I have a question regarding a flashing CEL. I know that a missfire can cause the CEL to flash, is there anything else that will cause it to flash. I am going to have the codes scanned, but this happened on the way to work and wondering if anything else can cause this, as the engine did not seem to be missing at the time. I pushed in the clutch and the CEL kept flashing even though the motor was definitely not missing at that time.

 

An engine can still miss with no perceptable change in engine speed or smoothness. I saw this first hand when a tech at the dealer I used to work at was demonstrating the service bay diagnostic machine to me. When you saw the scope output, you could see the miss, but it wasn't perceptable except under heavy load. Evidently the computer is very sensitive in that regard!

 

Thanks Bart99GT

I will have it scanned this afternoon and see what it tells me. This thing is turning into a real pain. It did have a little miss on the way to work at times, but not any worse than it has been the last couple of days. After CEL quit flashing, the truck ran great, power was back to what I expect from this little motor and ran the rest of the way to work great with no miss. Not sure what to think, but seems that it gets progressively worse until it does this, and then takes off running great for a little while. If I unhook the battery for 15 minutes, the truck runs great for about 150 - 200 miles with it progressively getting worse. Once it goes through the misfire problem, it will run better for a while. Put a vacuum guage on it last night off of the port for the fuel pressure regulator and the vacuum is pretty steady with only a very slight vibration of the needle. This intermittent problems are a real pain to find.

 

Yes, they can be a pain - pulling the codes will probably help you narrow it down a lot though. Just be aware that the flashing CEL is telling you that you may be damaging your cat converter, so don't ignore it! Probably it's not in danger, but not the kind of thing that you want to have to replace. Post again if/when youhave codes pulled...

 

Thanks NewEnglandHerdsman

I did get a chance to have the codes pulled this evening. Came back with P0303 (misfire on cylinder 3) and P1443. The 1443 is an evap purge low flow condition and seems to come and go. I have to go pick up the evap purge assembly from a Ford dealer. I have ordered it but they have not called to tell me that it is in. Don't think the P1443 is causing the missfire? I have changed spark plugs, plug wires, fuel filter, air cleaner, timing belt, and PCV valve. I ran a vacuum test last night and got a relatively steady 19 lbs with just a very slight shake to the needle. Bad fuel injector, fuel pump? I did run a pressure test when idleing a week ago and got 30 lbs at idle, and increased as throttle was opened. As it is intermittent, I am not thinking burnt valve, but will run a compression test pretty soon. The P0303 has came up one other time recently. Fuel problem?

 

Have a few other questions. Can the coil packs go bad for one cylinder and be intermittent? What would the symptoms be for one coil pack bad on one cylinder? Not sure where to look next. Advice is appreciated.

 

I'm not sure what the details of your engine/year/etc are, but in general there's no reason that one of the coil packs can't go bad, and if it did it could certainly cause a misfire on that cylinder. If they're interchangable you could swap the one on cylinder 3 with another one and see if the code migrates with the swap.

As for the P1443/evap, I'm going a bit over the edge of my expertise here, so someone sanity check me if I going down a bad road, but I think most evap problems will cause lean codes, not misfires. So it may be that the 303 and the 1443 are unrelated problems. Does sound a little suspisious if they showed up at the same time though...

Did you replace the plugs/wires/etc before the flashing CEL showed up, or in an effort to fix the flashing CEL?

 

The engine is a 2.3L 1996 4x2 5 speed with 156K. I got the truck with a miss from one of the kids who did not want to fix it. I changed everything to catch up on the maintenance and to aleviate the miss. So far no luck. The flashing CEL is something that has happened twice now and both times it was 303. The 1443 is something that has shown up since I got the truck. I ordered the part from a local dealer and just waiting for it to come in.

Since the 303 seems to be the only cylinder that comes back with any consistancy, I am try to isolate where to concentrate on the problem at. Resistance of coil packs need to be checked? I am hoping to run a compression check tonight along with swapping out the coils. There are only 2 coils, one for the intake side, and one for the exhaust side. I will look and see if changing them out will make a difference as to which one fires which cylinder.

