Engine Woes

[BigRedFord04]

i looked back thru posts, and the last time i addressed this problem was ~16 mos. ago...guess i never got it corrected.

Problem at hand: engine idles ~2700RPM when i stop at a stoplight. it used to vary where/how it would idle, being either bouncing off 500 and about to die, or ~2200. now it without fail idles REALLY high when i'm out driving around and have to stop at a light. wouldnt be THAT big of a deal except that it yesterday the heat index here was 113* and it doesnt take the truck long to get hot idling that fast. other than the fast idle, a sporratic problem i've noticed is that the brake pedal is sometimes excessively hard to push. doesnt seem to affect how it stops, the pedal is just really stiff. these symptoms have led me to believe that its a vacuum leak somewhere. so, in checking things out today, i realized that when its idling high, if i pull the vacuum hose off the MAP sensor the idle will drop back down to ~1000RPM. the check engine light doesnt come on when i do this, as it hasnt come on with any regularity since i've had this problem. i've replaced the IACM, swapped TPS's (used for used), and completely resealed the entire upper intake, all bolts torqued to specs. I've searched thru the engine compartment looking for vacuum leaks, and the only one i've found is on the heater actuator, but i'm sure it has been this way for a while as it has never worked on Floor/Mix/Defrost, just defaults to defrost. Can someone tell me what the MAP sensor actually does? i know it stands for Manifold Absolute Pressure, but what the hell does that mean? could this problem be fixed by replacing the sensor? it is original. i'd leave the vacuum line off if it werent for the fact that it started to blow black smoke after running for a few mins w/ the line disconnected from that sensor, otherwise seemed to run fine. TIA for your best guesses.

[Graystroke]

Have you tried the old carb cleaner trick to look for vacuum leaks? Another sensor you may check is the speed sensor. if these give a false reading they will cause problems in the idle circuit.

[StevenAg03]

hey austin....i have had this problem before where it would speratically idle at way to high an rpm....the problem with mine was that a pece of plastic was broken and wedged into the return spring where the throttle cable attaches to the upper plennum. i replaced that piece and it never did it again. i dont know if yours is the same but this could have happened to it and then when you pulle the vacume line off of the MAP sensor, it was no longer running right and therefore idling down and black smoking. if i recall correctly it is also where my kick down cable is located(on the same bracket)


here is what a MAP sensor does: Definition: Refers to a manifold absolute pressure sensor, a variable resistor used to monitor the difference in pressure between the intake manifold at outside atmosphere. This information is used by the engine computer to monitor engine load (vacuum drops when the engine is under load or at wide open throttle). When the engine is under load, the computer may alter spark timing and the fuel mixture to improve performance and emissions.

[BigRedFord04]

yeah, i've probably sprayed 3 whole cans of carb cleaner at my engine lookin' for leaks. its hard to get to the lower intake to head surface b.c. of all the sh!t on top, and the pass side would be impossible to see b.c. of the upper intake plenum. I've checked the throttle linkages, but will check them again, i had to make a slight modification to it when i put the TB spacer on.

[usmcagg02]

...i had to make a slight modification to it when i put the TB spacer on.

did this problem start when you put the spacer on? if so then you might wanna start checkin things in that area to see if you accidentaly busted something when you were puttin it on.

[uglyota]

can you test the MAP sensor? a yota AFM has certain resistance readings that it has to get across different prongs on the plug...

is it running rich with the MAP vacuums plugged, or just disconnected?

[BigRedFord04]

can you test the MAP sensor?

is it running rich with the MAP vacuums plugged, or just disconnected?

i'm gonna look thru the haynes here in a bit and see if i can test it.

it didnt seem to matter if it was plugged or not, just with it disconnected it started dumping greyish black smoke out the exhaust.

