2.5L ('98-'01) P0442 rough idle and stalling. Everything checks out.

[ben_2_go]

@RonD can you add any advice on this?

Let's start over from the beginning a few months back. Symptoms = Rough and variable idle, stalls when stopping, down on power, spark knock under any load level, and sometimes while coasting. This was not a gradual thing that happened. I was driving and everything was normal. Stopped at a red light and the truck died. Restarted fine with a low erratic idle.

Truck is 2001 2.5L 4R44E automatic 2wd no modifications at all. Engine/trans has never been touched except to do scheduled maintenance.

Well, same code I've been getting, but with different info with code. Problem still unresolved. Before the code said, "EVAP small leak detected", and nothing else. Screen shot shows the new info. Here is a list of what I have done since this started. Somethings I replaced due to age and it was maintenance time. Somethings I replaced because they're known to throw a P0442 code. Truck is a daily driver. I put about 100 miles a week on it.

I drained and refilled the fuel tank with fresh 93 gas.
new Fuel filter
New IAC
New purge valve-corrected the stalling when stopping issue, didn't improve erratic idle or spark knock
New timing belt
new cam position sensor connector- improved overall running condition, didn't improve erratic idle or spark knock
new PCV valve and hose
new ignition coils
new spark plugs
new spark plug wires
new egr valve
new DPFE sensor and connector-Corrected a DPFE code, improved overall running condition, didn't improve erratic idle or spark knock
New EGR/DPFE hoses
new EGR to manifold hard line
new intake gaskets
replace hose and check valve to brake booster
Several new vacuum hoses I thought were suspect and old.

I've sprayed all kinds of stuff around the intake and vacuum lines looking for leaks. Nothing changed the idle. Smoke test showed no issues. Checked heat/AC controls for vacuum leaks and no issues there. Checked the vacuum accumulator (aka the black ball) with no issues found. The only thing I haven't replaced is the evap canister solenoid and the fuel tank pressure sensor. I don't know what else to try. Everything I have done has improved the idle to the point it no longer dies when I stop. Nothing has helped the erratic idle or spark knock issue. I've had two well established shops, that my friends own, look over the truck. They all come back to bad IAC valve. I've been through 4 including the OE. The OE unit cleaned up is the only one that doesn't cause stalling issues. If I do the tests on the IAC and throttle position sensor, they all check out. I'm not talking about the unplug/replug tests. I'm talking about the full on diagnostic tests using a scan tool and electric multimeter just like any quality shop would perform. I am at a complete loss. I have no other vehicle to drive. I know I am damaging the engine running these hills and mountains with the truck spark knocking the entire time I am driving.

I was an ASE certified tech from '1993-2003 when I dropped out of the industry to pursue my aviation career. I've never been defeated so badly by a vehicle, ever! I'm almost to the point of parting out the truck. I won't sell a bad running vehicle, ever.

 

[-Nate]

This is a real head scratcher .

I'm too old to ken OBDII, I replaced the IAC valve on my 2001 2.5L and it *instantly* ran better and the stalling stopped .

I cleared the codes the old fashioned way by disconnecting the ground battery cable before working on it and using a jumper between the cables, it whistled through the SMOG test *except* the monitors weren't ready, apparently I need to put some miles on it before they'll be 'ready' whatever the hell that means .

In California the A.Q.M.D. rules say the monitor not ready is to be ignored on 99 ~ 200? gasoline powered engines but the dufus at the STAR SMOG station didn't know that so now I guess I have to drive it a few hundred miles then have my son check the codes and if the monitors are ready take it back so it can pass .

Interestingly the HURKO (?) brand IAC valve also made the throttle response much smoother .

I'm keen to learn what's ailing your truck .

