'99 EX V6 Sporadic Throttle Cut Out / Hesitation

kyonpalm

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Posting in Urgent because the issue this thread concerns makes my car arguably quite unsafe to drive and, like many other humans, I need a car. Go figure.

STATS:
Car: 1999 EX Sedan V6
Miles: 75k (I suspect that number was fudged by a previous owner, but I could just be paranoid, the voices in my head tell me all kinds of strange things)
Known issues prior to this: minor oil leak (valve cover), bad EGR

Super-long description incoming, apologies in advance for that. If you really like reading, you can also check out this thread* where a Mr. jacob.middleton appears to be my doppelganger from a parallel universe who is experiencing exactly the same problem as I am. Really, every detail in the OP (except the bit about injector cleaner, haven't done that before).

*can't post links as a newbie so you re-arrange this:
driveaccord(dot)net/forums/53-6th-generation/305634-99-v6-cutting-out-2k-rpm.html

Here's my description of things. My car developed a quirk a month or two after acquiring it. I would occasionally have a sporadic loss/cutting in-and-out of fuel delivery / throttle, usually after at least 15 minutes of driving (sometimes much later), occurring for maybe 30-40 seconds at a time. Not stalling, not losing electrics/power, nothing other than being unable to give the engine gas despite consistent pedal pressure. It would cut in and out of getting gas (maybe one spurt every 5-10 seconds) like this for 40-60 seconds then became perfectly fine like nothing happened. There has been no forewarning of this occurring, it just deteriorates to this condition within 3 seconds out of nowhere, (originally) last(ed) another 30-40, then normal. Idle is consistent, even when the cutting in-and-out occurs, still fairly solid. First thought was that the fuel filter was getting occasionally clogged, but after replacing it, the issue persisted. Environmental conditions (hot/cold, dry/wet) don't seem to be a factor, neither do bumps nor hills (a nonexistent concept here in the state of Florida [except maybe landfills]). Also, I got a P0171 (lean) and P0170 (fuel trim malfunction) when this issue popped up. The P0170 cleared after the fuel filter replacement, but I still have P0171 P (pending). Haven't checked in a little while though, will probably do so tomorrow morning.

Now here's a fun part. When I say "the issue persisted" after replacing the fuel filter, it did - but only after 120+ miles of smooth sailing. I thought I was in the clear until one day I fired it up and not even two minutes after driving off, the issue attacked with a vengeance. Fortunately this time I had ample opportunity to test the nature of the issue better. In addition to occurring much earlier in the drive than normal, the issue persisted far longer - it must have been eight or nine minutes from start to end. Four or five minutes in, I pulled into a CVS, put it in neutral and popped the hood.

I observed the throttle cable while slowly revving just for the heck of it. Cable worked fine throughout the testing that followed. I can say for sure that when I rev anywhere up to I guess around 2.5k it holds for maybe half a second then loses power for a few seconds, then comes in strong to rev past where I had it originally (imagine holding the pedal at 20%, getting 20% for half a second, 0% for three seconds, then like 50% out of nowhere, all while holding at 20% throttle). HOWEVER, it seems that when I hold the pedal anywhere past 40% it doesn't lose power at all, so I could just floor it and it would rev as if nothing was wrong. So this issue definitely only occurs in the 0-40% throttle range OR anywhere from anything above idle to maybe 3000 RPM.

Now, prior to this happening, I filled the tank from near-empty to full on 91 (previously 87). I had some stupid idea it would help. I have lots of stupid ideas. I'm realizing in retrospect that this might have been one of the stupider ones, since running a tank near-empty wears the fuel pump out, and a bad fuel pump is a top suspect. Take that info how you will.

At this point I changed the TPS since hey why not, and also ordered a set of new O2 sensors to hopefully address the lean DTC (still have yet to put those on). Started it up, and nope, TPS didn't help. But this time I got video: vimeo(dot)com/156790259

Note: just before the revs go back up, I can hear a ticking sound, perhaps electrical but I don't see any spark in the engine bay when it happens. Also the lights dim for a second in that same moment. When I say "ticking", I mean one "tick". More like a "click" maybe.

Now here I decided to go simple and start micro-managing. I checked my plugs, they looked bad (they also weren't the problem, but more on that later). I also found out the valve cover gaskets were the source of my already-known oil leak issue. I realized my leak was getting worse kinda hand-in-hand with this throttle issue, so I thought I'd go ahead and tackle that. This turned into an ordeal that lasted far longer than it should have and I'll spare all the dumb details, but suffice it to say, no, the leak didn't have anything to do with it. I successfully put on new gaskets, tube seals, grommets, yadda yadda, so at least the leak is no more. Oh and I threw on a new throttle body gasket too since I already had it off.

So today I swapped the plugs and wires today (NGK and Prestolite, respectively). Either the old plugs have gotten worse since I checked them or they just looked especially bad compared to the new ones. Drove it home. Got about five minutes into the drive before my throttle started cutting in and out like before, and far more erratically this time (though giving it more than 40-ish% still helps).

