Hey guys, over the last week or two my car has developed a really bad idle problem. Its quite difficult to explain but it will idle fairly normally, maybe a bit rougher but it will randomly 'jump' violently. It could be misfiring im describing but im hardly motor mechanical minded so it might not be what i mean. Does anyone have any ideas about what could be causing it. I noticed the lights will dim whenever it jumps so could it be an electrical issue? Or just the alternator not generaring power when it jumps. Its due for a service which im asuming would fix the problem but until then its still worrying me a bit.

How long since you had it serviced, since its due? If the mechanic labels it as 6 months/5000km being over by a month or two or a thousand or so won't be an issue unless pure mineral oil is used, and if a mechanic is using a straight mineral oil in a car as new as any third gen a different mechanic should be immediately sought!

Its hard to say what could be causing the problem, but here are a few suggestions:
- Idle control motor
- Dirty MAF sensor from using an oiled filter
- Faulty distributor cap (micro cracking)
- Faulty ignition leads
- Worn spark plugs
- Spoilt spark plugs

The spark plugs should never get to the point where they are worn. The front spark plugs are standard plugs, but these are changed by the servicing schedule. The rear spark plugs are changed at the same time as the timing belt, and are good for 100,000km. Its possible the mechanic used standard or the wrong type of plugs in the back row, which would be a pain if he did as it will cost labour wise a fair bit just for the mechanic to check. Spoilt spark plugs can occur a couple of ways. If the tube seals are gone, oil can contaminate the plug and the electrical connection of the spark plug lead causing it to 'miss'. If the spark plug has oil on it on the engine side, then thats a different issue all together!

In terms of the spark plug leads, a faulty spark plug lead will generall cause interference on the radio, so if there is interference on fm (go to a weak station) with the engine on then a spark plug lead or the distributor cap is faulty. The interference may not always be noticeable, you could simply run your hand along the leads from the distributor to the block, and when you get an extremely nasty zap from the thousands of volts you know you have found a fault :D - it would work but really not recommend! Really don't try it, its kinda dangerous. At least have someone there in case there's a problem, at least that way you'll have someone to laugh at your misfortune!

It last got serviced 10000km ago when i bought it, unfortunatly the car didnt come with logbooks so i dont know what has/ hasnt been changed over its service history. The odos at 76k so maybe someone could shed some light on what it would be due for.

Time wise I'd say the timing belt is probably coming up, I'd dare say its the original at the moment. You have to replace it every 100,000 or the certain time period whichever comes first. That would mean the rear spark plugs would be original, at 76k they'd be ok, but still replace them if the timing belt gets done. Without a log book service its probably just the front spark plugs that are passed their best, they probably weren't changed when they were meant to be.

In terms of servicing, what does the oil look like? Oil change intervals is one of those tricky things, if its too frequently you waste good oil, not enough and you can potentially damage/wear the engine more. I personally would only go 10,000 with a good full synthetic, at least you have the peace of mind then, and the cost isn't that much more. Most garages will use a synthetic blend, I'm guessing you have no idea what the garage uses? Check the colour of the oil, its a bad thing to let it get to the stage where its black. If it is, an engine oil flush may be a good idea! After the service, put in a bottle of Nulon Lifter Tuneup and free (which you can leave in till the next service) and check the colour of the oil every few hundred. The idea of putting in the lifter tuneup and free is it will slowly remove carbon buildup over time from the engine, which will show in sooner than expected darkening/blackening of the oil. If the oil stays clean, no harm done and you know the engine is relatively clean. If it goes black, its also good as it has removed some deposits. When that has doen just get the oil and filter changed, and repeat until it no longer goes black sooner than expected. This method is only because you don't know the servicing history of the previous oils used in the car. In any case, make note of the brand and type oil used when you get it serviced. I should point out that the colour of the oil is not an indication of when a car needs servicing, its only a guide if its blackened! Ideally the oil won't blacken too much and time & distance travelled should be used.

The only concern with getting it serviced is the fault finding for the roughness. It may end up being costly if the mechanic has to search hard to find it... You can buy a spark plug removal tool yourself and check/replace the front plugs before the service. When you take it for the service, tell them that the front plugs do not need replacing as you have already done it (especially if you use iridiums). If they do then replace them let them know again that you told them, if they deny it just find another mechanic!

You can even do the basic servicing yourself, the engine oil, oil filter change, and power steering fluid (which is probably well and truly due by now as its not a standard service item) are all very easy to do, and you can still take it to the garage after doing the servicing stuff like that for a checkup etc. The brake fluid and radiator fluid (both around 3 years max) are probably due too, and neglection can be a very costly exercise.

