Hi guys,

i am having some problems with my TL which I am getting conflicting advice on so I thought I would try here and see if i can get a straight answer.

Background:
From pretty much the day we got he car it has always had a rough idle when cold until the engine reached operating temp then all was fine, each winter service they would clean the throttle body etc which would improve it slightly for a while. Thanks to the nice dealer charging a fortune for this privilege we took it to someone else. No change at next place either, oh well it wasn't that bad and was mainly confined to winter.

Fitted with an injected gas system (Brand: sprint gas). Still no change to rough idle in colder months, though it would run fine on gas once it swapped over so the rough idle was on petrol only. Had the mob who did the gas conversion have a go at it. They changes alt cap plugs leads etc and improved it a bit more. They also considered that the seals the spark plugs go through could be leaking some oil out onto the plugs and leads. At this time I didn't have the cash so I said let it ride till next time.

Well about a month ago I was towing a trailer (empty for about 50km) from my place to a friends. When i got there i unhitched and loaded the trailer, problems began when i went to reconnect the trailer, the car would not idle and would stall as soon as you tried to move it. Let the car warm up in place (coughing and spluttering all the time) then tried to switch to gas. Now I had the same problem on gas?? with the added bonus that it now coughs and splutters when driving as well.........

Took it back to the guy who did the gas and got a full service on both petrol and gas as well as replacing the seals in the rocker cover. Hmm no change (except wallet $1200 lighter), back it went next morning. He tests the compression which shows 2 on front bank and one on rear bank down 15% the rest normal. puts a vacuum gauge on and can't find any leaks. Readjusts the MAP on the gas system to get the car to run ok on gas (MAP up from 130 to 230). Checks codes from both computers, no error codes on either.

Petrol is showing that it is running very lean when idling but gas is now set to rich to idle. So I can start on petrol and wait for it to warm up to switch to gas. This means it will run like crap on petrol till it warms up then it will switch to gas and run ok.

From here the suggestions for a solution start to vary from valve issues needing heads to be redone to timing belt slipping a cog to all sorts of other stuff. Most with a significant $$ attached. I won't be taking it back tot he guy I went to as he didn't like me asking him to explain exactly what he planned to do and provide a breakdown of parts etc.

So what i am looking for is some ideas on the most likely fault with my Magna and a reliable mechanic in the Adelaide area (Northern suburbs preferred) to get the work done by. I will put another post in to follow this one with the symptoms etc so you don't have to try and pull them out of this war and peaces post :o)

Cheers,

Womble

6G74 on injected gas dual fuel - approx 175k on clock, timing belt last changed at 130k

Symptoms:
Rough idle on both gas and petrol
engine will cough and splutter (sounds like not on all cylinders) until it warms up
once warm it will run fine on Gas (has been remapped to run very rich) and very average on petrol
once up to temp it will idle ok

Work done so far:
Replaced distributor cap, leads, all plugs (all platinum now), filters, rocker cover seals
throttle body cleaned
engine codes checked - no faults both gas and petrol
Re-tuned gas EFI computer to run rich to compensate enabling engine to run at temp.

Looking for:
What is the most likely solution
A good reliable mechanic to fix the problem (preferably Northern Adelaide Suburbs)

I'd change the ignition module which is inside the distributer...probably cheaper to get a complete dist from a wrecker. If the module (AKA coil) is dodgy it may give a weaker spark than normal - when engine is cold, more voltage is required from the coil to allow the spark to jump the plug gap....when engine warms up it requires less voltage for the spark to jump the plug gap. So when engine cold the plugs will misfire due not firing but once engine is warm they will fire.
The module would be under $100 max.

Idle stepper motor?

I put my bets down on engine timing. Check your belt for broken teeth or replace the belt.

How are the spark plugs and leads? Get the vehicle in a totally dark place and open the bonnet with the engine running. Blip the throttle (grab the accelerator cable and give it a lift) and see if there is any breakdown. If there is you will see sparks jumping, or in my case, you will see the inside of the leads as it arcs along the inner track. Either way, spark plug gap maybe too wide,causing the voltage required to jump the plug gap to be too high, causing the leads to break down.

I replaced the leads (and plugs, but it was the magnificent Bosch leads which I had recently bought) and voila, no a trace of acring anywhere. Car runs like a dream now. Wife very happy.

I am hoping spark plugs and leads are good as they have just been replaced.... I will start looking for a new ignition module (anyone happen to know a part number?? I tried Misfits ebay store but didn't find any)

For the idle stepper motor wouldn't that give rough idle when both cold and warm?

