170k miles, automatic. Check engine light goes on, but it doesn’t tell mechanic what is wrong and has him puzzled. The problem temporarily went away a few months ago, but it’s back and I need some troubleshooting before I try to get it worked on. Brother-in-law thinks it’s the throttle position sensor, but thought I’d see what others say. Don’t want to get taken for a ride. Dealer going to charge $110 for diagnostic, but maybe you know what it is?

Each time I start the car all is fine. Within 5-10 miles when I am at any cruising speed I start losing speed/power and my tachometer starts wobbling (even at idle now sometimes). If I push on gas pedal harder nothing happens, but if I tap the gas, it clears up most of the time. Sometimes I have to tap it a couple of times to get it to run smooth again. And sometimes the condition comes back within a minute or so. Once, when going up a gradual hill, no matter how much I tapped I could not get the acceleration to kick in and chugged up at 30 MPH, but that only happened the one time. Other hills have been okay.

No rhyme or reason around consistency, except this last time it seemed to start again after I filled up with regular (as usual) at my normal station, Costco. I did put in fuel injector a few months back and the symptoms disappeared shortly after, but I was told that isn't what fixed it at that time. I wonder... although it seems something more serious is going on and I don’t want to lose all my power at the wrong time.

I get my car serviced every six months and believe all regular service needs are up to date. Ideas?

 

I don't know if this is your problem or not, but it sounds possible, so you might want to check it out. Good luck
http://www.tegger.com/hondafaq/misc/t2t013.pdf

 

sounds like a restricted fuel filter your symptoms are pointing to that.

 

I would look closer at a Secondary spark leak based on your description, this means everything from the ignition coil, to cap and rotor, to plug wires and plugs. A misfire or series of misfires (all cylinders) is instantaneous. This means that a misfire does not gradually get worse, we are talking about a moment in time, it either is missing or it is not, nothing in between.

Going up hills or heavier loads with heavier throttle input is exactly what you are explaining, at least that is what I see from this side of the world. Goosing the throttle does not clear it up, letting the throttle off is what is clearing it up, no load. Then returning your foot to a normal throttle and normal load does not cause a constant misfire but going up a hill requires more throttle due to a heavy load to pull the car up the hill.

Higher temps and humidity will lower the misfire threshold along with higher loads. You can call around to see if any independent shops have a portable oscilloscope to go with you on a test drive up a hill or under increased load to see if the ignition coil is slightly shorted internally or if it is leaking spark externally which is what I am betting on. Along with a portable scope of some kind ask if they also have an Amp Clamp to go with their equipment.

The other tell tale sign is you mentioned that the tach was effected also, the tach gets its signal from the ignition coil. Now dont go spend your money without getting it tested just because I think this is your problem and only buy Honda OEM parts for this if it is your problem, good luck in finding a well equipped shop that does not charge and arm and a leg but do not ONLY think that the dealer can help you out.