2001 Explorer 5.0 P0174 Code

[Exploder321]

The saga continues... driving home from a day trip and the car started running horribly, had to leave the OD off doing 55 on the highway to get it to run smoothly. Similar problem prior to was plug wires that had melted, so I put in a new set. Ran better, still bad though. Likely culprit was the MAF sensor, replaced it, still have problems; replaced the TPS for good measure. Checked vacuum (see my previous thread on vacuum problems), found cracks in the grey line going to the dash, as well as a problem with the EGR valve diaphragm. Fixed the leaky thin plastic line and replaced the EGR, thinking the EGR solenoid may be flakey put in a new one (all parts Standard, from O'Reilly). I did check the voltage output of the DPFE for the EGR, it was good. Still getting better, now it throws a code for the Evap circuit - so I got a new purge valve to replace the original. Evap code clears and now the P0174 shows up. Put in a new O2 Sensor in the left side, no change - still running rough, poor power, jerky throttle response. So, I don't have a problem with 'throwing parts' at this as most of the components are 20+ years old. Anyway, now I'm off the check the fuel pressure - replaced the fuel pump and filter a few years ago, I doubt its that. Another thread said to check the vacuum line to the power brake booster. Going to check that next also, as well as spraying carb cleaner and listening for idle changes. I am running out of ideas... will report back on what I found.

 

[Exploder321]

The saga continues... driving home from a day trip and the car started running horribly, had to leave the OD off doing 55 on the highway to get it to run smoothly. Similar problem prior to was plug wires that had melted, so I put in a new set. Ran better, still bad though. Likely culprit was the MAF sensor, replaced it, still have problems; replaced the TPS for good measure. Checked vacuum (see my previous thread on vacuum problems), found cracks in the grey line going to the dash, as well as a problem with the EGR valve diaphragm. Fixed the leaky thin plastic line and replaced the EGR, thinking the EGR solenoid may be flakey put in a new one (all parts Standard, from O'Reilly). I did check the voltage output of the DPFE for the EGR, it was good. Still getting better, now it throws a code for the Evap circuit - so I got a new purge valve to replace the original. Evap code clears and now the P0174 shows up. Put in a new O2 Sensor in the left side, no change - still running rough, poor power, jerky throttle response. So, I don't have a problem with 'throwing parts' at this as most of the components are 20+ years old. Anyway, now I'm off the check the fuel pressure - replaced the fuel pump and filter a few years ago, I doubt its that. Another thread said to check the vacuum line to the power brake booster. Going to check that next also, as well as spraying carb cleaner and listening for idle changes. I am running out of ideas... will report back on what I found.

It appears that there isn't voltage going to the EGR Solenoid. I attached a vacuum gauge to the EGR Valve using a T connector and a long 1/4" line so I could observe when driving, there was no vacuum going to the EGR valve when accelerating. The gauge shows 22" vacuum at idle from the source to the dash, which is normal. Yes, the brake booster and line checked good, fuel pressure 52-56 w/KOEO; 62 psi running. Need to see about a replacement connector? The wires are bent 90 deg at the plug, suspect there may be a break at that point.

 

[Turdle]

Vacuum to egr is switched by the egr vacuum regulator, so vacuum should not be present at egr valve at all times. Check for vacuum at the connection on bottom of egr vacuum regulator. It splits there to the diaphragm on fuel rail. So, if you have vacuum there it'll also be present at regulator base.

 

[Exploder321]

Further testing on the EGR solenoid shows good vacuum to it; 12 v to the connection at idle (which is correct), but isn't opening to provide vacuum to the EGR Valve. Apparently when the voltage decreases, it opens? No significant voltage drop at the connector when revving the engine. Easyautodiagnostics.com has a procedure for testing this area, but doesn't go into how to test the solenoid for the problem I'm having, only suggesting the PCM/engine computer may be fried. The DPFE checked good the other day, going to check it again.

 

[Exploder321]

Further testing on the EGR solenoid shows good vacuum to it; 12 v to the connection at idle (which is correct), but isn't opening to provide vacuum to the EGR Valve. Apparently when the voltage decreases, it opens? No significant voltage drop at the connector when revving the engine. Easyautodiagnostics.com has a procedure for testing this area, but doesn't go into how to test the solenoid for the problem I'm having, only suggesting the PCM/engine computer may be fried. The DPFE checked good the other day, going to check it again.

The DPFE checked good, is there a way to know if the PCM is bad? One way was the fuel pump not running with key on, not the case here.

