Hi all,

I'm wondering if you can help as I've done some searching and can't seem to find the same problem.

My 97 KF Verada has a slight rough or low idle once warmed up, and when stopped whilst idling (in drive), ocassionally my check engine light will come on.

I've taken my car to an auto electrician to perform a diagnostic check, and no fault codes are present and the idle reports being in the within normal range (though they said it's at the lower end of normal).

Since then, I've noticed that if the check engine light does come on (when idling at the lights) and I take off, it won't go out until I decelerate for about 10 seconds (i.e. either taking my foot off the accelerator entirely and/or when braking). I presuming this has something to do with engine vacuum?

I've done a scan around the engine bay looking for any broken/cracked hoses, but can't seem to find any.

Just some other points to note, the car runs on LPG and petrol, but the same thing happens on both fuels (so I can presume there is nothing wrong from that perspective). Also, it appears this doesn't happen immediately when the car is started (whilst cold), and turning on the A/c keeps the rev's at the same level (if not a slightly bit higher when the compressor is on).

Also, when it's idling it almost sounds like a diesel engine (I presume the lifters are giving me that ticking noise - i have tried the nulon lifter free-up, no help).

Recent work on the engine includes:

- new leads and plugs
- full cooling system flush and radiator replaced
- new fuel filter & air filter
- new oil & filter (I think it's 10w-30 nulon oil?)
- throttle body clean

Any ideas would be greatly appreciated.

Cheers,
Jeff.

Any advice would be appreciated - even if you've have similar problems with idling or think it might be something else?

Thanks.

The only thing I could think of would be a manifold leak, once warmed up and everything expands a little, an air leak starts causing some issues.

Check engine light could be due to O2 sensor picking up the problem...

Never had this happen to myself, just thinking outloud.

if its something to do with the vacuum hoses check that there all on the right connection, this is what caused my problem. also check all your senses, like your oxygen senser, your Maf sensor etc... check that all the connection on them are clean. ill add more later but i gotta go to work.

Thanks so much for the reply.

Would I presume correctly that if I've had all my plugs replaced (which involves taking the manifold off) that a good mechanic would check the seal/gasket (if there is one?). Also, this problem was occurring before the plug replacement.

Also, if i disconnect the O2 sensor, would this make the light stay on permanently, or could it help in diagnosis?

if its something to do with the vacuum hoses check that there all on the right connection, this is what caused my problem.

Thanks lenda, may I ask was your problem similar?

Yes a mechanic should have checked/replaced the gasket (depending on if it was the original metal gasket or a fibre gasket).

Unplugging your O2 sensor I *think* will put the ECU into limp mode (running extremely rich).

I would leave the car at a compotent mechanic's to warm up and test, finding if there is a vacuum leak (be it a gasket or vacuum tubes) is not hard, tracking down the issue might take a bit of time, but is not overly complicated if thats the issue.

I presume the best way of finding a vacuum leak is to just listen around using some kind of 'stethoscope' (like a piece of tubing held to the ear?).

So if there was a vacuum leak, would it only affect the O2 sensor, are there any others?

Not really feasible to do it that way...

There's vacuum leak detectors out there and other gagets. It doesnt so much affect the O2 sensor, the O2 sensor would pick up on a lean mixture (due to extra air, as the MAF has already told the ECU how much air is going into the combustion chamber, ECU adds preset amount of fuel, O2 measures the gasses and then finds a lean mixture.....which could trip the check engine light).

Hey, i have a similar problem since i disconnected my battery. When in drive and ive stopped completely my idle is real low and bit rough. The engine light doesnt come on though.
I have done the transmission learning procedure but that hasnt helped. Should i be looking in same places as suggested in above posts.