MY03 AP1
65000 miles

Symptoms:
Cruising at 65mph, when applying moderate acceleration to pass car (not in VTEC, throttle not wide open) noticed that car was 'stumbling', as if losing power briefly, then regains power, then might stumble a few more times.

Pulled off hwy and car was idling fine, as able to through slow traffic ok (seemed to stumble a bit at low rpm at one point, but wasn't bad and soon went back to being normal).

Pulled into parking lot, popped hood and listened to motor-- seemed to be idling fine. Applied some light throttle, didn't hear anything that seemed like a spark plug wasn't firing.

Was able to merge onto hwy at slow acceleration, and nursed car back towards home at 55mph. When got near house decided to do a bit more troubleshooting so pulled onto an expressway and accelerated moderately again, and car almost immediately started choking, as if intermittently fuel is getting cut off... again, not in VTEC yet.

Nursed car home, thinking it must be the fuel pump. Came to s2ki.com, checked out the FAQ and found this thread:

"Intermittent Hesitation During Hard Acceleration, TSB 04-073 December 3, 2004"
https://www.s2ki.com/forums/index.php?showtopic=275228

When experiencing the issue, my acceleration wasn't 'hard', but the kind sufficient to pass a car or merge onto a hwy. I might go down and reseat my MAP sensor, maybe give it a light 'whack' as I remember that did something good back in the day but my gut tells me I actually have a fuel pump failing.

What are you thoughts? Any other things I might want to try?

Many thanks in advance!

 

No point in whacking it. Much more effective method is to actually clean it. I used mass air flow cleaner which worked well. Spray once into sensor (where it connect to the TB), let it sit for a minute, spray again, sit a minute, spray a third time, wait 5 minutes to let dry, shake any remaining out, and let it sit for a few just to make sure it's extra dry.

For the life of me I can't figure out why the TSB calls for a zip tie, but sometimes those zipties seem to be great fixes for random problems.

Also when I took my car to get an oil changed, they ran a pressurized tank (not sure what it was filled with) into the vaccuum line to the throttle body. That helped quite a bit as well.

 

The MAP whack is very effective, IF done like so.

From under the hood, lightly rev the engine from 1k-2500k rapidly. While doing so, lightly tap the MAP with a plastic screwdriver handle 15-20 times.

Tap no harder than you would tap yourself in the face with it Easy does it...

 

wow, I'm surprised. so this really does sound like the MAP issue, and not a fuel pump going out? I wouldn't consider the acceleration I was doing as 'hard' but who knows what that TSB considers 'hard' or maybe its just gotten bad enough that the MAP issue is showing up under moderate accel.

well I'll be sure to give the MAP a whack and perhaps do the cleaning.

I really appreciate it!! if you guys are right you will have saved me some $$$ and time at a dealership getting my fuel pump replaced. if not, ah well... not like a MAP whack/clean takes a lot of time or money so it's def a good first thing to try.

I'll update this thread this evening with any findings.

 

Not to hijack your thread, but I am experiencing things along these lines too. Mine bogs down really badly at times when I try to pull out at a stoplight and feels like it has no power. I think mine may be running really rich too because of below average gas mileage plus when it is acting up I'll park it in the garage and it will smell very strongly of gas.

Does this sound like a MAP sensor issue too? I thought it could be a vacuum issue too because it some times doesn't start the first try or will start and then idle at like 500 RPMs for a bit, sound like its choking/sputtering, and then it will jump up to where it should be idling. I'd appreciate any suggestions...

 

Maybe the beginnings of a bad TPS? Mine is experiencing similar problems sporadically, stumbling at stoplights before finally catching and going, I have ordered a new replacement TPS to mod and install on the TB, will report back findings.

 

the MAP whack WORKED!

pulled off the plug and whacked the sensor about 15 times with my closed knife handle, about as hard as I was willing to hit my face with it. I then used the knife to lightly scrape the top and bottom of the pins in the sensor (didn't see any corrosion or anything, but figured it couldn't hurt). then reseated the plug nice and tight and went for a drive on the same expressway.

acceleration from all RPMs in all gears was nice, in and out of VTEC.

my car and I are happy again.

I have to say, the TSB is for "Intermittent Hesitation under Hard Acceleration" but my acceleration was definitely *not* hard earlier in the day. I think this is unnecessarily confusing.

I also think that I must really not know how a fuel pumps works. (and a quick Wiki search confirms it. )