Random Misfire on all Cylinders
 

I own a 04 MDX [72k miles] and check engine light is on, went to smog and failed due to P0300 random misfire error code for all cyclinders. Has anybody seen this error and what could be casuing this misfire?? Is it always spark plugs, vacumm leak or fuel injector??

I had basically the same problem in my 2006 last week (as seen here). I thought I had the paperwork handy, but I'll see if I can find it. The bad news is that you're out of the 70K mile warranty, so it's probably going to be on your dime.

The tech told me the misfiring is corrected in their 100K mile tune-up, so it's something that's part of maintenance. He said sometimes the misfirings happen early and viola, the check engine light comes on (and sometimes VTM-4 light comes on too). He initially told me it was a $1000 job, but the final paperwork showed only $400 and change (luckily I was still under warranty at 66K miles).

Before the check engine light came on, my vehicle's signs were rough idle, poor fuel economy, and poor performance especially around 2-3rd gear.

I'll see if I can find the paperwork...that should help...if you're like me and checked google/azine, you'll get all sorts of information / possible causes for this problem...

I had the same problem. 04, had about 120K miles on at the time.

CEL would come on, VTM-4 would come on and off, I didn't know what to do. I put in a new EGR valve and had the EGR port cleaned & had the valve adjustment done.

Truck runs like new, hasn't happened since. I had misfire in 5/6 cylinders; don't recall what the code was.


There might still be a bulletin on EGR valves from Acura, I think it's up to 80K. Check with your dealer/do some research, you may get lucky there.


My MPG's were terrible, 15-16 on average and the truck shook a little when it ran - all of that went away :woot:

It's more than likely one cylinder misfiring. Clean / replace your PCV valve and EGR valve and run some b12 / seafoam through the tank to clean out your injectors. Then see if the symptoms are relieved. Less likely reasons are a fouled plug / bad coil / vacuum leak followed by valve adjustment / burned ringland / blown head gasket. Do you use 91+ octane religiously?

You need a valve adjustment.

Let me tell you my story. See if it compares to yours. My wife took my MDX into the dealer for the standard preventative maintenance. They performed a valve adjustment as directed by the service manual + spark plug + lubrication, etc. Total bill was about $1100. Prior to the valve adjustment, the car ran great. Gas mileage was 17/22. After the service, the car ran rough and gas mileage was 13/18. I took the car back and complained. The dealer told me the gas mileage would drop as the car got older and it wasn't an issue worth worrying about. Which of course infuriated me.

So I decided to check the car out myself. Upon inspection of the spark plugs, I found a loose plug and a bad coil (the acura tech didn't tighten the plug on the #5 cylinder and hot exhaust destroyed the coil). I replaced the plugs and the coil and the car seemed to run a little better but still had mileage issues. So I took it back to the same dealer who told me I needed a $1200 throttle body. I didn't believe him and left without the service.

Within a few weeks, my check engine light came on. Followed by the VTM-4 light. If I turned the car off, the VTM-4 light would turn off and maybe stay off or maybe come back on later. It seemed fairly random. So I used my $129 engine scanner (you can buy those at any car parts store) to read the codes and detected misfire on all 6 cylinders (P301 to P306 codes) + random cylinder misfire.

I decided to take the car to a different acura dealer. Their top mechanic swore to me that I needed an $850 valve adjustment (remember I just had that done). Then I went to 2 other non acura shops. No one could truly diagnose the problem. No one could tell me anything different than I needed a valve adjustment.

So, being mechanical and car savy, and having found the loose spark plug, I decided to check the valve adjustments myself. On the MDX, each cylinder has 4 valves. 2 intake and 2 exhaust. The adjustment involves setting the gap between the rocker arms and the top of each valve. According to my copy of the shop manual for that car (I highly recommend you buy one from helminc.com if you plan on working on your own car), the specs are 0.008" to 0.009" for the intake valves and 0.011" to 0.013" for the exhaust valves.

