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Doug, ASE Certified Technician
Category: Mitsubishi
Satisfied Customers: 8607
Experience:  Mitsubishi employed and Factory trained ASE certified technician
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Mitsubishi Endeavor: Doug i have this Mitsubishi Endeavor

Customer Question

Hi Doug i have this Mitsubishi Endeavor 2005 and showing a lot of codes from 455,401,1399,300,301,301 and some more first i did clean the throttle body, the egr port, then i remove all of my spark plug and wow they are soaked in oil, is this normal, could this be the cause of these codes i am getting what do i do next ?
Submitted: 2 years ago.
Category: Mitsubishi
Expert:  Doug replied 2 years ago.
The plugs being soaked in oil is typical, but not normal.
This is indicating that the spark tube seals are leaking. The tube seals are exactly what they sound like, seals that go on the top of the spark plug tubes. When you pull the valve covers off there are three steel tubes sticking up on each side of the engine which the spark plugs go down; on the top of each is a rubber seal... though it is more likely plastic at this point from years of getting hot/cold etc. The only solution to this is to remove the valve covers and replace the seals, of course replacing the valve cover gaskets at the same time. I do not normally recommend this job for DIYs unless you are extremely comfortable with this sort of work (it sounds like you probably are), as the valve cover gaskets are VERY hard to remove. Make sure you have a day or so set aside where you don't need the vehicle if you do not have a second mode of transportation. While not always necessary, the gaskets are extremely common to melt into the valve covers and can take hours of picking/chiseling away until they are completely removed. Again not always, but it happens enough that it makes sense to plan ahead just in case.
This condition -will- cause the PO300 and P0301 as well as any other P030x code. However it is important to note that these misfire faults can also be caused by the spark plugs if they are worn out or incorrect type, as well as by the ignition coil if one is faulty or aftermarket (aftermarket coils are a huge no-go on this model). The P1399 isn't a standardized code for this year/model, but generically it is normally used as a random misfire fault... meaning it is likely the code reader interpreting the P0300 fault.
The P0401 will not be related to the oil situation, and if your EGR are ports are all clean it is most probable that the EGR solenoid is faulty (part of the valve, one whole unit). The only other possibilities are the MDP sensor on the top of the intake or the computer itself, and neither are likely... especially without any related faults being set. Essentially.... all things being equal with the vehicle and no modifications/vacuum issues etc, if you get this fault and the ports are clear, the valve/solenoid assembly is most likely the culprit.
The P0455 will also not be related to the oil situation, it is indicating the fuel vapor system has a large opening in it... like a loose/missing/incorrect gas cap or a vapor hose installed wrong/torn/etc. One thing worth noting about this fault, if it happened right after engine work was done it is worth double checking your vacuum hose routing against the illustration on the hood. It is somewhat common to accidentally mix up the hoses on the purge solenoid etc which will result in a P0455 and depending on which hose is routed where, it could theoretically cause the P0401 too.
Customer: replied 2 years ago.
Doug i understand from reading and research that spark plug should only burn air/gas mixture and the gap is not supposed to have anything on it specially oil ! , what is the possibility that i have cylinder head gasket worn or cylinder head crack ? just making sure i am ready to sit on top of my hood and hold on to my tools well it is a DIY so where do you think i should start , valve cover gasket?
Expert:  Doug replied 2 years ago.
That is correct, you definitely do not want oil on the electrode! The thing to remember here however is that if your plug tubes are filled with oil, when you pull the plugs out all that oil is going to rush past and make it look terrible.
A head gasket issue is highly unlikely on this model. I would certainly not head to a conclusion like that based on your findings thus far alone.
I would definitely be changing out the valve cover gaskets and tube seals, as you know they need to be done regardless.
I would replace the spark plugs while you have them out anyway if you didn't already (I'm not clear on if you stopped when you pulled the plugs or not), and only use either NGK or Denso direct replacements (NO Bosch, and no specialty plugs with gimmicks like 4 electrodes etc etc). This vehicle is extremely sensitive to the electronics and only plays well with what it was designed for.
I would inspect the coils of the cylinders that had misfires on them to see if there are any white marks on them indicating arcing. You may not find anything there, but it doesn't hurt to look while it is apart. Obviously if anything is glaring at you there you'll want to replace the coil with a new Mitsubishi coil and so forth.
