Fuel injector failure.............I guess

[dochidalgo]

After the MAF,IAT,IAC and Throttle body cleaning, gas air & oil filters, spark plugs replacement, I got a DTC P0300 (XXI century....it could be more specific, for Christ's sake!!!). Stumble/hesitation presented after 20 minutes (closed loop) after the engine was started, never in cold start or open loop. The scan tool signed the cylinder number 4.
Electric system check was performed (I mean: spark plug exchanged with the "neighbours", wire, injector IAT IAC MAF's harnesses, even a PCM OEM reprogrammed to stock). The fuel pump delivers 42 lbs yet!!!. Same culprit...cylinder #4
So, the poor fuel injector clogged, too dirty or damaged was the culprit by exclusion......as always...

My questions are: Should I replace the 24 Lbs fuel injector stock alone or since the engine is 56K miles old, Should I replace the whole set?..Now, I found a Delphi/Lucas 28lbs set a very good price ($199 vs $128 ONE!! OEM fuel injector !!!...this world is crazy..indeed).
Could a 28 LB fuel injector be installed in my stock fuel pump and engine without a problem? Will the miles per galon rate increase?

I would appreciate your point of view
Thanks
Dochidalgo

[Injuneer]

You could probably get the stock injector for less than that from Dal???

If you upgrade to the 28's, you have to have the PCM programmed for the correct flow constant. Not a problem.

Either way will work fine. The stock fuel system will easilly support 28# injectors, and your engine won't use them to their full capacity anyway. 24's would be adequate. A 28 will just have a shorter pulse width, and the resulting lower duty cycle. You will notice no difference in the way the engine performs, good or bad - well, other than eliminating the miss on #4 if that is the cause.

Did you try swapping another injector with #4 to see if the problem moved with the injector?

[dochidalgo]

Yes Fred, I'm going to call Dal monday morning. But....
Today, The fuel injectors were professional cleaned and I feel a big difference in the engine performance. The mechanic did not want to do a fuel injector swap or dismount them because he was afraid to damage some O rings. It's very difficult to get some parts in this town.
This is the link about the Delphi/Lucas Racetronix fuel injector kit flow matched:
http://www.thunderracing.com/catalog...vid=4&pcid=163

However, A few minutes ago, I returned home and the SES light was ON again.
Now, the DTC were P1441 (Evap System Flow during Non Purge) DTC P0154 (HO2 S Insufficient Activity) DTC P0155 (HO2S Heater Circuit Bank2) and DTC P0122 (TP sensor Circuit low voltage). So, I'm not an expert but seems to me the electrical harness where are the Evap selenoid or valve, TP and Oxygen sensor wires (passenger side) is burnt somehow and somewere. Are you agree with me? or am I miss out something?
Now I recall when they swap the PCMs....it has 4 harness connectors with 4 different colors. Perhaps one of the harness involves the wires from that parts in trouble.....???
Gee, I prefer to do some clinic diagnosis in my patients....this mechanic issues make me crazy....
Fred, thank you
Dochidalgo

[dochidalgo]

Today I checked, clean with electronic cleaner the electrical connectors, even the 4 from the PCM.
Well, the DTC P0300 is there. The P0154 was there when the engine swap from Open loop to closed loop. I clear the DTCs and the P0300 came back again only.
Some data:
HO2S1B1: 550-650
HO2S2B1: 30-45
HO2S1B2: 260-350
HO2S2B2: 35-40

STFTB1: 0% 127
STFTB2: 31% 96
LTFTB1: 0% 127
LTFTB2: 19% 108
IAPWB1: 5.3
IAPWB2: 3.2
IAT 117ºF
MAP 46 kPa
Baro 99kPa
ECT 185ºF
IAC 59-60 counts ??? (closed loop)
MAF 10.8-11 g/s

Thanks for your imput

Dochidalgo

[Rob B (shoebox)]

Have you checked the plug wire(s) with an ohmmeter?

[dochidalgo]

No, Rob.....
How many ohms should be?...10 000 or 1000 ohms?

