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Discussion Starter · #1 ·
'99 EX, 190k miles, owned + self-maintained since new. Runs great except this problem.

Recently started idling and running rough (most noticeable at idle), sounds loud. No CEL, but I used the code reader anyway, and got P1399 (misfire). Cleared it and it has not come back. No other codes.

I did not know that it was possible to have codes without a CEL. I guess it is.

Coils seem OK. I replaced one a few months ago, so checked them one at a time - disconnecting the connector and confirming an increased roughness of idle for all 6.

EGR port is OK. I removed the intake manifold, and cleaned it out (2nd time doing this) really well with a drill bit + brake cleaner on the rest of the intake manifold. While I had that off, I cleaned the throttle body carefully (3rd or 4th time doing this).

EGR valve seems OK. I soaked some brake cleaner in there when I had it off, and cleaned it as well as I could. Also ran through all the troubleshooting electrical tests in the manual, confirming the valve is good.

Ignition switch was recently checked as good.

I adjusted the valves when I did the Timing Belt at 105k, 85k miles ago.

When I was trouble shooting last weekend, I changed the oil, ATF, coolant, and ran some seafoam through the brake booster line for good measure. (all the easy stuff first)

After searching the forum for a while, it appears that fuel injector cleaning may be in order. Any thoughts on that?

Any thoughts on the kit where it pumps solvent through the injectors while still on the car? Vs. pulling them and sending them in to get cleaned / rebuilt?

Thanks.
 

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Mine just did this last weekend, but only for a minute.

Usual idle problem suspects are the idle air control, coil packs, injectors. How old are the plugs?


I'd run some fuel injector cleaner as directed on the bottle.
It could be something else though. Please let us know if you figure it out.
 

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Discussion Starter · #3 ·
jondotcom said:
Mine just did this last weekend, but only for a minute.

Usual idle problem suspects are the idle air control, coil packs, injectors. How old are the plugs?


I'd run some fuel injector cleaner as directed on the bottle.
It could be something else though. Please let us know if you figure it out.
It's not just at idle, so I doubt it's the IACV (and that has failed before, so I know what that is like).

Plugs are OEM, replaced at 105k (85k miles old).

If it were a coil or a plug, I'd expect just one to have gone bad. When things go bad on this car, I'm usually on it as fast as I can. So the test where I removed each coil connector, one at a time, and the idle roughness got ~equally worse on all 6 cylinders, seems to rule out a coil or plug. With the coil connector removed, there is nothing firing there, regardless of the plug or coil. So if they all got worse when I pulled the connector, then they must have been working at least partially before that. How likely is it that they'd be working only partially (consistently bad, not intermittent)?
 

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It's not just at idle, so I doubt it's the IACV (and that has failed before, so I know what that is like).

Plugs are OEM, replaced at 105k (85k miles old).

If it were a coil or a plug, I'd expect just one to have gone bad. When things go bad on this car, I'm usually on it as fast as I can. So the test where I removed each coil connector, one at a time, and the idle roughness got ~equally worse on all 6 cylinders, seems to rule out a coil or plug. With the coil connector removed, there is nothing firing there, regardless of the plug or coil. So if they all got worse when I pulled the connector, then they must have been working at least partially before that. How likely is it that they'd be working only partially (consistently bad, not intermittent)?
Do you hear/feel the missfire even while driving? I'd change the plugs just for grins. I know a few coilpacks on mine were changed by the dealer in the service history due to intermittent missfire, so I think you can have a poor spark vs a normal spark.

I'm guessing mine might be a leaky fuel injector since mine is only stumbling after sitting... barely idles until I hit the gas and "clear it out."
 

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Discussion Starter · #5 ·
Do you hear/feel the missfire even while driving? I'd change the plugs just for grins. I know a few coilpacks on mine were changed by the dealer in the service history due to intermittent missfire, so I think you can have a poor spark vs a normal spark.

I'm guessing mine might be a leaky fuel injector since mine is only stumbling after sitting... barely idles until I hit the gas and "clear it out."
Yes, even while driving. It's my wife's car, so mostly she drives it, but I drove it myself yesterday. Noticeable lack of power, in addition to the roughness.

I guess it can't hurt to change plugs, and they're almost due anyway, so I'll do that.

When my #5 coil failed (hard failure, not intermittent or partial) a few months ago, I bought a second new one to keep as a spare, but it seems like it the problem is not just from one cylinder. From searching, I noticed that checking the coil resistance may be a worthwhile test to do, so I'll do that.

Any other ideas or tests to do? I've got a feeling I'll be chasing this for a while. It's tougher when no codes are thrown.

Any chance the power steering wire would affect things while driving (not just at idle)?
 

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Discussion Starter · #8 ·
Thanks for the advice so far. Here's an update. I'll be sure to follow through with posting the final answer, no matter how long it takes to find it. From finding other threads here, it seems I may be in for the long haul on this one.