[robertf03]

can you test the MAP sensor? a yota AFM has certain resistance readings that it has to get across different prongs on the plug...

vacuum pump and a multimeter, but I'd just replace it since they are cheap

every efi ford vehicle made for at least a 15 year span used the same MAP/BP sensor. My carbed f150 even came with one and I reused it on the mass air setup

[BigRedFord04]

i forgot to mention one other symptom....hasnt been happening as regularly as it used to, but every now and then, from a stop...when i start moving the RPMs will climb, but it just doesnt pull like it should...then at some point it just unleashes the power it supposed to, usually above 3000RPM and it'll throw you back in the seat. very odd.

i went by autozone yesterday...geez that place is always a clusterfuk....and the only tester they have is for OBDII vehicles. so, i'm gonna start digging under the hood here in a bit and see what i can find. if i can find a multimeter in the garage i'll start tryin' to test sensors.

[uglyota]

...when i start moving the RPMs will climb, but it just doesnt pull like it should...then at some point it just unleashes the power it supposed to, usually above 3000RPM and it'll throw you back in the seat...

this is the most messed up symptom I've ever had...the toyoda used to do it. Now how are you supposed to test stuff to see what's going wrong when it only messes up under load at 3grand? Mine hasn't done it since it totally died and they found the "main efi" and "main circuit open" relays bad.

[fbronco86]

are u running a mass air system?

If you are not running a mass air system with those mods to the engine the speed density system will run like crap.

[BigRedFord04]

it is speed density.....what mods are you talking about? it ran fine for more than a year after i rebuilt it. the 1st time the check engine light came on was in llano a long time ago when it started running like crap and i found the #7 spark plug wire off the plug. i plugged it back in and the check engine light stayed on, but it ran better. thats really when i started having problems w/ idle. i've tried a bunch of **** since then to remedy the problem and nothing's worked.

[robertf03]

i've got a ford code reader, but if the check engine light is off it won't do anything.

Do you know if yours is sequential efi? I heard that the later speed density stuff was. If it is sefi you can do a cylinder balance test and shut off each injector to see if it makes a difference. rules out dead cylinders.

i've also got a pile of 19lb injectors if you want to swap a few out and see if anything changes.

[mudtoy67]

I think our Ford are just MPI, not SPFI. The triton motors are SPFI and can shut off individual cylinders using a scanner. You can't run that engine without the MAP sensor, because the MAP is one of the main sensors that tells your computer how much fuel the engine needs, hence when you unplug the hose the computer reads zero vaccum and thinks you're at WOT, and pours the gas on. One other thing noone has mentioned is check the temp sender and wiring to make sure the computer is reading the engines temp correctly, if it's reading cold the computer will bump the IAC up like you just started it in the morning. It's hard to say exactly what's going on without hooking it to a scanner....sometimes you can replace sensors all day and still have a problem. If a scanner can't identify it, you may just have to realize like I have......our trucks are Fords!

[BigRedFord04]

If a scanner can't identify it, you may just have to realize like I have......our trucks are Fords!

hey, FUKK all that. i dont care what make it is, its going to have problems, and they can be fixed.

i got out the multimeter and started testing sh!t. initial reports are that the MAP sensor is good, but i dont have a vacuum pump here. all voltages are good w/o testing exact vacuum. then i tested the TPS. the haynes says w/ the ignition on, and engine off it should put out ~1.0V. Mine was reading 2.2V. so i tried adjusting it...BY THE WAY...who the FUKK makes a plug`n play sensor that needs adjusting when installing it?? FUKK that. stupid fukkers. Secondly, who's fukking bright fukking idea was it to put that god damn thing in the absolute least accessible place in the entire fukking engine compartment??? FUKK! Ok, and when the distructions say to plug it in, and test the voltage before you tighten the screws...adjust it by turning it until it reads 1.0V....how the fukk do you turn the god damn thing when there are two screws that hold it down, and the two screw holes on the sensor must exactly line up w/ the threaded holes on the bottom of the TB. WTF?!?!?? who's ever genious idea it was to design that sensor like that can burn in hell.



i'm a bit frustrated.