Engine hesitation, stalling out

Tiny
ARCMAN730
  • MEMBER
  • MAZDA
2004 Mazda 3, 2.0L, Manual Transmission, 49,000 miles, Fujita Cold Air Intake, OBX Header, Magnaflow catback exhaust with high flow cat.

Since installation of mods, engine "revs" itself when I start it up, until it warms up (revs from approx. 600 to 1100 rpm), then idles smooth, once warm.

Since then, it has also has been "chokey" when pressing down on the accelerator. RPM's climb okay from 600 but then there is a an almost "popping" sound and the engine starts to choke out.

So, that makes first gear interesting -- if I don't give it enough gas the engine will die out completely.

So far, that has not been a huge problem. But, yesterday, I went to shift from first to second and, upon disengaging the clutch, and giving it gas, the engine sputtered and died completely.

Restarted it, and discovered that it is now choking itself out between approx. 2400 to 2800 RPM's. Giving it more gas, with the clutch disengaged, only makes it choke out worse, again to the point of the engine actually dying.

With clutch engaged, it revs fine -- no choke out.

Shifting gears, if I shift below 2400 RPM or above 2800 RPM, from any gear to any gear, it does not choke out, engine stays smooth.

But, let out the clutch in that range of about 2400 to 2800 RPM's, when shifting up or down, and it chokes out, to the point of killing the engine.

Also, letting the revs drop into that range, say, while cruising in 4th, slowing down, and the revs drop below 3000 it starts to choke, and giving it more gas only makes it worse. If I put in the clutch, rev it back up above 3000 and let the clutch out, it's fine again.

Currently, I'm driving it by making sure to shift either below or above the problem RPM zone.

I'm in Seattle, and there I don't know of any reliable Mazda repair place -- only ones I know that work on these charge a fortune and want to replace half the car whether it's needed or not.

Anyway, any help that could be given would be very much appreciated. Thanks!
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Saturday, January 20th, 2007 AT 6:53 PM

4 Replies

Tiny
COSMO
  • MEMBER
When you put the CAI in, did you have to lengthen the MAF sensor wires? Also did you make sure that all the 'ground' points were re-installed?

Also were the 02 sensors lengthened in any matter.

Is the engine light on?

Cosmo. Mazda TEch
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Saturday, January 20th, 2007 AT 9:07 PM
Tiny
ARCMAN730
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Thanks so much for answering -- concerning the MAF, no, the MAF wires were not lengthened, the Fujita CAI had a direct plug in, positioned at the same point as the stock connection.

As far as I know, all ground points were re-installed, though, to be quite honest, I'm not sure what "ground points" are (I wish I was more savvy about cars, but, sadly, I don't know much).

With just the Fujita CAI installed, the engine light was not on.

When the header was installed, yes, the O2 sensor wires were lengthened, on one of the sensors.

Oddly, no one could seem to determine which O2 sensor went where. The muffler shop exchanged the sensors, twice, having claimed the wrong part was delivered, based on not having the right plug, on the sensor, to fit the available second plug-in slot on the engine.

In the end, they said that they could not figure out which was supposed to be the pre-cat versus post-cat sensor, nor could their parts store tell them which one, based on part number, went at which position. So, the shop simply ordered what they said was the "other" sensor (the one that was not the one already installed), and installed it by splicing the old plug onto the new sensor.

So, it has both sensors, one of which, according to the parts store, is a pre-cat, and one which is a post-cat. I can't seem to get anyone to tell me if they are in the right positions.

Yes, the check engine light came on not too long after that.

My main challenge with this has been the inability to find someone who knows about tuning a Mazda3. I wanted to have it tuned after the mods, because I think it's running lean, and I know the air/fuel ratio is probably off because of the increased air flow.

My frustration has been that the dealerships don't want to address issues with a modded car, and, unfortunately, there doesn't seem to be a tuner community, or even a local shop, in my area that does work on the Mazda3.

As I say, me being a total novice, I have to rely on someone else's expertise as I'm learning. Our one performance shop closed its doors, just after I sold my heavily modded '98 Eclipse and bought this Mazda3. I had no idea it would be so difficult to get help in modding this car, but, so far, I've found that parts are hard to find, and, in Seattle, shops, or even people, to advise and assist have been hard to find as well.

Again, any help is very much appreciated.

Oh, and I noted again tonight that the car warming up makes a big difference. I let it warm up at idle for about twenty minutes, before driving it, and no hesitation or choking out this time. But, drove it later after only a few minutes' warm-up time, and again could not shift in the 2200 to 2800 rpm range without the engine starting to choke out.

I have no idea why that makes a difference.

Standing by --
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Sunday, January 21st, 2007 AT 7:07 AM
Tiny
COSMO
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Well the main isssue seems to be in-experience with thte product. ONE no shop should lengthen an 02 sensor harness, it causes some rather strange things to happen, especially with a 02 sensor that might be an 'amperage' type sensor. You see these days alot fo car companies are using 02 sensors that create an amperage signal rather than a voltage signal. You see the amperage signal is far more accurate than a voltage signal. In this case Mazda has started using (we'll call them amp02's)amp02's for the front 02 and voltage 02's for the rear 02's. The idea being that the rear 02 doesn't really do much other than monitor the cat to make sure that the front 02 sensor is doing its job and to help calculate the fuel trims (fuel mapping).

Sooooo the big question is what does your car have well being a 2004 it probably has two voltage 02 sensors. BUT I know for a fact that the front and rear 02 sensors are NOT interchangable. Also if the wires were not connected properly the car will not run properly without the front 02 sensor operational.

I would be concerned about those 02 sensors for now.

Cosmo. Mazda Tech
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Sunday, January 21st, 2007 AT 4:18 PM
Tiny
ARCMAN730
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Turns out the less-than-savvy folks who installed the catback exhaust chopped up the main wiring harness. Once the harness was repaired, all the rest was fine and worked beautifully. There was no problem with the intake or the mass air flow sensor or the O2 sensors. I have since sold the Mazda and now have a Scion tC which is much easier to work with in terms of modifications because Scion has a much broader connection to the aftermarket parts market than Mazda.
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Thursday, April 19th, 2007 AT 12:11 PM

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