PGM-FI code 12!! EGR lift sensor

[shawncb11]

Have this problem for a while now. Light comes on after engine warms up and high rpms. Took off the EGR Valve and cleaned out the carbon with cleaner thoroughly. No Fix. While idleing, I reached down and lifted the valve manually causing the car to want to stall(does this mean the ports are clean?) Also removed the lift sensor to see if the valve was moving after the light had come on. No movement. Would the valve open if the car is idleing? Only thing i can think of is there is not enough of a vacuum to open the valve. Possible clogged vacuum chamber? Could the sensor be bad? Does it have anything to do with the operation of the valve itself or does it just report back to the ECM? What do I do?!?!

[Dr_Snooz]

What do I do?!?!

Start with a few deep breaths. Then do a search. Then download the manual. Then proceed through the troubleshooting section starting on p. 11-70 for carb and p. 12-79 for FI.

Try to include your model year and fuel supply system (carb or FI) in the future.

Good luck and welcome to the board. When you get a chance, introduce yourself in the Newbie Introductions section and post some pics of your car.

[kentwat]

I fixed my code 12 thanks to 3Geez and Dr.Snooz

[phrenology]

Get a vacuum pump connect it to the valve and see if it holds suction. I had the same problem. If the diaphragm is torn or worn out, the vacuum going to it won't do anything.

[charliekuney]

Try to include your model year and fuel supply system (carb or FI) in the future.

Snooz, I'm guessing the title gives away that his car is fuel-injected.

edit: So, reading his only other post, his car is an '86 LX-i. He posted the same thread two years ago.

[phrenology]

LX doesn't have a lift sensor on top of the EGR valve.

[charliekuney]

LX is carbureted, and I said LX-i.

[shawncb11]

My apologies. Charlie said it, I have an 86 lxi so yes it is fuel injected. I did post the same thing a long time ago, but I only came to the conclusion that the valve itself or the ports were clogged.

I had no idea there were a few other elements involved with the EGR system.

I initially tried screwing around with it a while back, but only managed to strip one of the nuts so I never bothered with it again since it passed inspection in my state(NJ).

I read on here that a malfunctioning EGR could cause performance issues and affect gas mileage which has been happening.

So I managed to get the nut loose with a Bolt-Out kit and removed the valve to clean it thinking that the carbon deposits were restricting the valve from opening.

I did that, and it didn't work. The light still came on after the engine got warmed up.

So I will read that manual and see what I come up with.

[phrenology]

My apologies. Charlie said it, I have an 86 lxi so yes it is fuel injected. I did post the same thing a long time ago, but I only came to the conclusion that the valve itself or the ports were clogged.

I had no idea there were a few other elements involved with the EGR system.

I initially tried screwing around with it a while back, but only managed to strip one of the nuts so I never bothered with it again since it passed inspection in my state(NJ).

I read on here that a malfunctioning EGR could cause performance issues and affect gas mileage which has been happening.

So I managed to get the nut loose with a Bolt-Out kit and removed the valve to clean it thinking that the carbon deposits were restricting the valve from opening.

I did that, and it didn't work. The light still came on after the engine got warmed up.

So I will read that manual and see what I come up with.

Did you vacuum test the valve? If you don't have a vacuum pump at least put your thumb over the valve stem and press up on the diaphragm. Hold your finger there and if there is a leak the plunger will slowly move back. Also the sensor on top could be bad (or the wires). The other problem may be the master vacuum in the black box has stopped providing suction. There is a solenoid that pulls vacuum when the engine reaches temp. If anything in that chain fails then the EGR will not open and allow exhaust to flow back into the manifold causing the mixture to be off and it will give you rough idle, bad acceleration, high exhaust levels. Here is CA it wouldn't pass. It took me a while to sort it all out.

[shawncb11]

When I test the valve, should I have the engine running or will the plunger stay up while i have a vacuum on the valve stem when the car is off?

Does the sensor just relay information to the ECM or does it control the opening of the valve in any way. Would a bad sensor cause any of the problems I'm experiencing(rough idle, poor mileage, lack of power) or would they be a result of the valve itself not opening.

Maybe if the sensor is bad its not sending the correct information to the ECM and the valve is not opening correctly allowing the right amount of exhaust flow back into the manifold. Does this make sense?

Either way, my next step should be to vacuum test the valve to see if its functioning, correct?

[gp02a0083]

ive had a code 12 thrown before in my 87 lxi. In the black box , there are a few sensors with filter elements. Clean those up.

Do the vac. tests and also check for leaks

[phrenology]

When I test the valve, should I have the engine running or will the plunger stay up while i have a vacuum on the valve stem when the car is off?

Does the sensor just relay information to the ECM or does it control the opening of the valve in any way. Would a bad sensor cause any of the problems I'm experiencing(rough idle, poor mileage, lack of power) or would they be a result of the valve itself not opening.

Maybe if the sensor is bad its not sending the correct information to the ECM and the valve is not opening correctly allowing the right amount of exhaust flow back into the manifold. Does this make sense?

Either way, my next step should be to vacuum test the valve to see if its functioning, correct?

Take the valve off of the intake manifold, clean your finger or put on a rubber glove. Press the rubber plunger on the EGR valve up into the body, place your finger over the valve and let go of the plunger. If the valve closes again it means its torn or leaking. Go to the J/Y and buy another EGR valve or pay like $130-180 for a new one. If the valve stays in place then I would repeat the test with a vacuum pump attached to the port your put your finger over, to confirm. Buy a new gasket when you in stall the EGR valve. The sensor on top only relays a signal back to the ECU telling it if it is open. Its actuated by the vacuum control coming from the black box (follow the tube).

[kentwat]

It is easiest if you just follow the flow chart in the manual. A vacuum guage helps greatly. I picked one up at Harbor Freight for cheap. My light was due to the green cvc disk. Mine is also an 86 lxi. I bought the whole black box from pullapart for like 10 bucks so I had extra pieces. I changed multiple egrs previous to the vacuum gauge and flow chart.

[ecogabriel]

My 0.02 (yeah, I know it is late)

If yours is 86-87 LX-i make sure that hose #17 is securely hooked to the intake duct connecting the air filter with the throttle body. Otherwise, you may end up clogging up the green disk.

Long story: because of the way the EGR management system was designed for 86-87s, they constantly suck up air through #17. When the EGR solenoid actuates the connection is closed and so the modulated vacuum (8in Hg?) reaches the valve.
If the hose is not connected (generally because the connector in the intake pipe is broken) then dirty air is sucked up continuously through that hose and lodges itself in the vacuum canister (a yellowish thing with three hoses attached to it) and in the vacuum modulator (the greenish thingy). Overtime, your EGR system becomes "lazy" as it does not operate as fast as it should (it happened to me) or it stops operating completely.

88-89s have a slightly different circuit that does not need #17. It uses a different solenoid and does not suck air all the time like the older system does.
If you use the 88-89 manual to troubleshoot a 86-87 you need to understand how the system works otherwise you may get lost.