11-12 hg vacuum? NOT good, Did this come on sudden? bent push rod (can still get good compression results ) Plugged cat maybe? would explain low vacuum. Time to remove one plug wire at a time to find the no change in idle cylinder, remove that valve cover and inspect. good luck keep us updated

 

These numbers are waaaaay low. I just replaced a bad TPS on my 92' 351w and it was reading better than this. The percentage of sweep in voltage is also very short in range.

The next thing I would do is to check the reference wire(orange)to black and make sure you have 5 volts. If you do, I can almost assure you that the TPS is no good. If you have less than 5 volts, unplug the harness from the EEC and ohm the wire back to this connection.

When I got my truck 2yrs ago it had a high idle/surge issue until restarted. Keep in mind that the truck ran perfect after restart and got 15-16mpg. It was due to the previous owner messing with the screw on the throttle body(which I'm sure resulted in high TPS voltage at idle).Because the truck ran fine after being warmed up and restarted(me being lazy) I just pushed in the clutch while traveling and restarted it. When the TPS finally went out last week, it about left me stranded. It ran like it had a bent valve or no fuel. After I replaced the TPS I reset the base Idle which also put the TPS within range. My TPS voltage readings are now .87 volts at idle and 4.52 at WOT. The truck now runs perfect.

I'm not at all saying that this is all that may be wrong, but until you get the voltages within range the engine is not going to run properly.

Still wishing you Luck!!!


ETA...Prior to the TPS going bad, I was getting no codes. When the TPS went bad I was getting a TPS voltage low and EGR opening not detected. Codes are now gone.

 

I have a good spare TPS, PM me if you want it.

 

well i put a new MAP sensor on it and redid the voltage test on the tps. koeo it is .99 and wot it was 4.67 so it fixed that problem. i restarted the truck and let it run for a bout 5 min (ran like crap) rechecked the codes. the other 2 codes were gone and now i have a code 34. EVP circut something ( iforgot) no clue. i will check the push rods tomorrow.

another question: the spout at the base of the oil fill tube, has a hose going to the air intake box, with the hose off, is it suppose to push air out or have vacuum. i always thought it should push but it has a good vacuum on it

 

thanks samsonitesamsonite, i just got a new one.

 

You usually get a code 34 when the EGR valve is open(or the EVP is malfunctioning and thinks its open) and the EVP is trying to close it.

Also double check vacuum lines and wiring.

More on the subject...

Ford Fuel Injection » EGR Valve Position sensor (EVP)

 

i just went through that website. has good stuff. a vacuum problem would also throw that code, and according to my vacuum gauge, i am having a vacuum problem. i guess i will be pulling spark plug wires to find a problem cyliinder and check the push rods for a bent one.

 

If the solenoid is opening up the vacuum to the EGR valve, and the valve itself is bad, it would result in a vacuum leak and the computer code. I would check the EGR system (EGR valve, solenoid, and EVP) to make sure it's functioning like it should.

 

would that cause low vacuum at idle?? or would the low vacuum cause that? i appreciate all help and suggestions.

11 to 12 at idle. was told that is way to low

 

There is suppose to be NO vacuum at the EGR at idle or WOT. Only while cruising...

 

did not know that. will check that tomorrow night

 

well took off the valve covers to check for bent pushrods. found none. but when i took off the upper intake mani, i small piece of the gasket came with it. it looks as if there was a crack in the center of the gasket between2 od the cylinder ports. so maybe possible that was the problem???? i am goin to go ahead and remove the lower mani and put new gaskets on them.

 

Alriiiiiiight, sounds like you're making progress. Keep us posted...

Good Luck!!!

 

hell, by the time i am done, i will have a new truck basically. now i will add an exhaust to the setup to get rid of that smog pipe crap, longtubes probably flowtech unless otherwise informed.

going to order gaskets from napa in the morning for the intake manifold. when i took the valve covers off, there are signs of someone being there before. blue felpro gaskets, heads are immaculate clean for the truck having 165k, so hopefully i will not have to tear into the motor for any thing any time soon.

 

what would a collapsed lifter do?? with the valve covers off, i turned the motor and watched all push rods. they all seem to be going the correct height. is there a way to chek them out with out taking them out? lower mani will be off saturday morning and i can get a better view hopefully