My girlfriend's 158k '94 LX has a horrible new problem. When you push the accelerator (in neutral or while driving), the engine will rev up to a point (depending on how hard you stomp anywhere between 1000rpm and red line), hold for about a second, then drop to idle revs, hold for a second, then rev back up again, down, up, down, up, etc. The cycle is about 4-5 seconds long, and it just repeatedly revs and falls over and over like a heartbeat. Notably, the car never stalls, and the cycle is also present (though hardly noticeable) at idle. I also tried this with the throttle directly to make sure it wasn't something in the cabling.

Perhaps related, the fuel cap doesn't seem to be venting. After a few minutes of running, I can unscrew it and the vacuum is pretty intense. I actually heard the fuel tank popping back out once, as if the vacuum had sucked in the sheet metal/plastic, whatever the Accord uses. However, running the car for 20+ minutes with the fuel cap off didn't change a thing.

Here's what I've done: performed a full fuel flush, replaced plugs and wires (needed this anyway), checked the air flow.

My best guesses: electrical (ignition switch that I've read about here, distributor cap/coil, sensor), fuel (pump, filter, lines)

Has anyone ever seen this before? I'd love to get some thoughts, as I don't have a lot of tools or time here at school, and she hasn't got any money to spend at the shop. I don't know when I'll be able to get a ride to the parts store, either, since she has my car until I can fix this.

Thanks in advance,
Emmett Lyman

 

It sounds like either a vacuum leak or a failing fuel pump to me. Since the gas tank hold so much suction after you cut off the car, that might eliminate the vacuum leak concern, but I'm not sure. Could also be something in the fuel return system .... that's a part of the car that I don't know much about.

 

does it go away once the engine warms up?

 

nafango2: unfortunately, it never goes away. Any thoughts on how I should begin to diagnose the problem? As I said, I don't have a lot of time or tools on my hands, so I'd like to be pretty efficient. Thanks!

 

Does the check engine light turn on at all? Does car idle and stay at ~750 rpm when your foot is off the gas pedal?

The DIY section has a thread called acc 5th gen... open the dhost link. That page has instructions on how to retrieve check engine light codes (all you need is a thin paper clip to do this). There is also a shop manual for a 94 accord split up in chapters as pdfs.

 

Hey all,

I ended up taking the car to a dealership, and they diagnosed the problem as the throttle position sensor. I was a little surprised when they said they have to replace the whole throttle body ***'y, and they're looking for $1200 to do it. So two questions arise: Can I replace the TPS by itself (and what should that cost)? and... What should they be charging to replace the entire throttle body?

FYI, the dealership is Brown Honda in Charlottesville, VA.

PS: thanks for the tip, PAhonda... I definitely would have tried that if I hadn't gone the dealership route.

Thanks again,
Emmett Lyman

 

You can replace the TPS, but the honda dealership does not sell the sensor. I found one from ebay, and there are instructions on how to swap out the sensor by doing a web search.

You can also buy a used throttle body from a junkyard and have that installed.

 

I would try to find a used throttle body assembly from a salvage yard. It may be easier to replace the whole thing (it would probablyat least be easier to find the part than trying to hunt just the sensor)and you can probably score a used TB pretty cheap.