Why does an unpluged egr valve run better then

indy4192

I have a EGR issue with my car according to my SEL and will be taking it to the meachinc in a couple of weeks to repair. A friend told me to unplug the vacum hose that plugs into the top of the EGR valve until I get it addressed and the engine will not ping and run as rough. I doubted him but he was right. Why is this so? My car is the 98 Ford Taurus stationwagon with a bad headgasket. With the vacum hose pluged into the top it shakes and shimmy for a long while, unpluged it does it for a few minutes and then it runs like it did before the issue arose, plus i am not seeing any loss of fuel milage.

eraser1998

I'm not going to be able to provide you an answer - but having missed your previous discussions and only seeing a couple of your posts, how do you know your car has a bad headgasket? You describe losing a gallon of coolant every 6-7 weeks, which seems like a lot to not have any in the oil or to notice more coming out the exhaust. Are you sure you don't have a cracked coolant tank? They were pretty common on these cars, and easy to fix.

Caddyman

Engines ran just fine without EGR valves for 80 years....They still do today....

missileman

Simply put.....the egr valve dumps exhaust gas into the intake. That's not a performance boosting act but it's required by the EPA. As Caddyman said "Engines ran just fine without EGR valves for 80 years....They still do today....".

indy4192

I took it in and my number 1 cylinder has very low compression and they did a leak down test and got air up through the radiator overflow jug and out the tailpipe, which I am told are all signs of a bad headgasket. I have 0 in the oil or out the exhaust, i have no white smoke coming from teh tailpipe nor have i seen any loss of power in the engine or loss of gas milage. If it wasn't for the antifreeze being blown out the overflow jug you wouldn't know there was anything wrong with the engine. I was just amazed at how differently the engine operated with the EGR valve unplugged over plugged in. After I get my passanger side ball joint replaced I will address the EGR issue.

fitjeep

The EGR system meters a little exhaust gas into the intake which lowers the combustion temperature which lessens the amount of NOx in the exhaust. The engine will run better without it but will produce more smog. Over a long period of time the higher combustion temperature can cause valve damage.

indy4192

What is a "long" time period? Are we talking days, weeks, months or a year or so?

missileman

Years. I have seen many engines torn apart that did not have an egr system and the valves were fine. A few minutes on the valve grinder and they went on for many years more. It's mostly theory and very difficult if not impossible to prove.

indy4192

So odds are my headgasket issue will kill my engine long before a problem from not having the egr valve working?

oldschool

It sounds like the EGR pintel valve is open with this vacuum line connected. There should be no vacuum to the valve at idle(pintel should be seated) perhaps the line in connected to an incorrect source.

A engine without mechanical defects (not yours) and a properly configured and operating EGR system will not cause a car to ping.

I answer this post as part of my effort to convince the public that keeping current emmission equipment in good order is not harmful to the auto. The idea that emmission equipment does nothing but harmful things came about with early techniques and the impression has been passed on through generations of mechanics and DIYers

indy4192

I am not sure what you mean? My car registerd a P401 code which the sheet says is an ERG issue of some type. My friend said until i get it fixed to just unplug the hose that connects to the top part of the mushroom shaped EGR valve and the knock and pinging would be less and it is. So are saying that by doing this it shows that it is the EGR valve itself that is bad as it must be open all the time?