New EGR or Not?

June 15, 2006, 07:15:41 PM

I ran the codes on my 88 5.0 Cougar and got a #34 - bad EVP sensor. I replaced it but am still pulling the same code. Sick88Tbird
suggested getting a new EGR as well. That may be what it needs but I would rather know before I spend another $70-$80 only to find it isn't bad either. Any suggestions?

New EGR or Not?

Reply #1 – June 15, 2006, 11:32:20 PM

Did you clear the computer out? also, it could be a bad vacum line.

New EGR or Not?

Reply #2 – June 16, 2006, 07:50:10 AM

well,, this is kinda tricky so you gotta look at the whole picture. Trace out the green vac line. On my coug the vac distribution starts with a red line from the intake and travels behind the coolant fill tank to a bank of solenoids.

the red line feeds this bank with suction.

the green line will be at the base of one of the solenoids
the green leaves this solenoid and goes to the egr to actuate it
as the egr gets vac, it moves the center rod which varies your evp
the electrical connection starts on pin 27 of the eec, grounds with the tps and a few other things, and signals a voltage on the same path as the tps and map back into pin 26 on the EEC.

page 51
illustrates the solenoids behind the coolant fill tank (red feeds this bank from the intake , up to the vac dist block on the fire wall, downto the coolant fill tank)
When the EGR Control Solenoid gets electrical signal, it opens a vac path for the green vac line that inturn moves the egr guts.
The egr guts move the output of the signal on the EVP and from that points is all FM to me:D (FM= f'ing magic)
The EVP is nothing more than a variable resistor.

page 55 (3.8L engine)
illustrates how the EGR vent and control solenoid wires

page 58 and 60(5.0 engine)
illustrates the egr system again.

If i were you, i would idle the engine
spray carb cleaner along the vac paths of the red and green
listen for engine rpm to change
if you hear a change, you have a leak

next..........
manually undo the red path and green path and put suction on one end while plugging off the other.
****I found a crack in the long piece of plastic that plugs in the base of the vac solenoids along the coolant fill tank area. ***

next,,,,,,,,,,
perfrom a good cleaning of the inside of the egr with carb cleaner and then test the egr that it holds suction.

next.......
you can put suction on the egr vac fitting but if you dont have a vac guage, you cant tell if it leaks back down or not. A vac tester is a must have for quick isolation of leaks. If the rubber diaphram inside has a pin hole, it will leak down either in a minor or major way. That said,, if its minor, you will only see it on a vac guage.

next,,,,,,
use your ohm meter and page 60 to hook up your meter to the EVP.
manually actuate the egr either by hand or with a vac pump.
first check for resistance across the whole egr sensor by connecting to the BLACK WHITE and ORANGE WHITE pins.

vary the egr vac while hooked to the black white and brown light green
vary the egr vac while hooked to the brown light green and orange white

OR>>>>>>>>>>>>>>>>> undo all the smog stuff including all vac and elec connnections as well as remove the pump and plumbing.

sorry for all the typing,, told you this is tricky but atleast you have some info to go with,,good luck

New EGR or Not?

Reply #3 – June 16, 2006, 08:48:23 AM

jcassity
Thanks for all of the good info! That's the kind of test info I was looking for. Is that a shop manual you got the info from? I have them for all my other vehicles - probably would make sense to get 'em for the Cougar. Thanks again for your time.

New EGR or Not?

Reply #4 – June 16, 2006, 09:02:48 AM

yep,
1987 evtm
i have detailed shop manuals but the small evtm gets the most use.