I know there are a million posts on issues like this and I've been through a lot of them. However I still can't work out the solution to my problem yet and was hoping for a bit of advice....

The link below is to short video of my tacho whilst the car is at temp, and in Neutral. Idle is very smooth. I can hardly hear or feel the engine running, but the RPM has developed this problem where it steadily bounces up and down between 100-300 rpm (as you'll see in the video) It doesn't seem to happen when the car is in gear and I'm at the lights (for example)

Tacho Vidhttp://www.esnips.com/doc/24b211d2-b33a-40fb-b93f-9c1861c9e0a1/tacho

Does anyone have any idea what could be causing this issue or any foolproof tests to work it out?

All the Vac hoses and PCV valve are clear, my throttle body is not spotless, but quite clean. I've just toothbrushed the ISC and TPS and it's made no difference.

Before I start replacing stuff, I'd just like to have a bit more of an idea what the problem could be!?

I thought Veradas were all 6 Cylinder? Your profile says you have a 4 cylinder...

Regardless, have you tried a new air flow meter? Or at least one from a wreckers? Occasionally this could be the problem, that or there's an internal problem with your engine, my TR used to idle like crap on a cold start, then it got progressively worse and I found a blown head gasket (check under your oil cap for a milky solution if you are worried)

I asked the same question once upon a time too lol

I've updated my profile so there is no confusion. It is V6 not an 4cyl.

I haven't changed anything yet as I'd like to know a bit more about what could be causing the problem. As I said, the idle is smooth. It's just the RPM slowly fluctuates up and down. It's got me stumped. :nuts:

Mate,
My TR did this to start with then eventually would idle At nearly 2,200 RPM constant when cold, then flare about as it was put into gear.
Fix was the ISC Controller. Cost me $80 but well worth it.
Cant say for sure, but yours sounds like the start of my dramas????
Bought a TJII sports now...never looked back!
cheers
Rich

Mate,
Fix was the ISC Controller. Cost me $80 but well worth it.
Rich

Thanks for the advice Richo. I'm assuming you bought a new ISC and not a recycled one. Where bouts did you find one for $80!?

try ebay first, otherwise your local spare parts shop.

my "new" one from bursons was a reco. lasted 2 weeks.

my "new" one from bursons was a reco. lasted 2 weeks.

take it back..:nuts: ask for a refund..

i did and got one. then got genuine mitsu one. not a prob now

For those of you playing at home, you might be interested to know that I've fixed the problem but not without the help of the 'ol service manual! :bowdown:

The problem was simply a matter of a minor TPS adjustment. The adjustment was a long way out for some reason. (See page 13-2-36 of the service manual) Not only has it fixed the idle problem, the auto trans seems to work better. It seems to be changing gears smoother and has also fixed an emerging 'clunking' sensation the transmission was doing when the car was slowing down! It's running like a dream!

Not only has it fixed the idle problem, the auto trans seems to work better. It seems to be changing gears smoother and has also fixed an emerging 'clunking' sensation the transmission was doing when the car was slowing down! It's running like a dream!

Thats what i needed to hear! You may have just done me a favour. :D thanks for posting your results mate, and good work on diagnosing the fault! I know alot of 'old time' mechanics who would sooner start replacing parts before consulting a manual for diagnosis. You've done well.