I know this site is for later model F150's, of which I've had 2, a 1999 and a 2000, but now I've got a '92 lifted 4x4. It's throwing a code 33 and a 77. I know the 33 is an EGR issue, but does anyone know what the 77 is? Also, is there a way to know if it's the EGR valve or the sensor? Thanks for the help. I love this truck-best F150 I've ever owned! -Al Nobles

 

Code 33 is no EGR opening detected.
It can be the EVR, the hose. the EGR or the EVP.
EVR controls application of vacuum to the EGR.
EVP is what reports the action back to the EEC.
Any failure in this hardware path will cause the code.

Code 77 is a failure to detect a WOT during self testing.
The IAC controls all the rpm self testing.

 

Actually, code 77 is an operator error. The IAC doesn't affect the TPS, and that code is set when the dynamic (operator) response of stomping the gas pedal isn't detected. For more info, read this thread. But you can ignore that code.

A common source for 33 (or any code that might result from a vacuum leak) is a crack in the hard plastic vacuum lines. Common locations include at the "coffee can" on the R wheelwell, the white vacuum line in the R rear corner of the engine bay going to the recirc motor, & the back of the engine near the EGR tube on 4.9Ls. (What engine do you have???) To fix this type of leak, break the original line apart, & slip some tight-fitting rubber vacuum line over the ends to rejoin & seal it.

 

thanks for the help - i appreciate it -al nobles

 

I replaced the EGR sensor. That didn't do it. I also vaccum checked the EGR. It seems to be working - took it off and cleaned it also. Valve opens and closes by hand when I push up on it, so I'm guessing it's okay. I'm not sure about the coffee can. There's a place under the two lines going in to it that has no line on it, but it looks like one belongs there. I can't find any breaks anywhere else. Any suggestions? Thanks. -Al

 

Did you test the EVR or EVP? The Haynes manual tells how with common tools.

Check your vacuum map to see how many lines go to the coffee can. It's probably labelled "V RES" for vacuum reservoir.

 

thanks again - i'm going to get on it this a.m. - al nobles

 

If you're not making progress, take it to a pro. It'll take less time & probably less money than if you keep fighting it.

 

If you find one of those rigid plastic vacuum lines is broken in one place but is otherwise ok, not brittle, best repair I know of is with milspec-quality heatshrink tubing, if you buy one of those expensive assortment packs in the auto store, you can sometimes get the weatherproof stuff that comes with a glue lining, you'll get a perfect seal, or, you can put some auto silicone on the rigid line a little distance from the break either side (you don't want to get silicone in the line!) and slip regular high temp heatshrink on, long enough to cover the silicone, then shrink using a paint stripper hot air gun set to low (usually specifically made for doing heatshrink) - don't overshrink it where the break is, or you'll constrict the line...

Should outlast the rest of the line.

 

Finally found a break in the line today. It took almost a freakin' week, but I finally found it. All I did was get a piece of rubber connector hose and stick the two ends back together. Will that work? I didn't heat shrink anything. My check engine light went off so I figured all is back to normal.