EGR position sensor test - code 31

RonD · Dec 16, 2014

Gas engines produce about 17-21" at idle, I doubt the EGR would use more than 6".

Found another Ford EGR PDF, for testing: http://www.tomco-inc.com/Tech_Tips/ttt32.pdf

kimcrwbr1 · Dec 16, 2014

When you run the KOER test the computer will open the EGR and look for a response with both engine rpm and MAP (manifold absolute pressure). If the engine rpm stays the same when you apply vacuum pressure to the EGR you probably have a plugged EGR tube or a plugged port on the head. The computer uses the inputs throttle position, egr position and MAP pressure to control the pulse width of the injectors. With a new EGR valve if you apply manifold vacuum to the egr the engine should stall at an idle when you open the egr fully. If not pull the egr valve and start the motor if it starts the tube or head ports are plugged.

kimcrwbr1 · Dec 16, 2014

What I meant is pull the tube off the egr and start it do you get exhaust out the tube?

swingjunkie · Dec 23, 2014

Kimcrwbr1,
The EGR tube (valve to exhaust) is clear. I inspected this when changing the EGR. I cleaned the EGR port into the intake at the same time. It had some carbon buildup, but not excessive.

I have not had a chance to get back to testing in an attempt to resolve the code 34. I was doing some more research on this and found two relevant documents. 1) Electrical tests which can be performed on the system sensors (including the EVP and the EGR solenoids). 2) A good annotated picture of the dual solenoid EGRC/EGRV system on my truck. I posted these on dropbox here
https://www.dropbox.com/s/hq308g245zsq6hz/EGRC-EGRV Solenoids Annotated.jpg?dl=0

https://www.dropbox.com/s/avg9prprk5q0tnz/Electrical Tests for sensors.pdf?dl=0

Both are relevant to the original question in this post.

tomw · Dec 23, 2014

From memory, my 85 EFI Lima has two solenoids under the plastic cover.
Some replacement (aftermarket? FoMoCo?) position sensors did not give a correct bottom/top voltage. Solution as add washer or grind pintle to adjust for x.xV closed.
The solenoids are part of a 'dithering' system. One applies vacuum to feed the second (cruise?) and the other vents vacuum to atmosphere to position the EGR valve.
If no response to 'apply full vacuum' command, the sensor is noted as suspect.
EGR is not used at idle. If you have idle problems, and applying vacuum to the diaphragm makes no difference, check the diaphragm for leakage or the pintle valve for sticky. Applying vacuum at idle should cause a BIG change in idle quality, perhaps stalling.
If you have mud daubers, check that the vent solenoid with the cube of sponge rubber to filter is not plugged by nest/cocoon materials.
The FoMoCo EVTM manual is PRICELESS. I got mine when I bought the truck in Dec 84 (CA EFI emissions 'spec' that failed SMOG test @5k miles!!!!)
Anyway, in addition, the VRESVR should be a large can(plastic?) and should have all vacuum 'users' on its side of the check valve. The 'other' side is manifold vacuum.
Maybe not all, see JPG, but at least the HVAC and brake booster as noted above....
tom

kimcrwbr1 · Dec 23, 2014

The egr control solenoid has a filter on it that filters the air that allows the egr valve to close. The round cap pulls off maybe spray some WD in the bleed hole as you work the throttle. I was able to stick my little finger between the vacume pod and the valve you con feel the egr open and close as you work the throttle?

kimcrwbr1 · Dec 23, 2014

My book shows two solenoids the air bleed solenoid only has one vacuum line and the filter.

swingjunkie · Dec 26, 2014

OK. After changing the EGR position sensor I no longer get code 31 on the KOER test, but I still have code 34. To be clear I have stored codes on this vehicle, the code only appears during the KOER test.

After researching the functionality of the dual EGR solennoids (EGR Control/EGR Vent) I also measured the resisitance of each solenoid. They measured 40.5 and 42.6 ohms (EGRC and EGRV). This is within range. I verified 12.8 volts at the solenoids with key ON. I then pulled those solenoids out of the truck for testing. I pulled the vent cap on the EGRV solenoid and verified it was not clogged by foreign debri. The small foam insert in the cap crumbled on inspection and so I replaced it with a fine brass mesh screen.

I then built myself a wiring harness to test the solenoids. The EGRC is normally closed and blowing on the vaccum supply line it is tight and will not pass air. When energized it will pass air out of the vaccum return line (to the EGR) and out of the EGRV vent. I then energized the EGRV and EGRC concurrently and the EGRV closes and does not pass air out of the vent, but air still flows out of the EGRC return line(to the EGR valve). So my testing seems to indicate that the EGR solenoids are working properly.

