Misfiring cylinder

[CrypticFall]

Hey everyone, I have been having a bit of a time with trying to figure out an issue with my 1995 mazda b2300 2.3L 4V. A bit of backstory first, as I have a hunch it has something to do with the issue.

I received this truck for free. It was a "get this of my property and its yours" kinda deal. I didn't have a vehicle at the time, so it sounded like a good idea. To my knowledge, the only work that was done on the truck to get it running was a new starter and a replaced timing belt. I was told all the fluids were flushed, but I'm beginning to think this was a lie. I drove it down to college (about 350 miles) and it ran fairly well. It wouldn't go past 75, and I couldnt accelerate in 5th gear, but other then that it was pretty smooth. After I parked it, that was the last it would ever run that well again.

Fast forwarding to the present, #2 cylinder is still misfiring. I have replaced the ignition coil, spark plugs, spark plug wires, air filter, fuel filter, oil and oil filter and i've even dropped and cleaned the gas tank. I was going to get the fuel injectors cleaned at pep boys, but I am running out of options, and I don't know how much more money I can put into the vehicle.

My only other thought is that I noticed spark plug #4 on both sides of the engine had been fouling up, even after I changed them. I also saw that my oil was far past the FULL line on the dipstick before I changed the oil on 10/4/15. I plan on wiping them back down to see if they start to spark again, but I don't think it will fix my problem. So am I leaking oil from my cylinder? Is this worth fixing? Or did I just find out this car has a shallower grave then I thought?

 

[tomw]

Interesting that you report cylinder #2 is misfiring, while cylinder #4 spark plug(s) is fouled with oil. Howzat work?
What does #2 plug look like? The exhaust side plug is the main sparker that ignites the mix to make the engine run, the intake side being emissions related, and fired only under certain circumstances, so exhaust side is the one to look at.
Did you check compression? Should have in the mid-100's in psi.
Does the engine misfire at idle?
If it does, is the misfire on every firing cycle or intermittent? Intermittent points to non-mechanical things, while every cycle could be valves or rings or ???, rhymes with money.
Have you checked the coil(s)?
Did you pull any codes?
Are you sure the plug wires are connected to the proper terminals on the coils?
A plug can get oily from sticking rings, hole in a piston, or bad valve stem seals for a few reasons. A compression test will insure that the mechanicals are good or not... while the seals & rings may be a bit more, some of which can be done without total disassembly, engine still in the truck.
Have you checked the fuel pressure & delivery volume? No point in cleaning the injectors, $$$, until you know they are being fed proper pressure and amount of good fuel. BTW, did you change fuel filters, with an S, as some have two possible filters. One in-line, the other in a canister mounted to the frame rail behind a U-shaped chunk of metal(protection) having two lines in and two lines out. Some have a fuel filter inside, some just are the canister.
tom

 

[CrypticFall]

Hey tomw,

I say cylinder #2 is misfiring because that is the code that is generated from the check engine light. I have a solid check engine, and then around 2nd or 3rd gear I get a blinking check engine light, but it still only throws a misfiring code. The #2 spark plugs look fine, no real issue with them. #4 have a light coat of oil.

I haven't check compression, something I will do this weekend. I'm not entirely sure, but I think its misfiring all the time. It gives me a lot of trouble starting cold, and a lot of backfire. Once warmed up it runs better, but it still rocks the whole truck at idle. Plugs are fine, and I made sure to connect them in the correct order. And i didn't know it had an inline fuel filter, I only changed the canister.

 

[Mark_88]

Welcome to TRS~!

And welcome to the wonderful world of four bangers (not sausages)...it looks like tomw covered most of the things you should be looking into, but I will elaborate a bit on the finer points of four banging...

If you got the truck up to 75 Mph then I'd say you are doing good...but the losing speed in 5th is common especially going up hills...it is called OD because it is more like a cruising gear than a power gear...although the engine condition could be a factor also. The revs are lowered in OD to save fuel and if you need to climb a hill, accelerate, or even slow down you need to shift down from 5th...aka OverDrive...

If you want a more expansive explanation you can read this at your leasure...

https://en.wikipedia.org/wiki/Overdrive_(mechanics)

The most important engine factor you have here is the condition of the rings and seals...this will cause the symptoms you are seeing as well as reduced power overall. As tomw suggested, do a compression test and a leak down test asap. The truck sounds like it needs ring work...especially on cylinder 4...but it could also be a head gasket issue...so you might want to do the glove test.

