EGR troubleshooting.
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Junior User
Joined: Dec 2005
Posts: 57
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From: Fullerton, Ca.
EGR troubleshooting.
I really want to make a concerted effort to solve my long running (many years) severe pinging problem. I believe it might be due to some anomaly regarding EGR operation. I have been able to mask most of the pinging by retarding the timing several degrees and running mid grade fuel during the summer months when the problem is more severe. I recently spent a little time reading the "strategy" section in Fordfuelinjection*com and now feel I am a little bit better prepared to delve into this a little.
Here are my questions, how thorough of a EGR test does the OBD-1 (90 F250, 7.5L) EEC IV perform. Does it just confirm EGR movement via a response from the EGR position sensor or does it actually measure changes in the exhaust gas from the O2 sensor to confirm that exhaust gas is displacing the oxygen in the intake? The reason I ask this is I'm wondering if perhaps some of the EGR passageways are clogged. Are clogged passageways a common occurrence? The reason I'm first investigating the EGR operation is I have retrieved some EGR code in the past although I don't have them handy.
Second, where does the passageway in the intake manifold go? I removed the EGR valve some time ago, cleaned and tested it, it seemed OK so I did not spend the money to replace it. I did not do any cleaning of the passage ways because I did not want to send any pieces of crud into the intake. Is the passage a simple straight hole into the engine intake or does it make a bunch of bends with no hope of a complete cleaning? Does the riser tube get clogged?
Any help, suggestions, or experiences would be greatlly appreciated.
Here are my questions, how thorough of a EGR test does the OBD-1 (90 F250, 7.5L) EEC IV perform. Does it just confirm EGR movement via a response from the EGR position sensor or does it actually measure changes in the exhaust gas from the O2 sensor to confirm that exhaust gas is displacing the oxygen in the intake? The reason I ask this is I'm wondering if perhaps some of the EGR passageways are clogged. Are clogged passageways a common occurrence? The reason I'm first investigating the EGR operation is I have retrieved some EGR code in the past although I don't have them handy.
Second, where does the passageway in the intake manifold go? I removed the EGR valve some time ago, cleaned and tested it, it seemed OK so I did not spend the money to replace it. I did not do any cleaning of the passage ways because I did not want to send any pieces of crud into the intake. Is the passage a simple straight hole into the engine intake or does it make a bunch of bends with no hope of a complete cleaning? Does the riser tube get clogged?
Any help, suggestions, or experiences would be greatlly appreciated.
Lead Driver
Joined: Nov 2002
Posts: 9,555
Likes: 40
From: Concord, NC
Does it just confirm EGR movement via a response from the EGR position sensor or does it actually measure changes in the exhaust gas from the O2 sensor to confirm that exhaust gas is displacing the oxygen in the intake?
I can't help you with the routing of the EGR passageways, but if they are clogged and the computer believes a certain flow rate based on valve position, the computer would inject less fuel and advance the timing to the calibrated values at proper EGR flow. If there is no actual EGR flow into the intake, this will cause a lean condition and too much spark advance possibly leading to pinging as you are experiencing.
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
I'm no 460 expert but if it's built like the smaller V8 there is a port in the head that connects to a port in the intake.. usually at the center. About the only way yo could test it for obstructions is to remove the EGR valve and see if you get exhaust gas flow out the port. If you don't then you're probably going to have to remove the intake to clear the port.
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