If anyone has any other suggestions for what to look for, I'd be happy to hear it. I'm fully expecting to find the unexpected in solving this.

other clues so far:
- still no codes other than that P1399 that showed up a while ago and has not reappeared
- the car starts up just fine
- the idle roughness is not very bad. Just there, and consistent. I'm more concerned about how it drives at speed. I'm worried that stuff may be damaged by running in this condition.
- same problems occur whether the engine is warm vs. cold
- I noticed an odd correlation between engine rpm and the fan speed for the rear AC. Could be unrelated.
- reduced gas mileage
- I checked the ignition switch by opening it up, and it still looks OK.
- battery voltage when running is 14.5 Volts
- I pulled the connector on the IACV - idle increases to ~2k RPM, surging slightly, but still rough
- I pulled the power steering pressure switch connector - no change
- air filter looks fine
- Checked for vacuum leaks by listening, wiggling hoses, spraying some brake cleaner around - did not find any

tests I'll do:
I've ordered new NGK spark plugs (OEM, exact same ones I put on there at 105k miles). When they arrive, I'll:
- pull the coils one at a time
- check resistance of each coil (looking for deviations among the set)
- attach an old spark plug; ground it; look for consistent blue spark
- when replacing, put in a new spark plug and coat the inside of each coil boot with dielectric grease before reconnecting to spark plugs
- If any coils are questionable, I'll swap in the spare new coil (Honda part) I bought when the #5 coil failed few months ago.

On the injector side, I'd rather not be down for a week while shipping in the injectors for rebuild, so I bought a set of 6 from ebay junkyard w/ 87k miles. If improvement is seen with those, I'll conclude that it was the injectors and will have mine rebuilt and swap in. This extra set reduces downtime while sending them in.

So after those arrive, I'll
- remove intake manifold/throttle body
- valve adjustment (last done at 105k), and will make notes of how far off they were prior to adjustment. If minor adjustments only are needed, I'll consider this as doing nothing to help.
- check intake manifold gasket
- Take out the injectors and watch them when turning on the ignition. If tips get wet, they are leaking.
- check fuel injector resistance (both sets). See if there are any other electrical tests I can do while it's off the car. Anyone know of any?
- Replace injectors with the 6 used ebay ones. I bought new seals/o-rings.
- maybe remove + clean IACV (since I'm in there)

It would be nice to measure fuel pressure. I see the connection point on the rear fuel rail. It looks like I need a special adapter for this. I'll also need to buy a pressure gauge. Has anyone done this - any info on that adapter (Honda part # is 07vaj-0040100 [$50] - do I really need the Honda part on this one, or is it a standard fitting?)
 

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Discussion Starter · #10 ·
Update - did almost all the above and it still runs rough.

other clues so far:
- still no codes other than that P1399 that showed up a while ago and has not reappeared
- the car starts up just fine
- the idle roughness is not very bad. Just there, and consistent. I'm more concerned about how it drives at speed. I'm worried that stuff may be damaged by running in this condition.
- same problems occur whether the engine is warm vs. cold
- I noticed an odd correlation between engine rpm and the fan speed for the rear AC. Could be unrelated.
- reduced gas mileage
- I checked the ignition switch by opening it up, and it still looks OK.
- battery voltage when running is 14.5 Volts
- I pulled the connector on the IACV - idle increases to ~2k RPM, surging slightly, but still rough
- I pulled the power steering pressure switch connector - no change
- air filter looks fine
- Checked for vacuum leaks by listening, wiggling hoses, spraying some brake cleaner around - did not find any
- Checked EVAP purge valve (vacuum test) ==> fine
- Checked with a Noid light the 3 fuel injectors (2, 4, 5 ?) I could reach without removing the intake manifold.
- attached an old spark plug; ground it; look for consistent blue spark
- checked intake manifold gasket
- check fuel injector resistance
- Replaced injectors with the 6 used ebay ones that I cleaned + tested, with new seals/o-rings.
- removed + cleaned IACV
- new OEM (NGK) spark plugs
- valve adjustment. About 4 valves were perfect. The rest were about 0.01-0.04 mm out of spec (0.20-0.24 and 0.28-0.32 mm). So, good to do, but should not have been the cause.
- replaced one coil (with OEM spare I had) that was furthest out of normal resistance measurements (kept it as a spare)
- new spark plug tube seals and valve cover gasket on rear (1-2-3) valve cover. Tube seals on 2 and 3 had been leaking, allowing plugs to be submerged in oil
- battery is 1 year old

After re-installation, it runs exactly like before (badly). This seems to confirm that all the stuff I did had nothing to do with the problem - e.g., fuel injectors, valve adjustment, spark plugs, coil.

