring, this had come loose, fitted this back in its ring and cleaned/lubricated the cable and housing.

while at it I stripped the injectors and cleaned these also topped up coolant and lubricated the various cogs powered by the auxiliary belt (AC, PS, Alternator).

powered her back up and she didn't hunt, pulse and sounds much cleaner and smoother... if nothing else it will make the garages life easier tomorrow being all clean and lubricated.

will see how it behaves after the drive home this evening!

Good stuff.

When you clean the MAF if you do only clean with MAF cleaner, they are rather delicate/sensitive.

Don't forget to check to see if your oil is on or just below max if its sounding rather clattery?

Also if you have any more issues, do a google search to see if there is a reset procedure for your throttlebody as some cars have one, where you need to do a combination on ignition or full depress the throttle etc, or it might be just as per before disconnect the battery and it shall just reset/relearn anyway.

Don't forget some injector cleaner and a couple of tanks of Vpower could be a good idea.

Richand · 22 Dec 2011 at 11:12

Drove home last night, throttle peddle dropped an inch while driving so the throttle cable assembly needs looking at again, the rubber "bung" is working loose due to the lost clip, will makeshift a new one, for now a cable tie will do.

MAF I will clean once its back from the garage, told them to have a look about and see if they can identify the rough engine noise and the pulsating engine issue, guessing an air/vacuum issue.

Oil was changed a month or so ago prior to MOT along with sparks, all filters, back and middle section of exhaust, from ball joints and antiroll bars....did all this myself and not had any issues.

hate to think how much all this work would have cost at a garage! just the cam, aux and water pump its in for today was £265!