EGR problem still
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Freshman User
Joined: Mar 2003
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From: Escanaba
EGR problem still
hey guys,
I have posted this problem before and have still not figured it out. I have a 1993 f150 302 that hesitates at about 30 mph, while cruising. If I plug the EGR, or disconnect the EGR vac. the problme goes away. I have replaced the EGR valve, EGR sensor, and the EGR regulator. Aside from the PCM malfunctioning, is their any other component under the hood that would control when the EGR regulator gets a signal from the PCM?
any response is welcomed thanks
vince
I have posted this problem before and have still not figured it out. I have a 1993 f150 302 that hesitates at about 30 mph, while cruising. If I plug the EGR, or disconnect the EGR vac. the problme goes away. I have replaced the EGR valve, EGR sensor, and the EGR regulator. Aside from the PCM malfunctioning, is their any other component under the hood that would control when the EGR regulator gets a signal from the PCM?
any response is welcomed thanks
vince
Senior User
Joined: Jun 2003
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From: Burnsville, MN
EGR problem still
If the engine thinks it is warmer than it really is, then when the EGR opens normally the resulting mixture could be too lean which would cause a hesitation, or other drivability concerns.
Just trying to think of other scenarios that would follow this set of symptoms.
Good luck!
Just trying to think of other scenarios that would follow this set of symptoms.
Good luck!
Senior User
Joined: Jun 2003
Posts: 439
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From: Burnsville, MN
EGR problem still
IMHO
The EGR control vacuum is a small vaccum source.
The EGR valve connects the exhaust manifold to the intake manifold through about 3/8 inch orifice when fully open.
Therefore the premature opening of an EGR can give you all the symptoms of a large vacuum leak without the ability to hear it or see it.
The EGR control vacuum is a small vaccum source.
The EGR valve connects the exhaust manifold to the intake manifold through about 3/8 inch orifice when fully open.
Therefore the premature opening of an EGR can give you all the symptoms of a large vacuum leak without the ability to hear it or see it.
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Joined: Mar 2003
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From: Escanaba
EGR problem still
all right guys, here is the deal.
KOER test gives me two codes 167 and 225. I have replaced the TPS and do not have any problems with idle--other than a little rough. yesterday afternoon I hooked a vacuum gauge up to the line going to EGR (new vac. hose Rob), taped the gauge to my windshield and went for a ride. The gauge reads no vacuum until I reach about 30 mph (about 5 inches of vacuum or so). If I drop below 30 the vacuum shuts off. Well that is exactly when my truck normally starts acting up. Should my egr be getting vacuum when cruising at 30mph? Steve83, I'll let you no after lunch when I pull the vac and let the EGR suck air.
KOER test gives me two codes 167 and 225. I have replaced the TPS and do not have any problems with idle--other than a little rough. yesterday afternoon I hooked a vacuum gauge up to the line going to EGR (new vac. hose Rob), taped the gauge to my windshield and went for a ride. The gauge reads no vacuum until I reach about 30 mph (about 5 inches of vacuum or so). If I drop below 30 the vacuum shuts off. Well that is exactly when my truck normally starts acting up. Should my egr be getting vacuum when cruising at 30mph? Steve83, I'll let you no after lunch when I pull the vac and let the EGR suck air.
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From: Escanaba
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Tuned
Joined: Jun 2003
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EGR problem still
Vince, I don't know if you have tried this or not, but they Haynes manual talks about testing the EGR by taking it off, and applying 5" of pressure to it and says that if it drops below 4" in 30 seconds that the valve is leaking too much. I'm trying to diagnose whether mine has a problem too, and I think part of the issue is whether the right vacuum is getting there, the other part is what does the valve doing on its own. I think if the valve leaks you get rough idle and other problems.
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Thread Starter
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Freshman User
Joined: Mar 2003
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From: Escanaba
EGR problem still
Duck,
The EGR is brand new. It holds at 5"--the problem seems to be associated with the valve is opening at the wrong time. Should the EVR be triggered at 30 mph while simply maintaining that speed?
The EGR is brand new. It holds at 5"--the problem seems to be associated with the valve is opening at the wrong time. Should the EVR be triggered at 30 mph while simply maintaining that speed?
Senior User
Joined: May 2003
Posts: 203
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From: San Diego
EGR problem still
Yes it should. Go to
http://fordscorpio.co.uk/egrmonitor.htm
and
http://fordscorpio.co.uk/egrsensors.htm
for an excellent explanation into the world of egr sensors. The second one gets technical and explains operation in detail. Look past the later improvements with the double vacuum sensing valves (we don't have those) and just read about the basic egr function.
Also, your vacuum is borderline low. Close off the throttly body at idle with something that won't get sucked in and see if the engine dies.
Regards, Robert.
Edit: the egr valve vacuum input isn't going to "suck" anything. The vacuum input goes to a diaphram held by a spring. As more vacuum is applied the diaphram is pulled back against the spring which opens the valve to let exhaust gas through.
2nd edit: also go to:
http://people.ucsc.edu/~kbrandt/mustang/smog.shtml
http://fordscorpio.co.uk/egrmonitor.htm
and
http://fordscorpio.co.uk/egrsensors.htm
for an excellent explanation into the world of egr sensors. The second one gets technical and explains operation in detail. Look past the later improvements with the double vacuum sensing valves (we don't have those) and just read about the basic egr function.
Also, your vacuum is borderline low. Close off the throttly body at idle with something that won't get sucked in and see if the engine dies.
Regards, Robert.
Edit: the egr valve vacuum input isn't going to "suck" anything. The vacuum input goes to a diaphram held by a spring. As more vacuum is applied the diaphram is pulled back against the spring which opens the valve to let exhaust gas through.
2nd edit: also go to:
http://people.ucsc.edu/~kbrandt/mustang/smog.shtml
Last edited by Robert at the Beach; Jul 18, 2003 at 11:39 AM.
Post Fiend
Joined: Nov 2002
Posts: 9,987
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From: Memphis, TN
EGR problem still
Originally posted by vinnean
...if there is a leak in the egr exhaust inlet pipe.
...if there is a leak in the egr exhaust inlet pipe.
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Freshman User
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From: Escanaba
EGR problem still
I was tinking more about the inert gases vrs. pure o2. does'nt matter any way, I checked this weekend and no leaks. I found a freakin' wire broke in my harness up by my radiator though. Guess what it goes to--the o2 sensor. I re-sodered it, but no difference(seems suspicious) PCM?
Post Fiend
Joined: Nov 2002
Posts: 9,987
Likes: 7
From: Memphis, TN
EGR problem still
The PCM has now learned how to do without the HEGO, so you have to make it forget & relearn. Unhook the battery for ~5 min, then go for a 10-mile test drive, changing speed frequently. Don't let it idle, and don't set the cruise. When you get home, check the codes again.