1991 f150 4.9 5spd 2.73 rear end. (axle 12)
Code 33: Egr opening not detected.
I am getting about 13 mpg doing mixed driving. I am not driving like a douche
I am cruising between 60-65 mph on the freeway.



Truck runs fairly decent except at part throttle in 1st and 2nd gear around 1600-2k rpm she seems to buck and stumble a little bit. I've also noticed that when you first start up the truck and you tip in the throttle a little bit she has a small stumble too.


What I have done. I have seafoamed the truck, put in motorcraft copper plugs, new cap and rotor and now I am waiting for my kingsborne wires to get in (did all this to eliminate any other issue just in case, plus old rotor looked alittle burned out). I have applied vacuum approx 4in hg to EGR with truck running. Truck started to stumble.


Tested the EVP according to oldfuelinjection and the EGR closed was showing .49v (in spec) on a centech dmm. Applied vacuum and voltage went up like it should.

I am suspecting something going on with the EVR. Ill be testing it according to
Fuel Injection Technical Library » EGR Vacuum Regulator (EVR)
If I am understanding correctly I need to have it plugged in and run a wire from the back of pin 13 and ground it somewhere correct?

Ill check resistance too along with vacuum lines and vacuum canister.
Anything else I should troubleshoot to get rid of code 33?



Also vid of what truck is doing.
<iframe width="560" height="315" src="//www.youtube.com/embed/Nb8VLROSLYU" frameborder="0" allowfullscreen></iframe>

 

Here's what I did to my truck.

https://www.ford-trucks.com/forums/1...d-evr-fix.html

 

I am not sure that 13mpg is out of the norm for that combination.

 

it is.he should be seeing mid to high teens mixed w/ this combo.300/zf5/2.73
pushing 20 if not over on his 60-65mph interstate runs.
13 mpg realm should be the hd truck with 351w/zf5/3.55 type mileage.

Check your timing guys!!!

 

I actually have the mazda trans. Also it looks like checking the timing on these engines looks to be a pain. LOL

I measured resistance between the 2 pins on the EVR and I got 35 ohms. Which is in spec.

Also have been testing stuff according to this article
EGR/EVP Codes 31/32/33/34/35 Troubleshooting

I haven't done #4 yet listed in the testing procedures. It's passed all the other tests. I am going to ground out pin 33 now for my next test and see what happens.

 

Ground out pin 33 and evr applied vacuum to EGR.

Will check timing.

 

could a tps, o2 or maybe even a map cause this issue? I'd think vac leak but the evr works...

 

A faulty TPS or MAP could cause the stumbling issue, but Code 33 indicates the EGR is not opening. You forced the EVR to apply vacuum to the EGR which in turn caused a signal change via the EVP. I would suspect a leaking vacuum reservoir. Very common issue on these old trucks.

 

While testing my EGR issue, I Tee-d a vacuum gauge to the EGR valve. Ran the KOER test and right after the goose code you should see vacuum of 5 to 7 inches and it will waver little bit while the ECU is checking EGR function.

While driving, I get about 5" vac at cruse and depending on engine load, I have seen up to 7-8" vac. Soon as you let off the gas, it will drop to 0"vac.


Next thing to check is the EGR sensor it self, it may be wore out and giving a good signal but not a CORRECT signal(had that happen with the 302 V8 engine). That one took some head scratching to figure it out.

 

I thought you already checked the output signal value. My mistake.

For reference: Fuel Injection Technical Library » EGR Valve Position sensor (EVP)

 

A good bit of info from that link: "

NOTE: Allow +/- .2 volts for all specifications Ford EGR valves will open 100% at 8 inHg of vacuum. Therefore, 50% opening will be obtained by creating 4 inHg, etc"


Going to watch the EVP signal next for s&g's...... That why explains I saw no more than 8" of vacuum on my testing.

 

Word, the can LOOKS fine but doesn't mean it is. Either way ill check values on these sensors to see what the hell is causing my stumble. I saw a youtube video where some guy just sprayed electrical cleaner on the iac and tps connections and apparently that helps a hesitation issue.
Hmm I should T in the egr line. Good idea. I have a boost gauge but it reads vac too. Perhaps ill just pull out the egr valve and clean it.

 

Ok I have an update and some codes. I get the typical 33, then it goes to a set of codes that flash faster. CM codes? Anyways I get 334. EVP circuit above the closed limit of .67 volts

I also did a koer test and got code 172. HEGO sensor circuit indicates system lean (right side)

 

You will get either two or three digit codes, not both. Your model year/engine/transmission combination will typically display two digit codes.

 

I can take a video of it. Maybe I messed up somewhere. I swear I got 2 3 digit codes though. Either way I got 15.6 mpg this fuel tank. But I am looking around for vac leaks.