Misfire engine at speed

Welsor13

Member
A long story short, have replaced spark plugs, ignition coils & leads ..... recent mechanic's check determined 'rough running' due to fuel filter needs replacement (Done).
Has run sweetly since BUT today developed a misfire/rough running at 100kph highway running. Bugger......checked plug condition, throttle body & air filter....ALL clear/good.

Has anyone experienced a sudden or infrequent loss of power due to rough running? Could it be a slug of water (in the fuel?), rough running lasted 10kms.
Should I check engine compression? Starts without difficulty & revs freely under no-load.

As you can see this DIY CH 'runner' is starting to run out of simple fixes? Appreciate some wise comments. Thanks
 
Hey mate,

Just want to check, it’s only played up once since the fuel filter was changed? And when it plays up does it get better or worse with more or less throttle?

Is it only at 100kph or does it play up when going uphill/down hill? Are there any conditions that cause it to happen more frequently?

Air flow meters are not uncommon causes of running issues on the 2L (4g94). Which motor do you have, 2L or 2.4l?

The 2.4 has a gold rocker cover with 4x ignition coils, the 2L has a silver rocker cover with only 2x ignition coils.
 
Not sure quite how to answer your first question. Initially we thought the long over-due fuel filter was the fix. The car always struggles uphill in 5th gear (overdrive?) Wife even comments "it's rather gutless dear!"
However more throttle doesn't seem to make much difference, I could still maintain 100kph & felt the 'rough running'....

FYI, I was told the CH (unlike the EVO's or 2.4's) don't start the fuel pump before the starter, rather immediately after resulting in a few cranks to fire it up! No probs anyway ......

But starting is NOT the problem, my 2Ltr (4G94) has 290,000Kms logged but usually runs well & looked after. It's just frustrating to have a intermittent fault like rough running.
 
Okay, so you have an issue at high speed… are you sure it’s definitely from the engine and not a wheel bearing or something else driveline?

If you’re certain it’s engine related, I’d try checking for air leaks. You can do this with a can of carb cleaner or brake cleaner (something that ignites easily and in spray form). Just spray it around all the intake parts between the airflow meter and the intake manifold gasket. I think it’s unlikely but worth checking. And cheap haha.

Be sure to check the vac hose on the fuel regulator is connected and not broken.

You could also get your injectors ultrasonically cleaned, but I probably wouldn’t start with this.
 
Thanks for the tips SDate42.......wouldn't have thought of a vacuum leak? (yet to check), also thought it might be one faulty fuel injector? Need to have professional help to diagnose that.
 
The car stopped, unable to start after some 'rough running' at speed. Looks like the fuel pump has failed? I'm told that Mitsubishi's (with high Kms) are likely to have the fuel pump needing replacement. I have 298,000Kms logged.
 
Easy test is to take the line off the fuel rail, it’s two 10mm bolts and with some wiggling it’ll come off. Get someone to crank the car for 5 seconds and catch the fuel (if there is any) in a jar.

It should absolutely pour out like a fire hose if the pump is good. If you have no fuel coming out or barely a dribble, check the pump is plugged in and the power supply is good. Then, new pump.

Pump is pretty easy to get to, lift the rear seat, undo the cover plate and the hold down bolts. It’s attached to the filter as a unit, so pull it all out and replace on a bench.
 
Yep! it certainly was the fuel pump. I've replaced it with a new GOSS pump.
Now (months later) I have a hesitation trying to accelerate .... suspect it might be the TPS on the throttle body. No issues starting, just hicc-ups at speed trying to accelerate.
Would appreciate any further advice guys.
 
Yep! it certainly was the fuel pump. I've replaced it with a new GOSS pump.
Now (months later) I have a hesitation trying to accelerate .... suspect it might be the TPS on the throttle body. No issues starting, just hicc-ups at speed trying to accelerate.
Would appreciate any further advice guys.
Had to clean out my throttle body after engine was going into limp mode at higher revs. Also started misfires after turning it off and starting up again. Throttle body comes off fairly easy and cleaned mine with degreaser and a toothbrush. If you still get any problems with acceleration take a look at cleaning it out. Code for my problem came up as P2101 when a mechanic ran his scan tool on it.
 
Hmmmm, sounds like you tried quite a few things and still no luck, do you have a standard air-box or have you changed it to a pod filter by chance?

Sometimes, a bad MAF sensor won't set a code, this is especially true on older vehicles with a type of self-diagnostics called OBD-1, like the CH Lancer 2 lt., it has OBD 2 port but runs OBD 1 protocols.

I agree with SDate42 comments above, especially about the air flow meters, they have the ability to make you chase your tail and suspect every other component except them.

I’m not saying it is this, but if you can find a spare air flow meter (MAF) that you know works, change it over with yours and see if that helps.
 
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