1994 Sub "Service Engine Soon" light

[Cusser]

1994 Suburban "Service Engine Soon" light has come on intermittently lately, then goes off by itself. I may be wrong, but it is my understanding that these pre-OBDII vehicles need to have that light on to read the error code? I changed the air filter, wires are two years old, I think spark plugs are overdue for replacement. Any suggestions as to what's causing this? 5.7 liter engine 2WD half-ton, dual AC, 190K miles. Engine temperature fine, fuel pump repalced about 3 months ago, same with fuel filter. Thanks.

[2000CAYukon]

Can't hurt to see if there are any codes stored. See www.troublecodes.net/GM

//2000CAYukon

[Cusser]

Thanks, I'll try that this weekend.

[Cusser]

OK, here's where I am:

The Service Engine light sometimes comes on, but then goes out. I red the error codes, got a "12" to show the computer was able to store codes (good) then an error code of "32" which is an EGR error. This morning I went outside, found the EGR, pulled off its vacuum hose, and attached my hand vacuum pump. It would not hold a vacuum, likely bad EGR diaphragm. I then started the Sub and pulled hand vacuum lever, but no affect, no mis-fire or stalling. So it looks like my EGR is bad, and if I can get clearance to swap it out, I will, this weekend. "Of course" I see at least two different EGRs listed for my year and model, it's a Suburban !!!

[2000CAYukon]

AC Delco 214-5073 is the right EGR valve for your Suburban. I prefer to stick with AC Delco for Emission parts.

By the way, it should hold a vacuum with the engine off so it does look to be a bad EGR valve.

//2000CAYukon

[Cusser]

Originally Posted by 2000CAYukon

AC Delco 214-5073 is the right EGR valve for your Suburban. I prefer to stick with AC Delco for Emission parts.

By the way, it should hold a vacuum with the engine off so it does look to be a bad EGR valve.

//2000CAYukon

I read that this specific EGR is a "negative pressure EGR" so the traditional test of just pulling a hand vacuum on it doesn't work. I went to CarQuest but the part there ($50) did not look the same as mine (#17087194), was more of a universal EGR with different numbered washers which you were supposed to look up on the chart and figure out which one to use. Nevertheless, it wouldn't match up exactly like my original one. So here's what I've done, before ordering #17087194/AC Delco 214-5073 for about $80:

I cleaned my existing EGR with spray carb cleaner, and reinstalled it. I disconnected the battery to clear error codes. I started up the Suburban, pushed in the EGR diagragm, and Sub shuddered and shook, nearly stalled, like it's supposed to (with a traditional EGR one could pull vacuum on the nipple and the same should happen). I'm going to try it and see; on a short outing last night the Service Engine Soon light did not come on. I'll update later.

[Cusser]

Two days later, with longer drive, Service Engine Soon light again came on, then went off again. Again the code read 32 for EGR system. Right now I'm reluctant to pay about $80-110 for a Delco EGR or pay my mechanic $200 to install same, only to find out two days later that money was thrown out the window.....

[2000CAYukon]

Autozone has the diags for the EGR valve and solenoid (you must register to see them). If you do have a Negative Pressure EGR (it will have a N stamped on it), it should hold vacuum with the engine off. If it does not, EGR is bad. Does EGR solenoid hold vacuum (TBI side)?

//2000CAYukon

[Cusser]

Originally Posted by 2000CAYukon

Autozone has the diags for the EGR valve and solenoid (you must register to see them). If you do have a Negative Pressure EGR (it will have a N stamped on it), it should hold vacuum with the engine off. If it does not, EGR is bad. Does EGR solenoid hold vacuum (TBI side)?

//2000CAYukon

Yes, I believe mine's a negative pressure EGR, the part number 17087194; I tested mine, it does NOT hold a vacuum when I tested it with my hand vacuum pump (neither did a replacement one in the store, didn't get it). A few sites said negative pressure EGRs could not be tested with a hand vacuum pump. FYI, my traditional EGR on my '88 Mazda truck DOES hold vacuum, and pulling vacuum on it while idling does stall-out its engine.

My EGR solenoid valve DOES hold a vacuum at the TBI side, and it does click when I apply 12 volts to it, although I didn't test it in that mode with the hand vacuum.