Too much fuel being injected in 1998 5.0

[1998rollover]

What causes the PCM to decide there's not enough fuel being injected and respond by opening the flood gates?

I've replaced the injectors, pressure regulator, fuel pump, filter, throttle position sensor, oxygen sensors, catalytic converters, plugs, wires, coils and cleaned the MAF, throttle body and IAC with appropriate cleaners.

It has a cat back dual exhaust too, but it was having issues before that with a persistent 0175 code.

Now it randomly has any or all of 1320, 1321, 1322, 0171, 0172 and 0175 codes.

I looked up the numbers on the Delphi FJ10236 injectors and they're supposedly the same 19lb flow rate as the original F6VE-A5A. I'm tempted to try some of the white 17lb injectors to see if those will cut the fuel flow down to what it should be. It pours in so much excess fuel that it only runs decent at over 65 MPH.

Could it be something gone wrong with the PCM and it's defaulting to a fail safe mode to avoid running too lean and melting the cats?

The vacuum line to the reservoir for the blend door got melted through (AC only out defrost). I repaired that but now it's doing the thing where under hard acceleration it switches to blowing hot air out the dash and sometimes shuts off the cruise control. The only hard line I could get where that happened was a bit smaller inside diameter. Too restrictive?

 

[shucker1]

I saw no mention of the coolant temperature sensor being replaced.

I think that year uses (2) coolant sensors. One runs the dash gauge and the other communicates with the PCM.

If the PCM thinks the engine is too cold it's going to stay in "Open Loop" and try to add fuel to warm up.

Rather than throwing parts at it you could get an active scanner that can tell you what kind of inputs the PCM is seeing.

 

[1998rollover]

Lemme guess, that coolant temp sensor is one item that will not cause a code if it fails or is out of spec? I do have a Harbor Freight branded version of an older Autel scanner, (only the name is changed, function and software identical) bought off Craigslist for $75 because it could read ABS codes - except it turned out to NOT be able to read the ABS on late 1990's Fords. I'll see if it can check the CTS readings.

I'd like to get the PCM flashed to the last factory update, I know it's not the latest in it and the updates address some spurious issues with O2 sensors and false readings of out of spec converter efficiency. None of the dealers around here will do squat on old Fords, they got rid of their NGS and WDS systems. I bought a VCM2 clone but the Ford IDS software falsely claims a "communication error" with the PCM when attempting to do certain tests or update the PCM. I know it's a bogus error because FORscan can do the exact same tests with the same hardware. IDS then helpfully pops up a note (minus any useful details) about updating the PCM out of the vehicle.

If only I'd needed/wanted an NGS 10 years ago, could have snagged one cheap when the dealers were dumping them. Now it'll cost a couple grand for a full kit with all the cards.

 

[CDW6212R]

I would see about getting it connected to a late diagnostic tool, and see if something in there will point to the issue. I too think it's something like an O2 sensor etc, that is telling the PCM to richen the fuel.

I'd like to get those Ford tools myself, but hadn't thought about it enough to make it a priority. They can be very helpful at certain times. Good luck,

 

[CDW6212R]

What are your TPS voltages, and how old are the O2 sensors?

 

[1998rollover]

THE OXYGEN SENSORS ARE ALL NEW

If you're thinking about asking if I've changed something else, read my list of what I changed already. Same @#%@#% as on computer forums where people *do not read every word* then tell the person to do exactly what they already said they tried which did not work.

Is there really any difference in the O2 sensors by price or brand?

Which temp sensor is for the PCM and where is it on the engine?

 

[shucker1]

Easy, Easy folks are trying to help you out. No need to start yelling.

Is there really any difference in the O2 sensors by price or brand?

Yes. In my opinion.

Before you start chucking money on sensors at the truck like I mentioned before you need to try and read the actual data going to the PCM.

Your not looking for codes but actual RAW values it is being given to work with.

That would be my first step. I think most guys use FroScan and an ELM327 converter to read input date like oil pressure, air temp, coolant temp that the computer needs to run.

How about a really stupid question? Have you ever tried to reset the computer by disconnecting the battery for about 30 minutes or so to let it try and relearn itself?

 

[1998rollover]

Yup, disconnected the battery, overnight once.

