Hi guys,
I'm kind of new to posting here but have been reading over many posts for quite a while so please excuse me if I make a newbie mistake.

I own a 1993 magna tr 4 cyl (more specific the elite model) with 318,000km on the clock.
I'm still having a rough idle while in gear that seems to come on and off as to how rough it is. It appears to be random regardless the weather outside or the temperature of the engine. A list of things I've done to the car includes:
- Replaced front and rear engine mounts (rear was buggered).
- Replaced ISC.
- Replaced spark plugs and wires.
- Replaced battery.
- Replaced auto transmission fluid and filter.
- Replaced all brake pads and front rotors (rears were still good and decided not to replace them even though I purchased new ones).
- Replaced all filters (oil, air and fuel) as well as serviced oil (and filter) every 3000km.

I'm absolutely stunned as to what could be causing the random roughness of the car, does anyone have any idea? Also when coming to a stop sometimes the gearbox clunks down into first gear, I'm assuming this could be something to do with the TPS reading from another post if I'm correct?

The clunk is a normal thing, someone explained to me that it was an ingenious invention by Mitsubishi in the 2nd gen Magnas that went horribly wrong.

The idea is that when slowing down it changes from first to second gear when idling and then when you take off it changes back to first gear, the problem with this is that it does it too quick and ergo the clunk sound.

As for your rough idle... Thermostat perhaps? Leaning towards thermostat or throttle body.

Ahh that makes better sense thanks

I have already cleaned the throttle body and i did burst a hose so im heading towards thermostat now. Where abouts is the thermostat located just so I don't replace the wrong thing?

Thermostat is on the drivers side of the radiator

With 318,000 km on it, I'd suspect the valves are no longer seating properly. Do a compression test on it.

Clunk: Definitely the TPS adjustment. As above, should drop to second when you stop, be in second when stationary, then select first when you accelerate. TPS is telling the ECU you are accelerating when you are actually still slowing down. Just turn the TPS slightly clockwise and test. You should get smoother gear changes too.

I tried turning the TPS clockwise and it seems to have a made the clunks when stoping less violent but time will tell.
Could this increase rpm while idling and also increase cruiseing rpm? I thought that was the ISC's job?

Keep experimenting with the TPS until the clunk goes away entirely. If no go, replace it.

The TPS has a switch in it, it should be closed when the throttle is closed at idle, lets the ECU know to use idle settings and use the ISC. So it can conceivably affect idle speed.

Thanks MadMax that makes a lot more sense now.

Okay so an update the clunks seem to be still there but very rare and very mild, only problem is that now while in drive and stopped at lights the idle seems to feel like the engines missing a beat every now and then. The rpm will be at around 600-800 then drop to low 400 for a second and then goes back up to 600-800 again. Does anyone know what could cause this?

That's a misfire. Literally missing a beat. Check sparkplugs, leads, rotor, distributor cap. Also the electrical connector on the distributor, check for corrosion.

As before, a compression test would be helpful to eliminate a burnt exhaust valve or two. If your engine has never been opened up I'd say it's time for a head job. (the automotive kind, not the other kind - JK)

(Missing at idle and low throttle settings was a classic early indicator in the old days when exhaust valves didn't stand up too well in the early emission controlled engines. lol Common to need to go and do another valve grind. They make special gasket sets called VRS kits - valve regrind set - just for this purpose.)

Hmm last time I checked all the leads, dizzy and plugs they were fine. I'm suspecting it could be the valves? If so I've found a company that does refurbished heads for $300 is this worth it? And is it difficult to replace the head (using the workshop manual as a guide)? I would probably do the timing chain at the same time.

Checked the centre electrode inside the distributor cap? A bit of carbon on a spring, can wear out or have bits break off.

The 2.6L Magna engine is dead easy to work on, at least compared to the V6 engines.

$300 is a good price, by the time you have your own head acid dipped, refaced, seats reground, guides replaced, worn valves replaced, etc it would cost that much or more.

BUT do a compression test first!

Will do those all tomorrow after work hopefully all is well and it's something simple lol
I was just moving the car before and noticed when the car seems to misfire all the lights also dim momentarily. I remember someone once said the problems I've been having can also be caused by the alternator is this true?

Might be worthwhile putting a voltmeter on the battery to check alternator output voltage, and that the battery terminals are clean and on tight.

So after checking the dizzy which was fine and a bunch of other things the car started randomly working fine again. Might be taking it in to get the timing chain replaced as its overdue and also to get the ticking of the lash adjusters fixed (hopefully fingers crossed).