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Posted: 2/20/2006 8:08:33 AM EDT
I have a 1994 Mazda 929 that was running okay until about two days ago. On Friday morning I got up to start the car and let it warm up before going to work. The car ran at high idle (1000 rpms) for about 3-4 minutes and then when it normally settles back to low idle it ran rough, belched smoke out the exhaust and stalled out. I sarted the car again and as long as I keep the rpms up to about 1000 it is okay, when I take my foot off the gas the car will either stall out or the rpm will fluctuate wildly between 0 and 1000 and then stall out.

My son thinks it's the fuel delivery system and I told him he was high and that I thought it was one of the many sensors gone bad.

Any advice?
Link Posted: 2/20/2006 8:14:58 AM EDT
[Last Edit: 2/20/2006 8:15:44 AM EDT by scuba_ed]
I believe you're son is correct in the fuel delivery diagnosis. When was the last time you had the fuel system cleaned? I had a similar problem. There's no quick fix, as I discovered.

Quickest and best is have the fuel system professionally cleaned. Slowest, and may eventually get you on the road again, is to add a fuel injection cleaner to your gas tank.

Best,

Ed
Link Posted: 2/20/2006 8:20:53 AM EDT
Thanks for the advice. The only reason I discounted his theory was because the car runs fine until it is warm. If it was bad fuel or clogged injectors I would have thought that it would have affected the car from start up and not just after it got warm.
Link Posted: 2/20/2006 8:25:29 AM EDT
My experience was on the road...as in ~ 200 miles from home. so my engine was warm...and then...experienced the same problem. Starting, it would rev to normal, then drop down, then stall. Same problem you seem to have.

Link Posted: 2/20/2006 8:52:43 AM EDT
Well, can't hurt to put some Gumout in and see if it helps.
Link Posted: 2/20/2006 8:56:08 AM EDT
That's why there is a diagnostic port.
Link Posted: 2/20/2006 9:03:35 AM EDT
replace fuel filter
Link Posted: 2/21/2006 1:52:04 PM EDT
Idle air solenoid.
Link Posted: 2/21/2006 8:02:56 PM EDT
[Last Edit: 2/21/2006 8:05:37 PM EDT by TRW]

Originally Posted By INI:
That's why there is a diagnostic port.



I guess I could have it towed to a diagnostic machine but was hoping to exhaust (no pun intended) all driveway options first
Link Posted: 2/21/2006 8:53:26 PM EDT
autozone has them,maybe they would have one on their loan a tool service.
Link Posted: 2/21/2006 8:55:17 PM EDT
Sounds like it's getting too much fuel. Could be the cold start valve, or whatever it's called on Mazdas, isn't shutting off when the engine has warmed up.


____________________________________
The only hope you have is to accept the fact that you are already dead. And the sooner you accept that, the sooner you will be able to function as a soldier is supposed to function, without mercy, without compassion, without remorse.
Link Posted: 2/21/2006 8:59:42 PM EDT
The O2 sensors flip over to a different mode when the warmup and they aid in fual ratios.


Just a thought.
Link Posted: 2/21/2006 9:01:45 PM EDT

Originally Posted By TRW:
Thanks for the advice. The only reason I discounted his theory was because the car runs fine until it is warm. If it was bad fuel or clogged injectors I would have thought that it would have affected the car from start up and not just after it got warm.



My guess is the engine temperature sensor. After it fails, the computer may think that the engine is cold all the time- and thus the engine will only run smoothly when it actually is cold.
Link Posted: 2/21/2006 9:09:44 PM EDT
[Last Edit: 2/21/2006 9:14:20 PM EDT by netwt12]

Originally Posted By INI:
That's why there is a diagnostic port.



which means nothing unless the CEL is on. find an automotive shop that carries BG products, (unavailable at all automotive parts stores) and ask for their 3 part fuel injection flush. expect to pay around $100 including labor. this includes a fuel additive for the tank and an intake cleaner that will be cycled into the fuel system via the cold air intake. the shop can also tell you what is wrong with your car by checking the fuel pressure (when did you last change the fuel filter), as opposed to the autozone lackey, who doesn't have a clue unless his scan tool spells it out for him.

p.s. my guess is its an Idle Air Control Motor, which are notorious about going tits up on mazdas & fords. it'll be expensive, even aftermarket, but it's fairly simple to install.
Link Posted: 2/21/2006 9:19:24 PM EDT

Originally Posted By MillerSHO:
The O2 sensors flip over to a different mode when the warmup and they aid in fual ratios.


Just a thought.



that shouldn't cause the car to shut off unless the ecm makes it run way way to lean or rich. normally the only effects of a shot O2 are burned out cat. converters, caused but too much fuel making it's way into the exhaust.
Link Posted: 2/21/2006 9:40:10 PM EDT
The onboard diagnostics in a 94 Mazda are dismal at best .
No OBD II so autozoo wont help and even with the factory
tool you will only see hard faults . Which are rare .

This one is pretty much a hands on diagnosis with a spec
book and a lab scope/DVOM . That is of course after you
eliminate the mechanical causes .

But if I had to take a WAG I would say an out of range
MAF or a CTS
Link Posted: 2/21/2006 9:53:25 PM EDT
Ran into this about 2 months ago on a 92 Mazda pick-up....ran fine cold...got warm...ran bad...ended up replaceing the computer.
Link Posted: 2/22/2006 12:27:42 AM EDT
What engine?
Mazda is part owned by Ford and the 3.0 v-6 has a idle motor (as I think it is called) on the injection system, about every 30,000 mile it is recomended to change or service it. I will cause similar problems. I now tke mine off and spray it with carb. cleaner when I change the air filter. Price at Ford $150 my fix $1.69. Oh and use the cheep stuff from autozone, the "green" enviro. friendly crap don't work as well. That is if this is your problem.
Reason for reply is it could be a Ford design in the Mazda.
Link Posted: 2/22/2006 12:52:45 AM EDT
Unplug the MAF and see if it runs.

The odds of fuel injectors all of a sudden getting dirty is slim to none.

Also, check fuel pressure, the car is old and fuel pumps fail all the time.


Hope this helps.
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