Acura MDX SUV Forums banner

1 - 15 of 15 Posts

·
Registered
Joined
·
13 Posts
Discussion Starter #1
I keep getting a P0304 misfire code. I also sometimes get a flashing engine light and AWD-SH light stays on. I always get the 304, and not the other cylinders. It seems like when I replaced the plugs a couple months ago, it solved it, but now it is back. Replaced the coils last week, and for a couple of days, seemed like it solved it, and now it is back. It doesn't feel like I am getting enough of a misfire to effect performance, since I changed the coils. Prior to that, there was an OBVIOUS drop in power. Also, probably an important detail is that the ignition coil at cylinder 4 had residue on it, as if there was some burnt oil or something? Also, I think someone may have over filled the oil, as recently the check oil light has been coming on and every time I check, there is enough, but now that I think about it, I think there may have been too much. Last night I replaced oil and for most of the day, it felt like it was fixed, but now it is back.

Other symptoms: fluctuating idol, rough start up

I have done a search and seems like it could be a vacuum leak, but other suggestions are EGR valve, EGR ports, idle air control valve, pcv valve.

The rough idol and fluctuating idol seems to point more to a vacuum leak, but is this a common problem with the MDX?
 

·
Registered
Joined
·
2,037 Posts
Probably not vacuum leak since you only have one misfire. Why don't you check fuel trim to see whether it is too lean too rich? More like a single cylinder issue, eg injector.

Sent from my Pixel 3 XL using Tapatalk
 

·
Registered
Joined
·
944 Posts
Compression test is a must at this minute. If compression is low, check valves. If compression is ok- injector, coil, spark plug, wiring is to blame. Good luck
 

·
Registered
Joined
·
13 Posts
Discussion Starter #4
Thanks guys for help. I should have also added that it doesn’t happen every time I hop in car and drive a few miles (after I clear code). It does seem to happen more when it is hot, wide open throttle/hard accel. Once it triggers engine light and it is flashing and then soon after the AWD SH light goes on and stays on. If I am driving and in higher RPM it seems like the engine light goes off. Example. On freeway if it is in normal drive mode and I am 2-3,000 rpm it might flash. But if I go into D3 trans Mode and maintain higher RPM the engine light immediately goes off.
I just drove home from work for 15-20 min and no issue, no engine light, no AWD light and no fluctuating idol. But I didn’t do any hard accel pulls, it is much cooler out and it wasn’t a very long drive. Seems odd that it is so inconsistent.
I also do have some oil residue on passenger of the motor and parts, but I do have a slow power steering leak that I think it is coming from (I know I have a slow steering leak, I am just not sure if I have another leak, perhaps it is from over filling the oil previously?).
 

·
Registered
Joined
·
2,037 Posts
The additional information makes it more likely a loss of compression. Sad news, but it is logical.

If you change to D3 without change throttle, engine has less time to suck, so cylinder pressure will drop. At the same time, same size leak has less time to leak in compression stroke. Both with alleviate loss of compression.

Sent from my Pixel 3 XL using Tapatalk
 

·
Registered
Joined
·
13 Posts
Discussion Starter #6 (Edited)
The additional information makes it more likely a loss of compression. Sad news, but it is logical.

If you change to D3 without change throttle, engine has less time to suck, so cylinder pressure will drop. At the same time, same size leak has less time to leak in compression stroke. Both with alleviate loss of compression.

Sent from my Pixel 3 XL using Tapatalk
Well that doesn't sound good, but ultimately, what does that mean? Drove to work tis AM, and engine light never came on.

UPDATE-just checked my dip stick and radiator. Oil on dipstick appears to be normal and coolant it green and clear.
 

·
Registered
Joined
·
1,187 Posts
where did you get your spark plugs from? Fake spark plugs are being sold on ebay/amazon and give very similar symptoms. Also have you checked the injectors?
 

·
Registered
Joined
·
13 Posts
Discussion Starter #8
where did you get your spark plugs from? Fake spark plugs are being sold on ebay/amazon and give very similar symptoms. Also have you checked the injectors?
O’Rielly auto parts. Have not checked injectors. I don’t have any special tools to do that type of thing.
 

·
Registered
Joined
·
944 Posts
CHECK COMPRESSION
 

·
Registered
Joined
·
17 Posts
I had the same issue this week for my #4, then the next morning I had #2 & #4 misfires on my way to my mechanic. After swapping plug & coils, it turned out only # 2 had the issue. After a deeper dive and a compression test later it was determined that I might have a cylinder head issue or worse. Do yourself a favor and get that compression test done ASAP!
 

