MAP sensor existence?

[rangerlove]

This is a '91 2.3L EFI Ranger S 2WD made in 06/91.

I haven't been able to find mine. The access port into the plenum where everyone says it should be is empty, so is the access port in the middle (which I figured anyway, but why not try...)
Some guys say the sensor is on top of the heater core and you either have to remove the dash, or remove the entire heating apparatus to get to it.
I've also read that if your truck says "Solely for sale in the state of California." it will have a MAF and not a MAP.
Still others say you can have both.

There is a phantom vacuum line that runs by the computer and up somewhere into the dash behind the heater core. But there's also one that comes back down to my heater vent controller.

I need some clearing up before I rip the passenger-side of my truck open possibly for no apparent reason (plastic pieces never go back together right, are brittle after 20 years, and you always end up with a rattle).

I've been hunting and pecking at this because it smokes like a Banshee, idles rough, and misses. All common problems to a faulty MAP sensor. I just can't find it. I'm starting to think I only have a MAF.

I cleaned my MAF with Brakleen at the recommendation of a mechanic and the smoke noticeably decreased and the idle turned to a barely noticeable quiver, which I've heard is common for 4-bangers, though mine never did it before. I could be hyper sensitive because I've been sitting in it trying to time the miss and feeling for every little bump.

I just replaced the head with a brand new one, lapped valves, new guides, new seats, entirely new seals along the intake route.

I checked the breather tube for leaks, as well as every line I could see with a soapy water solution and a paint brush (how I was taught to do it) and everything was fine and dandy. So I got out the trust vacuum gauge and went to town and everything was also fine.

The valve cover has insane vacuum and actually sucks oil up into the throttle body, and the PCV line also has a ton of vacuum, but that's normal.

I cleaned my oil separator thinking it was causing backpressure, but it's entirely the opposite.

I'll clean my IAC later, having that stuck open can be a really bad problem, too. When I unplug it at idle, nothing changes...

I got a code for my ECT and my O2 sensor, replaced those, still getting a code for my ECT. I've got about 12 ohms of resistance on the ECT harness and about 30 on the ECT.


Thanks!

 

[rangerlove]

Oh, I've also noticed while pricing MAP sensors (euuuuughhhh) that I keep getting results for a little round one that resembles an ECT sensor, but has a slightly different plug. It's located on the upper intake manifold by the fuel injectors. Not sure what it is...some sort of ambient air temperature sensor? Could that be my MAP sensor? It doesn't have a vacuum line going to it.

Just cleaned the IAC and it sounds better idling, but as soon as you rev the engine it billows out smoke and then acts like it wants to die. I dunno what else it could be. Guess I'll try a new MAF.

The dying part is a new symptom since I replaced the O2 and ECT sensors.

When I unplug the IAC nothing changes. Maybe the electronic part is just stupid.

 

[Bryan22]

a 91 ranger with a 2.3 has a MAF not a map sensor. It's located right off the airbox inline with the intake.

 

[rangerlove]

Thanks for the reply. That's what I've been hearing and I'm going to stop looking for the MAP sensor. Tomorrow will be a junkyard day.

 

[tomw]

QUOTE:The valve cover has insane vacuum and actually sucks oil up into the throttle body, and the PCV line also has a ton of vacuum, but that's normal.

Huh? There is a line from the cam cover to the air intake just before the throttle plate on my old Ranger. It is to provide filtered air that will be pulled into the crankcase and eventually pass through the PCV on the way to the intake.
The tube should not have a vacuum from the intake manifold if it is the same thing. The PCV should rattle when shaken, and should develop a slight vacuum on the crankcase with the engine idling. You can check that by placing some thick paper or cardboard over the oil filler with the engine idling. It should be held in place after a few minutes by vacuum.
tom

 

[kimcrwbr1]

After you cleaned the MAF did you reset the computer by disconnecting the battery for 1/2 an hour. You need to reset the computer every time you clean or change a sensor. That other sensor is probably the IAT or intake air temp sensor use rubbing alcohol or electrical clean for it same with the maf any harsh solvent will destroy them. I am not sure about brake cleaner it might be OK but rubbing alcohol is cheap and works just fine. You might be alright if you just reset the cxomputer.

 

[kimcrwbr1]

If you still have problems get a code reader or have them pull the codes for you at the part store before you start buying any parts!

 

[rangerlove]

QUOTE:The valve cover has insane vacuum and actually sucks oil up into the throttle body, and the PCV line also has a ton of vacuum, but that's normal.

Huh? There is a line from the cam cover to the air intake just before the throttle plate on my old Ranger. It is to provide filtered air that will be pulled into the crankcase and eventually pass through the PCV on the way to the intake.
The tube should not have a vacuum from the intake manifold if it is the same thing. The PCV should rattle when shaken, and should develop a slight vacuum on the crankcase with the engine idling. You can check that by placing some thick paper or cardboard over the oil filler with the engine idling. It should be held in place after a few minutes by vacuum.
tom

That line we're both talking about, from the valve cover to the throttle body (a little "L" looking guy) for whatever reason, shoots oil into my throttle body. This is abnormal.

