Only Error message is: Random Misfire

[mtnmama]

My husband's car started having this problem about two weeks ago. I've read several similar posts here about it, but all of the other posts talk about various error messages, but we only get the Random Misfire one.

Anyway, he's going along and then suddenly loses power. He floors the gas pedal, and the max speed is 35. The check engine light came on, and we made an appt a couple of days later. The computer said the problem was random misfire. The mechanic felt it needed a tune up, perhaps the spark plugs were corroded. So he put new plugs and wires on the thing and reset the CEL.

When dh got it back, it was even worse than before. He even had to pull over a few times while on the Interstate because it started slowing down and had no umph at all. CEL came back on.

So we take it back to that mechanic and after a few days of testing the fuel pump and exhaust, he felt it was probably a catalytic converter problem, but didn't really know. He suggested to take it to Mazda.

We took it to the family's mechanic instead. He said he checked the coil pack (which is what he thought it was), and it was normal. He really leaned towards the catalytic converter next, but the O2 sensors came back okay. Then he felt sure it was the fuel pump or filter -- filter had been partially clogged, he thought, and it had done damage to the pump. ? Anyway, after spending a few days testing this and that, he doesn't know for sure what it is. He still leans toward the catalytic converter, but he keeps saying that it's warranted and worth checking out, so I think it's just a "to be on the safe side."

Urgh! (bang) He will test the ignition module tomorrow, but his suggestion is to take it to Mazda. (bang)

Anyway, what could this problem be?? It's a 2003 Protege5 with only 55,000 miles on it. We've never had an inkling of a problem with this gem of a car. We paid it off 2 days before this problem happened, which is annoying, but whatever.

 

[Azaizai]

i think there are more threads on this somewhere in the forum-verse...but the last one I read said the code you mentioned lead to either new coil-packs or a new cat.

Do a full forum search with your P-code as the parameter...might lead to some results

 

[Captain KRM P5]

i am guessing the code it is throwing is P0300 - Multiple or Random Cylinder Misfire. if the timing belt was recently changed the cam timing could be off. weak fuel pump, faulty injectors, bad gasoline, bad fuel regulator, bad coil packs, vacuum leak causing lean condition....it could be any of these for a problem like this.

i am leaning towards timing, fuel pump or coils.

 

[mtnmama]

i am guessing the code it is throwing is P0300 - Multiple or Random Cylinder Misfire. if the timing belt was recently changed the cam timing could be off. weak fuel pump, faulty injectors, bad gasoline, bad fuel regulator, bad coil packs, vacuum leak causing lean condition....it could be any of these for a problem like this.

i am leaning towards timing, fuel pump or coils.

Fuel pump is expensive, so I'll eliminate that one.

Coils -- the last thing the mechanic wants to check is the ignition module. I've read on this forum about Ignition Coils -- if it is the ignition coils, will it be evident after checking the ignition module??

Or when you say coils, do you mean the coil pack? I'm guessing that's different than the ignition coils, anyway. The mechanic checked it, but from what I've read on the forum, it can look okay, but still be bad. (scratch) Is that something that you just replace while hoping?

Timing -- It only has 55K miles on it, surely it can't be the timing?

 

[Captain KRM P5]

if the timing belt was recently done and the timing was not set properly it will cause misfires. even one tooth off will cause power loss and a perceptible misfire. the coils atop the valve cover, there are two of them, which may be bad. the igniters are in the computer so i don't know what they are checking when they say ignition module. there are no distributors as this is more a coil on plug system than anything else.

fuel pump may be expensive but if the car is not able to pull the proper fuel pressure it will lean out and run poorly, misfire.

 

[i12drivemyMP5]

.....and the new plugs made it worse? I'd suggest making sure they are just ngk copper bkr5's. Of course that's not the problem. You can score a fuel pump or coils off the for sale section cheap instead of buying new parts to trial & error with. Coils aren't that much anyway. Nobody's mentioned the plug wires, those are cheap enough to eliminate that possibility. Cat seems to be a stretch but Mazda will replace that for free up to 80k miles. Gotta love ambiguous vague codes right? Anyone with a lick of sense about cars can narrow problems down to 25 or less things. LOL. What good is obdii if it can't be a little more specific? Ahh, but that's a different story for a different thread. Either take it to Mazda & find out exactly what it is or start trying to eliminate what you can. Fuel pump access is under back seat, carpet has flap to access tank without dropping. Coils are right up top of valve cover as are the 2 plug wires. Simple swaps. Fuel filter is sock on end of pump in tank. Cat would probably glow hot if clogged. Timing belt shouldn't be issue for another 40-50k unless you been drag racing, lol, the thing. Sux about the payoff thing then this. Good luck. Oh, & welcome to the forum.

 

[winston3x]

do the coils and wires first. I recently bought a p5 and had these symptoms right away (w/ P0300). the dealership thought it was a bad fuel pump ,and luckily, paid for a new one. It did nothing to correct the problem. I bought aftermarket coils and wires and (knock on wood) haven't had any problems since. I'm not a mechanic, but since the P0300 is a random misfire, i'm guessing the coils could test fine but misfire randomly.

 

[mtnmama]

do the coils and wires first. I recently bought a p5 and had these symptoms right away (w/ P0300). the dealership thought it was a bad fuel pump ,and luckily, paid for a new one. It did nothing to correct the problem. I bought aftermarket coils and wires and (knock on wood) haven't had any problems since. I'm not a mechanic, but since the P0300 is a random misfire, i'm guessing the coils could test fine but misfire randomly.

