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Doug, ASE Certified Technician
Category: Mitsubishi
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Experience:  Mitsubishi employed and Factory trained ASE certified technician
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Mitsubishi: Working on a friends 02 Mitsubishi Galant ES, auto

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Working on a friends 02 Mitsubishi Galant ES, auto w/ 3.0 V6. The engine has been missing for several weeks, with the check engine light on. The code was P0301 - cyl 1 misfire. I picked it up at his house and drove to my house, about 10 miles away. At stop lights, you could feel the engine vibrate and miss - but the engine rpm was steady at around 700rpm. When I pulled it in my garage, the engine was ticking - sounded like a lifter tick.

I pulled the intake off - replaced all 6 plugs, new wires, new dist cap and rotor. I had the battery disconnected while doing this.

When I fired it up, the tick was still there, and at times it sounded good, and then bad. Several times got new code Cyl 5 misfire. I checked everything - all wires, hoses ,etc connected properly. The ticking noise would come and go - and when it went, I reved the engine to 1800 rpm to see how it ran - I kept it there for 20 minutes - ran great, no ticking noise, no codes. Took to low idle, and it would hunt for the rpm, and almost die - but then get to 700 rpm and run steady. I then took for a test drive. The only issue was pulling up to the first stop light - the engine rpm at idle would hunt and almost die. I put car in neutral to rev the engine - then put in gear and drove off. Drove at 65mph for 20 miles, and all fine, even stop lights, no hunting.

At end of 20 miles, brought back to friend - had it idling in his parking lot - and it started to hunt after about 30 seconds at 700 rpm. If you rev it up, then back down - it is ok for about 30 seconds, then starts to hunt. Friend let it idle for 10 minutes after I left, and the engine light came back on - he says it is running good, not sure why light is on again.

Questions....does this make sense? Any ideas on why it was ticking, and now gone? Is there a computer relearn on these that takes a while - explaining the eratic running? Could there be something wrong with IAC - maybe needs to be cleaned? Thanks,

The ticking is more likely to be lash adjusters (lifters) as they are notorious for this. It will often come and go, typically going away after some revving. Whether or not the ticking stays away a long time or not is dependent on the condition of the engine. If the lash adjusters have significant coking going on there (pull the oil cap and look inside for a good indication. If it is all dark yellow/brown, then it has likely had a bit rough of a life), this will prevent the adjusters from staying pumped up. Depending on how bad it is, the tick could return from sitting over night in moderate cases, or in worse cases it could come back as soon as you return to idle for a few seconds/minutes. As the seal around the piston of the adjuster fails (or side gets carboned up preventing sealing), the worse it is the faster oil pressure bleeds off. If it is severe, oil pressure at idle won't even be enough to keep them pumped up.
Now worth considering is that if the oil pressure itself is low, identical symptoms will appear.... however they will likely be on the worse side (always noisy at idle) and you would have an oil light on in the meter.

With regard to the misfire, what type of plugs and wires were used? No Bosch I hope?

When was the last time the IAC and the throttle body were cleaned?
Customer: replied 4 years ago.

The ticking did go away, and stayed away during myXXXXX I did look at the back side of the oil cap and the valve mech - is was brown / yellowish - looked like a laquer on it - there was no thickness to it - not like a sludge. I thought of maybe using a rislone to clean it up.


I used autolite plugs -these were the same thing mitsubishing installed when it was new. They hadn't been changed in 146k miles. I used a premium wire - they called them import direct I think. I don't thing the iac or throttle body have ever been cleaned. I was thinking of doing this next if the idle instability continued.


No sludge is certainly good, but the yellow/brown discoloration is an indication it has either been run on the same oil way too long at some point (or points) or the vehicle has gotten very hot at some point and cooked the oil a bit.
In either of these situations the lash adjusters can be damaged and typically are. Since it is quiet now it is likely a light to moderate case (over night, two nights etc)..... not worth worrying about at this point.

