Rough Idle

[Suspense]

Yesterday, whilst driving my car and stopping at the lights, ocasioanlly the car would get into a sort of "rev Spasm".... It would drop revs almost to zero on the verge of stalling, then bounce back up to 1200rpm, and this would cycle over and over until I iether switched if the engine and started up again, or nursed the Idle( very hard to get idle back to normal by accelarating)

My AFM hasnt ever been playing up, however i am going to clean this tomorrow...

Is there anything else which can cause this? will the AAC Valve, be having an effect?

I also noticed on my boost gauge as it was trying to recover idle, the vacuum pressure would should up all the way up to zero, perhaps a little under. Which seems extremely wierd to me? does this signify a vacuum leak allong the lines somewhere??

Any help apreciated

[shmiddy]

maybe your bov has come loose, and its open on idle...

[Suspense]

maybe your bov has come loose, and its open on idle...

<{POST_SNAPBACK}>

Nope, checked it when i pulled over and it was doing the idle revving thing.... BOV was closed fully

[shmiddy]

before i got my car tuned my car did this, way to stop it havin a spazz, was to rev it so you got boost and vent the bov, and then it stoped serging, but it was really gay because at a set of lights you look like a tool reving ya car ahahah spechly if theres some shit hot car next to ya.... but thats how i solved my serge before i got the safc and tune so yeah....

[ECR033]

I had the exact same problem yesterday, but it went away once I turned the air conditioner off.

It was really strange as the car drove fine with the air con on for about 5 mins, then it started to idle really rough and drove like a dog. Once I turned the air con off and gave the car a few small revs, it seemed to rectify the problem and the car drove fine again. I thought perhaps it was a bit of bad fuel or something, but when I drove the car later in the day with the air con on again, it did the same thing again.

Car's going back to the workshop this week for a few other things, so I'll be getting my mechanic to have a look at it for me while it's there.

Anyone got any idea what may be causing this?

[Suspense]

Yeah my A/C was on aswell, however switching of the a/c didnt really rectify the fault?

ALso revving it till i hit boost and BOV vented, didnt really work either

[The Dan]

Cleaning your MAF meter should help. If switching the car off and then on again fixes the problem I would point towards a faulty MAF meter. Try other things like cleaning the throttle body and AAC valve at the same time and see if these help.

[bazr33]

Mine started doing this revving thing when i got my power fc installed

drives perfectly, but at idle just does this stupid down to 500 then to 1100 and yeah keeps going

it does look pretty stupid when ppl look at ya and they think you doing it. i just want to put the window down and say its the car ,

im takin it back to fist at wacol and they are going to have a look at it

let yas know what it is, if they do fix it.

Also on wednesday i turned my car off and when i went to turn it back on again, it just made a click sound and didnt start i had to wait abit till it would start again, a bit weird, but hopefully that will be sorted out too

and i went down the quarter last wednesday and the check warning light for the engine came on when the car is under load.

I'll post back on wednesday

THanks

[Suspense]

is MAf same as AFM>

[The Dan]

Sorta. An AFM is an Air Flow Meter and measures Air Flow via air flap and needle.

A MAF meter is a Mass Air Flow Meter and measure Air Mass via hotwire.

They both virtually do the same thing and essentially achieve the same results but through different methods.

[B0oStEr]

and i went down the quarter last wednesday and the check warning light for the engine came on when the car is under load.

If you're running pfc the check engine light could mean an excessive knock sensor reading.

[Midnight R33]

Yeah i have my car do that idle thing too.

Ive noticed its always on a hot and muggy day that when i start the car its idle rate will go up and down and some times even stall . But it seems to iron it self out after it gets running for a bit.

I will have to check my MAF. Good to hear that my car isn't the only one

[bazr33]

i went to fist

had the hand controller hooked up on the car

idle was put up to 900 instead of 850

some base setting was low and , didnt catch the other thing he said

but it was high, so he made it so it equalled out .

i drove it tonight , seems to go pretty good , havent noticed the idle go whacko yet but let yas know .

I'll try and find out what the things on the hand controller exactly were

i think i might have to get one,

[rd-runr]

Maybe change the O2 sensor. Worked for me but could just be masking the real problem.

[Gtr Glafche]

Hi Guys,

I had the problem a few months ago, not s much at idle but always before turbo's kicked in, it would cut out and gve a sharp jerk, its been fixed, the problem was that there was excess oil inthe airflow metres, got cleaned out, and works fine, but if the problem continues its time to replace air flow meters.

[sl33py]

Check your thottle position sensor. Tap it with a soft mallet while its running to check it's connections and internals are ok. Mine was fine when adjusted, but acted up after 5 minutes driving and drove all jerky and misfired and crap.

[The Dan]

Another thing you could try is check your alternator is putting out the correct voltage. Make sure you check it at the terminal on the back of the alt...not just at the battery. If your output voltage is low eg...11.80V, the battery light will still not come on but the fuel pump and ignition may not have enough to run them properly as the computer will only see about 9.5-10V of that.

Your problem is probably elsewhere but it doesn't hurt to check as it will cause idle probs.

[Viper1555]

any way it could be an Idle port prolem on ur throttle body? it can have trouble switching from air going through the throttle body, to it switching totally to the idle port. If it gets blocked up with gunk or carbon it can make that car act a bit like that at times or eventually make the car stall. just a thought.