 

[Exploder321]

If the EGR solenoid failed, it may have fried that part of the PCM... hmmmmmmm

PCMs typically fail for one of two reasons: voltage overloads (often due to a short in a solenoid or actuator circuit) or environmental factors (corrosion, thermal stress or vibration). If the shorted solenoid or actuator is not found and repaired, the voltage overload it creates may damage the replacement PCM, too.

What You Should Know About Powertrain Control Modules (PCMs)

 

[J_C]

When I see a code for a bank running lean, I start to wonder about the upper intake manifold gasket.

With all the vac line issues you've been chasing, I'd smoke test it.

 

[Turdle]

When I see a code for a bank running lean, I start to wonder about the upper intake manifold gasket.

With all the vac line issues you've been chasing, I'd smoke test it.

This, or a failing injector. A true vacuum leak would set a p0171 also. The code narrows it to the driver side bank.If the smoke test reveals no leaks, I would pull spark plugs, look at the ash color. If one is very white I'd replace the injector for that cylinder .
I take off the fan, then run engine using an unlit propane torch for vacuum leaks. The nozzle allows you to shoot raw propane to suspect areas, no mess.

 

[Exploder321]

The new PCM (Blue Streak Enterprises/BSE; from AutoZone) is installed and the Exploder is running, still throwing the P0174, running like crap, though the EGR valve is now operating. Planning one more run through all the lines to check for vacuum leaks, will pull the plugs on the driver side and check condition per Turdle's recommendation. Can't be a small leak for all the havoc it is causing with rough idle/acceleration. Efforts on hold for rain, inadequate garage.

Isolation to Bank 2 is a head scratcher, trying to eliminate sources that would affect both sides - like any connection to the intake manifold? I'm getting a bad feeling that the intake manifold has to come out, other threads indicate that the associated bolts tend to corrode in place with the aluminum of the manifold.

 

[Exploder321]

The new PCM (Blue Streak Enterprises/BSE; from AutoZone) is installed and the Exploder is running, still throwing the P0174, running like crap, though the EGR valve is now operating. Planning one more run through all the lines to check for vacuum leaks, will pull the plugs on the driver side and check condition per Turdle's recommendation. Can't be a small leak for all the havoc it is causing with rough idle/acceleration. Efforts on hold for rain, inadequate garage.

Isolation to Bank 2 is a head scratcher, trying to eliminate sources that would affect both sides - like any connection to the intake manifold? I'm getting a bad feeling that the intake manifold has to come out, other threads indicate that the associated bolts tend to corrode in place with the aluminum of the manifold.

Hindsight being 20-20, there should be a standard maintenance procedure for accomplishing an engine tear down in order to apply anti-seize lube to every bolt before they have the chance to corrode and break.

 

[Exploder321]

Rain abated, ran the code scanner - now along with the P0174 is a P0352: ignition coil B Primary and Secondary windings. Coil B, corresponds to Coil 2, drivers side - which has been the consistent side of the lean bank problem. When this initially happened, the other coil indicated misfires (for any number of reasons at this point) and was replaced; the other coil is now throwing the P0352. I'm wondering if the old PCM wasn't picking up on the problem, or the coil is now failed to the point where the problem is obvious to the PCM? Did drive it for an hour last night, it's cold now... may be contraction in the coil is making the failure more apparent (the coils are CarQuest Premium, about a year old - FWIW - Limited Lifetime Replacement).

 

[Exploder321]

The plot thickens... replaced the drivers side coil, still runs like crap after it warms up a little, the lean bank codes are gone but the P0352 code remains.

 

[1.8TTony]

.....still runs like crap after it warms up a little

Are you saying the engine runs fine before it warms up?

If so, I'd suspect the Ambient Air Temperature sensor has failed.

 

[Turdle]

Check the corresponding spark plug.

 

[Exploder321]

Are you saying the engine runs fine before it warms up?

If so, I'd suspect the Ambient Air Temperature sensor has failed.

It runs, still has a miss, but gets much worse as it warms up. I'm at a loss at this point, out of time to spend on it, going to let the mechanic go through it and see what he finds.

Check the corresponding spark plug.

Funny thing, after a burst of energy I went back and checked the plugs on the driver side, pulling each boot and reseating. As I was working on the #7 plug wire, the wire for the #8 just fell away . The back two wires have the metal shells, I must have gooned it on #8 thinking it seated when it didn't. Upon inspection, the plug boot had recessed into the metal shield beyond where it would have connected.

