MDX2004

Hey folks,
I'm being a little facetious with the thread title like I have a mysterious issue here. We have 140K on this vehicle. The coils and plugs have been changed before, awhile back now. About a month ago the car experienced a rough idle upon starting and we got all the P0301through06 and the P300 codes. I cleaned the EGR valve like in other recommendations I've seen. I'm not sure if that really helped although it went away for a couple more weeks before the rough idle and same codes came back.

It can smooth out after a prolonged warm up period and the car seems to run fine afterwards. But we tend to not want to run it until we understand what's going on or attempt a fix. My wife will report it and then take my truck to work or wherever. Then I go try out the MDX and it would be rough then I let it
warm up and drive around the block seemingly ok, but the codes are there.

Could all the coils and/or plugs go bad together? I understand you can foul up plugs when the coils start to go. Is there a part that distributes the charge to the coils that might be failing leading to the misfires across the board? I think its easy enough to replace all the coils and plugs but I'd rather not do it to just do it as a shot in the dark.

Thanks,
-Brian

justnspace

iTrader: (1)

you can trouble shoot the coils by unplugging one by one with the engine running.
engine note should change when unplugging one by one. if no change in engine note; that's the suspected coil

MDX2004

I unplugged each cylinder, one at a time, while the engine was running. I unplugged the harness from the top of the coil. Each made a slight change to the engine note; none made 'no change'. The one on the back right made a greater change in the note but I believe it was due to the plastic intake being attached on that side(more to rattle). The engine felt just about the same when each coil was disconnected from the harness.
-Brian

justnspace

iTrader: (1)

next step would be to pull the spark plugs and inspect said plugs. you dont have to replace them unless they are horrible and out of shape.

another thing to check would be the catalytic converters. make sure the substrate is not broken on the inside and rattling around, for example if substrate is broken on the inside..you could be able to shake the peices out.

Skirmich

Bad valve lash can also trigger a misfire, When were the last time the valves were adjusted?

MDX2004

I looked through the maintenance records and couldn't find any record of valve adjustments. It was probably never done. I also could not find record of the spark plug and coil replacement which I thought was done at least once.

I took one plug out to take a look and it seemed pretty clean. It's coil ( the wire inside the rubber shaft) appeared to be shiny as well. I didn't check all the others. I couldn't get at the catalytic converters yet to look at those.

I'm not sure I can tie up the car doing the valve adjustment at my speed. Might need to break down and take it to a shop.

-Brian

jcniest5

I'm in the same boat, but '06 MDX only has codes misfired cylinder 1, 4 & 6. When it first happened, I read all over the internet and valve adjustment was the recommended option. So, I brought it to the dealer for a complete timing belt change, supposedly the dealer also performed valve adjust as part of that...but never changed anything. The CEL went off for short time, then came right back on. It was really cold at that time, and it seemed to improve with warmer weather, but now it's summer and it's still on. I've swapped ignition coils around, but it makes no difference. New coils or old coils, no difference. I'm so fed up I just drive it with the codes on.

MDX2004

Hello,
I just spoke to our service advisor from the dealer we take the MDX to. He reported we had the valves adjusted at 94K along with new coils and plugs(that was in Nov 2012 though). Timing belt was done either then or just before. He didn't think we would have an issue now at approx 150K with the plugs and valves. He also suspected that we'd have a loss in power if the catalytics were blocking the flow, which I don't think we're having.
One thing he mentioned was that the E15 gas collects more moisture than the E10. He did think that if that were an issue it wouldn't go away after warm up. I'm not sure thought if my wife's putting E15 in yet. So I'll need to check and see if the usual gas stations might have switched something we didn't notice. Another thing mentioned was that the refineries may have switched to the 'winter blend' fuel as it was easier or less costly to make to get fuel to market after the hurricane.
I'll try looking into the gas and maybe try an injector cleaner or gas treatment depending on what I find out.
-Brian

thoiboi

What brand gas have you been using?

justnspace

iTrader: (1)

it could be as simple as bad fuel and would need a few tanks of good fuel to stop the misfires.

and your plug looks good!

MDX2004

Chevron, BP and sometimes from a 7/11 in that order. I just asked my wife about it. Usually the Chevron, and we always use the 93. It might have been from BP last. But now I'm curious about the E10/E15 levels, etc.

thoiboi

Licensed Brands | Top Tier Gas


Stay away from crappy gas.

Stick with Premium octane 91/93 always. Also throw in a bottle of Techron cleaner for good measure. This could be an easy fix.

MDX2004

Update:
About a week ago I was able to try a bottle of Lucasoil fuel injector/fuel system cleaner I got at PepBoys. It had too much gas in the tank to add the bottle to it so I waited until it was almost empty. I filled up with E10 93 octane. The misfire or engine light went away over this past 200 miles. There is about a 1/4 tank left so I think we're getting ok mileage. I can't say for sure why it's running ok now. Maybe it was the previous gas. I never really thought those cleaners in a bottle would be that effective either but maybe they work sometimes. My thoughts were that the engine being so old would have more build up than a fuel tank additive would handle for it to be the cure. Perhaps though the 3.5L engine is responsive to such products.
I think someone in another thread had a good experience after using one of those cleaners too. I'll chime back in later if the conditions change.
-Brian