Now regarding the miss.... hopefully it is gone now and was just an issue with the adjusters pumping up. Keep in mind that when the lash adjusters are collapsed, the valves are not opening all the way (we're talking about a 30% reduction if it is totally collapsed) and this will cause drivability issues or even misfire code if it doesn't pump up fast enough.
I would be concerned with the plugs though..... the plugs have been changed at some point. There were never any Autolite plugs used in this car (or any Mitsubishi for that matter).
Original equipment plugs are NGK plugs with one exception, that for several months they did run a batch of Champion plugs for comparison. This was changed back to NGK somewhat quickly due to quality control issues with the Champions.

Essentially.... you don't want to run anything but NGK or Denso in these if you can avoid it. If the miss is gone, we can probably write it off to a valve issue while the adjusters were flat, but if it persists I would be putting fresh factory replacement plugs in there. While we see the most problems from Bosch plugs, Autolites have more than their share of issues as well in Mitsubishis, but typically their problem is premature failure (2-10k miles before misfiring). Bosch on the other hand rarely work out of the box for this model, so at least we don't have that to worry about.
The wires should be fine... the only time we see any aftermarket wire issues is when people go with the super-duper-in-your-face brands that are 3x the size they need to be, glow in the dark, whatever other gimmick you can think of. Standard (aftermarket) replacement wires rarely cause a problem until at least 35-40k in my experience.

My only other concern with the idle issue apart from a fresh cleaning which is always a good idea if it is unknown the last time it was done, would be to check for vacuum leaks with a can of brake cleaner or propane. If the plenum gasket didn't make it for reuse it could cause similar symptoms; if a hose got missed (The FPR hose often is found "off" or torn from removal when cars come in after a repair with idle problems).
I am going to be stepping away briefly, but if you have any other questions or clarifications just let me know and I'd be happy to elaborate.
Customer: replied 4 years ago.

Interesting with the spark plugs. The wires still had the oem cyl #'s on them - so I assumed these were oem. I have never seen these on replacement wires. The #1 plug had failed - part of the porcelan was broken and floating around at the bottom of the plug - this is the same cyl as the original misfire code.


What is the FPR hose? I am normally pretty gentle when removing parts - so I don't expect any torn or missing hose. But then again there is always the possibility of missing something...or it was missed before me and I didn't notice.

I replaced the plenum gasket - so hopefully no intake leaks there. I'll try the brake clean trick tomorrow.


I had the same idea with the misfire and the collapsed lifter - good to confirm with another expert. Thanks,

The wires were OEM if numbered... I have never seen aftermarket numbered wires. If they were OEM they also will have the build date of the wires printed on them alongside the numbering (probably 2001 if original). This isn't an indication of plug life though, as the wires will normally make it 90k with no issues, and if the oil leaks are kept under control (the seals around the spark plug tubes leak oil into the plug holes) I have seen original wires over 200k. I wouldn't recommend going over 60k on them, but they will take it as long as they don't get oil saturated.

The FPR (fuel pressure regulator) hose is the one that goes from the drum at the drivers end of the forward fuel rail back to a nipple on the plenum just behind the throttle body. I don't have a good photo but I do have this diagram that should help (you can verify your other vacuum hoses against it too just in case):
Typically what I will see most often is that one end or the other gets pushed down under wiring etc and forgotten. I've done this myself on a few occasions... sometimes it just gets in the right spot where you don't see it and if you aren't thinking about it nothing looks out of place etc. On some occasions (typically higher mile cars or cars that have overheated) I will see the plenum end actually melt onto the nipple, then on removal will either create a small tear or pinhole from pulling it, etc.

Customer: replied 4 years ago.

ok - thanks - I paid specific attention to that hose and it is connected properly. I didn't notice any issues with any of the hoses, all seemed to be flexable - no brittle or cracked hoses.


Do I need to remove the IAC to clean it - or can I remove the intake hose and spray in there?

Good deal.

Good question......Do not spray in there to clean the IAC! There are a few issues this can cause but the botXXXXX XXXXXne is don't spray anything into the throttle body that doesn't evaporate instantly (ie, ether for starting etc).

