EGR causing a miss ?

[junkyardjeff]

I have been chasing what I thought was a miss in my 89 crown vic with a 5.0,at first I did a tune with,plugs,wires and cap along with making sure the two wires on one side did not touch and developed what I thought was a torque convertor shudder since it started when going into 3rd gear. Changed the trans fluid and was fine for a couple days but the miss appeared again and happened at idle this time so I know it was not the trans so checked and made sure all the plug wires were on tight but would still miss occasionally,not knowing what to do next I plugged the vacumn line to the EGR and now it seems to be running fine. I never had a EGR do that and when they went bad would loose idle but this one idled just fine.

[papastoyss]

I  have no experience w/your 5.0 Ford but on the imports I worked on when I had a real job  I have seen EGR ports in the intake manifold clog up w/carbon which would cause the ports w/the least carbon buildup to get all the EGR gases leading to a lean misfire on those cylinders.

[wayne petty]

I have been chasing what I thought was a miss in my 89 crown vic with a 5.0, not knowing what to do next I plugged the vacumn line to the EGR and now it seems to be running fine. I never had a EGR do that and when they went bad would loose idle but this one idled just fine.

hmm... misfire when the EGR is hooked up... do you have one of the 32 buck actron EECIV code testers..  or a scan tool that would allow you to run a KOEO and  a KOER self test?

do you also have a vacuum gauge you can tee into the vacuum line to the EGR valve and lay the gauge on the windshield..  while you take the car for a test drive to see if the EGR is receiving proper pulsed vacuum signals..

over on the fender is a EGR solenoid.. it has a RED hose to that should have manifold vacuum to it...

i don't recall the colors of the EGR tube..   the EGR solenoid pulses vacuum signal at the command of the ECM to vary the opening of the EGR.. the ECM knows how far the EGR is open because of the egr position sensor mounted on top of the egr valve...  it changes the voltage that goes back to the ecm..  there is a minimum voltage for it.. and it should go up from there...

during the KOER test.. the ecm speeds up the engine and then it starts to misfire slightly.. thats because the ECM is commanding the EGR open.. but its not looking at the stumble. its looking at the oxygen sensor voltage change to verify flow from the EGR...

the ecm also switches the TAB and TAD solenoids to turn the thermactor system on into the upstream exhaust for the change in oxygen sensor readings..


i have to warn you about an issue with a disconnected EGR valve on these and other motors...

the EGR flow into the intake dilutes the percentage of oxygen in the incoming air stream ..

during closed loop.. the ECM is looking at the air fuel ratio with the oxygen sensors.. so the motor does not go too lean...

during open loop when the computer figures out the EGR is not functioning.  it does not look at the oxygen sensors..  but the computer is preprogrammed to run at a specific fuel mixture.. open loop is also employed during acceleration..

when the EGR flow is NOT included in the incoming air charge. there is a larger percentage of oxygen and there will not be as much fuel.. so the combustion will be hotter and create NOX.. but it can also cause the Engine to PING..   pinging will tear up your pistons...  NOX will be very hard on your cats.

if you can run and pass the KOEO and the KOER tests.. the system will be restored to full function and any reduction in power the ECM has commanded will be removed..

once i got my sisters 87 5.0 town car past the 2 tests to get a pass 11.. she got like 29MPG in her lincoln on the highway..

that took an EGR valve.. an egr position sensor.. a smog pump.. a diverter valve. finding disconnected sections of the vacuum harness... and a pair of motorcraft oxygen sensors and an ignition coil to remove the high voltage leak..

the diverter valve was the hard thing to find.. had to grab one off a 92  as the 87 valves were not available at that point..

so during a test drive with the vacuum hose tee'd into the EGR supply.. the vacuum should vary... according to your speed and throttle angle..    you might have some carbon build up holding the valve part way open.. please don't scratch the shaft seating faces if you clean it.. it will leak.. and since there is 17 inches of vacuum on one side and 1 or 2 pounds of exhaust pressure on the other.. any tiny leak will be noticed and cause issues..

here are some links to the EEC4 fuel injection site online..


http://oldfuelinjection.com/?p=35

http://oldfuelinjection.com/?p=43

http://oldfuelinjection.com/?p=13

my crown vic manual has been boxed and moved into storage currently. but i recall you had one..

[junkyardjeff]

I have a Snap On MT 2500 scanner so I took it for a spin to warm it up for those tests and there was still a slight miss when cold and went away when it warmed up,no codes came up with the tests so I need to look somewhere else. Since everything is new and the miss still there the only thing I can think of is the distributor,years ago when I had a 84 crown vic I pulled a motor out of a 88 or 89 to put in the 84 and there were no spark coming out of one or two posts on the distributor cap so I am thinking about installing a distributor I have and see if the miss goes away.

[junkyardjeff]

I think I might have a dirty injector so I am going to put some Seafoam in the tank and see what happens,I pulled all the plugs and nothing out of order and did a compression test with all having 180 to 185 psi so nothing internal so all that would be left is a injector.

[wayne petty]

i use liquid barryman B12  in the POUR type tall thin container.  

Berryman/B-12 fuel treatment
Part Number: 0116
Alternate Part Number: 7518


this is NOT CARB DIP...


this is the same thats in their spray nozzle cans.. but not pressurized...

half a can poured into the  almost full gas tank... with a transmission funnel as this stuff will peal the paint off a car in seconds..  then drive the car as usual...

save the other half for a month down the road..

don't go crazy.. you don't want to wash the varnish off the injector coil windings.. or melt the fuel pressure regulator diaphragm..

[junkyardjeff]

Put some Seafoam in the tank and seen a improvement,might have to run it some more to get the injectors completely cleaned or get some professional strength cleaner but its running better. Since it wont act up at idle its going to be hard for me to determine what injector is causing the problem.