My 92 f150 with the 302 is not running right. I have codes 173 and 334. I tested the egr and evolve and everything was within spec. 334 is egr closed voltage is higher than expected. I think chiton said under .67v is good I tested mine at .63v. My fuel pressure is 40psi idling, 48 with the vacuum line disconnected. Connected again back to 40. Shut it off and it rose to 44 and after 5 min it still read 44psi.
I disconnected the iac and nothing happened. Idle was still a bit over 1000rpm. Replaced it with one out of the junkyard and no difference. Something is not right here.
When I start the truck cold in the morning it spits and stutters for 30 seconds then snaps out of it. And Obviously it is running really rich. At about 35 mph it surges and bucks bath and forth. Which to me is egr. I'm confused at this because it tested good. Also when I drop into gear the rpms drop to normal but put back into park it idles back up.
New parts include tps, ect, plugs, wires, cap, rotor, coil, thermostat, and I swapped out a used iac
Does anyone have any ideas?

 

Kind of sounds like what my 92 f150 with 5.0 was doing when the TPS was going out. Actually that is exactly what my truck was doing with a bad TPS.

 

I replaced mine, it was terrible, took it back and got another. This one test out perfectly within spec. Is there someway to adjust it? I can't get the rpm change when I unplug the iac like I used to. Do I have to bite the built and drop 65$ on a new iac?

 

Is my fuel pressure too high? Also these codes are CM codes

 

What voltage are you getting from the TPS? closed throttle and full throttle. To adjust it you just loosen it up and turn it by what I read on the mustang forums. I have never tried it so not sure.

 

40 psi is fine for fuel....If you have not replaced your O2 sensor in the last 30k miles or so might want to do that also.

 

Here is a thread I found for code 334

trouble code 334 - Ford F150 Forum - Community of Ford Truck Fans\

https://www.ford-trucks.com/forums/9...ough-idle.html

 

Don't quote me it was Monday when I tested it. I was to say.97v closed and 4.87v wide open? I can check again in the morning.

The O2 sensor is next on he list

 

I'll look into that. Everything on the valve tested good according to chitons and threads I found on here. Could it be farther up in the system on that sylinoid by the tab and tad?

 

I don't know, "but it seems you have a good TPS by what readings your getting."

Here is a link I found on the Tad:

TAD Solenoid Function Testing - FSB Forums



On my 92' I currently have the Upper Tab and Tad vacuum line connectors pluged...For my EGR I have a block off plate, "piece of thin sheet metal." Between the EGR valve and the upper intake manifold. Smog pump removed and heads and Y-pipe plugged. Yes the truck runs better and I seem to get better gas mileage the way it is now. 18-20 mpg highway if I baby it. Most of the time I still run around 15 mpg, "lead foot syndrome."

 

Copied and paste from another post on different forum:

For the 332, the older systems had a position sensor on top of the EGR valve. The newer systems used some kind of differential pressure measurement. Not sure which system you have - but this is one direction I would head for - IIRC - the differential pressure systems had problems with tubing plugging up. The other thing to check is the valve control solenoid - just follow the vacuum tubing from the EGR valve. I've had experience with this solenoid plugging and not able to move the EGR valve around to the computer's liking.

Any possibility that the EGR system is pulling in air instead of exhaust gas, like with a cracked tube or loose fitting? Would tend to screw up the expected / learned fuel-to-air ratios as well as make thing idle a bit high.

 

wait you unplugged the IAC valve when it was running and nothing happened?

 

also i had a high idle and bucking and hesitation when i had a really bad vacuum leak from my intake manifold

 

40 psi idling and 48 psi with vacuum line disconnected is to high. That is your running rich problem.

I would double check those numbers. You shouldn't be any higher than 35 idling and 40 with vacuum line disconnected. Check to see if fuel is leaking from the FPR when you turn the key to ON and then again a few times, without starting the engine.

 

that is correct!

will try that in the morning, so could a bad pressure regulator cause fuel pressure to be high? i recently (month ago) replaced the tank, pump, sending unit. could there be air in the system still?