Hi Guys,
Thanks again for all your input. I hooked it up to a computer and got two errors, both of which had the same code. What do you all think? Cat converter for sure?
Hmm! I’m thinking the excessive EGR flow may be due to the increased back pressure caused by a plugged converter. By the way, this car has three catalytic converters, a small one on each exhaust manifold and a larger one underneath the car. I would suggest just replacing the large one under the car first. It’s a lot cheaper than the smaller ones.
EGR code on a Ford? There was another poster here with a recent model Ford recently who had a problem with the EGR modulator. Apparently this is a common problem w/certain Fords. I forget what that part is called on Fords, but it controls how much EGR to apply based upon the operating condition. Suggest to OP to search these forums to see if you can find that thread, just the last two or three weeks, might be informative.
It would probably be a good idea to follow @GeorgeSanJose 's advice before plunging into a catalytic converter, although I’d be surprised if an EGR problem would cause it to run that poorly.
I think (and this IS a hypothesis) an exhaust restriction could cause the inert exhaust gas to force its way past a stuck or weak EGR valve and feed the induction system with basically an inert gas rather than oxygen. Exhaust gas oxygen is already bound up with carbon and nitrogen so it cannot contribute to combustion chemistry and forcing it in through the induction system basically displaces too much of the needed oxygen.
A vacuum gage as suggested by OK4450 is an excellent way to test for a plugged converter, as is a test pipe to eliminate the cat converter for diagnostic purposes.
There may be even more going on here. Cat converters generally plug up because misfires combined with carbon buildup on the substrate create hot spots that can then be fractured by the shock of continued misfires and/or unburned hydrocarbons burning in the converter. Modern converters are, in fact, designed to promote that “second burn”. When the substrate, which is a ceramic honeycomb, crumbles it gets pushed to a pile in the converters rear end where the exhaust gas flows out. Sometimes you can actually shake a failed converter and hear the broken up substrate rattle.
In short, I still support the theory of a plugged up converter. But once that’s solved, the engine needs a more in-depth look to ensure reliable ignition and proper metering.
Low vacuum, can cause the egr problem, check and see if the brake booster diaphragm is ruptured.
Thanks again for all your input, guys. Here’s is what I understand, and some things I’m confused about:
It seems as though the most likely cause for the lack of power, poor idling, and occasional malfunction of power brake booster, is a blockage of exhaust, or a possible loss of vacuum pressure. If it’s a block in the exhaust, it’s most likely in one or all of the catalytic converters. A vacuum leak, could be in a variety of places; a vacuum pressure gauge can help narrow down to where the loss of pressure is occuring.
Do both of these possibilities still remain valid? Or is it less likely to be due to a vacuum leak, and more likely due to blocked exhaust?
When plugged into a sensor the P0402 code indicates the exhaust’s recirculation flow is too great. Many of you feel this still supports the notion of blocked exhaust–if that gas can’t make it’s way out of the engine it’s very likely recirculating itself via the EGR valve.
My2cents said that it’s unlikely a problem with the EGR itself would cause such severe problems. Couldn’t a problem with the EGR vacuum regulator (or the pressure sensor that controls it) that made the EGR valve stay open (or if the valve is simply just stuck open) be responsible? Or would the problems not be so severe, even if this were the case? Also, if it was a problem with the cat converter, wouldn’t it have given a p0420 code as well?
Currently (pending your approval) I’m planning on testing the EGR first. If I disconnect the line from solenoid to EGR valve, will this remove the EGR from the equation, and improve the idle (if it is EGR problem)?
Next I’ll check for pressure at the Brake booster to see if I’m losing anything there. I’ll then check for exhaust blockage via pressure.
Thanks again for all your advice and explanations to help me wrap my head around this.
Sometimes a diy’er will temporarily disconnect/bypass the cat as a way to test if the cat is causing the problem or not.
I found this guide, which I plan to follow to systematically test the EGR component by component:
http://easyautodiagnostics.com/ford/4.6L-5.4L/how-to-test-the-egr-system-1
I’m hoping the problems we’re experiencing are due to the EGR valve, pressure sensor, or solenoid. I really don’t want it to be 1, 2, or 3 of the cat converters
Thanks agian for all your input!
Good Luck! Let’s hope George was right.
Hey guys, I had something come up, so wasn’t able to get to this as quickly as I would like. Here’s an update.
I removed the vacuum line going directly to the EGR. The idle immediately improved. Then I hooked a vacuum pump up to the EGR. When I put a vacuum on it the rough idle returned. The vacuum pressure did not stay steady, but quickly decreased. I checked the connections between the hose and pump and hose and nipple on EGR and I don’t think that’s where the vaccuum pressure was escaping. I interpreted this as a bad diaphragm in the EGR Valve. Then I hooked the vacuum line back up and headed to auto part store to pick up a new EGR valve. TO my surprise, the car was running remarkably better on the way to the Napa. Unfortunatley, we got hit with a crazy storm while I was in the sotre, and the power went out. I didn’t end up buying the part.
So now, the car is running A LOT better. Also, the check engine light hasn’t returned, though it’s probably only been driven 30-50 miles. I’m wondering if somehow I inadvertently cleared a blockage somewhere when testing the EGR valve initially. Does this make sense? I’m still planning on spending the $50 for a new valve and replacing that in the next day or two. While I have the old valve removed, I’ll check where I can for built up carbon.
Does it sound to you guys like this is good to go when I replace the EGR valve? Is my diagnosis of a bad diaphragm inside correct? Thanks a gain for all your help!