I shouldn't have expected any change, honestly, but it's still bringing me to my wit's end. My gut is telling me it's either fuel-related (pump, pressure regulator, injectors, whatever) or somehow directly throttle-related. It's such a nice driver otherwise so I really wish I could figure this out already. Does my book of a post tell you, kind reader, anything? Any suspect in particular looking to be the most likely?

For reference, here's a list of already-performed fixes to date:
-Fuel filter
-TPS
-Valve cover gaskets/seals
-Throttle body gasket
-Spark plugs/wires

To do list:
-Oil change (just for kicks)
-O2 sensors
-Clean EGR (has had the ever-famous P0401 since before I owned it)

List of potential culprits, sources from various other forums and friends:
-IACV
-Cat
-MAP
-Intake/vacuum leak(?)
-FPR
-Fuel pump
-Fuel injectors
-O2 sensor

P-Please help.
 

Jpocolypse

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I had a slightly similar thing happen with my 98. It would cut out for a few seconds out of no where then come back to life like nothing ever happened. Turned out to be oil in the distributor. My car has the 4 cylinder tho and I'm not sure how different the ignition system is between the I4 and V6, but it should be fairly easy to check. Just pop off the distributor cap and run your finger along the bottom of the distributor. It shouldn't be oily.
 

Connie

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Wires?
My V6 has coil-over-plugs; no wires. I thought all the v-6 cars had COP....I know the JDM cars were old-school with distributors and plug wires, but I've never seen a USDM V6 6G that doesnt use the one coil per plug system.

The problem sounds like a bad coil pack. I have had 2 go bad on me over the course of my ownership of my V6 6G over many, many miles.

When the car is running badly (problem is happening) try unplugging the coil packs one by one.

If the engine sound does not change when unplugging one of them, then you have found your problem. Takes literally 5 minutes to replace it.
 

Sino

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I don't really know much about it but I've read here multiple accounts of the V6 engines having heat soak issues, something to do with fuel evaporating when the engine's shut off. Not sure if that's your problem, but it's something to look into.
 

Connie

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I don't really know much about it but I've read here multiple accounts of the V6 engines having heat soak issues, something to do with fuel evaporating when the engine's shut off. Not sure if that's your problem, but it's something to look into.

Makes sense, add any heat beyond normal and the ignition system will get sketchy. Electricity hates heat. Both times I had coil packs go bad was in 30 plus degree heat (celsius). Very simple replacement, one Allen bolt and one plug.

Has anyone else seen plug wires on a north American Honda Accord though? They were all coil over plug since 1998, right?

This guy saying he replacd wires on a 6gv6 is driving me crazy lol.
 

kyonpalm

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I had a slightly similar thing happen with my 98. It would cut out for a few seconds out of no where then come back to life like nothing ever happened. Turned out to be oil in the distributor. My car has the 4 cylinder tho and I'm not sure how different the ignition system is between the I4 and V6, but it should be fairly easy to check. Just pop off the distributor cap and run your finger along the bottom of the distributor. It shouldn't be oily.
Will do that soon, thanks for the suggestion.

Wires?
My V6 has coil-over-plugs; no wires. I thought all the v-6 cars had COP....I know the JDM cars were old-school with distributors and plug wires, but I've never seen a USDM V6 6G that doesnt use the one coil per plug system
IIRC it was the '00-'02 models that had COP, the '98-'99 had wires. Mine absolutely has wires. Run a Google image search on "99 accord v6 engine" for proof.

I don't really know much about it but I've read here multiple accounts of the V6 engines having heat soak issues, something to do with fuel evaporating when the engine's shut off. Not sure if that's your problem, but it's something to look into.
Good to know, I'll have to research that more.
 

Chris S

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My guess is dirty fuel injectors or a bad fuel pump. See Scotty Kilmer's YouTube video, "Fixing a car that shuts off randomly" and "How to clean fuel injectors in your car"
 

kyonpalm

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Thanks for all the suggestions so far everyone, and sorry for the late update but here's what's new:

I tried testing the fuel pressure but since there's no schrader valve, I consulted my service manual and discovered I can just take off the pulsation damper to fit a gauge on... I soon found out I need a special Honda©™ adapter AS WELL AS a special Honda©™ gauge. Both of these cost around $50+. I would like to believe there's a special place in hell for the engineer responsible for this decision.

So, furious over that proprietary parts bull****, I decided to check up on my distributor like Jpocolypse suggested (since I was already there and all). Lo and behold, I go to unscrew the distributor cap and while unscrewing one of the screws, I noticed some grimey stuff. Took the cap off, and...

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Needless to say, I have a new cap and rotor on the way. Also grabbed a new o-ring in case I need it. Dunno if this is the fix, but will update when I know.
 

mx5kev

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You will need a spi seal the inner one. Just changed it on mine.
 
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