At any rate, reconnected it, swapped the coils, cleared the codes, drove it. Still rough idle, though it has power and doesn't knock, shifts good and the P0174 and the P0352 came back - I'm thinking it could be the intake manifold gasket, or possibly a fuel injector, maybe a fuel pressure regulator diaphram (only checked one, held vacuum OK). Off to the mechanic in the morning.

 

[Exploder321]

Took a break for a few months for the weather to improve. Decided to replace the fuel injectors, and the plenum gaskets. The connectors on the injectors were brittle like potato chips and just broke away, so had to replace those as well. I did find two vacuum leaks getting past the gasket to the lower intake and at the EGR housing to the plenum. Worthwhile effort, sort of - I think I can use the original injectors to upgrade the '93 Bronco - so, I fired up the Exploder and same symptoms, missing on cylinders #3 and #5, this is after replacing the ignition coil. The existing coil was replaced a year ago, this morning the spark tester indicated no spark from the coil for #3 and #5, so I got a replacement. Cleared the codes, #2 (P0352) came back, testing the wire and found that it was likely bad - came apart at the boot internally leaving the metal terminal on the spark plug. Replaced that thinking 'this is it!' No dice, now no spark on the new coil, #3 and #5, direct testing after seeing the codes. Now I'm really stumped. Is there a problem with the wiring or the signal to the coil? How does one trouble shoot that? The PCM was changed earlier in this pitched battle after being fried by the EGR solenoid. At some point this thing should run like new if I can run this problem to ground. My cousin said to push it off a cliff... I'm not there yet.

 

[Exploder321]

It runs, still has a miss, but gets much worse as it warms up. I'm at a loss at this point, out of time to spend on it, going to let the mechanic go through it and see what he finds.

Funny thing, after a burst of energy I went back and checked the plugs on the driver side, pulling each boot and reseating. As I was working on the #7 plug wire, the wire for the #8 just fell away . The back two wires have the metal shells, I must have gooned it on #8 thinking it seated when it didn't. Upon inspection, the plug boot had recessed into the metal shield beyond where it would have connected.

At any rate, reconnected it, swapped the coils, cleared the codes, drove it. Still rough idle, though it has power and doesn't knock, shifts good and the P0174 and the P0352 came back - I'm thinking it could be the intake manifold gasket, or possibly a fuel injector, maybe a fuel pressure regulator diaphram (only checked one, held vacuum OK). Off to the mechanic in the morning.

The mechanic was stumped, after two weeks he said he thought it was likely a fuel injector and he couldn't spend any more time on it with other jobs backing up.

 

[Exploder321]

Took a break for a few months for the weather to improve. Decided to replace the fuel injectors, and the plenum gaskets. The connectors on the injectors were brittle like potato chips and just broke away, so had to replace those as well. I did find two vacuum leaks getting past the gasket to the lower intake and at the EGR housing to the plenum. Worthwhile effort, sort of - I think I can use the original injectors to upgrade the '93 Bronco - so, I fired up the Exploder and same symptoms, missing on cylinders #3 and #5, this is after replacing the ignition coil. The existing coil was replaced a year ago, this morning the spark tester indicated no spark from the coil for #3 and #5, so I got a replacement. Cleared the codes, #2 (P0352) came back, testing the wire and found that it was likely bad - came apart at the boot internally leaving the metal terminal on the spark plug. Replaced that thinking 'this is it!' No dice, now no spark on the new coil, #3 and #5, direct testing after seeing the codes. Now I'm really stumped. Is there a problem with the wiring or the signal to the coil? How does one trouble shoot that? The PCM was changed earlier in this pitched battle after being fried by the EGR solenoid. At some point this thing should run like new if I can run this problem to ground. My cousin said to push it off a cliff... I'm not there yet.

Just found this, possibly the Crank Position Sensor... =:-o Part 3 -Ignition Coil Test -No Spark No Start Tests (Ford 4.9L, 5.0L, 5.8L)

 

[allmyEXes]

That happened to be what was wrong with the '97 4.0 truck that is my wife's. I repaired it with a new connector and wired it backwards. I had to swap the wires on the Crank Position Sensor then it worked. It took me twice as long to fix but it hasn't been a problem since.

 

[Exploder321]

That happened to be what was wrong with the '97 4.0 truck that is my wife's. I repaired it with a new connector and wired it backwards. I had to swap the wires on the Crank Position Sensor then it worked. It took me twice as long to fix but it hasn't been a problem since.

Thanks! It will be next weekend until I can get to it. It better run like new after that!