Fuel Problem?
Senior Member
Joined: Oct 2002
Posts: 7,295
Likes: 125
From: St. Louis (Out in the woods)
Chris,
While a restrictor plate may be needed, it doesn't address the reason for the vacuum being applied to the EGR valve at inappropriate times. The PCM should command EGR flow only during steady-state, off-idle cruising. EGR flow at any other time is undesirable as the computer cannot compensate for something it didn't command in the first place.
Uncommanded EGR flow can be caused by a defective EVR solenoid or by a defective D/PFE sensor or the associated sample plumbing.
Steve
While a restrictor plate may be needed, it doesn't address the reason for the vacuum being applied to the EGR valve at inappropriate times. The PCM should command EGR flow only during steady-state, off-idle cruising. EGR flow at any other time is undesirable as the computer cannot compensate for something it didn't command in the first place.
Uncommanded EGR flow can be caused by a defective EVR solenoid or by a defective D/PFE sensor or the associated sample plumbing.
Steve
Senior Member
Joined: Sep 1999
Posts: 3,083
Likes: 0
From: Ventura, California
Steve, believe me, I'm very old school when it comes to finding the cause. Understanding a problem is the best way to prevent and/or recognize it in the future. I never could have stayed in business by throwing parts at a problem until one of them happens to fix it, which is what you end up resorting to if you don't try and find the source of the problem first. I'm with you in the way you reason, I just disagree with your conclusion. I'm not convinced there is vacuum being applied at inappropriate times. If you're right, though, a restrictor plate won't have an effect.
My personal belief, based on what I've read in this thread, and on personal experience, is that this problem is caused by too much EGR flow (at appropriate times), and dirty injectors. Both are very common problems with EFI 4.9L's, both create a stumble/miss condition that feels very similar, and both usually start to appear anywhere after 50k miles, and often around the same time as the other. Too much EGR flow while cruising would create a steady speed stumble/miss that goes away with heavier acceleration, while dirty injectors often cause an off-idle stumble on light acceleration, as well as create a low speed stumble/miss at lower steady speeds. Both problems clear up at WOT. Between the two of them, that pretty much covers his complaint.
Who knows, I could be a million miles off on this one, it's just that I've seen this before several times, online and in my shop. Still, it can be difficult to say without being able to do the diagnostics in person.
Take care,
~Chris
My personal belief, based on what I've read in this thread, and on personal experience, is that this problem is caused by too much EGR flow (at appropriate times), and dirty injectors. Both are very common problems with EFI 4.9L's, both create a stumble/miss condition that feels very similar, and both usually start to appear anywhere after 50k miles, and often around the same time as the other. Too much EGR flow while cruising would create a steady speed stumble/miss that goes away with heavier acceleration, while dirty injectors often cause an off-idle stumble on light acceleration, as well as create a low speed stumble/miss at lower steady speeds. Both problems clear up at WOT. Between the two of them, that pretty much covers his complaint.
Who knows, I could be a million miles off on this one, it's just that I've seen this before several times, online and in my shop. Still, it can be difficult to say without being able to do the diagnostics in person.
Take care,
~Chris
Thread Starter
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Member
Joined: May 2006
Posts: 12
Likes: 0
From: arizona
The both of you have given great help on this. Thanks alot. I am learning. I have ran Seafoam down my throttle body on a regualr basis and since this problem started. I have also put it in my gas. I have listened to my injectors through a screw driver and can hear them tick. I keep thinking it has to do with this EGR situation somehow. Only a thought which I'm about out of. Thanks again.
Thread Starter
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Member
Joined: May 2006
Posts: 12
Likes: 0
From: arizona
Still having some problems. I have installed restrictor plate and that has helped.
Ran great for about two days, then started bucking (but not as bad as before) and will come out of it upon acceleration, then will start again. Checked EGR vacuum solenoid and is same a new on compared to. Cleared codes and light came back on and read the same as before. I have also tested my Thermactor system. The book says if I put contant vacuum to the exhaust port that it should change and bypass exhaust to other exhaust port. So I am assuming this
isn't working right. Could this cause some of my problems too? It has two vacuum feeds, one is constant and the other seems to stop as engine warms up. Anyone got anymore suggestions?
Ran great for about two days, then started bucking (but not as bad as before) and will come out of it upon acceleration, then will start again. Checked EGR vacuum solenoid and is same a new on compared to. Cleared codes and light came back on and read the same as before. I have also tested my Thermactor system. The book says if I put contant vacuum to the exhaust port that it should change and bypass exhaust to other exhaust port. So I am assuming this
isn't working right. Could this cause some of my problems too? It has two vacuum feeds, one is constant and the other seems to stop as engine warms up. Anyone got anymore suggestions?