Get a latex glove, the kind doctors use to probe your insides with, and stretch it over the rad cap opening (remove the rad cap first)...remove the distributor power connection and crank the engine...if the glove blows up even a bit you have a leaky head gasket...if not...your rings are probably toast...

I say this with a great deal of experience...I spent two years nursing my 2.0 from the same symptoms thinking I will find a motor sooner than later...didn't happen...since I was using a carb setup and the number of engines in junkyards was dramatically reduced when they started crushing anything older than 1998...

So...once determined you can either rebuild it if it is rings and maybe do a head job to replace valves and seals...and your little truck will serve you well for many years if you take care of it and keep it away from overheating...

If it's just the head gasket you can do that in a couple of hours on these engines and not even break a sweat...

 

[CrypticFall]

So I'm glad to here that the reduced speed in 5th gear is relatively normal. This is my first manual, so I really didn't know what to expect. I'm less excited to hear that it will probably need either redone gaskets or redone o-rings.

This is the first car I have worked, and as such, everything I know about cars is what I've worked on listed above. So if its not the head gasket and the engine needs to be rebuilt, is it something that novice with a haynes manual and the internet can do in his spare time?

Thanks again for the information?

Also, I don't know if this means anything, but I put one of the spark plug defoulers on the ignition side of the engine, and it doesn't seem like it really did anything. I would also like to point that it went 75 at its best. It now cruises at 55ish, anything past 60 the engine cuts off once I let off the gas.

 

[adsm08]

I'm interested in the part about the overfilled oil. Over-full oil generally comes from gas in the oil, generally due to a leaking injector. Improper atomization of the fuel (bad spray pattern) can cause a misfire, and is a symptom of a leaking injector.

See, liquid fuel doesn't burn. Fuel vapors burn. If you want to see that in action get two matches and a bowl of gas. Throw one lit match in to burn off the vapors, then throw the other in. It won't flame up, but it will go out. The fuel injector sprays the gas in a very fine mist to get it vaporized in the intake so it can burn in the cylinder. If you are getting poor atomization because the tip is shot, well you will get a misfire.


The flashing check engine light is also misfire related. A flashing light doesn't mean a new code, it means a severe, catalyst damaging, misfire.

I wouldn't clean them, I'd get on Ebay and look for a cheap set of Bosch units. I've picked up whole sets of Bosch injectors for less than the price of one at the store. Haven't had issues with them yet either.


A compression test is also in order at this point.


Finally, while I encourage people to learn everything they can and do anything they are able, engine building is very precise and delicate work. It is not difficult, but it is not a place for an unguided novice to do "in his spare time" as you put it. It requires many specialized (pronounced "expensive") tools, and skills. It isn't something I would suggest fumbling your way through with a Haynes manual and the internet. It would be far better to find someone who knows what they are doing and ask them if they will teach you.

 

[CrypticFall]

So I'm sure this is a pretty difficult question to answer as you don't know the exact issue, but when you say "severe, catalyst damaging, misfire", what exactly is it damaging? Should I just not be driving this at this point?

Thanks for the heads up about the injectors on ebay, I didn't even consider it, and I wasn't about to drop 280 bucks on fuel injectors that might not fix the problem.

Went by O'Reilly and picked up a compression test, really hoping its not the case.

 

[adsm08]

The catalytic converter is what is being damaged. It is a "device" that causes a chemical reaction in the exhaust after reaching +400*F that converts the various components of the untreated exhaust to less harmful, or inert forms. The basic components of untreated exhaust gas are carbon monoxide, which is toxic to everything NOx, which is toxic to everything, and a little bit of HC, which is a minor amount of unburnt fuel. The cats take that stuff and convert it to CO2 (not an environmental pollutant like that moron Al Gore claims), which is good for plants, and not toxic to animals (even though it will suffocate us), and H2O, more commonly known as "water".

The functional portion of the cat is a plaster-like matrix that holds the chemicals that incite the reaction. It can withstand extreme high temps, but raw fuel getting into it will cause it to get too hot and it will slag the matrix. When that happens not only can the cats not do their job, but the exhaust can't flow.

It would say that you should be judicious with your driving until you get this sorted out. Walk places that are close enough and troll craigslist for a cheap bike. A "catalyst damaging misfire" as determined by the computer is based on intensity, rather than cause. The computer doesn't know any more about the situation than you do at this point, and maybe even a little less. It knows that it see a misfire of a certain intensity. If the injector is plugged, or not opening at all, giving no fuel, the computer can't tell the difference between that or a total lack of spark and will judge both events to be "catalyst damaging" even though the first scenario will not do any damage.