Once the plugs are new, coils look OK and the valve cover/tube seals are new, I'd clear it out and see what misfire faults return, if any. If you get misfire faults again, then I would rotate the coils around the offending cylinders to see if the misfire follows the coil... if it does, then you know you have a bad coil(s). If it does not, then further investigation would be needed.
Customer: replied 2 years ago.
well i am on it now replaced all six spark plugs (NGK) next is valve cover gasket and tube seals well the last time i drive this Endeavor it was ok only that is was rough idling and the last code was PO401 that made me check the EGR port pipe cleaned the EGR valve itself , how do you check the EGR out of the engine?with voltage, can i do that supplying voltage on the correct terminal which one is that?
Expert:  Doug replied 2 years ago.
The EGR is pretty difficult to test on-car on these all inclusive units but can be bench tested.
First a basic primer on the operation....Basically what occurs is the computer monitors the MDP sensor on the intake and when it commands the EGR on it expects to see a certain drop in vacuum on the MDP sensor. If the vacuum does not change the expected amount, then it sets a P0401 flow control fault.
This means that as long as the pipes are all clear and there are no obstructions, if there are no unusual conditions (wiring damage to the EGR, vacuum hoses on backward etc), then your only possible causes are the EGR/Solenoid assembly, the MDP sensor, or the PCM. The sensor is highly unlikely if it is not setting other fault codes too, as they rarely fail in such a way that they set an EGR fault only. The PCM is also unlikely to be at fault, as they rarely fail in any capacity beyond complete failure (engine won't run etc). That pretty well leaves you at just the valve/solenoid assembly at fault.
I am attaching below the steps to bench test the valve. Note that these will not test air flow, that can not be effectively tested. Only motor operation.
Please save it to your computer for viewing as the link is temporary.
Customer: replied 2 years ago.
getting late here in Canada and i just came from work i am a welder Doug but i am an electronic/computer technician by choice and i think i can bench test this EGR is it ok if i chat with you all about this Endeavor once i replaced valve cover gasket spark plug tube seals and test this EGR maybe by tomorrow?
Expert:  Doug replied 2 years ago.
No problem at all. I will be in tomorrow afternoon through evening as well. You can just reply back here when you need and the question will reopen and be placed in my queue... no need to open a new question as long as the subject matter is the same.
Customer: replied 2 years ago.
thanks Doug and goodnight!
Expert:  Doug replied 2 years ago.
You're welcome!
Customer: replied 2 years ago.
Hey Doug just got my valve cover gasket and the spark plug tube seals today together with a new torque wrench (i guess i am gonna need it) got the valve cover out on the right side out now can you send me pictorial or anything where to start taking out which , now that i see the valves it look to me it is not easy as it seem , a friend stop by and told me it is not a weekend project but have to do it for my own pleasure and experiance, thanks!
Expert:  Doug replied 2 years ago.
I don't have any pictures handy, but it is pretty straight forward. You won't be messing with the valves or anything like that.
Look at the exposed head and you will see the three steel tubes sticking up where the spark plugs go in. On the top if there is a black donut like seal sitting up there, pull it off and install a new one. If it is not there, look on the underside of the valve cover as it likely melted to the cover. Take a chisel and gently tap it loose, then install the new seal to the top of the tube, and repeat for all six plug tubes.
For the valve cover gasket itself, again flip the cover over and look at the channel around the perimeter, that is the gasket pressed in there. Use a right angle pick to try to pry it out... be prepared for it to potentially break into small pieces if it is hardened and melted in. This is the time consuming part.
Customer: replied 2 years ago.
well i don't see any donut looking seal inside and out of the tube black or otherwise should it sit on the inside of the tube or outside of it?
Expert:  Doug replied 2 years ago.
It sits on top like a hat. Did you flip the valve cover over and see if they are stuck to the underside? They are roughly 2" diameter and about 1/2" thick, and of course have a hole in the center about the size of the plug tubes..
Customer: replied 2 years ago.
Wow Doug they were in front of my eyes just like you said, stuck underside of the valve cover and looking at them they are not in perfect round condition somewhat oblong hopefully this will fix the spark plug soaking in oil, and some codes giving like the misfiring but anyways will let you know how it will go from here! thanks chat with you again...
Expert:  Doug replied 2 years ago.
Yeah once you feel the new ones you'll recognize the problem... the new ones will be nice and soft and the old ones will feel like concrete by comparison.