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Old 12-04-2012, 11:26 AM   #1 (permalink)
koa
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Valve lash adjustment

Based on what I have been reading about valves being on the tight side when checking the valve lash, I decided to go ahead and check mine also. My vehicle:

2004 MDX
96K at time of check

I won't post the steps, as I believe it has been sufficiently covered else where, but I do want to share what I found.

Prior to checking the valve lash, there was no indication that it needed to be adjusted. My MPG was roughly around 15 city and 21 highway. No knocking or tapping noises and CEL was not showing anything.

This is what I found, all clearance was on the tight side, including the intake. The exhaust was especially tight. It was so tight, I was not even able to use the intake feeler gauge on the exhaust side.

I'm not sure about everyone else, but in my case, I can confirm that the valve clearance is indeed on the tight side. Although I had no problems before adjusting the valve lash, it does seem like the motor is idling a lot smoother.

No regrets about checking the valve clearance. Thanks to previous posters for sharing their own experience with tight valve clearance.
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Old 12-04-2012, 12:24 PM   #2 (permalink)
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Keep us posted on any MPG fluctuations, please.
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Old 12-04-2012, 01:13 PM   #3 (permalink)
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Hello phins2rt, I'll try to remember to keep an eye on the mpg to see if it improves or gets worse. Too early to tell yet, as adjustment was done only a week ago.

On another topic, I had to remove the intake plenum to even get to the valve covers. While I had them off, I thought I just go ahead and clean them. They weren't too badly gunked up. A can of carb cleaner was sufficient to remove most of the build up.

Although there was not a lot of oil, there was some evidence of it being there and was curious if an oil catch can would be of any benefit. Any experience, thoughts?
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Old 12-04-2012, 01:24 PM   #4 (permalink)
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definately post back.

My 04 has 130k and I have never had the valves adjusted. The car idles and runs fine, but I also have horrendous gas mileage (15mpg) and a rough idle/stallling problem after a cold start overnight for the first minute or so.

I thought I read a mechanic check the valve clearance by hooking the car up to a computer and reading the map/maf sensors?
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Old 12-04-2012, 07:32 PM   #5 (permalink)
koa
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Don't know about checking valve clearance with a computer; besides, didn't want to pay someone anyways.

As far as rough idle on start up is concerned, if it's any consolation, my 04 also has a high idle on cold start ups, which is a bit rougher as compared to when it reaches operating temps. To my understanding, high RPMs on cold start ups is not unusual in most cars; although, stalling or stumbling is not normal (IMHO) and could be a symptom of a problem.

From my experience, rough idle can be a symptom of a vacuum leak, gunked up PCV/EGR valve/passages, bad plug(s) or bad coil pack.

If you were thinking that the rough idle may be due to valve clearance out of specs, I would tend to think that the rough idle would be present even after the engine has warmed up. The same goes for plugs and coil pack(s).

Seals around hoses tend to expand when warmed up and contract when cold though, so you might want to check for a vacuum leak. A PCV/EGR valve could also stuck close when cold, especially if they are all gunked up.

Not sure if any of these could be the cause of your rough idle, but at least it's worth a check and shouldn't cost you anything to verify.
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Old 12-04-2012, 09:37 PM   #6 (permalink)
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I picked up a couple MPG when I had mine adjusted. Said the exhaust valves were tight. I think it's a must when you do the timing belt.
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Old 12-04-2012, 11:10 PM   #7 (permalink)
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Quote:
Originally Posted by koa View Post
Don't know about checking valve clearance with a computer; besides, didn't want to pay someone anyways.

As far as rough idle on start up is concerned, if it's any consolation, my 04 also has a high idle on cold start ups, which is a bit rougher as compared to when it reaches operating temps. To my understanding, high RPMs on cold start ups is not unusual in most cars; although, stalling or stumbling is not normal (IMHO) and could be a symptom of a problem.

From my experience, rough idle can be a symptom of a vacuum leak, gunked up PCV/EGR valve/passages, bad plug(s) or bad coil pack.
Thanks for the help. The problem with my 04 is that it won't go into high idle when cold and sometimes stalls. The idle is so low that even after I do get it to idle (very low idle) - the load from shifting the car from park to drive cars it to stall.
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Old 12-05-2012, 06:23 PM   #8 (permalink)
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Quote:
Originally Posted by CODOG2 View Post
Thanks for the help. The problem with my 04 is that it won't go into high idle when cold and sometimes stalls. The idle is so low that even after I do get it to idle (very low idle) - the load from shifting the car from park to drive cars it to stall.
Have you tried the PCM idle learn procedure? To my understanding, this is typically done when any of the PCM inputs, i.e. PCV, EGR, MAP measurements changes.

Since this procedure is fairly simple and won't cost you anything, it could be your first step in isolating the problem (assuming you haven't already done this of course).

Here is what you could try:

1. Clean the PCV valve and passages (also confirm they are functioning properly)
2. Clean the EGR valve and passages (also confirm they are functioning properly)
3. Perform PCM idle learn procedure

To clean the PCV valve, just remove it and spray it out with carb cleaner. The PCV valve should be located near your engine oil dipstick.

To clean the EGR valve, do the same. Be careful not to spray any electrical connections though.

To clean the PCV/EGR passages, I'd just access the top of the air plenum first to see how bad it is. You can use carb cleaner here too, just don't go too crazy, just enough to clear clogged passages. If you find that it is really gunked up, you might want to go deeper and actually remove the air plenum so that you can clean all the way to the intake manifold itself. Allow any carb cleaner to dry out before proceeding (to avoid possible hydro locking the cylinders - not really a danger since carb cleaner is combustible, but I just like being extra cautious).

To perform the PCM idle learn procedure:
1. Disconnect negative lead from battery terminal
2. Turn on head lights to dissipate any residual charge
3. Reconnect battery lead
4. Start engine and hold 3000 RPM with no load (in park or neutral) until radiator fan comes on.
5. Let engine idle for 5 seconds.
6. Drive vehicle at steady speed between 50 and 62 MPH for about two minutes
7. With A/T in "D" position, M/T in 5th gear, decelerate from 62 MPH by completely releasing throttle for 5 seconds.
8. Bring vehicle to a stop. Leave engine running at idle speed. If engine is stalls or is shut off during this part of procedure, repeat procedure starting in step 6.
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