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EGR KOEO & KOER Code 327

I have a 1994 Mercury Grand Marquis GL with ABS that I have owned for about 8 years. I am the second owner and bought the car with 70,000 miles. The car now has 149,000 miles and mostly still runs very well. However I have always had problems with the EGR system. The check engine light comes on almost every year or two and I need some type of EGR or idle air component replaced.

On two or three occasions I have replaced the EGR valve, Idle air control valve, Idle air position sensor, DPFE, EGR Valve position sensor…etc. Every time the problem went away but returned after a year or just a few months.

I have also taken the car to the Mercury dealer and they cleaned the EGR ports and the replaced the EGR valve. They also replaced the the DPFE sensor. Things were fine for a while but the problem returned.

Finally, about a year and a half ago I took the upper intake manifold off and replaced all the air intake gaskets, cleaned all the ports, replaced most of the same parts (EGR valve, idle air control valve…etc) but the problem has returned again. Check engine light with error code 327.

Is there something wrong with the Mercury/Ford engine design. I cant imagine that in 8 years I need to replace these parts this many times ?

Is it possible that I am not getting to the root of the problem and thus when I replace these components its only a temporary fix because the real underlying problem causes the new components to go bad again?

What should I be looking at when I investigate this problem?

Early 4.6 l engines had EGR problems that were corrected in later models. That said, I have never seen this kind of severity. When you say “I replaced…” do you really mean with your own hands or you paid someone to repair your vehicle? I suspect parts are being thrown at and insufficient EGR flow problems. Is that what 327 is?

Note that the IAC has nothing to do with the EGR system. They do wear out. It will not set a code or illuminate the CEL.

In thinking this over, the other problem with early 4.6 l engines was the valve stem seals. This was also fixed with later models with revised seal material. Do you get a puff of smoke at startup and after idling for a while? I think that oil burning like that can coke up the EGR passages. Get a second opinion by surfing over to You should be able to get a lot of service out of this car and you can get a lot of experienced advice there. If the seals need to be replaced, you can avoid removing the heads by holding the valves up by stuffing the cylinders with rope or using air pressure. People say it is not too hard of a job.

One area that can cause this code is the orifice in the exhaust gas tube to the EGR valve. This orifice can get a build-up of carbon where it restricts the flow/back-pressure of exhaust gasses to the EGR valve. And since this system is a back-pressure-induced EGR system, the lack of exhaust flow/back-pressure doesn’t allow the EGR valve to open far enough. This then causes an inefficient EGR gas flow code.

Have the EGR valve removed to gain access to the top of the exhaust gas supply tube. Using a aerosol brake cleaner, spray down the tube for five seconds and wait five minutes. Repeat this until the brake cleaner is gone. Reassemble the EGR system, start the engine and bring the idle speed to a 1,000 RPM’s for two minutes.


A possibility could be a partially clogged catalytic converter. This can cause the engine to run somewhat rich which in turn can lead to EGR ports clogging up more often, gumming up the EGR pintle, etc. The engine may also appear to run fine even in this condition

This could easily be tested with the use of a vacuum gauge; a handy little tool that apparently many techs don’t even use. :frowning: