Intermittent "stumble" at idle
 

Stumble is the best way I can describe the issue but it almost seems like a misfire. Happens intermittently, only in idle and generally when the engine is warm with a load on it(like the A/C and fans).
It happens so quickly that the RPM gauge doesn't fluctuate but you can definitely feel it in the cabin. If I bump the RPMs to anything above idle the stumble goes away. Park or in gear has no effect. No OBD codes triggered so I doubt it's actually misfiring and it runs like a top otherwise considering it has 300,000 on it.

Can an alternator intermittently drag?

Thanks guys,
Iggy

Basically you're describing the same symptom I did years ago on here and spent a lot of time and money chasing this issue.
Its the transmission causing the stumble at idle, as the Torque converter spins the clutches are engaging and that throws the engine out of balance.

Thanks Eric,

How did you finally diagnose the TQ as being the culprit? I wouldn't be surprised if that's my problem.

Did you replace the tranny or just the TQ? I may have an Accord trans swap in my future.

Thanks

Well lots of studying of the Honda 5 speed, I will look for the thread I made about it and post it here as soon as I find it.
A quick test you can do is unplug the front engine mount vacuum hose and plug it then see if you feel a difference on how it idles.

No difference with vac line disconnected. I do however keep throwing a P1456(EVAP purge system) which has been going on for a while. I can't imagine that is related to intermittent idle issues but maybe.

I would be very surprised if a stumbling idle had anythng to do with the transmission!
I think it's just the usual suspects: carboned-up combustion chambers, spark plugs, fuel injectors, dirty intake, lazy sensors, etc.....

I have a random stumble too and I'm 6mt. Usually happens when I don't let it get to operating temp. I've had it actually misfire and I pulled over, let it sit and it started back up fine. I'm guessing the coil packs are tired. I've never replaced them.

Keep a couple of spare ignition coils in the trunk, as you've been warned!

ya that is my plan, I have someone local who's going to sell me a few from a spare engine. I just hope it's not the front bank because there's a whiny thing blocking them.

I'm kinda thinking it's something other than the Trans also. I just replaced the spark plugs so tired coils may be the culprit but wouldn't a plug misfire eventually trigger some kind of CEL?

Doesn't it store 'pending codes' that can be read by an OBD2 reader before a CEL comes on?
When I had two ignition coils fail, there was no CEL for about 3 miles, even though it was running on 4 cylinders.

Doesn't it store 'pending codes' that can be read by an OBD2 reader before a CEL comes on?
When I had two ignition coils fail, there was no CEL for about 3 miles, even though it was running on 4 cylinders. I replaced all 6 with aftermarket ign coils, tossed the 2 bad ones, and kept the other 4 old ones as spares in the trunk.

Yes those are the usual,I encourage you to look up more information about the honda 5 speed and will find out why it drags at the converter clutches at idle.

Erick,

I don't doubt what you say. Could you point me in the right direction where I could research the TQ clutch idle issue? Thanks

Very strange. Now that the outside air temps have fallen below 90 I haven't had a single idle "stumble" in a couple of weeks.

Erick, I pulled the trigger on an AV6 BAYA transmission and will be installing it this week so we shall see if you are right.


iggy

Have you replaced the front O2 sensor? They only have a life of about 100K or less and then they get extremely lazy not enough to through a code but enough to cause a drop in power and create a sporadic idle. Your last post stating that the problem improved with the drop in air temps further points to the front O2, because the base maps shift with air temp fluxuations and cause the learning process of the ECU to reset.

Good point. I have an extra one lying around so it's worth a shot. May never find the culprit until next summer. Thx

Spent $60 for a new Denso unit and call it a day:2cents:

Any chance you are just feeling the aircon compressor kicking on?

My '02 TL gives a subtle shake when the compressor kicks on... Perhaps this is what you are feeling.

i didn't notice it until I had the car for many years; either it was always there and I just didn't notice it, or as the mounts, compressor or clutch age the stumble is more noticeable.

just a thought...

-Tom in SoCal

Tom,
Definitely not compressor engagement related.

I just installed a BAYA transmission in the old girl and while it was out I changed the upstream O2 sensor so hopefully my stumble is gone for good. Probably won't know for sure until next summer.

Thanks guys,
Iggy

UGH!!!!

Intermittent stumble is back.

Ruled out transmission, O2 sensor and spark plugs. I'm considering checking the valve adjustment but I did that about 50k ago. EGR system is clean as a whistle. Could be a faulty coil but with no code? I'm at a loss due to the intermittent nature of this problem and no codes to work with. I'm still baffled why it only happens when the outside temperature is above 80 or so.

Anyone have any ideas for diagnostics?

If your ignition coils have over 100k on them I would replace them all as normal preventive maint, and avoid a nasty surprise like I got one day.

Otherwise, carboned-up injectors and combustion chambers is normal. Use fuel system cleaner in every tank for one year, and report back. I use 'FP Plus.'

edited to add that mine still stumbles or hickups occasionally when stone cold, but smoothes out within a minute, and I think that's because I'm at 132k on original plugs.

Thanks for the reply. I will do the coils. I got a line on a core support. going to chop it out on my lunch break while at the office. Just got to try not to goof my tie. Brought a saw to work with me. We are doing this guys.

Musta brung a CHOP SAW?!

Possibly a Weak Alternator not providing a strong enough for the Load buildup as it comes to a stop?
I have noticed this on my car and am leaning to that being the culprit.

As the OP I figured I'd give you all an update. I got a hair up my ass and pulled the trigger on some cheapo ignition coils. At 300k they were due for replacement anyway. Not sure how long they will last
but so far it seems the intermittent stumble has gone away.:wish:


https://cimg5.ibsrv.net/gimg/acurazi...74e8b3b357.jpg

FYI, it was probably only one coil but instead, you replaced the Acura parts with some, uh, brand, interesting decision... Maybe those will work for ya too, who knows. May as well replace your spark plugs and clean your EGR maze too. Makes a huge difference.

:werd:


why did you throw all of them out though for crappier quality ones :rofl:

Don't recall ever saying I tossed the oem coils. Due to the very intermittent nature of the problem I was never sure if it was indeed a bad coil, now I know for sure and I have at least 5 spare coils. Laugh all you guys want. And yes plugs are new and egr is clean as a virgin's vajayjay

No laughing here, I just know there's some things you can skimp on and others you shouldn't. Ignition parts are some that you definitely should not. But again, they may last another 100k, who knows.

Those OEM coils are nothing to brag about. At 111k I merrily replaced mine for cheapies (although I saved the 4 working OEMs for spares).

It's a gamble for sure but the other part of the equation is that I've been eyeballing some J35's for a motor refresh(and fun factor) and was hesitant to spring for oem because the "newer" motor will have it's own set of low mileage oem coils.

For now, I have a couple of coils in the trunk with a hex wrench so I won't miss a beat if one shits the bed while on the road.