Engines dies in low revs / bursts

[js_og]

Hey-ho!

I've bben having this problem with my little Festiva for around 8 months now but now it's terrible.

The car is a 93 L with 160k miles on it. Automatic.

In gear, still, on the brakes, the engine started going up and down in rpm. That was last summer. Now, when it's not in neutral and I'm still, its dies in about 2-5 seconds if I don't give it fuel. Every red light I have to put it in neutral in order for this not to happen.

Other symptom: if I give just a little gaz upon liftoff the rpm is still not stable. Going up and down.

One thing you may want to know is that the engine overheated on a few occasions last summer because of a defective temperature gauge.

I was told that it may be related to an failing TPS sensor. To my limited experience, this sounds too constant to be a TPS issue. Mr. Haynes says :

" A broken or loose TPS can cause intermittent bursts of fuel from the injector and an unstable idle because ECM thinks the throttle is moving"

I do have bursts of fuel, but not intermittent. And I do have an unstable idle.

I cranked my minimal rpm to help with the problem and it does. Still very annoying.

I will be swapping a B8 in there in about a month or so, but I'd like to give a shot at solving this issue, for the kicks.

Thanks!

[kartracer46]

First thing I would check is the breather between the vaf and the throttle body for leaks. I had one that I rushed one day and didn't get it completely together and it ran irattically.

[htchbck]

^X2 could be something loose or possible a crack in the piping somewhere. I've never had it happen on a festiva but it could, and proteges/mx3s/mx6s are notorious for it. My MTX MX6 had a similar problem and when I pulled the pipe it was completely cracked through halfway around. Would die at idle, sometimes randomly surge, and it was a pain taking off from a light because when the engine/trans were under load it would rock back little opening the pipe and sucking tons of air, which would in turn cause the engine rock forward and close the crack back then a burst of power again... vicious cycle, my motor mounts were already not the greatest and a couple days of driving it like that waiting in the new pipe to come in just about finished them off. New pipe is on though and its all good now

[econoaddict]

Just had a mazda in the shop with the same symtoms.
They had a leaking intake gasket.
Someone had adjust the throttle cable up to the point it wasn't reading correctly at the tps, once tha gasket was replaced it quit stalling, it still revv'd up and down on its own. Adjusted the throttle cable back to allow the throttle plate to fully close and the revving went away.

[js_og]

First thing I would check is the breather between the vaf and the throttle body for leaks. I had one that I rushed one day and didn't get it completely together and it ran irattically.

Will do that today.

I have to say my downpipe is in down pieces right now, I don't think it is related, but I guess it's better that the medical team knows.

htchbck, when you say a crack in the piping, you mean in the air intake pipes, right?

They had a leaking intake gasket.
Someone had adjust the throttle cable up to the point it wasn't reading correctly at the tps, once tha gasket was replaced it quit stalling, it still revv'd up and down on its own. Adjusted the throttle cable back to allow the throttle plate to fully close and the revving went away.

I do have an extra Aspire throttle body. Would it be worth replacing it?

Today I'll check the intake piping for leaks an the TPS according to Haynes.
Updates tonight

[js_og]

Sorry for the late reply!

I did all was suggested, including spraying brake cleaner fluid onto the intake to check for leaks. Had no clue.

Last week, while fixing the muffler, I noticed my O2 sensor was cut. In the meantime, I saw no difference.

So I thought I'd share that with all. I'm getting my new sensor tomorrow and will come back for confirmation of the culprit. I had all the symptoms. Running rich, can hardly keep it's rpm, dying under stress at low rpm...

[js_og]

O2 sensor was done this morning, but the real reason behind all this was a thing slice in the air intake, right on the accordion 90 degrees.

[htchbck]

O2 sensor was done this morning, but the real reason behind all this was a thing slice in the air intake, right on the accordion 90 degrees.

Good to hear ya found it! Hopefully your new O2 will help some with the MPGs, on the MX-6 I jumped about 3 MPGs from one tank to the next when I did the O2. had been getting around 27is so that makes for a more than 10% jump!

[js_og]

I'm currently in the 25s. Not so good. I'll try checking the rear brakes this week. I know they're due, but strangely, they were done last winter :S

It sounds like the E-brake could be mis-ajusted, cause this premature worn on rear brakes and this low MPG.

More to come... in another thread.