Misfire on 2.3

[mazda-fla]

Just got done installing 3 remanufactured fuel injectors (Beck/Arnley). Bought them on Amazon for $52 each, they seem to be a very good quailty reman part. The 1999 Workshop manual doesn't match my 1999 Mazda. The connector drawing in the manual shows the ohms checking terminals for 2, 4, 6. But mine is the other way around 6, 4, 2 in the harness. So the "Misfire on cylinder 2" was really cylinder 2. And the dead injector (open circuit) was the injector in cylinder 2. (not 6 like the manual shows). Anyway, I replace all three on that bank so I don't have to deal with that side again. I pulled the left intake manifold with fuel rail still attached as a one piece unit. Then took it over to the bench to work on it. I think that way is easier. I also didn't need to pull the entire CAC. I just unbolted it and left it in place with all the hoses and connectors, then lifted it up gently about 2 inches, enough to give me clearance to wiggle the intake and fuel rail out as a unit. Then after I was done replacing the fuel injectors, just brought it back over to the car and lifted the CAC and wiggled it back in. Also, you won't have any junk drop into the intake this way. There was about a teaspoon of sand/dirt/silt in the channel behind each of the three injectors. So either pull the intake out with the fuel rail attached, or blow it out with compressed air first. I'm also glad I bought a few extra copper crush rings for the fuel line, because it's easy for them to drop when installing the fuel line, and almost impossible to find them when they drop or go flying somewhere in the engine compartment.

Total hours was about 6 hours end-to-end. I think I got lucky that it was on the front(left) side. The back(right) side would be double the amount of work.

Car seems to be running fine now.

It's like what Ken was saying, in the early days when you had a misfire on these cars you would just switch coil packs and plugs around. Now it seems like fuel injectors are starting to fail due to age on these cars now. So when you have a misfire, do a simple ohms test at the pigtail connector, in addition to the standard coil pack and spark plug test.

[bigb]

thats good news! and wow are those cheap! I remember only 1-2 years ago the same beck arnley parts were like $2-300 ea.

did you happen to take any pics during the project? it might help others if they have to do the job.

[keninn]

yah, see. i never get that lucky. mine was #5, and i first did the coil/spark plug. although, this last one, which was a coil, was on the front bank. and there was no check engine lite, just an intermittent miss.

on another note, i have had lots of injectors cleaned. back in the early days, when bmw had cis injection, injectors were mechanical, so cleaning was marginal. and new ones were cheap. but with present day injectors, every time i would get them cleaned, before and after improvement was about 20%. plus, you would be surprised at how the flow rates would differ from injector to injector. in the galant, i was running 18 lbs boost, and as boost gets higher, it becomes more critical that each cylinder gets the same amount of fuel. i have a valve cover gasket job coming up, and i am having cleaned injectors going in at the same time

[mazda-fla]

I didn't take pictures, but here is how to change the left side (front):

(1) Remove battery.
(2) Loosen right-hand intercooler.
(3) Remove left-hand intercooler.
(4) Remove all bolts and nuts from CAC assembly.
(5) Remove the two vacuum hoses that run under the left intake manifold and the PCV hose that runs through the intake manifold.
(6) Remove the four 6mm hex head bolts from the left intake manifold, and the two nuts.
(7) Remove the 17mm banjo bolts holding the fuel line into the fuel rail.
(8) Lift the CAC up about 3 inches, and gently wiggle out the intake manifold and fuel rail as a one piece unit.
(9) Take the unit over to a bench and remove the fuel rail from the intake manifold.
(10) Remove each fuel injector from the fuel rail. Wiggle and twist them out, you can also get them started by prying them out a few millimeters with a flat head screwdriver on the notch along the side of the injector, just a bit so you can break them loose.
(11) Clean up the injector holes in the intake manifold and fuel rail with a rag dipped in gasoline.
(12) Dip your finger in fresh motor oil and lube up the 2 o-rings on the replacement injectors.
(13) Install the replacement injectors into the fuel rail by turning left-and-right while pushing them in gently.
(14) Reinstall everything in reverse order.

You also need new copper crush washers for the fuel lines. I also replaced the fuel injector insulators (rubber/metal washers that sit in the intake manifold), but it looks like you could probably clean those up gently with a rag dipped in gasoline and reuse them.

[bigb]

thanks mazda-fla I was wondering how you got in there with the CAC still installed. I just took the whole thing off when I did mine but at least now we know it is possible by just moving it slightly out of the way.

and ken, my hat is off to you sir. totally nailed this diagnosis. I would have never thought a 0ohm injector would be an intermittent miss. hrm. apparently our cars diagnostic system is crap if it cant even figure out an injector is dead. jeez. it's just a simple ohm test by the ecu which it does for many other sensors to make sure they are in spec...

[Saint_]

Originally Posted by bigb

thanks mazda-fla I was wondering how you got in there with the CAC still installed. I just took the whole thing off when I did mine but at least now we know it is possible by just moving it slightly out of the way.

and ken, my hat is off to you sir. totally nailed this diagnosis. I would have never thought a 0ohm injector would be an intermittent miss. hrm. apparently our cars diagnostic system is crap if it cant even figure out an injector is dead. jeez. it's just a simple ohm test by the ecu which it does for many other sensors to make sure they are in spec...

Thats tricky though. It has to apply some voltage to the injector and it can cause some unwanted fuel leak. Just like it doesnt test the coils. Not impossible but harder.

[bigb]

since the injector is a solenoid, it is actually current that makes it work (think electromagnet)

it is fairly easy with a transistor (current controlled) to apply a voltage to measure DC loss while at the same time not actually turning on the injector. I think the ECU already does this for a number of other sensors on the car, for example the vacuum solenoids.