pcbell

99 Civic DX, A/T, 240,000 miles, bought it used about three years back as a runabout, haven't done much to it except to fix things that break.

Start 'er up. Will idle fine for about 8 seconds, will misfire for about 8 seconds, with blinking CEL, then will idle fine again. Cycle repeats indefinitely.

Pull out. Barely any power, goes from 0 to 20 in about 20 seconds while CEL continually blinks. Then there's a sudden surge in power, almost like a turbo kicked in. At that point it seems to run fine, once I've gotten up to speed... unless I hit a hill... now we're back to low power, and it can't maintain velocity.

This all gets gradually worse as the engine gets warmer. After 15 minutes of driving, it might have to reach 25 or 30 mph before the power suddenly returns to normal.

If I stop at a light after the engine is warm, the idle is very rough, shaking the car and feels like it's gonna stall, unless I shift into neutral, when it's still rough.

Engine codes: P1399, p300, p301, p302, p303, p304.

Local guys at Monro said it needed a new distributor. I popped one in, reset the ECU, it didn't help at all.

After extensive research, it seems like there could be about 20 different causes of this sort of thing... and most of the threads seem to just die without any resolution.

BUT... I'm hoping SOMEONE might have an intelligent guess based on the symptoms above, or might help me decide between the following options:

1.) Buy a used ECU, pop it in, see if that fixes it.
2.) Disconnect the TPS and see what happens, because it helped this one guy in this one thread with a kinda similar problem
3.) Take it back to Monro (they've done good work for me in the past and will diagnose for free, usually I pay them to do the fix but I was pressed for cash and the dizzy was pretty easy to install)
4.) Scrape up enough money to pay the dealer to diagnose it, since they have the best chance of figuring it out

Thanks in advance for any advice!!!

Poopies

iTrader: (4)

If Monro will diagnose for free and you like them, you might want to consider taking that route. How do your plugs look? Is it possible your timing is off? Fuel injectors dirty?

pcbell

Thanks... all of those are possibilities... that's the frustrating thing about this issue, there are so many possibilities!

Possibly useful tidbit... if the car is cold, the weather is cold, and I turn it on and drive away immediately, it actually runs fine for the first 10-30 seconds... which, as I just discovered, is about how long the O2 sensor takes to warm up!

So... any ideas on
1.) Easy way to test the O2 sensor, and/or
2.) Easy way to disable the damn thing and see if it drives OK in that case?

pcbell

So, I decided to simply unplug the connector to the upstream O2 sensor.

And... it made the problem worse.

So apparently the O2 sensor is trying to fight the good fight.

I guess I'll limp along for now, take it to Monro when I get paid, and hope for the best.

jhammermil2008

I would check your ignition timing.