Hello to all on the forum! Newbie here.

First two days with the car were great, then the misfiring started. Engine light came on, but it has turned off each time I bring it in to get the codes checked. It only misfires noticeably after it is at full op temp (usually after 20 min of driving) and then most noticeably at idle. It never threatens to stall. I usually lasts a second, but as you continue driving, there is some loss of power.

My initial steps were to check the vacuum hoses and intake boot, and all seemed in much better shape than they should be for 140k, so I'm assuming they've been replaced. All pliable, black and no cracks. Unless I can pull a code, I am planning on

1. Pulling the plugs to check for damage/condition
2. Listen to the injectors (told I could do this with tubing)
3. If nothing there, clean the MAF sensor
4. EGR valve
5. Ignition Coils

Am I on the right track? Of course, if I can pull the codes, I'll have a better idea of what I'm dealing with.

Thanks all...

 

2.0L
140,000 miles
manual trans
no service records - just purchased

Thanks all...

 

This is just a wild guess, but the Protos are notorious for bad intake hoses. Pull the hose completely off the air box and flex it around to see if there are any splits/leaks.
Also, how's the condition of the battery? I have discovered that when a battery is on it's last legs that it can cause stumbling and misfire issues as well.... not enough voltage to the FI system.
Though w/140k on the clock it could probably be a number of things.

 

Thanks for the response... never even considered the battery. I just purchased a Bluetooth scanner for my Android - hopefully it will work and I can track it to see if it's giving consistent power. Hopefully it can check a lot of things! Tomorrow morning it's pulling off the boot and inspecting it and then cleaning if MAF. If that doesn't work, then I'll move to the next items on the list, which now includes battery... my reader comes Saturday.

 

There will be a code in the PCM even if the light is not on. More than likely ignition coils. 50 bucks on Ebay for the whole set. Coils should be replaced every 100k.

 

Went to a different autozone and they read the codes just fine. Cylinder 1 misfire and cat conv. code. So... replaced the plugs and the ingnition coil that corresponds to cylinder 1. So far, so good!!!

BUT.... yesterday a loud (at times) high pitched squeal started - around 8-10k kHz I would guess - sometimes at idle and sometimes at high speeds, but usually if the throttle is in the same position for a while... any clues?

 

You have a converter code so it is likely going to need at least one. There are no moving parts in a converter. They generally go bad from the engine not burning all the fuel and overheating them or running too lean and overheating them. Ignition coils take 12 volts applied and turn that into 40,000 volts for spark. This creates a lot of heat in the coil and they degrade over time. A coil that has 100k miles on it will still throw spark and the car will run with no noticeable problems,however the converter is taking a beating without proper spark. If you have 1 coil go bad then you need all the coils. They all have the same wear on them as the one that went completely bad. They are probably putting out half the voltage that they were when new. The noise you hear is probably a partially restricted converter forcing back pressure through an old gasket/crack. It could just be a vacuum leak i suppose but the car will need a new converter and 3 more coils minimum.

 

Hindsight - should have changed both coils... the problem is back after 1 week without any issues. This time though, it's only when I'm in bumper to bumper traffic. In regular driving, rarely an issue.

It may be coincidence, but it started right after I filled up. I added some fuel injector cleaner and it helped. If it's a coil issue, would that make sense?

Thanks all..

 

This time it's a general misfire code, not cylinder specific.