01 Protege with engine problems......please help

[rumdig]

Hello Everyone,

As an intro I have an 01 protege 1.6L, standard trans with no mods. Recently I had the head removed, machined and replaced due to stripped threads in one of the cylinders. After ~2 months of driving the car start hesitating very badly, mainly in first gear.

It runs fine when idling, however, it tends to bog down and yerk when under load such as when starting out in first gear or travelling at a low rpm in a higher gear and hitting the gas. I have had CEL's such as "lean bank" and "cylinder 2 misfire". Below is a list of my findings so far:

-switched coil packs around and CEL changed to cylinder 4 misfire, then replaced that coil pack with no avail, same CEL still comes back.
-cleaned and inspected EGR valve
-replaced cracked air intake tube
-probed MAF sensor and seems to be functioning fine
-O2 sensor 1 seems fine, voltage bouncing from 0.2 to 0.8, O2 sensor 2 stays around 0.8V for quite a while when driving(is this bad?)
-sprayed carb cleaner around intake when running, no vacuum leak there.

I'm sure there's more but i can't even recall all the things I've tried to do to fix this. Any more suggestions?

[1Mazda323Fan]

1) You say the head was removed and machined because of 'stripped threads in one of the cylinders'. I'm assuming you mean one of the spark plug holes? Which one had to be redone? When you replaced the head, did you use a new gasket? Was the proper torque sequence done on the head bolts?

2) When you say you replaced the coil pack (after switching them around), what did you replace it with; new, old? How many codes exactly do you have?

3) How long has it been since you replaced the fuel filter? It may be clogged, restricting fuel flow when it's needed more (engine under load, at higher rpms). Running a good fuel system cleaner (I like Techron myself) and a few tanks of 93 octane wouldn't hurt, either.

4) Has the timing belt been done? It's possible it could have slipped a tooth or two.

5) 0.8V is not a good reading from your post-cat O2 sensor. That's really high. It should be around 0.45V, give or take a few hundredths. Not a constant value, mind you, but damn close to it. 0.8V actually means you're running rich...or you have a problem with the sensor, and possibly even the cat itself. You may want to pull the sensor, carefully, and check the tip. If it looks scorched or burnt or otherwise in a bad way, replace it, clear the codes and try again. I'm thinking that you may have an exhaust leak somewhere, maybe in the cat, or the cat has disintegrated. That will definitely cause running problems. There may be other factors associated with it, though. Any more information you can provide would be helpful.

[rumdig]

1. Yes, the spark plug hole was redrilled - cylinder #2. gasket was replaced with proper torque sequence. Actually - the head gasket starting leaking oil not too long ago so I would suspect that something is not torqued exactly right.

2. When I replaced the coil pack I purchased one from a local junk yard hoping it would work. I was getting cylinder 4 misfire all the time prior to that. I have a new CEL today - I'll post back my findings on that.

3. Never replaced the fuel filter, where is it located? It could definitely help with the current mileage.

4. Yeah, I'll pull that sensor later today and see what it looks like.

Thanx maxda323 fan, I'll be back with more information as I find it.

[sethro_GT]

Do a compression test to make sure the head gasket service didn't fail. Slap a vacuum gauge on the intake, should be around 20inhg at idle. Check the air intake system from front to throttle body, make sure everything is in good order. Make sure the cam sensor didn't get jacked. The above suggestion to check timing belt, also if its properly tight.

O2 sensors oscillate between 0 and 1 as the system constantly tries to get stoich; they do not put out a constant value. If the car is cold the ECU doesn't even use the O2, just runs on programed mixture. Though an average value would be around .45 not .8. Check your coolant temp sensor as well, perhaps the system isn't switching out of cold running mode.

[rumdig]

Ok, I have checked further and here is what was found:

The post cat O2 sensor was replaced and...............same reading! The engine does seem to run slightly better during warm up, only slightly.

Another note, with the car at an idle and turning on the AC, the engine starts to run very erratically, stumbling and trying to die. This is what I described happening in the higher gears.

I don't have a vacuum gauge handy, maybe I'll have to look into one!

I'll check the timing belt again soon, it was still aligned with the marks I had left on there.

So what would cause the post cat O2 sensor to read high (rich) and how do I check for a cure?

Thanks for all the replies

[sethro_GT]

Oh, right the second O2 will be more constant since it is post cat and the cat is doing its job in removing hydrocarbons.

If you have a multimeter take a voltage drop measurement from the engine to the neg battery terminal, should be less than .25V

[kamprotege00]

I would definitely check for cracked air hoses... I had a cracked hose that went from the intake to a small inlet the back of the engine bay and it caused the exact same problems you're describing... I will try and take a picture of which hose it was so you can check yours as well.