What you will want to do is first pull the intake hose and clean out the throttle unit; use brake cleaner if you can (carb cleaner is OK but is oily and makes for more work). It sounds like you are probably familiar with this, but spray it liberally onto a rag then reach in and wipe it out while holding the plate open with your other hand. Go all the way around the inside and if there are any brown/black marks on the bore, use a brush, scotch brite, etc to knock them loose and wipe it out again.
Once the throttle is clean then pull the IAC for cleaning. It will be held in with three philips screws. When you pull it out go slowly... there is a rubber o-ring on the end that just loves to fall off to forever be lost somewhere on the tranny... good luck replacing it on short notice.
With the IAC out, you can spray the end, however I prefer to again spray the rag and wipe the pintle clean. There will be very little carbon on there even if it is pretty bad, it doesn't take much to cause issues. You can give the pintle a little wiggle and twist as well to make sure it isn't seized up or anything.
With the IAC out, you can spray into the IAC port to clean it. Since it is on the bottom any residual spray will run out the bottom anyway and is safe to do without issue.
Customer: replied 4 years ago.

I normally use a throttle body spray - someone once told me there were coatings on those parts -so I use it - not sure how necessary, but that is what I normally do.


I have brake clean as well - can I use either of these?

Either is fine.

The coating situation is not an issue with Mitsubishi. All throttles have a finish on them but these will not remove them.

As an aside.....Lexus and some Toyotas had a slick finish that would deteriorate from cleaners and they advised against using any cleaning products.... I'm sure other manufacturers may have as well. The problems with these, at least in reference to Lexus/Toyota, are that the finish cooks off with years of heat anyway and you simply can not operate the vehicle without cleaning them.... they expect the computer to compensate for build up indefinitely which is not possible, and even if it were the memory is lost when power is cut. The end result was you had no choice but to clean them. Effect? None. I'd always be "gentle" just in case, but I know guys that really gave them a run through and there were never any side effects.

Back on subject though.... this is not an issue at all with any Mitsubishis.
I prefer brake cleaner as it is just stronger than any other cleaning agent I have tried. Given the choice, I always choose brake cleaner. Throttle cleaner is fine to use, it just typically has a bit of lubricant in it as well (expecting people to spray it into the throttle and in turn lube the axle shaft). This makes it oily and a bit more work to clean properly, but will still work fine.
Customer: replied 4 years ago.

Thanks - was thinking more about the idle instability....does it make sense that it idles fine for about 30 seconds, then has instability. I'd then rev it to 2000 rpm for 15-20 sec, and let it go back to idle - it would idle fine for 30 sec or so and flutter again.

Well there are a few things there.
First, at start up it will go through a fixed idle adjustment based on temperature. This takes a bit to go through. Once it has hit it's stable speed a few things happen... if the engine is not completely cold (does not need to be full operating temperature), the sensors go live rather than map based fueling. If there is a mixture control issue of any type, it will appear now. Second, the evaporative system will run it's tests (though somewhat dependent on temperature) which can have a drastic effect on idle speed especially if there is any vacuum leak to be found.

My primary interest would be the throttle condition (and IAC) simply due to the work that was just done. You did the cap and rotor so you certainly had the battery out. Once that happens your IAC learned value is gone.
Get the thing cleaned out first and foremost and compare behavior. If it is not resolved, then look into vacuum leaks. If the problem was not there before (it was steady prior), and the misfire is appeared to be resolved, your only realistic possibilities are going to be IAC learned value being lost and needing throttle cleaning or a vacuum control issue (be it leak or hose backwards etc).

My money is on the throttle being gunked up though.
Customer: replied 4 years ago.

My friend did say that the idle at times would jump this may not be new - he may have had two issues- the misfire due to cyl 1 plug being broken, and a dirty iac or throttle body. I'll clean tomorrow and let you know what I found.


Thanks for the help and insight....I like how thorough you are in each response. That helps especially with an issue like this.


No problem at all. If you need further assistance I will be here tomorrow afternoon/evening as well.
If you have other Mitsubishi questions you can just put "For Doug" on the question if you would like to deal with me next time.
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