P0401 EGR and effect on A/F ratios
12-06-14, 05:10 PM
#1
P0401 EGR and effect on A/F ratios
Hello,
I've had this code for many months now and don't have the resources to resolve it (moved, no tools here).
One thing that I'm worried about is that it randomly affects my reading on my A/F ratio gauge.
The engine will go lean (A/F over 17) and stay that way for 30 minutes +.
Here's a video of it happening. Exactly 2 minutes later, my A/F ratios went back to normal.
I replaced the diaphragm near the intake manifold and that had no effect. I know another possibility is the VSV by the heater control valve but I haven't replaced that. ALso the EGR itself or ??
Literally 2 minutes after I stopped recording it went back to normal:
I know it's not the O2 sensor because I replaced it about 5K miles ago, and it obviously works.
I've had this code for many months now and don't have the resources to resolve it (moved, no tools here).
One thing that I'm worried about is that it randomly affects my reading on my A/F ratio gauge.
The engine will go lean (A/F over 17) and stay that way for 30 minutes +.
Here's a video of it happening. Exactly 2 minutes later, my A/F ratios went back to normal.
I replaced the diaphragm near the intake manifold and that had no effect. I know another possibility is the VSV by the heater control valve but I haven't replaced that. ALso the EGR itself or ??
Literally 2 minutes after I stopped recording it went back to normal:
I know it's not the O2 sensor because I replaced it about 5K miles ago, and it obviously works.
12-07-14, 08:19 AM
#2
That is due to insufficient EGR flow, check the EGR vacuum valve, open up the top cap and remove the filter. Chances are it's plugged with carbon buildup. If you suck on the bottom inlet on the vacuum valve, and you're able to suck air through, the valve is faulty. Just watch out when sucking all that carbon out, your lips will turn black lol.
05-30-15, 03:57 PM
#3
Hello, still having this issue months later and tired of getting 12MPG.
The EGR modulator valve is OK. I cannot suck any air through the bottom port. The filter is clean.
I've spent about 2 hours looking over the issue today and did a few things-
-Discovered that I think the vacuum hoses might routed wrong (see below)
-Tested the power supply line to the EGR valve itself = +5V (at idle)
-Sucked on the bottom of the EGR valve itself (not the modulator) with the engine running and had no effect.
What I'm asking of fellow CL people - please take 3 minutes to go outside and take a picture WITH flash of the vacuum lines around the EGR area. I've looked on google for 20 minutes and did not find the picture here. I asked about this a looong time ago and someone posted a picture without flash so it didn't quite work out.
What I noticed is that I have a "T" connector going from the heater valve, to the intake manifold, which then goes down into the abyss into a hard line.
The canister is going directly to a hard line which is the opposite of what the under hood diagram shows.
A side question - which specific hoses could prevent the EGR from working? I don't understand the logic from another thread that suggested sucking on the bottom of the EGR (which I did) to make the car stumble if it's only on during a certain speed over 35?)
The EGR modulator valve is OK. I cannot suck any air through the bottom port. The filter is clean.
I've spent about 2 hours looking over the issue today and did a few things-
-Discovered that I think the vacuum hoses might routed wrong (see below)
-Tested the power supply line to the EGR valve itself = +5V (at idle)
-Sucked on the bottom of the EGR valve itself (not the modulator) with the engine running and had no effect.
What I'm asking of fellow CL people - please take 3 minutes to go outside and take a picture WITH flash of the vacuum lines around the EGR area. I've looked on google for 20 minutes and did not find the picture here. I asked about this a looong time ago and someone posted a picture without flash so it didn't quite work out.
What I noticed is that I have a "T" connector going from the heater valve, to the intake manifold, which then goes down into the abyss into a hard line.
The canister is going directly to a hard line which is the opposite of what the under hood diagram shows.
A side question - which specific hoses could prevent the EGR from working? I don't understand the logic from another thread that suggested sucking on the bottom of the EGR (which I did) to make the car stumble if it's only on during a certain speed over 35?)
Last edited by ISFFUN; 05-30-15 at 04:06 PM.
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