Based on my understanding of this dual solenoid configuration, the solenoids always have 12V suppy and then the computer applies ground to the solenoids to open/close them. By varying the rate/duration at which these solenoids are open/closed the computer manages the level of vaccum applied to the EGR valve.

So all that said I now have a new EGR valve, new EVP sensor, and my EGRC/EGRV are working properly. As suggested I tested the EGR directly by applying vacuum at idle. This immediately stalls the engine.

I'm not sure where to go next with this. I suppose it's possible that the EGR port further inside the throttle body is plugged. I cleaned the port where the EGR attaches but it could be clogged further inside?

Suggestions appreciated.

kimcrwbr1 · Dec 26, 2014

I was able to stick my little finger under the vacuum pod on the egr and feel the egr open and close as you give it throttle. You are correct on the operation of the solenoids but to be clear disconnect the single vacuum line solenoid and plug the vacuum line then give it gas the egr should open up at higher rpms and stay there when you let off the gas and run rough at idle until you release the vacuum on the egr. For the KOER test the computer will bring the rpm up and stabilize then open the egr and looking for a drop in the rpms. If the singlr line solenoid does not close all the way the egr will not open. What I did was while the engine is running disconnect the vacume to the egr and spray some WD in the vacuum line and feel for vacuum pressure when you give it gas. A vacuum guage would be nice. If you dont feel pressure pull the cap off the release solenoid and spray wd in the relief hole It should suck air in as you work the throttle. I bet the relief solenoid is not fully closing allowing the egr to open.

kimcrwbr1 · Dec 26, 2014

The egr is working properly if the engine stalls when you apply manifold vac to it, your problem is in the solenoid valves or a cracked bad vacuum fitting/tubing.

swingjunkie · Dec 27, 2014

kimcrwbr1,

Thanks for the reply but it not clear to me what you are suggesting. I've posted some pictures of the EGRC/EGRV solenoids here along with some short videos of the testings.

https://www.dropbox.com/sh/6zuxpriop8s281r/AACQ7ajZU_MdMIm-2K3ldrhRa?dl=0

kimcrwbr1 · Dec 27, 2014

You need to pressure test the solenoids and vacuum lines all it takes is a little leak for the egr not to operate correctly. Another possible leak is at the egr where the senser bolts on. I just use my tonge to plug the hose after sucking on the tubing. If its leaking it will lose pressur fairly quick. The piece of tubing between the two solenoids is another possibility. I got lucky and found some solenoids at the bone yard. Maybe try spraying WD-40 through the solenoids as you energize the coils to clean the valve seats good? Your getting close those kind of parts can be real hard to find around here in WA.

kimcrwbr1 · Dec 27, 2014

http://www.ebay.com/itm/Ford-NOS-E53Z-9J466-A-EGR-FILTER-pack-of-4-/201211762947?pt=Vintage_Car_Truck_Parts_Accessories&hash=item2ed927d903&vxp=mtr
I found these but I suppose you could use a lawn mower fuel filter to filter the air going into the vent solenoid to keep it clean.

kimcrwbr1 · Dec 27, 2014

If your still confused the way the solenoids operate with the computer. First off erase the memory and then disconnect the battery for 1/2 hour to reset the computer to preset values. After the engine comes up to temp it goes into closed loop and all the gagets start working. When the computer wants to open the EGR it closes the vent and then provides pulses to the control solenoid until the EGR senser sees the egr is at a certain position and stops. The vent solenoid holds the egr open until there is a command to close it then it will deenergize/pulse the vent until the desired position is reached. After a few complete warm up cycles the computer learns the best position for the EGR looking at all the inputs as in throttle position, manifold pressure, O2 and RPMs and set new values. Is the code 34 the only on demand code your getting? Allways fix the lowest number first erase the memory and reset the computer then run at medium speeds for at least 20 minutes before pulling the codes again when the engine is still up to temp. Confirm the repair and move to the next code.

swingjunkie · Dec 28, 2014

In my initial post I had codes 31, 34, and 41. Code 31 was resolved with replacement of the EVP. So working up from the lowest code to the highest as suggested. I cleared codes and left the battery neg unhooked as suggested. After a 20 minute test drive I still have codes 34 and 41. I did run some WD40 through both solenoids.

EGR position sensor test - code 31

Official TRS AI

Well-Known Member

Well-Known Member

New Member

Well-Known Member

Well-Known Member

Well-Known Member

New Member

Well-Known Member

Well-Known Member

New Member

Well-Known Member

Well-Known Member

Well-Known Member

New Member

Sponsored Ad

Sponsored Ad

Member & Vendor Upgrades

Truck of The Month

Recently Featured

Follow TRS On Instagram

TRS Events

25th Anniversary Sponsors

Check Out The TRS Store

Sponsored Ad

Sponsored Ad

Sponsored Ad

Amazon Deals