Part of the Engine Miss?

mazda
protege
hesitation
heating

#1

I have a random miss at low RPMs while driving, and a hesitation off the line, both of these problems are only when the car is hot. The second one almost feels like a clutch slip because the car does not buck, but that…doesn’t make sense, as I can drive around the world and as hard as I like with 1st gear selected and never have it actually slip. Though is an automatic, which I have less experience with.



Anyway, I pulled the coils tonight and found that the boot on the tube to the number 3 cyl. was cracked. I have some new coil tubes on order. The ignition wires are 6k miles old, so they are in great shape. The coils checked out fine according to the manufacturer’s manual.



Also, there are no codes in the ECU, check engine light is not on.(That is something else I should probably ask about, but we can have that in a later discussion.)



Does anyone know if the second symptom is directly related to the miss, or is it something else that I should be taking a look at?




#2

What about the spark plugs and engine condition? An engine miss due to a misfiring plug or a plug that misfires due to lowered engine compression could cause this.

A vacuum leak could also cause this. The engine is getting extra fuel when cold. When warmed up the vacuum leak, which may have been covered up to some extent by the enhanced fuel mixture, now appears. The best way to test for a vacuum leak is with a vacuum gauge; a tool that should be in every tool box and is worth it’s weight in gold in my opinion.

There’s other things that could cause this problem also but there’s not enough info known about the car to sort it out. It’s also possible to have problems with something like a TPS switch, ECT sensor, etc. that will not set a code.


#3

I know it’s a little volatile, but ether works well for finding vacuum leaks. All though, WD-40 is safer.


#4

It is all sadly a moot point now, I was driving to a job site, and was 2 miles from home when the engine started making a loud, thumpy/clicky racket. Got it towed home and then went and got a brand new compression gauge (that I will never lend out again). #4 cyl is @ 110 psi, all the others are around 150 psi, time for a rebuild :-(. The head was rebuilt earlier this year, and I knew then that a block rebuild was coming as #4 was showing lower compression, but not quite out of specification compression, once we had the head back on.

So that you know, I test for vacuum leaks every 2 months, shows you what kind of trust I’ve had for this car. I bought it for $700 for two reasons, first, because it was a death trap, and second because it was in bad shape. The tranny fluid was black and burnt, the engine is heavily varnished, and the oil was low at the time of purchase.

So I have some research to go do, and figure out what the future of my transportation is going to be. I’m very lucky I live in an area with good public transportation.