Thanks
Dochidalgo

[Rob B (shoebox)]

No, Rob.....
How many ohms should be?...10 000 or 1000 ohms?

Thanks
Dochidalgo

It can vary widely, depending on the brand of wire. Comparing a few wires would be a good idea.

[dochidalgo]

Ok Rob. The wires are the stock ones (8 years old) yet.
I'll check the data.
Thanks
Dochidalgo

[Rob B (shoebox)]

Ok Rob. The wires are the stock ones (8 years old) yet.
I'll check the data.
Thanks
Dochidalgo

You might expect ~ 800-900 ohms per foot for stock wires. Some aftermarket ones are 100 ohms/ft or lower (that does not necessarily mean they are that much better). IMO, as long as the wires can pass the voltage that the coil puts out, they don't need to be any lower resistance. If you run a mega-zillion volt coil, then you might need some better wires to make use of that voltage. I run stock wires with no problems.

[Injuneer]

Its always difficult to do an evaluation with a single frame or two from a scanner. The big problem is the O2 sensors, since they are actually changing about 9 times per second. That's why I can't just take the 2 readings as meaningful, because if they were, it would show the Passenger side running lean. But that's not what everything else is showing.

The PCM is trying to correct a RICH condition on the passenger side by deducting about 50% of the fuel that should be flownig to the passenger side of the engine. The long term corrections have bottomed out at 108, so the PCM has dropped the short terms to 93 to try and reduce the fuel further. The pulse width confirms this, with the passenger side injector pulse only about 2/3 of the drivers side pulse width.

But, the drivers side pulse width looks very high. Under what conditions did you capture this frame of scanner data? Appears the engine was not at idle.... MAP is 46kPa, which indicates the throttle is open. Exactly how was the engine being operated when you captured that frame?

A misfire will generally cause the PCM to see a false lean condition, and start to add fuel using the long term corrections. But yours is reducing fuel. That means its trying to correct what it sees as a rich condition. That is the possible result of an injector that is stuck open. The cylinder consumes all the oxygen, and then releases the combustion products and the unburned excess fuel on the exhaust stroke. The unburned fuel combines with the small amount of residual O2 in the exhaust, and it causes the O2 sensor to think the engine is running rich.

So.... one possibility is a leaking injector. The check would be to pull the rails up, pressure the fuel system and see if there are drips out of the #4 injector. You could also just try checking the fuel pressure by turning the key on (not starting engine) and then turning it off. Watch how quickly the fuel pressure drops from the 40psi range. A fast drop might indicate a leaking injector.

While it is good to be concerned about damging the injector O-rings, I've pulled the injectors many times without damaging them. Might want to spray a little WD40 into the sockets before you try and pull the injectors out. Or, have him order a set of O-rings in advance.

[dochidalgo]

Fred:

The frame data was taken at idle, 8 hours after I cleaned the harness connectors from TP sensor, fuel injectors, EVAP puge selenoid and valve, even the PCM 4 connectors. When I saw the IAC counts I performed a reseting procedure, the exhaust made a big explosion (gas not burned?) when I start the engine.

I replaced both precat oxygen sensors because that kind of readings. Obviously that was not a smart decision. A year ago, the P0300 was set because the cylinder one; a professional fuel injector cleaning solved the problem.

You're right about the O rings, but I was not supported by the mechanic in order to perform the injector swap or test the flow pattern. He assured to me the gas pump reached the 42 psi and stayed at 40 psi several minutes after the engine was off.

With all your diagnostic procedure I could confirm that a fuel problem, fuel injector specifically, is the cause of my engine problem.
I couldn't thank you enough for clarify for me those scanner data and lead me to the diagnosis. If you have another ideas, they will be welcome.

I'm going to purchase a new set of fuel injectors. Racetronix Delphi/Lucas 24 lbs (disc design.. no pintle.....better??) is my choice unless you advice me otherwise. The ""mexican't gasolines are dirty and uncertain quality, the fuel pumps have paid for that, many friends of mine had to replace theirs because the gasoline, my car's fuel pump has escaped but the fuel injectors don't.

I truly appreciate your time and your knowledge.
Dochidalgo