Manifold Abolute Pressue sensor, and I believe you do have one. Also an EGR sensor, and Throttle Position Sensor. Each will wreak havoc with drivability. You truly need a code reader.

 

 

I pulled the codes today with the ignition on and engine off I got 334 which says EGR closed valve voltage high. Now with the engine running test I also got 334 and 172 HEGO ( HO2S) sensor fault/lean, 536 brake on/off (boo) circuit not activated during KOER, 538 invalid cylinder balance test due to throttle movement during test and 632 overdrive transmission cancel switch/ no action during self engine run test. What do you think needs to be done? I appreciate all of your help.

 

EGR sensor high voltage, sensor sits on top of EGR valve. Possibly hung vavle or hung sensor, this one will degrade performance to the point it is undriveable.

O2 Senor lean, it's expecting air and not getting getting it. another driviability issue. TPS is reading open, did you throtlle it during the test? If not it's going bad and reporting open throttle when it's not.

OD cancel and brake circuit are other sensors, but will not effect the engine like the others.

Do you have a reapir maunal? It walks you through the KOEO and KOER tests.
You have to follow the correct sequence to test all sensors. The EGR and O2 sensors should be your main focus. They are the root cause of your problem. The sensors are reporting a diffrent condition and the computer is acting on those. That's why you are powerless.

 

Lean conditions are seen when there is too much oxygen( vac. leaks, egr not seated-closed,- Low fuel pressure-Map sensor probs.-mass air out of calibration range,etc.I would like to see what fuel pressure you have.Low engine power is caused by poss -no exhaust flow- low or no air flow into intake-low fuel pressure- or engine mechanical prob.(broken valve springs, bent push rods, stuck valves, worn cam lobes,piston damage,etc) as sensor or pcm probs.I have found that engine power loss concerns are found more qiuckly when they are mechanical in nature-- Stick with the engine theory of SUCK (air) FART (ign, spark, fuel) BLOW (exhaust) and I think you will find your prob LOL Blue

 

There maybe multiple problems but the lean condition and EGR are the ones I would address first and the Throttle movement.
They have given you suggestions on the EGR, and possibly the throttle position sensor. If the engine believes the throttle plate is constantly moving it will adjust the fuel flow to match according to the position of the throttle plates, use a multimeter and hook up as suggested by Fordfuelinjection.com to read this sensor output.

For the EGR, follow the fordfuelinjection.com instructions for egr operation. If you have the EGR like my 91 bronco you should take out three screws and be able to look at the valve itself from the vacuum canister side to see if it is stuck open or not. Also you can apply vacuum to this valve with a vacuum hand pump to also check to see if vacuum is holding in this valve and for functionality of the valve.

From things I have seen on this board if you have a fuel system problem it is usually a rich condition caused by the fuel pressure regulator going bad. Low fuel pressure would be a bad seal in the system or possibly a bad pump or even a stuck in open Fuel pressure regulator. The only way to test is with a fuel pressure gauge at the valve on the fuel rail.

If all those check, it could be just a bad oxygen sensor giving a bad reading to the computer. Usually these are replaced every 100,000 miles just to be sure there is a good one in place.

 

I agree with alxsnmr on checking fuel pressure at shrader valve but not only at idle, put it up on the windshield where you can drive it, had one 6 months ago and found lost fuel pressure(low) on hills, flow tested injectors already and checked good, found dirty sock (filter pressed on fuel pump in tank)on fuel pump in tank. Tank had fine particals of tan -brown sand like materials. Had another with about 1/2 gal of diesal in tank.After sitting overnight diesal settles in tank at pickup drop down area- turn key on first time and fuel pump primes pure diesal,truck moves and mixes up gas and diesal but fuel filter is contaminated- replace fuel filter and runs much better after about 20 miles untill it sits overnight again--no power and stumbles on takeoff, removed tank , cleaned- blew out lines replaced fuel filter, ran prem and injector cleaner through it and drove for about 20 miles ran great and ran great next morn.3 months in one shop 2 months in another and 25 days at our Ford dealership. Lol Blue Ps never seen a fuel presure regulator cause low fuel pressure BUT I seen things fix probs. that made no sense at all too!!!!!

 

yes go check fuel presser, I am dealing with one that the pumps are going hay wire, and no it is wiring or the controller because I flow tested the tank pump, main is new, filter is new, fuel gauge would 38 psi, 2 volt meters 1 to each pump, I am looking at all this, main pump gives 7-10v most the time, back pump none most time when it dose its 1-2v for a sec, then out of no where I thur the tank pump will never get no power or main pump will stop get power and fuel pressure will go 17 psi and hold some times die, if stay running you can drive it but runs rough and with a loss of power, you can't give the tank pump full power all the, it ran great like that till the bowl over filled after a weak but I left wire with a switch so the tank pump can pirme bowl when the bowl is emty, feed main pump with full power, ran great, now the back pump when went out running of gass to many time(fuel gauge don't work, it's the board I found that out when I clean the tank of shuger) in all I going to deleat the the tank pump

 

A few months ago I put up a post asking if having no emissions pump hooked up and all the lines from it plugged up could cause any problems? everyone said no, what do you think? It froze up on me so I put on a shorter belt to over ride it. Thank you.

 

All the sensors in play use a voltage reference and then go up or down as engine variables change. At startup the system runs open loop and ignores some sensors until engine operating temperature is reached. It runs rich until the engine reaches operating temperature, then goes closed loop and evaluates the sensors.

I reckon if you put resistors on the plugs to keep the computer happy, you'd be able to by-pass them all. The computer is still expecting a signal from the sensors.

The other folks mentioned fuel delivery, you need to check that as well.

 

Today I replaced the oxygen sensor and the sensor on the egr valve, the truck still ran the same. I ran a code check again and 172 was gone (hego) but there was a new one 311. All the other ones remained also.

 

311 is the Thermactor -MTA- (TAB/TAD) solenoids that are located on the fender apron. These solenoids send air to the exhaust system or the catalytic converter.

Did you run the engine to operating temperature for the code reading?

Did you check fuel pressure at the rail yet?

 

I ran the codes again, engine was warmed up and still 311. Checked the egr valve out and it's working properly. Is that the tps sensor under the front of the thottle body, so it will have to come of to get at it?

 

The TPS is in line with the throttle cam. You won't have to pull it to test it. Just unplug it. If you do, then you'll have to read ohms on the wires. If you leave it plugged in, you can read VDC. Either way, it should be a perfect arc of reading changes as the TPS is moved. Any flat spots, or erratic meter movement denotes a bad unit.

 

I would probe the recommended wires using the voltage meter and leaving the TPS plugged in. The TPS is basically a glorified voltage potentiometer, which translates into it has a constant voltage in but changes voltage out based on where the voltage pot is pointing, in this case degree of change from the base or idle position. Ohms will go down as the TPS approachs full open position but everyone can read voltage change easier than the ohm change. I recommend Ford fuel injection because the specs are much easier to read there and it is free to read up on it. Otherwise you need to buy a proper service manual to diagnose and get the proper specs for your sensors.