1993 F150 EGR Diaphragm leak
01-05-2019, 07:45 AM
#1
1993 F150 EGR Diaphragm leak
Greetings.
I have a previous thread here: https://www.f150forum.com/f10/4-9l-h...433958/index4/
I think I narrowed down the issue to a vacuum leak in the EGR Diaphragm on my truck.
As you can see in that thread, I was told that the EGR is "designed to leak". I have seen conflicting information about this all over the web, and I'm hoping that this thread can focus on this specific part and whether or not the designed leak is true or not. I've spoken to multiple ford techs still in the industry and in independent shops and they are telling me that the EGR Solenoid leaks some vacuum to the diaphragm via the vacuum line allowing the diaphragm to move the Pintle off its seat faster to add the exhaust gasses to the intake tract, and then it also will bleed vacuum off when the solenoid is closed to allow the pintle to return to its closed position. I get this.
What I am seeing when smoke testing is when the intake is pressurized, smoke is leaking OUT of the diaphragm inside the EGR valve. This was confirmed to be a leak when I had the engine running, and directed a stream of propane at that same area, and you can hear the idle change. To my understanding, this should not be leaking.
I have confirmed that I have a leak somewhere in the system by doing the following:
Smoke test: EGR diaphragm is sucking vacuum at idle. Smoke emanates from the diaphragm, I cannot see WHERE exactly, due to the construction of the valve. Confirmed not to be the gasket or the egr to position sensor junction.
Propane test while running: Directing a stream of propane at the diaphragm itself causes an idle change consistently.
The smoke test revealed that the vent from the Charcoal canister is also leaking, but I think that SHOULD leak. There is also a VERY slight leak at the throttle shaft, on the TPS side.
Propane does not make the idle change when directed at these areas.
No other leaks were found with the propane or smoke method.
Truck has a high idle when warm. Idle is roughly 950-975 RPMs. This is consistent.
Ignition timing is verified at 10* BTDC, Spout out.
Truck has roughly 1K miles on a new distributor, Autolite copper plugs, Napa Belden wires, Motorcraft Ignition coil; New TB, Lower Intake, EGR, Valve cover, and IAC gaskets.
The ECM has been inspected, and with a magnifying glass there appears to be zero issue with any of the solder joints, no issue with capacitors leaking, looks factory fresh.
At idle, the IAC is sitting at 19-20 % Duty cycle. This indicates that it is completely closed according to the ford service manuals.
When you turn the A/C on, the idle does increase as it should when the compressor cycles.
When you rev the engine and shut the throttle suddenly, the IAC duty cycle increases as it should, eventually returning to the 19-20% duty cycle reading. This indicates that the IAC is operating correctly. The idle returns to its high state.
When doing a KOEO test, memory code 542 occasionally shows up. I've never had any stalling issues, so i'm guessing that its a possible connector issue as detailed in other threads on this forum.
KOER, the only code that shows up is 411. This indicates that it was not able to properly control the idle speed during the low idle portion of the test. This is true, as after you goose the throttle during the KOER test, the computer is supposed to adjust the idle much lower, and you can hear that it does not.
The TPS sensor was tested on the vehicle. .95 Volts when closed, and it steadily increases in voltage with no dead spots as you open the throttle. I have tested this with a sweeper type voltage tester, not a digital one. A digital voltmeter was used to verify the closed voltage reading.
The IAC was cleaned while I had it off of the vehicle, and appears to be operating correctly (its OEM)
The EGR valve pintle appears to be seated and properly sealing when off of the vehicle. The entire upper intake was hot tanked and all passages were cleaned when it was off of the truck.
The throttle body itself appears to be closing as it should, and all IAC passages were cleaned up while it was off the truck. Proper cleaning procedures were used to make sure no damage occurred.
The throttle stop screw appears to be unmolested, and never adjusted.
The coolant temp sensor has been replaced, as the old one was very corroded. The ohm values correspond with the actual coolant temperature, and on the scan tool the readings are correct as well when checked.
Am i missing anything here? I THINK that all my testing points directly to the EGR valve being the cause of the high Idle and code 411 at the KOER test. Is there anything else I can test? Are there any other tests that I can perform that will tell me if my diagnosis is correct? I have been through Steve83's documentation he compiled on line, and don't really see anything else I can do other than blocking off the vac line from the EGR solenoid to the valve, clearing the keep alive memory, and seeing if it idles properly. Or replacing the valve. Any additional advice would be appreciated.
On a side note, I know there is another thread about my high idle. I have read through virtually every thread about vacuum leaks, EGR issues and related issues on this forum and when it comes to the EGR valve diaphragm leaking there appears to be a lot of conflicting information.
I have a previous thread here: https://www.f150forum.com/f10/4-9l-h...433958/index4/
I think I narrowed down the issue to a vacuum leak in the EGR Diaphragm on my truck.
As you can see in that thread, I was told that the EGR is "designed to leak". I have seen conflicting information about this all over the web, and I'm hoping that this thread can focus on this specific part and whether or not the designed leak is true or not. I've spoken to multiple ford techs still in the industry and in independent shops and they are telling me that the EGR Solenoid leaks some vacuum to the diaphragm via the vacuum line allowing the diaphragm to move the Pintle off its seat faster to add the exhaust gasses to the intake tract, and then it also will bleed vacuum off when the solenoid is closed to allow the pintle to return to its closed position. I get this.