Ignore my ignorance, please, but when you say, "coils," is that the coil pack or the ignition coils? Or are they just the same thing altogether?

I think I'm going to ask the mechanic to just change the coils and see what happens. The last mechanic did a tuneup and did replace the wires (I'm assuming you mean the plug wires).

The Mazda dealer (no offense to anyone) in our area is notorious for doing more work than is necessary, replacing parts that don't fix the problem, etc. -- they don't have a good reputation at all. I really don't want to deal with them, if at all possible.

 

[winston3x]

-yes, coils/coil packs/ignition coils - same thing. There are only two, they are on top of your valve cover. try to get them from NAPA or other parts store. coils from the mazda parts department are obscenely expensive.
-yes, referring to the plug wires.

It's a fairly simple installation, any mechanic can do it, no more than 1hr worth of labor$. maybe less if they charge you for the time it actually takes them. hope you get it sorted out.

 

[Beau M]

I had the exact same thing and it was the coils. you can get the at autozone for 17 bucks a pop, takes all of 10 min to install.

 

[mtnmama]

Update to the only error message being random misfire

Replaced coils -- they weren't the problem, unfortunately. Car started squealing like a pig and mechanic suggested we tow it to Mazda. He still had a hunch that it was the cat.

Within 2 hours, Mazda diagnosed it. Which is kind of funny since we've had it in shops for almost 3 weeks with lots of head scratching.

ANYWAY, Mazda says it IS the cat. (cool) It's covered under warranty, so that's pretty awesome.

Also, one of the O2 sensors is bad -- we were quoted $359.50 to repair that.

I will reupdate when the issues are "fixed."

 

[i12drivemyMP5]

Also, one of the O2 sensors is bad -- we were quoted $359.50 to repair that.

I will reupdate when the issues are "fixed."

OK, that seems quite a bit over the top for one to be replaced. They show to cost 149.00 each from onlinemazdaparts.com. 210.00 for a 5 minute no hassle take nothing else apart install that involves taking the sensor out of the exh & unplugging an electrical connection then the reverse to complete???????? Highway robbery!!!! They should be replacing BOTH o2 sensors for that much.

 

[mtnmama]

OK, that seems quite a bit over the top for one to be replaced. They show to cost 149.00 each from onlinemazdaparts.com. 210.00 for a 5 minute no hassle take nothing else apart install that involves taking the sensor out of the exh & unplugging an electrical connection then the reverse to complete???????? Highway robbery!!!! They should be replacing BOTH o2 sensors for that much.

What do you do when this happens? The mazda dealer still has my car and is now saying that the rear cat is also bad, so they'll be keeping it until at least Wednesday. They can't give me a loaner, they say. that annoys me, too.

Should I wait until the car is replaced to question the amount or should I give 'em a call?

 

[808MP5]

let us know if this. Solves ur problem. When u sat cat do u mean the pre-cat or main cat? Cuz if u change either of them and u still get missfires ur cat will prematurly wear and die. I have the same problem and still do. I changed coils, egr, iac, plugs, timing belt, and fuel pump. The only things left to change are wires, cpk sensor, first 02 sensor, pcv, coolant temp sensor and recheck timing. I'm leaning towards either bad vacum hose or coolant temp sensor cuz I only get it in the morning when its cold.

 

[crazybassmp5]

Hey there guys. I just found this thread, and I've been having this same prob for the last few months. Car has 107k miles on it, and have had it for almost 7 years now, with no problems until recently. I actually blew a plug out of the head to start things off, not fun! But was having these problems before that happened. So shop replaced plugs and wires, not coil packs. Misfire kept happening, and when it happened the engine would sound louder and I would lose power if stepping on the gas, BUT, if I let off the gas and let the engine drop down to idle, power was restored(uhm) I have also replaced both cats and O2 sensors, but problem is still there. Took it to dealer and they said coil packs should be replaced and there is an error for the cat now. So, now I'm waiting for the coil packs, yes I bought them from the dealer(ripped) I'm getting super annoyed by this problem and hope coil packs help solve this long going issue. I have even replaced ECU from another P5, and same prob. (help)

 

[bazooka joe]

are you getting any black smoke? i had a similar prob with another vehicle and it was a bad o2 sensor....pig rich condition under heavy throttle, no power and lots of black smoke!

 

[crazybassmp5]

are you getting any black smoke? i had a similar prob with another vehicle and it was a bad o2 sensor....pig rich condition under heavy throttle, no power and lots of black smoke!

No black smoke, but the exhaust smells different though, hard to explain but I can smell a difference.

 

[mildearth]

I had a similar problem after 135,000 miles on my P5 and it was one ignition coil and the pre-cat that had to be replaced. Unfortunately at that time no more warranty so the pre-cat came out and new headers that bolt direct to the main cat is in; now I just have to hookup the "non-fouler" to get ride of the check engine light. I was quoted $2000 to replace the pre-cat and plugs and they didn't mention the coil yet but I know they would have called and added that to the tab. Shop markup is ridiculous but if you are going to have your repair done at a shop then that is what you are going to have to pay, I don't think you can haggle with them.

 

[mildearth]

When I think about it it seems the problem starts with cylinder misfire which then leads to clogged up converters that cost way to much to replace. So I suggest if anyone starts to have a problem with occasional bog in your ride then replace your coils and plugs fast.

 

[808MP5]

Well i solved my idle/misfire issues....

Turned out to be a bad Throttle Body. It had carbon build up inside the TB and coolant lines going into the TB.

Anyupdates mtnmama?

A clogged cat will cause problems... mine was blown out naturally and is currently hollow. Hollow cat will cause no problems but a clogged one will kill you.