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2001 MPV Misfire MIL/CEL P0300 P0306
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GAborn73
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PostPosted: Thu Jul 08, 2010 7:50 pm    Post subject: 2001 MPV Misfire MIL/CEL P0300 P0306 Reply with quote

First thanks to all the helpful people on this site!

My 2001 MPV with 105k miles is misfiring badly.
Let me give some history.

Around 75k it was shifting worse than normal.
It never stuttered under acceleration and threw no CELs. I thought it
was the tranny. I took it to a mechanic and had the trans cleaned. No help.

Finally it started misfiring/stuttering under acceleration and threw CELs P0431 & P0300. I think the P0431 might have been due to the excess fuel getting past the plugs and clogging the cat. The O2 sensor has since been replaced and I changed the coil, wires and plugs.
All was well for a month and now it's misfiring again - worse than ever. It's throwing codes P0306 and P0300. I replaced the PCV valve and its hoses are good. I've sprayed throttle body cleaner all around the TB, intake, PCV, and fuel injectors but detected no leak. I jury rigged some cracks in the intake hose with liquid electricians tape. It seemed to have sealed the cracks.

I can only think that maybe the fuel filter is bad and have read on here that the 2001's only have a filter in the tank-arrrggg. I've previously run Lucas fuel cleaner through it but it never helped either. I saw the intake manifold is extremely dirty and thought about running Seafoam through it.
Any ideas? Sorry for such a long post. It's been Hell trying to resolve the misfire.

2001 ES STOCK
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GAborn73
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PostPosted: Fri Jul 09, 2010 11:16 pm    Post subject: Re: 2001 MPV Misfire MIL/CEL P0300 P0306 Reply with quote

anyone?
2001 ES STOCK
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z00m
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PostPosted: Sat Jul 10, 2010 7:20 am    Post subject: Re: 2001 MPV Misfire MIL/CEL P0300 P0306 Reply with quote

Did you use OEM coil/wires for the replacement? I would still start from coil/wires/plugs, and check to make sure no leakage/arcing, etc.
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GAborn73
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PostPosted: Tue Jul 27, 2010 6:23 pm    Post subject: Re: 2001 MPV Misfire MIL/CEL P0300 P0306 Reply with quote

i used ngk wires/plugs. Replaced MAF today.
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bmazak
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PostPosted: Sat Jan 01, 2011 10:03 pm    Post subject: Re: 2001 MPV Misfire MIL/CEL P0300 P0306 Reply with quote

What was the fix? I'm thinking bad gas too or low fuel pressure. Is there a code for that? Do you ever wish you could get one of those Mazda engineers to talk too? Do you know there is a massive Diag plug at the very edge of the driver side close to the top of the fender. Does anyone know of a dealer that allows you to have it plugged in and see if your problem can be figured out?
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GAborn73
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PostPosted: Sat Jan 01, 2011 11:02 pm    Post subject: Re: 2001 MPV Misfire MIL/CEL P0300 P0306 Reply with quote

I meant to update this so many times. I finally took it to a mechanic. after two months and many parts he diagnosed
a frayed wire harness too the pcm. PROBLEM 1 resolved.

When returned the exhaust y pipe rear clamp was cross threaded and I broke both bolts trying to fix that myself.
We settled on 100 bucks to repairthat since I felt it was
their libility. PROBLEM 2 resolved. kinda

I took it back in to get the exhaust y pipe checked again
since it was still leaking and the abs sensor died same day.

This whole time its losing coolant somewhere and oil.
I found a hairline crack on the back of the radiator.
It looks like a rear seal leak for the oil. I just ordered
a new radiator and pipes for 212 shipped at rock auto.

This cars an albatross.

2001 ES STOCK
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bmazak
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PostPosted: Sun Jan 02, 2011 3:53 am    Post subject: Re: 2001 MPV Misfire MIL/CEL P0300 P0306 Reply with quote

Now I would really like to know how you got a frayed wire? I don't have the money for all this stuff. Thanks for your help.
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GAborn73
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PostPosted: Sun Jan 02, 2011 8:47 am    Post subject: Re: 2001 MPV Misfire MIL/CEL P0300 P0306 Reply with quote

that would make two of us. I never saw that repair as its
behind the block next to the firewall. I can only trust the
mechanic whick I do. A very odd thing is a after I replaced the wires, cool,plugs I Ebayed a MAF and it wouldnt fit the
orifice. The mechanic said the housing was not from an MPV but another car. $360 to get a new MAF sensor and housing.
Anyway all things were swapped prior to the wire the wire
harness. He checked the O2 sensors and one was even replaced prior.
He advised me he could measure the return voltage on the harness.

