Rough Idle

Hi all,

I have a problem with the idle on my '01 Jimny. It has the M13A motor in it.

After going for a drive and stopping at a set of lights or somewhere, when the idle reaches about 750rpm it suddenly drops to around 300-500rpm before it picks up again to 750-800rpm and then it drops again. It does this a couple times, each time dropping less (i.e. 300 first, 400 second time, 500 third) until it eventually sits at 700-750rpm. Also, ontop of this issue, when the revs are at 700 or below, it feels like it has a miss, making the whole car shake, with the lower the rpm, the worse the car shakes. The problem is also intermittent as some times it runs smoothly the whole trip, but runs like a pig more often than not. The car doesnt miss a beat when driving though.

I have done the following to no avail (no noticeable change):

• Changed oil, oil filter and air filter
• Replaced crank angle sensor
• Replaced spark plugs
• Increased idle to 800rpm (temporarily)
• Used fuel injector cleaner
• Used carburettor cleaner
• Replaced ignition coils and leads (second hand) (dud set?)
• I have played around with the cam position sensor, cleaning it and both running with and without it connected

I have had the throttle body serviced (very basic one, dunno what they did) which changed the feel of the car shaking, but didnt alleviate the problem.

I have a mate who is a mechanic who experienced the problem and said that a rough idle is usually the IAC valve. So I sprayed some carburettor cleaner in it to flush it out but to no avail.

My next step is to pull apart off the throttle body and give it a good thurough clean. Would it be worth sourcing a second hand throttle body (including IAC and TP sensor) or buy a new IAC valve?

Does anyone else think that this could be the source of the problem or should I be looking somewhere else?

Any advice is appreciated

Regards,

David

Thanks Martin,

I had a look at the PCV valve and it had a bit of gunk around the inside of both ends, I could shake it and hear it rattle but when I blew into it, it worked both ways (restricted one way tho). It was also loose sitting in the manifold and could be pulled out easily (and possibly air getting in or escaping), so based on what you told me I decided to replace it as I dont have the resources to clean it ($22 part anyways).....

And it has made a massive improvement!

It seems as tho the irratic idle problem has been fixed, still feels like it has a miss when sitting on 750rpm but it is much much more feint and the rpm's dont drop as much, if at all anymore. I've only tested it for a short time so time will tell if I'm not just having a string of good runs.

Thank you again Martin, you have saved me plenty of $$$

Now to work on that miss feeling and I'll be happy