I had only recently replaced the ignition leads with new Bosch ones because of intermittent misses. The misses were still there with the new Bosch leads and I was advised to replace the igntiion module, the whole distributor, the engine - you name it. I actually had the gas converter repalced (it probably needed it) but it still missed and backfired. It was only when I checked the Bosch leads in total darkness that the problem came to light (pardon the pun). As for TopGun leads, I had them on my Pajero and they were an absolute disaster - even worse than the Bosch. With the new leads (Eagle), the misses have gone and the Mrs is very happy.

Incidentally, I was extremely careful in installing the new leads. You are dealing with very high voltages here and it is important to avoid any places where the leads lay on the engine frame, or where the leads cross over another. MMA has gone to the trouble of giving us little clips which separate the HT leads. Use them, and use them properly so that there are no crossovers. It took a long time to set them up, but I am 100% sure that none of them are touching wither earth or each other. That is easy with a Magna - try that with a Pajero where you cannot even see the spark plugs and where the leads are running. It is even more important with a Pajero because they use only silly little 5 mm dia leads. And, when you next disturb the leads to get to the plugs, ensure that the disturbance to the leads is kept to an absoulte minimum.

check pcv valve, clean and reinstall it. it can be found on the drivers side of the front rocker cover, it is attached via vacuum hose to the lower intake manifold. make sure the air can only flow 1 way through the valve. i used carby cleaner to clean mine.

Sweet, I have some things to check out but can anyone help out with the other piece of info I was chasing? Is there any recommendations for a mechanic to fix my car? (Northern Adelaide areas)

I am hoping spark plugs and leads are good as they have just been replaced.... I will start looking for a new ignition module (anyone happen to know a part number?? I tried Misfits ebay store but didn't find any)

For the idle stepper motor wouldn't that give rough idle when both cold and warm?

Hmm does the 6G74 have an ignition module? I was searching through the Bosch parts catalog and they don't list any for a 6G74 Magna only a DOHC 6G74 for a Pajero?

They're listed here @ $145 ea:
http://www.cyberspaceautoparts.com.au/contents/en-uk/p784_Mitsubishi_Ignition_Module.html

Nice, that gives me a starting point. plenty of other parts there too

The module referred to looks as if it goes into the distrivutor of a 6G74. The listing includes reference to a Pajero NL (and others). I have a NL Pajero, but have never seen that item before. My vehicle has 3 coils, triggered by low voltage signal wires. The module does look as if it will fit a model with a distributor.

As suggested before, it will be cheaper and simpler to obtain a distributor from a wrecker......new is nice though.

Good lord, whatever happened to auto diagnostics? I started watching "RealFixesRealFast" 2 years ago on YouTube and since then bought myself a cheap oscilloscope (DSO Nano) and an inductive clamp for measuring amps which I feed into the oscilloscope.
These two tools let me measure all sorts of stuff like injector pulses, peak volts from crank sensors and even the coils (low voltage side of course). You can measure MAF/MAP sensor output, knock sensor signals, O2 sensor readings, you name it.
I also have OBD tools for my other cars and motorcycles (not for the Magna though, although EvoScan can do it cheap). It seems like you have been charged an insane amount of money over time by various people but nobody has done proper fault diagnosis.

The best part about diagnostics is it lets you eradicate sources of problems and narrow it down to the possible ones. It's a science which anyone with a brain can learn, and it will cost you a heck of a lot less than a single $1,200 service to get the knowledge.

It seems like you have been charged an insane amount of money over time by various people but nobody has done proper fault diagnosis.

The best part about diagnostics is it lets you eradicate sources of problems and narrow it down to the possible ones. It's a science which anyone with a brain can learn, and it will cost you a heck of a lot less than a single $1,200 service to get the knowledge.

I fully agree, hence why I have been asking here for someone reliable to take it to instead of just burning cash with no results.

As much as I would love to have the time to self learn and do all my own maintenance unfortunately I don't have the time these days. If it was a hobby vehicle that I could just tinker along at my own pace then fine, but I still need this one to drive to and from work each day :(

I fully agree, hence why I have been asking here for someone reliable to take it to instead of just burning cash with no results.

As much as I would love to have the time to self learn and do all my own maintenance unfortunately I don't have the time these days. If it was a hobby vehicle that I could just tinker along at my own pace then fine, but I still need this one to drive to and from work each day :(

Ahhh OK yeah that sucks. I have the same problem with my motorbike (main mode of transport) but thankfully my retired father has a garage full of 'em and loans me one of his when mine's off the road.