All 12 of my intake valves (with the appropriate piston at TDC) were set correctly to about 0.009". Not one of the exhaust valves was set correctly. 5 of my six cylinders had 1 valve set to < 0 clearance. Meaning the valves were not sealed well during combustion and the other 7 exhaust valves were set to the clearance specification for the intake valves.

I supposed I should have guessed this right up front after finding the loose spark plug but I gave the $150/hr acura mechanic the benefit of the doubt. Silly me. So, I reset the gaps to factory specs and put the car back together. Now it runs perfect. No check engine lights. Gas mileage back to 17/22.

My message to you is this. It is highly likely that you need a valve adjustment. I demonstrated the connection between valve adjustment and random cylinder misfires (the check engine codes + VTM-4 light) by adjusting the valve gaps. It is also feasible that if you just had that work done, it may have been done incorrectly.

If you want to check or set the gaps yourself and you are mechanically inclined, it certainly a do-able task. But it may take awhile (it took me about 4 hours total and I've been working on cars for about 30 years). The valve cover on cylinders 1-3 (the back cylinders) is difficult to get to. And you'll have to take the intake manifold off. Once you have the valve covers off, set each piston to TDC by rotating the crank and lining up the appropriate mark in the viewing window on the front timing belt/gear cover. intake valves are closest to the fuel injectors. Exhaust valves are closest to the exhaust manifolds (the outside of the engine).

good luck.

Thanks for sharing your experience but the OP only has 72k on his X and he didn't mention having a valve adjustment done so saying it's absolutely his valves being out of spec is a poor assertion but is still a possibility. Usually, if the valves do go out of spec it's the exhaust valves and it's usually within the first 12k miles of an adjustment / new engine.

You should have filed a case with Acura Client Services against your dealership. That's unacceptable service, borderline fraudulent. Luckily irreparable damage wasn't caused. You could have easily burned your exhaust valves. I'm surprised your #5 spark plug didn't blow out of your engine completely.

Friends of ours had a tune up at a shop a few months back. They called us 4 miles from our house saying their car broke down. Come to find out that the mechanic didn't tighten the plugs in.. blew out all the plugs except one and we needed to helicoil one of the sleeves completely since the lower threads were destroyed. :whyme:

Thanks for all the replies which is very helpful. Here is rest of the story : I changed all the spark plugs and the CEL is back on but with only P0301 misfire code. So suspecting cylinder1 coil i swapped the coil-plug to cyclinder 2 to see if CEl comes back on with P0302, but after 4 days CEL is on with misfire for all cylinders. So sounds like i need a valve adjustment, any other suggestions??

top engine clean, pcv valve , spark plugs oil change, clean the egr.

[quote=MNIO;12187110]You need a valve adjustment.

Let me tell you my story. See if it compares to yours. My wife took my MDX into the dealer for the standard preventative maintenance. They performed a valve adjustment as directed by the service manual + spark plug + lubrication, etc. Total bill was about $1100. Prior to the valve adjustment, the car ran great. Gas mileage was 17/22. After the service, the car ran rough and gas mileage was 13/18. I took the car back and complained. The dealer told me the gas mileage would drop as the car got older and it wasn't an issue worth worrying about. Which of course infuriated me.

So I decided to check the car out myself. Upon inspection of the spark plugs, I found a loose plug and a bad coil (the acura tech didn't tighten the plug on the #5 cylinder and hot exhaust destroyed the coil). I replaced the plugs and the coil and the car seemed to run a little better but still had mileage issues. So I took it back to the same dealer who told me I needed a $1200 throttle body. I didn't believe him and left without the service.

Within a few weeks, my check engine light came on. Followed by the VTM-4 light. If I turned the car off, the VTM-4 light would turn off and maybe stay off or maybe come back on later. It seemed fairly random. So I used my $129 engine scanner (you can buy those at any car parts store) to read the codes and detected misfire on all 6 cylinders (P301 to P306 codes) + random cylinder misfire.

I decided to take the car to a different acura dealer. Their top mechanic swore to me that I needed an $850 valve adjustment (remember I just had that done). Then I went to 2 other non acura shops. No one could truly diagnose the problem. No one could tell me anything different than I needed a valve adjustment.

