P0302, P0304, P0174

Several of you may remember my recent post about having the lower intake manifold gaskets replaced. That all seems to be doing fine.

Now I get the above mentioned codes, all together...in the order listed.
I notice on and off missing.
My mechanic told me that it is a fouled fuel injector, and gave me a bottle of Berryman's Chemtool B-12. He told me that cleaners, such as Techron, Redline, and Fuel Power (FP60) are detergent cleaners, and do a good job at keeping a fuel system clean. But that I needed a solvent based cleaner to clear up the injector.
He told me that it might take several tanks treated with the B-12 to clear it up.... Also, that it would likely be a full tank before I noticed any improvement.
I have seen improvement....but I am still having problems on my 4th tank!

I bougth a new injector from FORD and replaced cylinder #4 injector, as the P174 is a lean code for bank #2, which is the one that P0304 is on. Also, my original code was with P0304.

Still have the problem. From what I have read, a fouled injector would be expected to act up the most at higher RPMs. I do not notice the problem getting any worse at high RPMs. Sometimes there is no miss.....and sometimes there is. I can accellerate, taking the RPMs up to 5000 RPM with very smooth operation.
I have a 1 year old "improved" CCRM, which is where the fuel pump relay is on the '96.

I am thinking that the problem could be along the lines of a weak electrical connection for the wiring for the injectors....as that gets flexed during the lower intake manifold removal.
Other thing is a vaccum leak....which would be at the passenger side of the manifold.
I have checked the vaccum connections, found 1 loose, and PCV valve popped out of the gromet....but they did not improve things.
Will look more at the vaccum connections.
The IMRC is working just fine, pulling in to the stops.
I got 1 CEL in a 525 mile trip Wednesday night, with the same codes I listed.
So, I guess it is "better", but not fixed yet.

Several of you may remember my recent post about having the lower intake manifold gaskets replaced. That all seems to be doing fine.

Now I get the above mentioned codes, all together...in the order listed.
I notice on and off missing.
My mechanic told me that it is a fouled fuel injector, and gave me a bottle of Berryman's Chemtool B-12. He told me that cleaners, such as Techron, Redline, and Fuel Power (FP60) are detergent cleaners, and do a good job at keeping a fuel system clean. But that I needed a solvent based cleaner to clear up the injector.
He told me that it might take several tanks treated with the B-12 to clear it up.... Also, that it would likely be a full tank before I noticed any improvement.
I have seen improvement....but I am still having problems on my 4th tank!

I bougth a new injector from FORD and replaced cylinder #4 injector, as the P174 is a lean code for bank #2, which is the one that P0304 is on. Also, my original code was with P0304.

Still have the problem. From what I have read, a fouled injector would be expected to act up the most at higher RPMs. I do not notice the problem getting any worse at high RPMs. Sometimes there is no miss.....and sometimes there is. I can accellerate, taking the RPMs up to 5000 RPM with very smooth operation.
I have a 1 year old "improved" CCRM, which is where the fuel pump relay is on the '96.

I am thinking that the problem could be along the lines of a weak electrical connection for the wiring for the injectors....as that gets flexed during the lower intake manifold removal.
Other thing is a vaccum leak....which would be at the passenger side of the manifold.
I have checked the vaccum connections, found 1 loose, and PCV valve popped out of the gromet....but they did not improve things.
Will look more at the vaccum connections.
The IMRC is working just fine, pulling in to the stops.
I got 1 CEL in a 525 mile trip Wednesday night, with the same codes I listed.
So, I guess it is "better", but not fixed yet.


Are cylinder 2 and 4 "sister" cylinders as far as the ignition system is concerned?

I have seen testers for fuel injector wiring and signal but I would imagine that the test is more or less binary (IE allow you to differentiate between working or not but perhaps not intermitant troubles.

You may have something amiss with the fuel delivery system. It could be that the cleaner has only affected this system in some way ... perhaps moving something thru ("cleaning") a filter or inlet screen.

Have you tried to perform an injector power balance test? I know the rear bank of injector connectors is a little tough to access, but it might be worth the trouble.

I have not checked the injectors, other than make sure that they were clean when I had things apart. Putting a new injector in place of the #4 one, and having the same issue tells me that it was not the issue for that one.