·
Registered
Joined
·
13 Posts
Discussion Starter #11
I had the same issue this week for my #4, then the next morning I had #2 & #4 misfires on my way to my mechanic. After swapping plug & coils, it turned out only # 2 had the issue. After a deeper dive and a compression test later it was determined that I might have a cylinder head issue or worse. Do yourself a favor and get that compression test done ASAP!
dang. Would your engine light stay off for extended periods? I can’t figure out why it stays off for several drives and then goes back on. At the moment I have driven around 4-5 drives ranging 3-15 miles and the engine light hasn’t come back on. (I am hoping that when I checked the coil and plug the last time, perhaps one of the 2 wasn’t “seated” properly and that was the problem, I never get that lucky tho).
 

·
Registered
Joined
·
1,187 Posts
check the wires going to the connectors, a loose wire on a coil plug can cause these issues.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #13
check the wires going to the connectors, a loose wire on a coil plug can cause these issues.
Thanks. I will check that out. A couple more drives today and still no light, but I have been driving conservatively (not sure if that matters). Wondering if maybe from over filling oil or maybe the spark plug wasn’t tightened enough (residue on the old coil had to come from somewhere) and now having reinstalled it and/or having proper oil level and giving some time to burn oil off the plug may have “fixed it”. I don’t want to really push the car right now because I need to get it smogged (it’s months over due) and I need to have a certain amount of driving on it without the engine light coming on or else they detect that and won’t pass it.
 

·
Registered
Joined
·
56 Posts
I'm actually surprised no one else has noticed this or brought this up to OPs attention. 1st it would help if you notified everyone the year and mileage of your car. 2nd OP mentioned residue, oil in your spark plug chambers is never a good thing and has very little to nothing to do with overfill of oil. You'll need to do a Spark plug tube seal change, and while you're there you might as well do a valve cover gasket change.

dzionassi is right, no harm in doing a compression check but at this point if you wanted to be sure it's solely a cylinder 4 issue or parts issue you could've done some further troubleshooting before replacing parts, ie.. If you're having misfire on bank 4 then remove the coil pack, remove the spark plug and observe the parts, you could then swap coil packs with another cylinder to see if the misfire jumps to the newly replaced cylinder and that'll confirm if it's a coil pack issue (same can be done for spark plugs). But my opinion is that if you're seeing oil in the chamber then it's going to continue fouling out your plug and coil pack.

CIL turning off and turning on at random is a result of the ECU not receiving errors. If you drive the vehicle with no misfires for a certain amount of miles your ecu will think the issue is resolved, UNTIL the next time it misfires (CIL returns). You can do a compression test just to be on the safe side, its not hard, then make sure you do the valve cover job, extremely tedious but definitely a DIY'er job. Good luck!
 

·
Registered
Joined
·
944 Posts
I'm actually surprised no one else has noticed this or brought this up to OPs attention. 1st it would help if you notified everyone the year and mileage of your car. 2nd OP mentioned residue, oil in your spark plug chambers is never a good thing and has very little to nothing to do with overfill of oil. You'll need to do a Spark plug tube seal change, and while you're there you might as well do a valve cover gasket change.

dzionassi is right, no harm in doing a compression check but at this point if you wanted to be sure it's solely a cylinder 4 issue or parts issue you could've done some further troubleshooting before replacing parts, ie.. If you're having misfire on bank 4 then remove the coil pack, remove the spark plug and observe the parts, you could then swap coil packs with another cylinder to see if the misfire jumps to the newly replaced cylinder and that'll confirm if it's a coil pack issue (same can be done for spark plugs). But my opinion is that if you're seeing oil in the chamber then it's going to continue fouling out your plug and coil pack.

CIL turning off and turning on at random is a result of the ECU not receiving errors. If you drive the vehicle with no misfires for a certain amount of miles your ecu will think the issue is resolved, UNTIL the next time it misfires (CIL returns). You can do a compression test just to be on the safe side, its not hard, then make sure you do the valve cover job, extremely tedious but definitely a DIY'er job. Good luck!
He already stated that coils and spark plugs were changed. There is not much more to it, maybe injector.
He said that thee is some kind residue on sprak plug, but I am pretty sure that it is not oil. Whenever cylinder is misfiring or there is some other combustion problems, there will be film on spark plugs that looks like oil and piston is "wet":
115840


Whenever misfire happens and there is no signs off failed part, compression/leak down test must be done.
 
1 - 15 of 15 Posts
Top