Rough Idle
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Joined: Oct 2010
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I've replaced the MAF with 3 different units. It still acts the same way.
Cargo Master
Joined: Aug 2003
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From: BC Canada
I have done a smoke test and used a vacuum gauge. The smoke test was done through the intake elbow with a halloween type fog machine. There was plenty of smoke going through the system because when I unplugged the PCV elbow, smoke was coming out of there at a decent amount. Blocked off the dip stick and valve cover, and still did not find any leaks, used a high powered light to try and find anything. Even did starter fluid around all of the vacuum lines, and all over the intake, and i really mean ALL OVER...nothing at all.
The vacuum gauge read 17 inHg at idle, even with it roughly idling. I did not monitor it while driving, because I didn't have a secure place to mount the gauge while driving to check it out.
The vacuum gauge read 17 inHg at idle, even with it roughly idling. I did not monitor it while driving, because I didn't have a secure place to mount the gauge while driving to check it out.
Good Vacuum is 19inHg and steady at idle . Duct tape it to the windshield if you need to monitor in motion....
are you sure you have not crossed any plug wires, especially bank 2..?
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Motorcraft Copper Core Resistors
I figure the 2 inHg vacuum difference is possibly from 210,000+ miles. And I'm positive I did not mix up the wires. I did one plug/wire at a time.
I went through that scenario with that type of smoker, did not get results until I applied 2psi to the mix......
Good Vacuum is 19inHg and steady at idle . Duct tape it to the windshield if you need to monitor in motion....
are you sure you have not crossed any plug wires, especially bank 2..?
Good Vacuum is 19inHg and steady at idle . Duct tape it to the windshield if you need to monitor in motion....
are you sure you have not crossed any plug wires, especially bank 2..?
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Well I'm almost 100% that I've narrowed down the problem.....It's the EGR valve. Here is why I think it is the problem, please tell me if I'm wrong. I took off the vacuum line from the EGR pressure sensor and sprayed carb cleaner in it, and the motor stalled out....which tells me that the EGR is stuck open, therefore making a BIG vacuum leak.
Does this seem correct?
Only thing now is, I'm scared to remove the EGR and replace it. It's the original one from Ford, and it's got 210,000 miles of use....needless to say, it is VERY rusted. And I'm using "VERY", very lightly.
Does this seem correct?
Only thing now is, I'm scared to remove the EGR and replace it. It's the original one from Ford, and it's got 210,000 miles of use....needless to say, it is VERY rusted. And I'm using "VERY", very lightly.
Logistics Pro
Joined: Jun 2009
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From: Cedar Rapids, IA
The EGR pressure sensor meters vacuum to the EGR valve diaphragm to open and close the EGR valve, but not directly in to the EGR valve/intake.
If you have a vacuum pump, you could attempt to manually operate the EGR valve diaphragm by pulling a vacuum on the valve while the engine is idling. If it stalls when you start to apply vacuum, that would suggest the valve is working fine. If it doesn't stall, you might have a stuck valve or you might have enough of a vacuum leak elsewhere that the EGR valve is not a significant contributor. With 17 inHG at idle though it doesn't seem to me like you have a very large vacuum leak. The gauge accuracy could account for some of that too. It would be interesting to monitor manifold vacuum while modulating the EGR valve with the vacuum pump to see what effect, if any, it has.
-Rod
If you have a vacuum pump, you could attempt to manually operate the EGR valve diaphragm by pulling a vacuum on the valve while the engine is idling. If it stalls when you start to apply vacuum, that would suggest the valve is working fine. If it doesn't stall, you might have a stuck valve or you might have enough of a vacuum leak elsewhere that the EGR valve is not a significant contributor. With 17 inHG at idle though it doesn't seem to me like you have a very large vacuum leak. The gauge accuracy could account for some of that too. It would be interesting to monitor manifold vacuum while modulating the EGR valve with the vacuum pump to see what effect, if any, it has.
-Rod
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Shorod, I think we might not be on the same page here....
The Pressure Sensor has 2 lines. An upstream and a downstream. One has vacuum, one has exhaust coming out of it. The one that had vacuum to it, I sprayed Carbon/Choke cleaner into it. When I did, the motor revved up, then died. Those 2 hoses, (upstream and downstream) both go into the pipe that supplies off the manifold, to the EGR. But they are both BEFORE the EGR valve.
The Pressure Sensor has 2 lines. An upstream and a downstream. One has vacuum, one has exhaust coming out of it. The one that had vacuum to it, I sprayed Carbon/Choke cleaner into it. When I did, the motor revved up, then died. Those 2 hoses, (upstream and downstream) both go into the pipe that supplies off the manifold, to the EGR. But they are both BEFORE the EGR valve.
Logistics Pro
Joined: Jun 2009
Posts: 4,818
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From: Cedar Rapids, IA
That's sort of how it works. There is a metering orifice between the two ports going to the DPFE. The orifice creates a pressure differential across the two ports and that difference is measured by the DPFE sensor. The PCM uses this measurement to determine how much exhaust gas the EGR valve is re-circulating. There isn't really an "exhaust" and "vacuum" side, just an orifice that allows a pressure differential in the flow of exhaust through the EGR valve.
But, I get what you are saying. If at idle you spray carb cleaner into the port on the EGR valve side of the orifice and you noticed the engine speed increase and stall, that would suggest the EGR valve is flowing at idle. Now you should try the same experiment with the vacuum line going to the EGR valve diaphragm removed. If the engine still revs this way and stalls or attempts to stall, that would indicate the EGR valve is not fully closing when no vacuum is applied. If it doesn't rev with the diaphragm vacuum disconnected, that would suggest that there is an issue with the EGR vacuum regulator or the DPFE/hoses.
-Rod
But, I get what you are saying. If at idle you spray carb cleaner into the port on the EGR valve side of the orifice and you noticed the engine speed increase and stall, that would suggest the EGR valve is flowing at idle. Now you should try the same experiment with the vacuum line going to the EGR valve diaphragm removed. If the engine still revs this way and stalls or attempts to stall, that would indicate the EGR valve is not fully closing when no vacuum is applied. If it doesn't rev with the diaphragm vacuum disconnected, that would suggest that there is an issue with the EGR vacuum regulator or the DPFE/hoses.
-Rod
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I forgot to add a couple things....if it makes matters better.
When I unplugged the vacuum line from the EGR and replaced it with a constant vacuum line, the car ran worse. And when I did the whole spraying of carb cleaner trick, I did it while the vacuum line on the EGR was off.
When I unplugged the vacuum line from the EGR and replaced it with a constant vacuum line, the car ran worse. And when I did the whole spraying of carb cleaner trick, I did it while the vacuum line on the EGR was off.
Logistics Pro
Joined: Jun 2009
Posts: 4,818
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From: Cedar Rapids, IA
It sounds like the EGR valve still works, but is not closing all the way. If you can get the EGR valve off without the tube breaking, you may be able to clean the valve with the carb cleaner and get it to where it can fully close. Be sure to put antiseize compound on the threads for the tube when reassembling.
-Rod
-Rod
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