 

[RonD]

EVAP codes generally don't cause running issues, P0422 "small leak", for sure won't cause running issues
And it's not a direct "vacuum leak"
The computer uses vacuum to put negative pressure in the gas tank, then closes all EVAP valves and watches the gas tank pressure sensor to see if it holds the negative pressure long enough to "pass the test"
If it holds pressure but not long enough then P0442 "small leak"
If it doesn't hold pressure at all then P0455 "big leak"
And this can be a computer issue, error in EVAP software

You can apply vacuum manually to Gas Tank and see if it holds negative pressure, if it does then bad pressure sensor or bad computer
If it slowly looses pressure then code is correct, there is a small leak, you can then apply less than 3psi positive pressure and see if you can hear the leak, more than 3psi can blow off EVAP fittings



1998-2001 2.5l SOHC wasn't as prone to pinging on 87 octane because it runs 9.1:1 compression ratio
The 1994-1997 2.3l SOHC ran 9.4:1 CR and would ping on 87 octane if anything was out of spec, lol

You can do a compression test and should see 155-165psi
If its at or above 170psi then there is carbon build up issue
But the 93 octane fuel should take CR off the table

The 2.5l SOHC will start and run using only 1 coil pack(1974 to 1988 4cyl SOHC ran just fine on 4 spark plugs )
So I would unplug the 3 wire connector on one of the coil packs and start engine
Drive it and see if pinging is the same, any steady misfire means a spark plug or wire on the working coil pack is bad
One of the down sides of Dual Spark plugs is that you can never tell when one spark plug or wire in one cylinder fails, lol
Then test other coil pack the same way

You should get a code when a coil pack is unplugged, but it will go away on its own when its plugged back in

If pinging is gone when only 1 coil pack is in use then could be computer is not firing the coil packs at the exact same time, not sure there is any other test for that, so computer would need to be replaced

I would expect Lean Codes if fuel pressure was low enough to cause pinging, but not hard to test fuel pressure, should be a test port on fuel rail, 60psi is expected, but would need to be under 35psi to cause an issue


When you have tested and taken things "off the table" then you are left with computer issue, and there is no test for that
You can unplug sensors one at a time and make sure you get the correct codes, basically a "sanity test" for the computer, but not conclusive on if its operating correctly

 

[ben_2_go]

@RonD thanks. You helped me a while back with some of these same issues caused by my IAC. I did most all the test you speak of back then. My recurring P0442 may be because I need to replace the filler tube from my filler neck to the tank. I have that part on hand. I cleaned the OE Ford IAC and reinstalled it again. This time I disconnected the battery and left it disconnected while I did other stuff for a few hours. I took my truck for a 30 mile drive. The idle is way more stable, the P0442 code is gone, and the spark knock issue has drastically reduced for now. If the spark knock that I have now doesn't get worse, I can chalk it up to probably a bad tank of fuel. I made a mistake and got fuel from one of the worse stations in my area because I needed fuel late in the evening. I should have only gotten a few gallons but I filled it up. Oops. I'm going to consider this solved for now. If anything changes, I will be back with an update. Thanks again for your help over the years, RonD.

 

[-Nate]

Wow Ron ;

I love your knowledge and ability to write it do folks can grasp what's what .

 

[ben_2_go]

Well, I'm back to square one. Idle is off but not bad and the spark knock is back to being really bad. I failed to mention that when I replaced the EGR system I also replaced the oxygen sensors. There wasn't any really bad carbon on anything. I absolutely can not wrap my head around what would be causing this spark knock issues. 93 octane fuel doesn't seem to make a difference either.

 

[RonD]

What are you using for spark plugs
AGSF32FM (SP432)
Gapped at 0.044"
If the spark plugs you are using are a hotter heat range that can cause the knocking

Does it knock when cold or only after it warms up?

 

[-Nate]

Just for shiggles, try applying vacuum to the E.G.R. valve at idle, the engine should stumble or stall .

If not the valve may well be stock open by accumulated carbon deposits .

Also, the E.G.R. valve *must* hold vacuum indefinitely .

 

[ben_2_go]

What are you using for spark plugs
AGSF32FM (SP432)
Gapped at 0.044"
If the spark plugs you are using are a hotter heat range that can cause the knocking

Does it knock when cold or only after it warms up?

Denso Platinum TT 4511 pre-gapped but I checked and they're spot on.

Mostly when the truck is hot and been driven for awhile

Just for shiggles, try applying vacuum to the E.G.R. valve at idle, the engine should stumble or stall .