 

[VR4]

P1320, 21, and 22 are not even listed in the pced. Not valid codes for the truck. Try a couple other scanners and if they all report the same it's gotta be something in the computer.

 

[Dono]

I see you changed the injectors. even though the flow rate is the same, the injector slope might be different. My first life lesson on this was with some eBay injectors and my 4.0ohv. edit.... oops, I see you changed injectors to try to fix your current issue.

Check your sift's and ltft's with forescan. The front o2 sensors tell the pcm what the fuel ratio is at in closed loop(truck warmed up, back to the temp sensor idea). if the fuel trims may show that the pcm is removing as much fuel as it can, and you are still running really rich.

 

[Centaurus5.0]

Did you reuse your old upper-to-lower intake gasket when you replaced the injectors? All of your vacuum hoses connected good?

P0175 = Vacuum Leak



*Edit*


"The vacuum line to the reservoir for the blend door got melted through (AC only out defrost). I repaired that but now it's doing the thing where under hard acceleration it switches to blowing hot air out the dash and sometimes shuts off the cruise control. The only hard line I could get where that happened was a bit smaller inside diameter. Too restrictive?"


Sounds like you have a major one.

 

[1998rollover]

I used new gaskets. Also used a new PCV valve and grommet. Had to use some RTV to glue the grommet into the intake.

Is there a place I can send the PCM for testing and updating with the latest software etc?

 

[VR4]

P0175 is not a vacuum leak. P0171/p0174 is 98% of the time a vacuum leak on a ford.

172/175 is usually a bad PCM or maf

 

[Centaurus5.0]

How many miles are on the engine?

Weak/broken valve spring can cause air to blow past the valves and can signal to the O2's for more fuel.

VR4: Yeah, you right.

 

[1998rollover]

Not the engine coolant temp sensor. Got up to 185F then started surging at idle, and even when I revved it up to around 2,000. I checked the MAF reading and at idle it showed 0.02 lb/sec where it stayed unchanging while surging. When I revved it up it went up to 0.04~0.05. Shouldn't that track with the surging RPM if it's not the cause of it?

Looks like when it's supposed to go to closed loop, instead it cracks the injectors wide open.

Edit: Checked my other 1998 and its MAF reading is only 0.01 at idle and correspondingly lower at around 2000 RPM. Hrrmmmmm. Difference between 0.02 and 0.01 is 1.2 lb/m VS 0.6 lb/m. Welll now, if the MAF is mis-reporting too much air then the PCM should respond by injecting too much fuel, eh?

Edit 2: Picked up a used MAF and it reads the same flow. Switched MAFs from the other 1998 which runs properly and guess what? In the sick rig it shows a minimum of 0.02 while the one from it installed in the good running one idles at 0.01! So it's not the MAF *reporting* incorrectly, something is causing it to be *read incorrectly*.

I have a CENTECH 60794 which is identical to some Autel model. Exactly the same software, just with the CENTECH Harbor Freight branding. Autel hasn't sold it in a long time and has stopped releasing updates, but it's still available from HF.

 

[VR4]

Switch to metric to read the maf. G/s is much more accurate

 

[Turdle]

did you swap the entire housings or just the sensors? Reason I ask, is turbulence , lack of or excessive, can cause weird readings from a maf sensor. Could the prescreen be clogged or dirty? different air filters? Something (foriegn debris-dirt-mud) in the sampling tube of the maf housing?

 

[1998rollover]

Swapped whole thing. The sensor is secured with a pair of security Torx screws with one filled with a blob of epoxy. I left the sensors swapped since the vehicle that runs fine still runs fine with the MAF from the one not running fine.

 

[shucker1]

Since you are still getting strange readings with a know good Air Flow sensor and the suspect faulty unit works fine on another rig, my next stop would be to start taking a hard look at the wiring between the sensor and the PCM.

Especially any associated grounds.

A bad ground on a computer system will drive you nuts. (Don't ask me how I know...)

 

[Rich A]

1998rollover,

I see you have a scan tool, have you checked/compaired the;
TPS "Throttle Position Mode" against the "Absolute Throttle Postion %"
or the
MAF "MAF lb/min" and "Engine Load %"?


Do you have a digital multimeter?
Have you checked TPS voltage signals and MAF voltage signals and resistant?