EGR QUESTION
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Senior User
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EGR QUESTION
99 Ford F250LD 4x4 Lariat w/ 5.4
Still trying to diagnose p401 problem. My question is ; after reaching operating temp I have egr intermittently . It will cut off and not come back most of the time. Even on accelleration it's not always there. Sometimes I can cut the motor off and restart and it will come back. Should I always have egr vacuum after the engine reaches op. temp.
and I'm accelerating or is it suppose to be intermittent? This will tell me
if it's a vacuum regulator or pcm problem. Everything else checks out.
Still trying to diagnose p401 problem. My question is ; after reaching operating temp I have egr intermittently . It will cut off and not come back most of the time. Even on accelleration it's not always there. Sometimes I can cut the motor off and restart and it will come back. Should I always have egr vacuum after the engine reaches op. temp.
and I'm accelerating or is it suppose to be intermittent? This will tell me
if it's a vacuum regulator or pcm problem. Everything else checks out.
New User
Joined: Dec 2010
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From: Ocala, FL
Hey I had some EGR trouble codes I couldn't get rid of. Pull the intake elbow off the intake and check the two smaller holes coming from the egr port into the elbow, might have build up, mine was horrible.... Not sure if it helps...
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You should have vacuum to the regulator. From the regulator to the EGR only when the engine is warmed up, but not at idle. TPS, MAF, and DPFE supply the data used to regulate when the EGR is opened. So I guess the answer to your question is no, if you warmed the engine, have it idling in the driveway, and check the vac line at the EGR. Engine will stall most likely, if you have vac there at idle.
Dave
Dave
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Here's what is happening. I'm checking vacuum to the egr , from the vacuum regulator as I'm driving down the road and the engine is warm. It
starts out showing vacuum on acceleration but it goes away and doesn't or hardly ever returns until I turn the engine off and start the test over. Then sometimes it will return and after a while it stops again. My question is , should I have vacuum to the egr each time I'm accelerating , after reaching normal operating temp?
starts out showing vacuum on acceleration but it goes away and doesn't or hardly ever returns until I turn the engine off and start the test over. Then sometimes it will return and after a while it stops again. My question is , should I have vacuum to the egr each time I'm accelerating , after reaching normal operating temp?
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You have to know what is suposed to happen before you can conclude what the issue is.
The EGR does not open until certain conditions are arrived at.
Here is how it is supposed to work.
'ONLY' under cruise conditions at light throttle above about 45 mph in OD or 3rd gear will the PCM request the EGR to open by commanding the Vacuum regulator to open allowing vacuum to open the EGR.
When extra throttle is called for power, the EGR closes. This is normal.
If the Vacuum regulator is dirty and hangs open, the EGR will not close up reliably.
The Vacuum regulator is a 3 port device such that once the vacuum opens the EGR air must be let back in thru the third port of the regulator so it can close the EGR again when vacuum is closed off.
Bottom line is no EGR operation at idle or under acceleration at any time. Only under light throttle above a min road speed.
This is sensed by the position and length of time the TPS is at small throttle angles and the transmission speed sensing to tells the PCM to enter the EGR routine.
Get this right before you come to any conclusions.
Check for a dirty filter under the regulator's cap. This is where the air is filtered to return to the EGR to close it.
Good luck.
The EGR does not open until certain conditions are arrived at.
Here is how it is supposed to work.
'ONLY' under cruise conditions at light throttle above about 45 mph in OD or 3rd gear will the PCM request the EGR to open by commanding the Vacuum regulator to open allowing vacuum to open the EGR.
When extra throttle is called for power, the EGR closes. This is normal.
If the Vacuum regulator is dirty and hangs open, the EGR will not close up reliably.
The Vacuum regulator is a 3 port device such that once the vacuum opens the EGR air must be let back in thru the third port of the regulator so it can close the EGR again when vacuum is closed off.
Bottom line is no EGR operation at idle or under acceleration at any time. Only under light throttle above a min road speed.
This is sensed by the position and length of time the TPS is at small throttle angles and the transmission speed sensing to tells the PCM to enter the EGR routine.
Get this right before you come to any conclusions.
Check for a dirty filter under the regulator's cap. This is where the air is filtered to return to the EGR to close it.
Good luck.
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Was going to check vacuum regulator today. I thought I would start by checking voltage to the solenoid when egr kicked in to make sure I was getting a signal from the pcm when I lost vacuum after engine was at normal operating temp. I thought that would confirm a bad vacuum regulator or no signal from pcm. Before I did this I thought I might check and make sure I had 12v to regulator. Low and behold I have 12v to both sides of the regulator with koeo. Doesn't this confirm a bad solenoid by itself?
