Contour Enthusiasts Group Archives Forums General Troubleshooting Rough idle - Cats clogged or EGR??

99 SVT 2.5L with 99k miles.
I just had my car in to check the CEL and it returned 4 codes. I don't have them handy but I will go to AutoZone today after work and get all the exact codes involved and plug them into this thread. I did have my CEL on for about 4 months now. When it originally came on, Ford told me I needed all my cats replaced which would have been around $2,000+. I said the heck with that. Recently, I remember one of the codes stating that the EGR flow was excessive.

Here's what I've done so far. Took the car to a muffler shop.. they did a temperature test on different parts of the exhaust. One area was close to 450 degrees. They guess that I a clog was around that vicinity. It was just after the cat closest to the firewall and before the main cat.

I obviously need to post more information here as to what the codes are. Will the EGR being clogged cause a rough idle? Sometimes the idle will bounce when I come to a stop and it will even stall the engine. I'm going to clean the EGR today when I get home. I found pics on HOW TO w/Pics thread and it looks easy enough. I have already cleaned the throttle body for a sticky gas pedal but I never removed the gasket to expose the EGR chambers. Since it's free, I figured what the heck.

Now if this doesn't fix the rough idle then I'll be looking into the most cost efficient way to unclog or replace the cat.

Thank God for AutoZone and the free diagnosis!!!
Here are the codes I have..
P0133 Upstream Heated Oxygen Sensor circuit Slow Response - Bank No. 1.
P1131 Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1.
P0402 EGR Flow Excessive at Idle.
I cleaned out the housing behind the throttle body as shown in this link. It wasn't anywhere near as dirty as in the pictures. It was barely dirty at all. Of course, that didn't really help anything so I'm still stuck with the 3 codes above. I've been searching the threads but really haven't found a solid answer. I'm think about replacing the O2 sensor in bank 1 but some people say that's not the cause. I'm going to change my fuel filter tomorrow. I bought the car new with 11 miles on it.. No it has 99k and I have only change the fuel filter once around 60k miles.

EGR excessive / rough idle


While idling:

Pull the vacuum hose of off the EGR valve.
If the idle smooths out you now know that the EGR valve is not stuck open. Put the hose back on.


Unplug the electrical connector from the EGR EVR (between the coil pack and the IAC). If the idle smooths out the DPFE is at fault, if not, the EVR is leaking.



I would not replace the DPFE without fixing the cat problem as this will be hard on it.

You can temporarily remove and plug the EGR valve vacuum hose although this can cause pinging. Use the best gas available to help mitigate.



And replace that O2, the top one behind the engine.

Forgive my ignorance..
Where exactly is the EGR valve located? What does it look like? You mentioned pulling the vacuum hose off but I see all kinds of hoses going all over the place. How's that for nontechnical?

Suggest you get some kind of manual - pretty pictures!

Top of the EGR valve looks like a small UFO. It's just aft of the throttle body. Bolts to the UIM, and has a tube that goes behind the engine to the exhaust manifold.

Here, the finger is pointing at the IAC and the EGR valve is under the finger. Above is the smaller round plastic top of the EVR.

No kidding your egr was clean. Excessive egr flow means that it is putting in TOO MUCH! That how-to post was meant for insufficient egr flow. Most likely your egr valve needs to be replaced. $43 at any autoparts store.

Looks like the new O2 sensor in bank 1 on the cat nearest the firewall upstream was the trick. I pulled fuses 4 and 11 to reset the computer. 100+ miles and no CEL yet. Crossing fingers!!