Hey mate, cheers for the helpful info. I just went out and checked all the fluids, they are all at a reasonable level, the engine oil doesnt look too bad however the tranny oil is brown so I'm assuming needs a change. I also checked the air filter (it is an oiled K&N) and MAF but didnt really know what to look for, the filter is still clean. I havent checked the spark plugs, can I remove them with just a normal socket set? If so what should I be looking for on the plugs?

if a mechanic is using a straight mineral oil in a car as new as any third gen a different mechanic should be immediately sought!

why..?

why..?
Heh, what do you think they run for the breakin period dude?

For breaking in yes, but thats the exact reason why its not good for general use!

When replacing the trans fluid, also replace the power steering fluid as it will be at least as old. A brown fluid definitely indicates it needs replacing and it should be done asap. As others will atest to on here, make sure the correct trans fluid is used!

Its not just the levels that need checking, its the ability of the fluids to work like they should. For instance, brake fluid absorbs moisture, over time this can corrode brake system components that will eventually need replacing. The radiator fluids break down over time, and even if it is still a nice green colour (like it should be, since it should be running between a 25 (min) to 50 (max) percent coolant mix), there still may be suspended metal in it. Remember the Magnas are alloy, the brown rusty coolant in older cars occur because they are iron blocks. Even if still green the coolant can contain suspended aluminium particules which apparently isn't a good thing (causes water pump failure?)???

In any case, a full fluid exchange is usually recommended, as then at least you know whats in it, and how old it is.

Spark plugs to be checked requires a tool that can go down the plug tubes. DO NOT use any socket sets, even if you can get an extension that goes down there. Reason being, if the socket gets stuck on the spark plug you could be in a lot of trouble. A spark plug tool (can't remember the name), basically a socket, extension, and crossbar handle as all one piece can be bought from a car place like Supercheap auto. If you do buy one, a single size tool works better as the multiple size tool won't fit down the tube. Only the front spark plugs can be removed easily, the back ones should have been replaced with the timing belt. Basically on the plug, look for oil on top of the plug (as the tube seals can leak), and any signs of incorrect running on the bottom of the plug.

Check out this help guide for diagnosing some engine problems by how the plug looks, check page 21 of the following:
http://www.bosch.com.au/content/language1/downloads/Spark_Plug_Australia_Web.pdf

I'm not saying get Bosch plugs, just that the guide might be useful!

What the hell is wrong with something like GTX3? Nothing at all, You can use a mineral oil no worry's. These are basic OHC motors not ferrari engines.

Alot of mineral oils may not meet the spec of the engine, i know the cheap stuff doesnt. Plus the factory fill is synthetic (here in NZ anyway) so thats what i use, plus the benefits and the fact l do give it assholes sometimes!!!!

;1247550']What the hell is wrong with something like GTX3? Nothing at all, You can use a mineral oil no worry's. These are basic OHC motors not ferrari engines.

totally agree..

A good semi synthetic is better than a good straight mineral oil, and worth the few dollars extra. Castrol GX3 isn't bad, but there are many cheaper crappier oils out there. My point about the mechanic was if they save on the oil they probably take cheap shortcuts elsehwere too. Hey, no need to go buy the Mitsubishi spec transmission oil, this Dexron III or ford spec will do the same thing... Its a good brand and everything...!

The other point its service intervals. A mineral oil has only a 5000km service life, its the synthetics that are used when manufacturers list a 15,000km service interal. Aren't straight mineral oils are also more prone to carbonisation?

Mate im with ya, I go off the spec grade required by manufacturer (they would know!) and alot of the cheap stuff doesnt meet the grade. Plus alot of the vehicles on here have modifications such as exhaust etc, and its worth having the higher protection synthetic enhanced/fully syn offers.. better to have excess protection than been caught short with an inferior product that may cause extra wear.

I agree, a good quality oil is essential. But when is the last time someone on this forum posted a message about his engine wearing out prematurely? The engine will outlast the rest of the car, usually. I prefer to use a good mineral oil with frequent oil (5,000Km) and filter changes. If I did huge mileages every year I would use Mobil 1 and change it annually, but I don't. Castrol GTX3 will do.

20 years ago it was common for cars to develop crank bearing rattle and piston slap due to wear, at 160,000 km, if you used poor quality oil or didn't change the oil and filter the required 5,000 km or 3 months, but I think the technology in current oils and metals have progressed a lot since then. I'm thinking old Holden red motor, Sigma engines.

Just an update, on the drive home from work i think I narrowed it down to the gearbox, at the traffic lights I was switching between N and D and the idle was relativley normal in N but as soon as I switched it to D the vibrations would start again. Would anyone have any idea what part of the transmission it could be? Looks Like it might be a costly exercise to fix.