Summary:
- no codes. No CEL.
- starts just fine, right away
- idles rough, runs rougher
- pulling coil connectors on each coil makes it worse, so it is not as if I've got a dead cylinder.

My plans:
find my compression gauge and do a compression check.
Rig up an adapter so I can test fuel pressure.

Any other ideas? After that, I don't know what to do ... wait for a code to eventually show up?

I saw somewhere that a crankshaft position sensor could cause rough running but no codes. Anyone have insight on that?
 

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just to add to the brainstorm...

You may have checked this before, check the Ground to the engine from battery using another cable from battery direct to cylinder head ground? I'm guessing but if 99 is like 04, the ground would be in the same place. close to the battery enough to try it. and its pretty easy as long as you have good 4GA wires. the theory is you're engine is not getting enough juice.

Another thing is you mentioned you did the timing belt 85K mi ago... maybe its time to do it again?

CK
 

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You've certainly done a lot troubleshooting the rough running lack of power symptoms.

But there's one thing mentioned in the OP that I find intriguing...."sounds loud?"

Where from? Under hood, or downstream? Idling, or on the road?

Could be the problem? Need addressing?
 

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Seeing as you have run a fairly thorough inspection and diagnostic on the rough running. I might suggest a compression leak down test. There are situations where a valve can be partially open (due to carbon build up ) that will still give a fair compression reading but cause rough running and poor performance. Also if the test indicates anything more than 5 to 10 % leakage you should be able to find the exit point of the compression lose by listening to the intake (with throttle wide open ) or the exhaust (at the tail pipe ) or the engine ( through the oil filler hole in the valve cover ) This will give you a good starting point for further inspections/repairs. Good luck!
 

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Discussion Starter · #15 ·
just to add to the brainstorm...

You may have checked this before, check the Ground to the engine from battery using another cable from battery direct to cylinder head ground? I'm guessing but if 99 is like 04, the ground would be in the same place. close to the battery enough to try it. and its pretty easy as long as you have good 4GA wires. the theory is you're engine is not getting enough juice.

Another thing is you mentioned you did the timing belt 85K mi ago... maybe its time to do it again?

CK
Good idea on the ground check. Compared to everything else, it's easy enough to do. By the way, I replaced the battery ground cable a couple of years ago (unnecessarily, it turns out) while I was trouble shooting a problem that turned out to be the ignition switch.

T-belt ... my thought is that that would be a hard failure if something is wrong. Not due for another 25k miles. I may end up doing it if I have to dive in far enough to get something else done.

Thanks for the ideas.
 

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Discussion Starter · #16 ·
You've certainly done a lot troubleshooting the rough running lack of power symptoms.

But there's one thing mentioned in the OP that I find intriguing...."sounds loud?"

Where from? Under hood, or downstream? Idling, or on the road?

Could be the problem? Need addressing?
Sounds loud when in the car, not especially noticeable when standing in front of the engine. At idle and at speed. Sounds like it's coming from up front, near the rear of the engine if I had to guess. But when outside the car, in front of the engine, with it running, it just sounds a little bit louder than normal. No sound of exhaust leak.

The "rough" idle is detected by putting my hand on the intake manifold. I can feel it stumbling. RPMs on the gauge are pretty much constant. I can see the engine move slightly more than it should, and the radio antenna wobbles more than it should.

I'll take a closer look to try to eliminate the possibility of an exhaust leak, although I doubt that is the cause of the rough running.

Thanks for the ideas.
 

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Discussion Starter · #17 ·
Seeing as you have run a fairly thorough inspection and diagnostic on the rough running. I might suggest a compression leak down test. There are situations where a valve can be partially open (due to carbon build up ) that will still give a fair compression reading but cause rough running and poor performance. Also if the test indicates anything more than 5 to 10 % leakage you should be able to find the exit point of the compression lose by listening to the intake (with throttle wide open ) or the exhaust (at the tail pipe ) or the engine ( through the oil filler hole in the valve cover ) This will give you a good starting point for further inspections/repairs. Good luck!
I have not done the compression test yet (I did find the gauge last night). But your suggestion prompted me to look up how to make a leakdown tester. I'll rig something up to convert my compression gauge to also allow leakdown tests. A cool project, even if it does not find the solution. And most importantly it gives me another chance to use my compressor.

I'm thinking it's got to be something electrical, or some engine sensor, but will keep chasing it.
 

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"when replacing, your fuel filter your car will run find" ... check the pressure 'psi' readings on your fuel lines output!
* about 190k + miles with out the new fuel filter that... :smile:

Note: Honda & Toy not say about this on them MSFSC (owner's manual)... hihihi! Why? 190k + miles inside a fuel filter more... hihihi!
 

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How about the mass air flow meter that is on the airbox after the filter. If it is dirty can cause trouble but may throw a code too. Also - what about oxygen sensor?
 
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