89 F150 4.9L
Have a code 42R that I'm trying to resolve. The 02 sensor voltage is .895 (should be between .35 and .55). It has a slight/short hesitation when i press the gas pedal. I'm being told to check for a vacuum leak as the likely culprit.

I did a smoke test (using a multi use pump and a cigar smoke). unplugged the hose the MAP and capped it and put gloves over the pipes to the airbox. A small amount of smoke was coming out of the port I connected to for inserting the smoke. Do I need to do a better smoke test or will this suffice?

results:
The new EGR valve has smoke coming out of it, but not much and not for long and only after loading up a bunch of smoke. It took a while before I saw anything come out of it.
The throttle body spring (I guess that is what it would be called) has a similar leak the EGR valve, minimal and not for long. It took a bunch of smoke before I finally saw something come out the spring.
The return hose for the charcoal canister has a small hole in it. I'm going to get some new hose but I don't think that will have any impact, right?
The charcoal canister has smoke coming out from the top *****, which aren't sealed so I'm not concerned (should I be?)

video of EGR smoke - https://photos.app.goo.gl/BtGgvj2FQSCKXke66
video of Throttle body smoke - https://photos.app.goo.gl/2WiLSHfeRhRj8Ukz6
video of Charcoal Canister smoke - https://photos.app.goo.gl/uhDZWsbYYcAxxDA19


Replaced: PCV valve, IAC, TPS, EGR valve, EGR position sensor, Combo TAB/TAD unit, Distributor w/ICM, Ignition coil, spark plugs, spark plug wires, 02 sensor, reservoir fuel tank selector valve, low pressure fuel pumps

 

All of those small vacuum leaks add up and cab trigger a lean condition. A new EGR valve, or old one actually, should not leak to atmosphere.

Does your truck use a Canister Purge (CANP) solenoid? This is triggered by the computer to allow fuel vapors to be pulled into the intake. Early model EFI trucks may not have one.

 

I'm guessing the throttle body shaft is leaking, much like a worn out carb.

 

My CANP does not have a solenoid.

When i do a vacuum test with the EGR, it holds the vacuum (after applying 5 in./Hg of vacuum). That would be a bummer to replace the new EGR valve.

 

Then you do not have a CANP. Regardless, replace the vacuum line

The EGR valve should not leak during a smoke test ever. 5 inches of vacuum is not much to test with.

What is the EGR valve brand name?

 

So it's just called a charcoal canister if it doesn't have a solenoid? Trying to learn all the terms.

I don't know the brand of the EGR (son bought it). I'll find out tomorrow when I pull it off. I was going to pick up a Standard EGR. Is there a brand I should be buying instead? I don't see a Motorcraft EGR valve anywhere.
The EGR had

 

For the Throttle Body, is my only option to replace it if the new EGR valve doesn't do the trick?

 

Most likely you will need to find a new/rebuilt throttlebody. At one time I thought RockAuto had a service available to send yours in to a rebuilder. Not sure they do that anymore.

 

I put in the new EGR Valve (Standard is the brand) and the hesitation went away and i no longer have a code 42 R when doing a KOER OBD1 test. Thanks!
I'm going to keep an eye at the junkyards for a Throttle Body assembly (right term?), but it looks like I might be alright for now.

 

Thing that bugs me is carbs develop leaks on the shaft & cause bunches of problems.

There are repairs & rebuilds for such, but I've yet find anybody with kits or services to do the same for TBs.

Glad you've made progress.

 

Glad you made some progress and the update.

 

they have rebuilt-->1989 FORD F-150 4.9L 300cid L6 Throttle Body | RockAuto

 

So after about 10+ minutes, the miss/hesitation is there. I first noticed it this morning so I tested it again tonight. When i start it up, there is no hesitation when I increase the RPM's (from an idle). I would pull over every couple of minutes to check for hesitation when i increase the RPM's (from an idle in neutral). No issues for the 1st few times and then it started happening.

I'm wondering if there is something about the truck warming up for a good period of time that is causing the miss to start showing up.

I ordered the Throttle Body from RockAuto. I'm really hoping there isn't some other cause for that miss.

 

Got my Throttle Body from RockAuto and installed it. The hesitation is gone when i accelerate in neutral.......but now the idle is at 1000 rpm's. Starting a new thread for that.
I'm taking baby steps forward.