So, being mechanical and car savy, and having found the loose spark plug, I decided to check the valve adjustments myself. On the MDX, each cylinder has 4 valves. 2 intake and 2 exhaust. The adjustment involves setting the gap between the rocker arms and the top of each valve. According to my copy of the shop manual for that car (I highly recommend you buy one from helminc.com if you plan on working on your own car), the specs are 0.008" to 0.009" for the intake valves and 0.011" to 0.013" for the exhaust valves.

All 12 of my intake valves (with the appropriate piston at TDC) were set correctly to about 0.009". Not one of the exhaust valves was set correctly. 5 of my six cylinders had 1 valve set to < 0 clearance. Meaning the valves were not sealed well during combustion and the other 7 exhaust valves were set to the clearance specification for the intake valves.

I supposed I should have guessed this right up front after finding the loose spark plug but I gave the $150/hr acura mechanic the benefit of the doubt. Silly me. So, I reset the gaps to factory specs and put the car back together. Now it runs perfect. No check engine lights. Gas mileage back to 17/22.

My message to you is this. It is highly likely that you need a valve adjustment. I demonstrated the connection between valve adjustment and random cylinder misfires (the check engine codes + VTM-4 light) by adjusting the valve gaps. It is also feasible that if you just had that work done, it may have been done incorrectly.

If you want to check or set the gaps yourself and you are mechanically inclined, it certainly a do-able task. But it may take awhile (it took me about 4 hours total and I've been working on cars for about 30 years). The valve cover on cylinders 1-3 (the back cylinders) is difficult to get to. And you'll have to take the intake manifold off. Once you have the valve covers off, set each piston to TDC by rotating the crank and lining up the appropriate mark in the viewing window on the front timing belt/gear cover. intake valves are closest to the fuel injectors. Exhaust valves are closest to the exhaust manifolds (the outside of the engine).

good luck.

[Yes, it was the valve adjustment fixed the random misforeson all the cyclinders, SMOG passed today and saved 130$ for diagnostics with the deler, idling is very good after the adjustment and also the mileage. THANKS! ]

i had this issue and my brother in law mentioned that it could be a lightly stretched t/belt that is causing it, he's a Acura mechanic. I proceeded to do the tbelt since I'm right at 92,000 miles. So far I don't have any more misfires and car runs great. When he hooked up the car to read the MAF he noticed that I could also use a valve adjustment which he will do at home, he mentioned it'll improve my gas mileage a lot.

Hmmmm I think I'll do some of the things suggested on our '06 even though it has just 37K miles on it. But it's mostly doing city driving so I can see where it might be getting carboned up.

I have a 2006 MDX and getting CEL & VTM4 light comes on and off with error code (P0175, P0300, P301, P304 and P305). Did you find out what was the problem? I thought of Oxygen sensor, but it can be ignition coil or valve adjustment, etc... need help trouble shoot.

I had this problem also. Misfires on all cylinders were reported. On my 2004 MDX, it didn't have the "ant farm" style EGR ports and was relatively clean. It's extremely easy to check this by removing the upper intake manifold cover. You can reuse the gasket, so it's basically only time. My problem was solved by adjusting the valves. All but three were tight. I did the adjustments myself, and would recommend it to others who are comfortable working a little more deeply inside the engine. Otherwise, it's not a job for someone who is inexperienced - as you need to remove the upper intake manifold and surrounding pieces. There are a couple of good DIYs and videos. See "Eric the Car Guy" for a great video to pre-acquaint yourself with the procedure. My MDX runs great now and the CEL is gone.

I have experienced one bad coil pack throw a random cylinder misfire code. When I pulled the codes it was a P0300. The only way i found the bad coil was to have the engine running and pull each electrical connector off the coil packs, one coil pack at a time. This allowed me to "feel" if the engine ran worse when I stopped spark to each cylinder. Well i found it when I pulled the connector and there was no change in engine idle or running, or feel. The engine was already running rough because one of the coil packs was bad. Keep in mind it could be a bad coil pack (maybe more than one), a cracked or bad spark plug, a bad fuel injector or a bad valve adjustment.