If not the valve may well be stock open by accumulated carbon deposits .

Also, the E.G.R. valve *must* hold vacuum indefinitely .

I rebuilt the EGR/DPFE system and changed all of that around 300-500 miles ago. It does shut down with a vacuum on the EGR at idle.

 

[-Nate]

Never, EVER believe in nor trust 'pre gapped spark plugs ! .

Just -once- you need to see how the cases are thrown around and you'll see why not .

 

[ben_2_go]

Never, EVER believe in nor trust 'pre gapped spark plugs ! .

Just -once- you need to see how the cases are thrown around and you'll see why not .

Yep, I always check'em.

 

[ben_2_go]

What are you using for spark plugs
AGSF32FM (SP432)
Gapped at 0.044"
If the spark plugs you are using are a hotter heat range that can cause the knocking

Does it knock when cold or only after it warms up?

Last night I had to do a nearly 100 mile round trip. The truck kept randomly dropping a cylinder. I did the uplug one coil and drive test. Everything is new from the coils to the spark plugs. Both coils would randomly drop a cylinder. Both coils and spark plug wires are Motorcraft branded parts. Spark plugs are Denso Platinum TT. All quality parts that I'm familiar with. I'm not sure if it's possible to test the signal coming from the ECM to the coils. I know I can test the coils, and I will once all this rainy weather breaks. Spark knocking stopped while running on one coil even though it kept dropping a cylinder. Am I looking at this wrong? Could this be an injector issue or possibly a ECM issue?

 

[RonD]

From the test of driving with just one coil pack connected and having the pinging/knocking going away I would suspect PCM(ECM/Computer)
(did the pinging go away with either coil pack unplugged?)

There are 2 coils in each coil pack, so 4 coils total
2.5l PCM has 4 separate Coil "Drivers"
If one of the coil drivers is "off-time" you can get pinging
Pinging/knocking "noise" is from a secondary explosion in one cylinder, which can be pre-ignition or detonation
Running dual spark plugs requires that both spark plugs/Drivers in a cylinder spark at exactly the same time, so just one primary explosion that consumes all the fuel

Running on just 1 coil pack, either one, eliminates off-time spark since the other spark plug in that cylinder is not firing at all


4cyl Rangers didn't get PATS(passive anti-theft system) until late 2001 with the 2.3l Duratec engine PCMs
So swapping your PCMs is plug and play, just needs to be for a 2.5l and match transmission type
Manual trans PCMs are different from Automatic trans PCMs in any year with any engine, so not interchangeable

 

[ben_2_go]

From the test of driving with just one coil pack connected and having the pinging/knocking going away I would suspect PCM(ECM/Computer)
(did the pinging go away with either coil pack unplugged?)

There are 2 coils in each coil pack, so 4 coils total
2.5l PCM has 4 separate Coil "Drivers"
If one of the coil drivers is "off-time" you can get pinging
Pinging/knocking "noise" is from a secondary explosion in one cylinder, which can be pre-ignition or detonation
Running dual spark plugs requires that both spark plugs/Drivers in a cylinder spark at exactly the same time, so just one primary explosion that consumes all the fuel

Running on just 1 coil pack, either one, eliminates off-time spark since the other spark plug in that cylinder is not firing at all


4cyl Rangers didn't get PATS(passive anti-theft system) until late 2001 with the 2.3l Duratec engine PCMs
So swapping your PCMs is plug and play, just needs to be for a 2.5l and match transmission type
Manual trans PCMs are different from Automatic trans PCMs in any year with any engine, so not interchangeable

No knock or ping with just one coil active. The power is way down with either coil active and a random cylinder would drop out with either coil active. It was way worse on one coil than with both. It wasn't constant like a dead spark plug.

 

[RonD]

See if you can get a timing light, like $5 at a garage sale or maybe a friend has one, lol
I would check the timing on #1 on both coil packs, warm idle should be about 20deg BTDC

No pinging with only 1 coil pack in use would point me at PCM issue in a 1995 and up 2.3l/2.5l lima
Not definitive but certainly could be the issue