What I am seeing when smoke testing is when the intake is pressurized, smoke is leaking OUT of the diaphragm inside the EGR valve. This was confirmed to be a leak when I had the engine running, and directed a stream of propane at that same area, and you can hear the idle change. To my understanding, this should not be leaking.
I have confirmed that I have a leak somewhere in the system by doing the following:
Smoke test: EGR diaphragm is sucking vacuum at idle. Smoke emanates from the diaphragm, I cannot see WHERE exactly, due to the construction of the valve. Confirmed not to be the gasket or the egr to position sensor junction.
Propane test while running: Directing a stream of propane at the diaphragm itself causes an idle change consistently.
The smoke test revealed that the vent from the Charcoal canister is also leaking, but I think that SHOULD leak. There is also a VERY slight leak at the throttle shaft, on the TPS side.
Propane does not make the idle change when directed at these areas.
No other leaks were found with the propane or smoke method.
Truck has a high idle when warm. Idle is roughly 950-975 RPMs. This is consistent.
Ignition timing is verified at 10* BTDC, Spout out.
Truck has roughly 1K miles on a new distributor, Autolite copper plugs, Napa Belden wires, Motorcraft Ignition coil; New TB, Lower Intake, EGR, Valve cover, and IAC gaskets.
The ECM has been inspected, and with a magnifying glass there appears to be zero issue with any of the solder joints, no issue with capacitors leaking, looks factory fresh.
At idle, the IAC is sitting at 19-20 % Duty cycle. This indicates that it is completely closed according to the ford service manuals.
When you turn the A/C on, the idle does increase as it should when the compressor cycles.
When you rev the engine and shut the throttle suddenly, the IAC duty cycle increases as it should, eventually returning to the 19-20% duty cycle reading. This indicates that the IAC is operating correctly. The idle returns to its high state.
When doing a KOEO test, memory code 542 occasionally shows up. I've never had any stalling issues, so i'm guessing that its a possible connector issue as detailed in other threads on this forum.
KOER, the only code that shows up is 411. This indicates that it was not able to properly control the idle speed during the low idle portion of the test. This is true, as after you goose the throttle during the KOER test, the computer is supposed to adjust the idle much lower, and you can hear that it does not.
The TPS sensor was tested on the vehicle. .95 Volts when closed, and it steadily increases in voltage with no dead spots as you open the throttle. I have tested this with a sweeper type voltage tester, not a digital one. A digital voltmeter was used to verify the closed voltage reading.
The IAC was cleaned while I had it off of the vehicle, and appears to be operating correctly (its OEM)
The EGR valve pintle appears to be seated and properly sealing when off of the vehicle. The entire upper intake was hot tanked and all passages were cleaned when it was off of the truck.
The throttle body itself appears to be closing as it should, and all IAC passages were cleaned up while it was off the truck. Proper cleaning procedures were used to make sure no damage occurred.
The throttle stop screw appears to be unmolested, and never adjusted.
The coolant temp sensor has been replaced, as the old one was very corroded. The ohm values correspond with the actual coolant temperature, and on the scan tool the readings are correct as well when checked.
Am i missing anything here? I THINK that all my testing points directly to the EGR valve being the cause of the high Idle and code 411 at the KOER test. Is there anything else I can test? Are there any other tests that I can perform that will tell me if my diagnosis is correct? I have been through Steve83's documentation he compiled on line, and don't really see anything else I can do other than blocking off the vac line from the EGR solenoid to the valve, clearing the keep alive memory, and seeing if it idles properly. Or replacing the valve. Any additional advice would be appreciated.
On a side note, I know there is another thread about my high idle. I have read through virtually every thread about vacuum leaks, EGR issues and related issues on this forum and when it comes to the EGR valve diaphragm leaking there appears to be a lot of conflicting information.
Last edited by Axios; 01-05-2019 at 07:57 AM.
01-05-2019, 09:31 PM
#6
Martin
The diaphragm on the EGR won't make a difference at idle. Test it yourself, there is no vacuum at the EGR at idle as it is supposed to be closed. The hard line EGR to manifold cracked or broken could cause a vacuum leak at the manifold. Try pulling everything off the vacuum tree and capping. Also pull the purge line off and cap. If the idle stays high that eliminates a lot of leak points. If all else is fine it might well be the slight leak at the throttle body.
01-05-2019, 09:49 PM
#7
I see a leak at the diaphram. The egr line to the exhaust is intact and perfect. You can see it in the video I posted in the other thread. Holding my finger over the end of the green vac line at idle, I can feel a pulse. How is the egr leaking where it is, verified with smoke and propane at idle?
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01-06-2019, 08:35 AM
#8
Senior Member
I see a leak at the diaphram. The egr line to the exhaust is intact and perfect. You can see it in the video I posted in the other thread. Holding my finger over the end of the green vac line at idle, I can feel a pulse. How is the egr leaking where it is, verified with smoke and propane at idle?
01-06-2019, 12:27 PM
#9
Martin
The only way the green line will have vacuum at idle is the computer or EVR malfunctions or some other type of vacuum leak. But this problem would present different symptoms, the truck would stumble or even die. Again to solve for high idle cap vacuum at tree and purge. This will narrow down the problem area.
01-07-2019, 07:07 AM
#10
Senior Member
The only way the green line will have vacuum at idle is the computer or EVR malfunctions or some other type of vacuum leak. But this problem would present different symptoms, the truck would stumble or even die. Again to solve for high idle cap vacuum at tree and purge. This will narrow down the problem area.