Here is a video DIY for spark plug replacement on Honda / Acura j series engine V6.

2004 MDX Touring

I’ve read lots of post on the multiple misfire but I haven’treally seen one that I believe fits my case.

A month or so ago the check engine light came on, so I hookedup the code reader. It said my Cat wasn’t working properly. I cleared the codeand moved on. This week it came back on and the car started running bad and allthe lights came on. I know I should replace the PCV valve, EGR valve, sparkplugs, and so but I saw on one of the post a bad cat could cause the misfires.Right now, isn’t the best time for me to be spending a bunch of money on valveadjustment and I was hoping a DYI Cat replace would fix the problem for now.However, if everyone thinks the misfires are not from that and maybe I’m gettingthe bad cat code from the misfires or something I’ll try a different route.

thanks,
jason

:blink:

Are you sure there's not a wayward cat in your brain chasing a laser?

A bad tank of gas or excess gas being spit down the pipe related to using regular can foul a catalytic converter. Is it the precats (front / rear bank) or 3rd cat? Make sure the o2 sensors are good, and run a IR temp gun on the precats after a drive. One should have a higher inlet and possibly lower outlet temp than the others. If it's really bad, it will glow at night and excrete a sulfurous odor.

thanks for the reply. It's actually my wifes car and I never really drive it, so I'm still trying to collect all the details. I'm pretty sure he uses reg unleaded. I guess that could be the reason. Would using upgraded gas make the codes go away or do you think that ship has sailed and now i need a new Cat?
The code didn't specify one from another. I thought she had one cat and two mufflers. At least that's what I saw from a diagram.
i just figured the car has 150K + miles on it maybe the factory cat finally went and it would be a quick and easy DYI swap.

Nope, if the monoliths are melted / clogged, damage is done. New cats and start using primo. I have over 150k on ours, no issues (knock on wood).

You have two primary cats (precats) from each bank of the engine that flow into the main cat (3rd cat) at the end of the j-pipe. What code did you pull?

The reader I was usuing didn't actually flash the code. It flashed the issue. I'm sure it will go off again then I'll see what it says.
Q: do you know which would most likely be bad ?

Q2: Do you think this would be the casue of the misfire? Or does it just happen to be all at the same time...

It's probably the rear bank if I had to guess. Go to a part store and have them read the code. Their code reader will tell you the exact codes, which will identify the cat and possibly where the misfires are being experienced.

The misfires were all six individually and then an overall code for themultiple misfires.
thanks again I'll look into it this weekend. My luck it will be the rear two and I'll have to spend 500 not 250...

Pull the code to the cat and post it here. Don't throw money at the car because a misfire is very particular. Diagnosing it is not trivial since it can be a myriad of things.

these misfires are very commonly caused by the egr system being clogged. very easy to clean, especially on 01-03

2002 Acura MDX Missfire Solution...Excellent!!! Found this information priceless.
 

We spent over $1000 at mechanics before they discovered that our 2002 Acura MDX needed to have the valves loosened. The missfire stopped and has never returned. Thank you for posting this solution!

I'm aware that this thread goes back several years, but the information on here solved my problem on my daughter's 02 MDX. Random misfire, poor mileage, ect. I did all of the usual checks and replacements, all to no avail. Decided to take the plunge and do the valve job. I found that almost all of my exhaust valves were tight with no clearance. The intake valves were fine with the exception of a couple that needed tightening. The most difficult part of the job were the exhaust valves next to the firewall,(cramped space). Put it all back together and the car has never run better. No lights, no more dying, smooth as silk. Total cost, $49 for valve gaskets, and about 4 hours labor. Thanks for all of the previous posts and advice. I probably saved myself $6 or $700 dollars by doing this myself.

The actual valve adjusting was the easy part and most enjoyable IMO. What sucked for me was replacing all the spark plug seals.
Shoehorning the rear bank valve cover wasn't all that fun either.

:cheers:

Thanx
 

I bought this vehicle and replaced plugs and coils. Thought it may be the timing belt. I'm glad i read this thread.