Hello everyone,

I have a 2001 Mazda Protege, 2.0L automatic, with about 216,000KM (approx 134,000 miles) on it.

During a recent trip to my sisters house, right after I filled up at a gas station it began misfiring when I would begin to accelerate from a dead stop, until right about 2000RPM at which point it runs like normal. So highway driving remains normal, but any driving I do around town is tricky because I know every time I stop, it's gunna take a while of chugging and sputtering until I hit 2000RPM, at which point I get a big surge of power because it stops misfiring and I pull away like normal.

The only other time I have experienced something similar, I was getting a P0171 (system too lean) code along with my P0300 (random misfire) code. I found that the hose connecting my air filter to my throttle body was all cracked open on the underside, so every time I accelerated from a stop, the hose was letting in a bunch of unmetered air causing it to run way to lean and misfire. That one was an easy fix but this time it's a little more elusive.

I checked that hose first, to see if it was the same problem, and it's still looking good, no cracks. I can't find any other vacuum leaks or intake leaks of any kind. However, this time I have the P0300 code again, and the only other code was a P0131 which is upstream O2 sensor voltage low.

My first instinct was that the sensor is bad, and that must be causing my misfire problem. But the more I thought about it, maybe that is just a symptom of the problem and not the cause, because I would think that if the O2 sensor has failed then I would have misfires throughout the RPM range and not just at take off. Similarly, I had suspected that it could have been bad gas (water in the fuel) since it begin right after I filled up. But again, I would think this would cause misfires throughout the RPM range and not just at take off. I did put a bottle of dry-gas (fuel additive that removes water from the fuel) in just to be sure, and it did not fix the issue.

Furthermore, I am only experiencing these misfires when the engine is under load (in gear), because when I am in park or neutral I can rev the engine up just fine from idle.

Has anyone had a similar experience? Could the O2 sensor really be the cause of misfires only from the idle-2000RPM range while under load or is it something else?

I have read a couple of other threads that say the EGR valves on these cars are bad for carbon buildup, which would not allow it to close fully which would effectively cause an unmetered air leak into the intake. However, being an automatic, getting to the EGR valve bolts to pull it off and inspect it is virtually impossible. I would love to hear a couple of opinions if anyone has had similar problems before I remove the entire intake just to get to the EGR valve.

Any input is greatly appreciated!

 

With the mileage that you have, giving the EGR valve a good cleaning wouldn't hurt. It's not that hard too do from under the hood, just a little finesse required. I was chasing a P0300 random misfire code on a 2001 2.0L protégé automatic for over a year. In that time I cleaned and checked everything on that vehicle. Two things that I found were bad grounds on the multi-ground block on top the front drivers side strut tower and the simplest thing that fixed my problem was that the ignition coils needed a better ground, so I cleaned under the coils and added a ground wire from the valve cover to the engine block. For your problem, that would be the cheapest and easiest thing to try first. Good luck

 

First off, thank you very much for your help.

Now for an update; I know that at least a very large, and hopefully all of the problem, was water in the fuel after all. I know this because once I had burned through half a tank of that fuel, I refilled that half tank with fresh, clean fuel and a little more additive and right away my hesitation/misfire issue were greatly reduced. The car is once again driveable, although I still get occasional hesitation problems and even a little misfire while at speed/higher up in the RPM range that I hadn't noticed before. So I won't know for sure if water was all of the problem until I burn through virtually all of that old fuel or if there is more to the story.

That being said, I took a quick look at that ground on the drivers side strut you mentioned and sure enough it's got some pretty heavy corrosion. That will get cleaned up tomorrow. As for adding a ground wire for the ignition coils, did you just use an eyelet terminal to ground where the coil pack bolts clamp down to the valve cover, attached to a wire and then run it down to the block? And if not the bolts, where/how did you attach the ground to the coils? I will definitely try this as well because it's cheap, simple and I did have one single P0301 occur throughout all this so it could be a plug or coil as well. I had assumed the plugs, wires and coils are all good because I replaced them all less then 20,000KM ago but I didn't think about the possibility that even if the coil is working fine, if it doesn't have a reliable ground it's still going to give you issues. Furthermore I will pull all the plugs just to make sure none of them have been fowled in any way during the 20,000KM they've been in there for any reason.

I will definitely try all this first, because the EGR valves on the Canadian models have coolant supply and return lines run to it, as well as a vacuum line and a significantly larger valve body to accommodate all those connections and relative functions/fluids. Which is all attached to the same electric solenoid as the US version so that it can use the same connector/harness, and uses the same gasket, because it has to mount up to the same intake manifold of coarse. (see this picture here for the comparison: http://www.mazdas247.com/forum/attac...2&d=1234510895 )

So all of that, combined with having the automatic transmission means there is just no way to fit my hand along with a wrench up underneath the throttle body/intake manifold in order to get to those EGR valve bolts.

However, if clearing out all the rest of the bad fuel and cleaning up the grounds doesn't work, I can use the service pit at my work to get to the EGR valve bolts from underneath the vehicle with a couple of extensions and some leverage. At which point I could slide the valve out from under the throttle body from up top of the vehicle and clamp off the coolant lines and then disconnect all the hoses and electrical connector, and finally disassemble the solenoid from the valve body in order to clean up any carbon build up and make sure it's moving freely. Apparently having the Canadian EGR valve, being heated by coolant and being of a different metal type caused it not to become gunked up with carbon nearly as much as the US ones and as such was a popular conversion in many of the Northern United States.