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laurenwhit · Sep 13, 2008, 09:12 AM

Mechanics have no idea what's wrong with my car. PLEASE HELP!

In the past 2 weeks this has happened 3 times:
I have a 2002 Mazda Protégé 5 with 115000 miles.
I'll be driving and I can start to feel my car or engine shake so I pull over and slow down and when I get under 15 mph the whole engine starts shaking, the check engine light flashes. I turn it off for about 3 minutes turn it back on. WORKS FINE! The check engine light still stays on. So I took it to autozone they ran the code and it was P0300: cylinder misfires. They said to change sparkplugs check wires. I did that changed the spark plugs, they definitley needed to be changed. Then took it to a mechanic and he said he drove it couldn't find anything mechanical wrong with it and suggested that I have bad fuel. So I bought some fuel injectors and the problem keeps happening. ANY IDEAS?

mechanickid · Sep 13, 2008, 09:28 AM

Do you always get gas from the same place?

Also you replaced the fuel injectors?

TxGreaseMonkey · Sep 13, 2008, 09:36 AM

. Replacing the distributorless ignition coils should solve the problem:

While we find your parts, please enter your ZIP Code at PartsAmerica.com

. Replace ignition wires.

laurenwhit · Sep 13, 2008, 10:06 AM

Originally Posted by mechanickid

Do you always get gas from the same place?

Also you replaced the fuel injectors??

No I don't. I get from a lot of different places.
Haven't done anything to the fuel injectors yet

TxGreaseMonkey · Sep 13, 2008, 10:22 AM

mechanickid, it's not just a start--it will solve the problem. You are way off base focusing on fuel and it's definitely not related to fuel injectors.

TxGreaseMonkey · Sep 13, 2008, 10:32 AM

Coils are likely breaking down under heat, due to mileage on the car. Be sure to reset the ECM, after replacing the coils. Easy job.

Ensure the new spark plugs are the same brand as the ones removed and gapped to OEM specs. Going from single platinums to double platinums, with different plug gaps, often causes misfires. Stick with what came in the car. Coat porcelein and tip of plug with a light coat of dielectric grease--this helps prevent misfires. Also, ensure the coil-on-plug boots are properly installed over the plug. If they are off, a misfire can result. On a 4-cylinder engine, any misfires can make the engine shake.

mechanickid · Sep 13, 2008, 11:25 AM

I wasn't focusing on the fuel, in her post I read

So I bought some fuel injectors and the problem keeps happening. ANY IDEAS?

Which is why I asked if she did and was going to ask why :)

ALSO, I've seen that many people who get fuel from the same place every time end up with simlar problems , that's all

But yes what you are saying about the coils is correct

Don't go giving people negative raitings before you even know where they are headed

laurenwhit · Sep 14, 2008, 12:49 PM

Thanks I'll try all this

wildandblue · Sep 14, 2008, 01:08 PM

Try heavier grade of oil maybe what you have is not keeping cylinders lubricated since your engine has over 100k

wildandblue · Oct 2, 2008, 02:04 PM

I was thinking along the lines of the piston is seizing which is causing the misfire in a hi mileage engine maybe due to sludge deposits
Or carbon deposits on the valves.
Should the timing belt be changed?

wildandblue · Oct 3, 2008, 11:59 AM

Or something in the automatic transmission? If the engine is running hot the fluid which is cooled by the radiator could be affected and it's shifting at funny points, you are giving it the gas while the engine is still in neutral causing a stall
If the engine is misfiring it's just more noticeable at slower speeds because at higher rpm the shaft builds up momentum, right?

P4KILLER · Jan 16, 2013, 04:41 PM

I had p304 p305 p306 p300-random misfire . I added dry gas (heet) and a bottle of fuel injector cleaner to a full tank of gas . Honda odyssey 2002 214.000 miles disconnected battery to reset code/ no engine light or rough idle for 3 days 75 miles (so far so good) will post if any change signed p4killer