2001 ES STOCK
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bmazak
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PostPosted: Sun Jan 02, 2011 2:26 pm    Post subject: Re: 2001 MPV Misfire MIL/CEL P0300 P0306 Reply with quote

That brings us to a question of real concern. I read somewhere that Ignition timing is set by the computer and any modifications are inputted to the computer during a factory service. So, I wonder is that modification lost when I disconnect the battery terminal for 10 min to reset the codes or hit reset on my OBD2 reader to clear codes. I now have a misfire that does not register a P0301 or P0300 and the engine check light is off. How is that possible? None of this makes any sense
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bmazak
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PostPosted: Sun Jan 02, 2011 2:37 pm    Post subject: Re: 2001 MPV Misfire MIL/CEL P0300 P0306 Reply with quote

One more thing I would like to make known to those who drive in wet areas. On the 2001 on the passenger side of the engine compartment located halfway down the strut housing is a 1 1/2 inch hole that will flood the coil and all those electrical connections on the left side of the motor. Driving through a puddle will cause the water coming off the tire to spray water all over that part of the engine. I suggest removing the bold that holds the mount and placing a peace of rubber about 3" by 3" square over the hole and then remounting the mount. The hole was made to allow a foot of the mount to go through the fender in order to keep it in position. Dumb idea. That may be why so many coils are sold. Enjoy the ride. Anybody try one of those wind tunnel add on to make the air swirl around in the combustion chamber?
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GAborn73
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PostPosted: Sun Jan 02, 2011 3:36 pm    Post subject: Re: 2001 MPV Misfire MIL/CEL P0300 P0306 Reply with quote

anytime you reset the ecu or lose thepower source (battery terminals) your ecu
resets to factory presets. this is the basic way to reset CEL or MIL codes. dependent on how severe the trouble the CEL will return.

thanks for the notice on the pass. side hole. will look for that.

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GAborn73
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PostPosted: Sun Jan 02, 2011 3:42 pm    Post subject: Re: 2001 MPV Misfire MIL/CEL P0300 P0306 Reply with quote

im unsure how severe (threshold) the misfire must be to trigger a misfire.
mine existed for over a year before throwing a series 300 code.

dont waste money on those atomizerfunnels. you will run too lean
ive read.

a there's great DIY CAI article on this site if you want better air flow.

btw I also replaced my intake boot due to severe cracking on the bottom.

good
luck!!!

2001 ES STOCK
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scross
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PostPosted: Sun Jan 02, 2011 7:01 pm    Post subject: Re: 2001 MPV Misfire MIL/CEL P0300 P0306 Reply with quote

I've had to deal with many misfire issues over the years with our 2002. An intermittent (soft) misfire can take a long time to ever throw a code; as I recall it took over a year to show up one time when we having problems with a fuel injector. On the other hand a hard misfire should show up right away, but you never know.

Proper misfire detection is a hit-or-miss (no pun intended) proposition. The reason being that a certain number of misfires are considered normal with today's engines, because they are always kept running right on the edge as far as fuel economy and emissions go, plus using certain misfire detection methods it would be easy to misinterpret something like hitting a bump in the road as a misfire. For this reason, as I recall you have to have on the order of several dozen misfires detected in a row, or maybe even several hundred misfires detected within the last 1000 cycles or so, before the computer decides there's actually a problem with a particular cylinder. On the other hand, I've managed to get our MPV to throw a P0300 (general misfire) code almost instantly when I was spraying around with a bottle of throttle body cleaner, trying to find a vacuum leak.

Over the years I've also learned that the ECU can compensate for an awful lot of bad behavior in the engine. This is great from a "keep on trucking" perspective, but it can also make it hard to diagnose intermittent problems, because the computer is masking them so much. I wish there were a diagnostic mode that told the computer not to try so hard (maybe go "open loop", as they call it); perhaps there is and I'm just not aware of it.


Last edited by scross on Mon Jan 03, 2011 12:06 am; edited 1 time in total
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GAborn73
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PostPosted: Sun Jan 02, 2011 8:41 pm    Post subject: Re: 2001 MPV Misfire MIL/CEL P0300 P0306 Reply with quote

I agree with your last. thanks for the info
and/or theory on misfire. I ran thru a can of stater
fluid checking vacuum leaks also.
After the radiator and hoses I will have to fix the
rear seal and it should be good for a while.
ooooh that's almost funny.

Any advice on the radiator? I'm concerned about the
trans cooler since I don't have flare wrenches. Is
t ahere way to remove the rad without removing
the trans cooler?

2001 ES STOCK
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