Try a different set of terminals on the TPS. On my 88 4.9, it's the bottom two terminals on the TPS. I read the Haynes manual wrong, and was trying to check the resistance between the top two, and got those wierd readings you got.

 

The one thing I "Don't see" in all of the "idle threads" is checking the "vacuum pressure"! If the vacuum is too low at the map sensor, you will have idle problems, loss of power and poor fuel economy. This is a step overlooked with the computer-controlled systems and is very important!

Also a key step in diagnosing these problems is a compression check and possible a leak-down test.

There are always exceptions to the rule but this is among the first steps in drivability issues.

 

See if I can do this, Map sensor specific testing:
IN"HG FEQUENCY IN"HG FREQUENCY IN"HG FREQUENCY
0" 159HZ 2" 153HZ 4" 147HZ
6" 141HZ 8" 135HZ 10" 130HZ
12" 125HZ 14" 120HZ 16" 114HZ
18" 109HZ 20" 104HZ 22" 99HZ
24" 95HZ 26" 90HZ 28" 86HZ
30" 80Hz
readings should be within 2-3 hz at the respective vacuum values.
Dwell testing = 50% all readings, not fluctuating
0"IN HG=Barometric pressure
use a vacuum guage, plug it onto the intake manifold, backprobe the center wire at the MAP sensor with your multimeter that reads "HZ" turn on key, Multimeter needs to read within 2-3 HZ of information given in chart at 0"IN HG, start up engine and compare HZ on multimeter to guage, cross reference to chart. If you have a dwell on your multimeter, test at both KOEO and KOER, there could be a problem here also, needs to be rock steady plus or minus '1' "49-51 % dwell" if the dwell is off, it screws up everything. Usually the engine won't even idle, maybe low, blows smoke, pings hard, no power, just a bunch of odd ball symptoms. Broken Wire

 

Yes this is what I did too.
So my TPS checks out then.

 

Guess I'll have to spend some MORE money and get a nicer multimeter or and a vacuum gauge before I can do this

 

This idle value is in PARK or in GEAR?

 

I'm not sure - it should be on the vehicle emissions label under the hood. Or it might say idle is not adjustable, I'm not sure. I'd say that would be in gear for an automatic if I had to guess.

 

I set the TPS to .93 volts at idle and it gives me 4.63 volts at WOT. Runs smoother now. I removed the EGR and pluged the hole on the intake, made no difference on idle speed.

I checked and rechecked all the sensors and connections. I cannot find the source of the hanging and high idle.

Can the aftermarket TPS be the problem? Do I need to get a Ford TPS from the dealer?

If all else fails, I will bring it to a shop with a full diagnostic machine.

Ed

 

I refuse to bring it to a shop. I'm gonna spend the 100 bucks and get an Automotive multi=meter so I can check the sensors more in depth

 

Get a craftsman multimeter for 20 bucks, it'll do all you need it to do. I have this one here, and I found out today it will even test freqency on the MAP sensor: http://www.sears.com/sr/javasr/produ...26+Accessories

 

Sears Canada is really subpar compared to Sears USA. I doubt they will have that item here, but I'll have alook anyways that's a good price .

 

I have a really good Fluke multi meter, I checked everything and cannot find my problem. It is running pretty good now, just with a hanging and high idle. The only code I have is 13, unable to reach lower idle limit. I just cannot figure this one out. I'm getting frustrated and desperate here. I'm ready to buy a Nissan, LOL....

Ed

 

The idle speed is in gear or park, idle with fuel control is idle, when you are in park it is idle, the IAC makes the change through the Engine Computer values, IAC position is an output from the computer, when you pull it into gear it brings rpm back to that point, TPS adjustment for idle is not going to make a difference at WOT, TPS adjustment is .95 volts DC (specification is +/- 10% of this value) KOEO or KOER measured to the center wire of the TPS, you may want to also test the TPS running at idle, I have seen on occassion a TPS get very noisy in electrical with vehicle running, potentiometer inside TPS is loose. I am going to push the limit here, this can cause you more greef though, do this on your own, to test for an absolute vacuum leak, get a piece of plexiglass 1/8" or thicker that is bigger than the throttle plate throats, start up the engine and let it go to the idle it wants, take out the PCV valve and plug the tube or place a piece of cardboard over the PCV valve so no air leaks in the valve,take the piece of plexiglass and place it over the throttle body so no air can get into the engine, it should stall, if it does not stall, change the intake gaskets and upper plenum gasket or look for the vacuum leak, the down side to this, if you thought you had good gaskets in the intake, it just tested them to the maximum limits, vacuum is so high at this point it can suck them into the manifold area, but if it was going to do this they where junk anyways. This is a valid intake test as far as I am concerned. 5.0/5.8 are known for upper plenum intake gasket failure. Broken Wire

 

^ Good point there about setting idle speed - set it in park, and the computer will correct the idle speed when it is put into gear. I have my TPS at .8V at closed throttle - as long as it is above .6V and below 1V, you should be fine for the idle TPS voltage. WOT won't be more than 4.8V, and yes, the idle adjustment has a little effect on WOT voltage, but it doesn't matter anyway. The computer learns the range of the particular TPS that is installed after driving for a while.

 

This is a reply to Ed (BLACKFLARESIDE) in regards to the external leak on his EGR. I have a 302 in a 92 Flareside and recently found this same external leak. I like the propane approach, I used carb cleaner. I replaced this valve twice and both new valves allowed the engine idle to increase when carb cleaner was lightly sprayed in the openings below the sensor. I think it is normal. I did find my leaks which were in a very short piece of tubing connected to a solenoid leading to the purge canister and a distorted piece of tubing leading from the back of the upper plenum to the PCV valve. The piece between the throttle body and the solenoid had very small cracks only detectable with a vacuum pump.
Years ago I also encountered a loud leak that affected the engine by an occasional stall and a hard miss at highway speeds. The gasket between the upper plenum and the intake manifold is thin and deteriorates easily. I found the gasket was missing on the left side (facing the engine) in a hard to reach area. Replacement of the gasket (about 5 bucks) put me back in business.

Hope this helps. Will