This code can mean no EGR flow is detected, manually open the valve and see if the engine starts to stall, if it doesn't you have a plugged EGR exhaust gas passage
Use a Mityvac brand vacuum hand pump test tool or any such tool in a cheaper brand, Autozone has them for about $15.
also make sure the EGR is getting a Vacuum signal to open, with the engine at normal operating temperature slowly open the valve and watch the vacuum gauge of the Mityvac, it should slowly rise to about 16-18 inches of vacuum, if not the EGR vacuum source at the throttle valve is leaking or disconnected or the EGR vacuum regulator is defective.
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Continued..
Have you run the tests I've recommended?
This an an EGR code not an airflow code
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The Engine Control Unit (ECU) commands the EGR valve open by activating the EGR Vacuum control solenoid. The EGR solenoid then places manifold vacuum to the EGR Valve vacuum port. The ECU verifies EGR opening by watching the voltage at the EGR Temperature Sensor. Test 1 - ECU B+ Circuit Trouble Terminals Condition Trouble Standard Voltage BATT-E1 At All Times No Voltage Battery Voltage (10 - 14V) +B - E!, +B1-E1 With ignition on No Voltage Battery Voltage (10 - 14V)
Code 71 sets when the ECU commands the EGR open and there is no change in EGR Temperature Sensor voltage. (See the wiring schematic below)
You could have a bad EGR control solenoid, You could have no vacuum to the solenoid or no vacuum from the solenoid to the EGR Valve, the ports in the intake manifold could be clogged to where the EGR gasses cannot flow and cause the sensor to heat, or the EGR sensor could be bad, or the wiring to the ECM could be faulty. (See the troubleshooting chart below.)
That was supposed to be a table, and for some reason the pictures didn't post...sorry!
I don't know why this !@#$ thing won.t let me post pictures!!! I have pictures of what you need!
Anyway, the EGR VSV is mounted on the right fender area. There should be 2 of these things mounted side-by-side with vacuum lines going to them. The one towards the front of the vehicle is the one for the EGR.
You made a comment about VSV being in spec...VSV stands for Vacuum Solenoid Valve...This is what you are looking for!
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TESTING
This is a test of the sensor only. A complete test of the circuit requires the DRBII scan tool, or equivalent.
Unplug the wiring harness connector from the intake manifold temperature sensor.
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First answer was a link to OBD II codes. I already have the code and definition, AND it's an OBD I engine.
Best way to manually open the valve?
Dug my Mityvac out and it still works. Just to track down the T-fitting. Hoping I wont have to dig out the VSV to test it.
Where is the EGR solenoid located? Top of the manifold near the throttle body?
Is the EGR solenoid on top of the manifold near the throttle body?
Yes, engine stalls when vacuum line to EGR is connected to the manifold directly. However, with the Mityvac connected I'm not getting vacuum readings at 3500 rpm, even when when R on the regulator is connected directly to the manifold, although the FSM isn't all that clear about where that connection should take place.
Not sure my replies are getting through. VSV resistance is in spec, but airflow through the filter with voltage applied seems low, EGR valve tests OK. Airflow through the regulator seems low when blowing into Q with P and R plugged and engine off. Cleaning the filter and regulator didn't make any difference.
I've cleared the CEL by pulling the EFI fuse. I'm just going to have to drive it and see what happens.
So you're saying it can't be the vacuum modulator? [Would be nice if the site should my replies.]
FSM pages I found set out several tests related to the EGR system, including vacuum and electrical for the VSV and EGR temp sensor. Both passed the electrical tests.
However, when air is blown into Port Q with P and R blocked, per the FSM, the flow around the filter of modulator is pretty minimal. As for the VSV, blowing air through with no voltage applied, the air escapes from the other port as is normal. With voltage applied, it's supposed flow past the filter and it's minimal at best. Autozone doesn't offer a VSV, so it's likely a dealer only part. If the CEL comes back, I'll replace the vacuum regulator.
Here are the four pages from the FSM
http://personal.utulsa.edu/~nathan-bucha...
I dug that out from under the spaghetti of vacuum lines and god knows what else. Electrically, it's in spec. Not so sure about whether it's flowing correctly. Same for the vacuum modulator.
I dug that out from under the spaghetti of vacuum lines and god knows what else. Electrically, it's in spec. Not so sure about whether it's flowing correctly. Same for the vacuum modulator.
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