Tracking down an intermittent issue makes things more difficult.
I plan to pull and look at the #2 spark plug.
I did look at the #4 plug and it was fine, light colored, and dry, which seems to indicate that the issue with #4 cylinder is not ignition (spark) related, or that plug would be dark (carbon) and / or wet.

I also plan to look at the vaccum lines that connect to the back of the upper intake manifold. They were all in place, and everything is working....as in IMRC, heater controls, etc, so if I have a leak further down in those lines.....it is a leak, and not a completely open line.

At least, I am confident that it is not coolant causing the problem.
Also, the sensors, coolant, intake air, etc are all working just fine, as I have monitored them with my scan tool.

I just looked up how the 3 coils are paired up.
with PCM connector facing you, first listed # is closest to PCM connector
Coil #1 Far right , #1 and #5
Coil #2 Far left, #3 and #4
Coil #3 Center, #2 and #6

In the PCM connector,
Pin 1 (left) Coil #2,
Pin 2 Coil #3
Pin 3 Coil #1
Pin 4 Battery voltage.

I do not know how to do a injector power ballance test, and if it requires any special tools, I would take it to the mechanic.

I will continue to look, and be open to ideas.
Certainly will post what I find.

Good thing you have a scan tool, since you're likely to set an error code during the test. You'll need a scanner and/or tachometer (forget the in-dash tach, since it is about as refined and accurate as a hand grenade). You'll also need a note pad and crayon. If you're lucky enough that they let you have a sharp pencil or pen, use that. I'm stuck with crayons, chalk, and things with which I can't hurt myself.

Start and warm the engine to operating temperature. Shut it off, disable the idle air valve (unplug the PWM solenoid connector). Turn the throttle stop about 4-5 turns to increase idle air, then start. Adjust the throttle air to maintain about a 900 RPM idle, counting the total turns from the original position. Assuming the throttle stop screw for minimum air position is/was set properly, mark it or count the turns required to maintain an idle RPM. Restart the engine if you can. If it will not idle, adjust for more idle air until it will run. Disconnect the vacuum line from the fuel pressure regulator and plug it to prevent the leak. (A second sharp pencil works great for this.) This will assure full and steady fuel pressure regardless of idle vacuum changes, and provide a more accurate test. Changing fuel pressure due to idle changes will skew the results. Note the idle RPM. This will be the basline RPM. Disconnect one fuel injector electrical connector, and allow the engine RPM to stabilize. Allow at least 20 seconds for the RPM to stabilize, since a streaming or dripping injector can cause fuel puddling, and the excess raw fuel may take a while to work through the cylinder. Make a note of the RPM change for that cylinder. Reconnect the injector electrical connector and allow the RPM to stabilize again. Perform the same test on the remaining five injectors, noting the RPM change for each cylinder. Shut off the engine, reconnect the FPR vacuum line, back off the throttle stop screw the same number of turns you increased it, clear any DTCs, and remove any other diagnostic equipment (Tach, whatecer).

Any cylinder that does not have a relatively equal RPM change is suspect. Performing the test at a high idle RPM is closer to part-throttle cruise conditions since injector pulse widths are similar. Streaming or dripping injectors are difficult to diagnose, but can be identified by this test.

If you discover there is one cylinder that is not reacting, or if you determine that the replacement injector is different, don't be surprized. I've had several replacement injectors that don't flow quite the same as the original injectors. If you can spare the vehicle for a few days, remove the injectors, box them up, and send them off across the lake to Rich Jensen at www.cruzinperformance.com. He does excellent, and reasonably priced work. He will clean, test, and flow-match your injector set for about $11-12 apiece. I've had new "factory" sets that have more than 5% variation.

Thanks!
This is great information.
Yes, getting to the electrical connections on the rear injectors, on a HOT engine will be a challenge.

I also read that the factory specification for the flow test results for the fuel injectors is no more than a 5% variation.

The engine is running better, but is "not there" yet.

Have you trie the fuel pressure test. If the miss fire in the high rpm. It should be the fuel pressure problem.

Just an update....
Engine IS running much better....still has a "slight" miss at idle and low RPMs.
No CEL in over 700 miles.
5 tanks of fuel with Berryman's Chemtool B-12. More than I expected to use.
I paid my "new" mechanic, and followed his advice.....and it does seem to be working.
Fuel economy is good....at just over 20mpg on the highway. ("oxygenated" fuel that is sold in my area)