94 EGR System

[LtMercDaddy]

OBD I
codes 332, 337 ( I think )

1 of them is EGR flow insuffecent. the other is EGR/PFE circuit voltage out of range.

well the EGR system is known as a Pressure feedback system the way it works is the PFE or (pressure feedback) sensor monitors the exhaust gas pressure via rubber hose connected from sensor to manifold. difference's in pressure relate to the actual EGR valves position. the EGR vacuum solanoid controls the egr valve's actions.

Well the check engine light has apparently been coming on, flashing, and sometimes go's out. (thats what my grandmother told me it was doing.) It was solid on when I was handed the keys this morning. So I scanned it KOEO test pulled no immideate codes. only those 2 memory codes mentioned before. codes have been cleared and definitions wrote down.

Checked the EGR valve using a vac pump and it did show movement both engine idle and smoothness, so i would assume that the passage is open and the valve does move when VAC is applied.

I think is a faulty PFE sensor.

the engine had a very slight miss/unsmoothness at idle. I also noticed a slight pinging under heavy accelleration. its about to roll 100k plug and wire set has already been planned along with fuel filter. I'm trying to keep them from going and trading it in cuz I want it and eventually they will prob give it to me. both this 94 & my 87 mercs were both owned by my LATE greatgrandfather aswell as my grandfather.

any help would be appriciated.

[88grandmarq]

Very first thing to check is the exhaust supply tube, these are notorious for breaking on 93-95 cars. I have replaced several of them. this is the metal flexible tube that goes from the passenger exhaust pipe, just behind the manifold to the back of the EGR valve. the best way to inspect the tube is jack the car up and go from underneath on the passenger side. using a flash light you should be able to see most of the pipe. look for black stains/soote on the tube, this will mean the tube is cracked and leaking.

[Dereck]

Hi LTMercDaddy

Next thing to check is that the EGR channels in the intake are not blocked up, then start to worry about the DPFE sensor.

Regards

Dereck

[LtMercDaddy]

I've visually inspected both the egr supply tube aswell as the tube going to PFE sensor the hose going to the sensor isnt burnt threw as I have seen on other ford vehicles. no indications of any exhaust leaks.

I applied VAC to the vac port on the egr valve and noticed a change in idle and smoothness when it was applyed. I would assume that passages are clear and that the valve is working.

only things I havent been able to do is test the voltage and resistance on the PFE circuit. aswell as check for exhaust pressure on the PFE line.

is there a way to activate the VAC solinoid for the egr valve, so i can test for a VAC reading?

[93 Marquis]

With a 337 code you'll want to replace the sensor. The tests you have run so far indicate that the EGR passages and valve are clear and working. Until you get a working sensor in place you won't know if there are other problems or not.

Ray

[LtMercDaddy]

Well Installed the new PFE/sensor along with new plugs (wires were ok) 8mm motorcrafts. Also replaced the fuel filter and air filter. The PFE sensor was a PITA to remove, the hose connecting from the exhaust to the sensor runs threw the bracket so removal of the bracket is required.

the plugs weren't too bad, brownish at the bottom grayish on the ground. all of them were at about .056" so we replaced them with fresh champion coppers again.

I located a vac leak when looking the vehicle over. I thought I heard it before when it was at the shop but was unable to locate it then, thought it was the throttle body whistling. further inspection found that the crossover tube connecting both manifold vac ports to the PCV had a collapsed/deteriorated rubber hose on the driver side of the crossover tube.

Check engine light since hasn't come on. The only codes were for the PFE/EGR. no EVAP codes. During test drive noticed no more pinging under heavy acceleration as well as no more jumpy/rough idle.

They are about to take it for a 300mi ride to Delaware so if its not fixed im sure it will show up then.

I also disconnected the POS/NEG battery cables and pressed the brake pedal for a few to reset anything.

very very smoooooooth now

[porschpow]

You know what, I just found this thread out, my 97 Lincoln whistles after it warms up. The sound comes from what I guess could be the throttle body/IAC area. It goes away when you give it gas , but comes back when you let off the pedal. Now I am looking into this. It just seems to me that mine could be a vacuum issue