Hello

Sorry about this long-winded description, but I’ve read many of the forum posts on this issue and have to cover what we’ve tried from the posts.
Our Mazda 2003 Protégé5 hesitates on acceleration and at idle when the engine gets hot. When the engine is cold, the engine is fine. So far I have checked the MAF sensor, IAT sensor, PCV valve, coolant temperature sensor, IAC valve, TPS sensor, cleaned the throttle body, and replaced the EGR valve.
There are no cracks in the air intake tube, and the hesitation only happens when the engine is hot. The hesitation is getting worse (especially on hills).
The rough idling has occurred for about 3k miles with no warning lights and hence no codes. Now that hesitations are getting worse, we get the cylinder P0304 cylinder 4 misfire code.
At 150k miles, the mechanic replaced the car’s plugs, wires, PCV valve, ignition coil, fuel filter, cap & rotor and cleaned the throttle body. The odo is now at 175k miles. We just took it to our mechanic who said it’s misfiring on each cylinder randomly and also said they couldn’t do anything until there’s a code - otherwise it would be a costly repair.
My dad and I have run out of things to check. Is it possible that the timing belt can cause hesitation when the engine heats up? Any suggestions would be greatly appreciated.

 

SOLUTION

Since we got the misfire cylinder 4 we swapped coil 4 with coil 2 and then the car’s OBD code showed us misfire cylinder 2. So we knew it was the coils. We got new coils for cylinder 2 and 4 and the car worked good for 2 days then it started hesitating again.

We then got the idea to turn the engine on and push down on the spark plug wires 1 and 3 where they go into the valve cover. Suddenly the misfire stopped. So we decided to replace spark cables 1 and 3. When pulling #3’s spark plug cable off, the wire’s rubber cap remained on the plug, so the valve cover had to be removed. After replacing #1 and #3, the misfire problem stopped and hasn’t been a problem for a couple weeks now. Success!

Somehow the heating of the plugs/engine caused the connection between the plug and the cable to fail. We never would have thought it was the coils/wires because they were “supposedly” replaced by our mechanic 25k miles ago. Unfortunately there isn’t any brand info stamped on the coil/wire.

Note: we noticed that the Mazda coils are different from coils on other cars because these coils do not have bolts holding the coils in, rather the Mazda coils have a rubber design holding them in. This is bad because after time this rubber goes soft and lets the coil loose when you go over a bump this leads to are problem.

 

Glad you got that fixed. Reading your first post it smelled like a coil issue. Did you buy Mazda coils? I've been told the coils are a part one should try and stick with Mazda for. If the same issue crops up and you didn't use Mazda parts, replace with Mazda parts.

Not much traffic on this board anymore.

 

The coils are aftermarket, but the wires are OEM. We don't know what the mechanic before us used.

To bad there is not much traffic, we really liked this website.

 

I bought my son his first car a couple years ago. 2003 Protege5. It had a miss and we replaced the coils and wires. The dealer was able to locate coils for us, but it took some work.

When vehicles get older traffic on enthusiast boards like this one starts dropping off. I have a Gen 1 Sienna and there isn't much traffic on that board either.