Is there any visual checks that I should be doing to the coils? Since I do not get any lean codes or anything besides misfire, it must be something the computer does not monitor very closely. I do not understand why resetting the computer will make it run much better for a short time.

Any insight?

 

The low evap purge code wouldn't be causing the misfire. It just means that it isn't detecting enough flow between the charcoal cannister and the intake manifold. Usually the sensor or control valve (usually its one in the same) is faulty, or perhaps the line between the valve and intake manifold is crudded up.

 

I think you're on the right track swapping the coils as the next test, if that doesn't cause any changes I'd consider swapping the plug wire and plug too (I know you said you replaced them, but...)

The misfire detection is actually done by monitoring the crankshaft rotational speed as each cylinder fires - it really has nothing to do with monitoring fuel or spark directly. What it's really detecting is a lack of power for that cylinder. So if you swap all the ignition parts and #3 still misfires, it's probably time for a compression check. Did you notice anything suspicious looking about the #3 spark plug when you replaced them/

Oh, and although a visual check of the coil would be a good thing, there's lots fo things that could go wrong with them that are "invisible".

Resetting the computer should restore it to default settings, after which it should start to "learn". If it finds too many problems it can go into "limp" mode, but where you're only seeing a couple of codes, seems strange that it would run worse as it learned more rather than better...

 

I drove mine with a spark plug wire about halfway off causing a mis fire and it never through a code. The only way i could tell was that my gas milege went to crap and i was having to downshift to 3rd to make it up hills it's always done in 4th. I poped the hood and could hear that non mistakable ticking sound of an arcing plug wire. I popped the wire back on and didn't have any other problems.

I would recommend going to Auto Zone and having them pull the codes, it's free.

 

3" snow last night kept me from doing anything with the truck. I drove it to work today and will pull it in the bay tonight after work and see what I can find. I looked over the plug wire routing last night online. It looks like swapping the coils will still put the #3 cylinder on the same post, just a different coil. Does this truck fire both 1 &2 cylinders together? and then 3 & 4 together? Both coils fire at the same time? If it is indeed firing both #3 and #4 together can I swap out the 3 and 4 on both coils and see if the problem moves or not? I did find how to measure the coils for a problem and will do that at the same time.

On the way to work it started the flashing CEL again. I will run at lunch and see if it is still the same cylinder. Will do a compression check tonight. The miss was there when I started with the truck, and it was bucking after putting new wires, the plugs had already been changed. All plugs were worn when replaced, but no damage to them. I will check and replace both plugs on cylinder #3. The first set of wires I bought were defective and I got a better set and replaced them again, that did help with the miss, but it is back again and almost as bad as before. After I replaced the timing belt everything ran great for about 200 miles and then slowly degraded from there. After rechecking the timing marks at about 300 miles and resetting the computer, once again good for about 150 - 200 miles. Back to the same problems and it is doing it more often. HELP!!!

This thing has become a quest to find and fix the problem. It is not my only vehicle or I would take it to a garage. Want to fix it myself and make it run right.

Anyone ever use one of the ODBII to laptop units? Wondering if it may be worth the $200 to get a more detailed look at what is happening? A lot of money for a unit that will get very little use from me.

 

Did not get as much done as I wanted last night. Check plug on drivers side #3 cylinder, looked fine. Measured out both coils and they seem to be in spec. Disconnected front coil and it fires right up. Disconnected rear coil and it is definitely harder to start, but it does run. Must be a lag in timing for front coil. Does anyone know if both coils fire at the same time?

Anyone know an easy way to get the connectors off of the 2, 3, and 4 fuel injectors? Wanted to measure them, as they seem like a possible cause. Tried to get the #3 injector connector off for 15 minutes, and ran out of time. Will try again this weekend. Hopefully someone has an idea?

 

I have used the OBDII->serial port box you can buy here for several years. It's under $100. Coincidentally, first use was to discover P1443.

 

Thanks for the link. What kind of data can you pull from this. Does it give you data real time? Would love to find out what is happening when the misfire occurs.