There is a ton of vacuum on that line. The weird part is if you remove or clamp this line off, the engine dies. I have an '81 Fairmont with the inline 6, valve cover line goes into air breather above carburetor to allow intake so PCV valve can spit fumes down at the carburetor. Doesn't make much difference if it's on or off. When I got it, it was hooked up all wrong, and was spitting orange stuff that looked like pizza grease into the breather because someone had just taken the PCV valve and plugged it off, so the fumes had nowhere else to go, but backwards. This is the only other time I've ever seen that line cause any sort of problem on any vehicle. And it seems like the exact same problem...somewhere in the bowels of that four-banger...but the vacuum is the part that throws me off...I've run a couple cans of Seafoam through the oil system, give it a drive for an hour or two on the freeway, up and down hills, in city traffic, and change the oil and filter about 100 miles later when I get home.

If you go around to my PCV valve, it also has a ton of vacuum. If you hold your thumb over the valve at idle, it about sucks your thumb off. (Normal to have vacuum here, but not that much.)

If you stick the palm of your hand over the oil filler port, it will clamp it to the valve cover and make a seal in about half a second.

So I have vacuum going up into the throttle body from the top end and vacuum going up into the air intake from the bottom end. Two ways!

I've been trying to solve that one for a year. Taken it to a bunch of professional mechanics. They don't believe me when I give a list of symptoms, then go "huh, that's weird." No one has any idea why this engine does what it does. Ford basically told me I was SOL. And up until it started idling erratically and billowing out white smoke without using oil or water when you rev it, it really wasn't acting abnormally. When you hit freeway speeds it goes like it's new and the smoke isn't noticeable. But every time you take off in first gear, wooh, you'll kill every bug at the interchange. I wear sunglasses, a big hat, and sink down in my seat when I'm in first or second.

Right now I just don't want it to run like crap, so I'm trying to figure out this sensor problem. I'm starting to wonder if some sort of air intake sensor could be at fault for the vacuum overload. Blowing too much air in?

Reset the computer, you say...the shop manuals leave out so much. But that's why I'm here!

I was hesitant about the Brakleen as well, but he swore up and down, and it ran better after I used it.

I do have an OBD-1 reader (which got me started thinking it was sensors after I tried all the usual suspects because it posted codes for a faulty O2 and a faulty ECT), and the only code it posts now is 52. Well, funny story, I don't have power steering. I've done KOEO, KOER, reset the codes multiple times. Nada.

But, I have a new head, new valves, all new seats, guides, seals. All my cylinders had compression between 195 and 205. There are new seals from the intake manifold back up to the throttle body. I replaced the fuel rail, injectors, pressure regulator. I checked the resistances of all the wiring harnesses that go to my injectors, sensors, ICM...I cleaned my oil separator, bought a new Motorcraft fuel filter and PCV Valve. I replaced the O2 and ECT. New EGR solenoid, new EGR valve. I triple-checked all my vacuum lines. I thought that vapor canister was causing me problems, but that thing's been ruled out. I put a new airbox on it because my last one had a crack. I cleaned out my exhaust like a boss about a year ago, Cat was completely clogged so I got a new one. I put a new muffler on it about two years ago.

I had bad valves, bad compression, and I thought the smoking and oil consumption were due to that. I had just put a clutch in it as well as a new slave cylinder, redid the brakes, bought a canopy, and got new tires when everything started going to pot about a year ago. So between all that I was down enough money to make fixing this truck rather than trading it in on another used clunker the better of my two options financially right now.

Honestly, you can buy these motors for $400 at the junkyard with about 100K on them. Between everything I've spent on the head, valves, sensors, gaskets, head bolts...I could have just plopped another one in there and that still seems like an option...but it's foolish pride that won't let me toss out a block with that good of compression.

If it isn't the MAF, it's got to be the ICM...or there is a giant blockage somewhere down in the engine that's allowing two directions of vacuum which throws everything off...

To be honest, I have nightmares about this engine. I haven't had a free day/evening in a month, when I decided I was tired of living with a ghetto truck and I was going to fix it. I don't eat right, I don't see my friends, I spend more time at junkyards and at auto parts stores than I do at home. The guys at Autozone know me by name and when I walk in they punch in the specs for this truck before I make it to the counter...

But I'm mostly just here for the sensor info. Sorry to hijack my own thread. Sorry to write a book. Sometimes you need to vent and have a .

 

[rangerlove]

Well, I jerry-rigged a check-valve so air can only flow into the valve cover, not out. No change in the engine or amount of smoking. But that should solve one problem for the minute, so I don't have to put a quart of oil in every 30 miles. Worst case scenario oil jumps up past the trap and clogs the valve and if there's enough negative pressure in the system, it should suck air back through. Maybe the PCV valve will quit freaking out, too, and operate a little more slowly.

 

[kimcrwbr1]

Alot of info there I am kinna confused on the breather tube tho. Normally you have a pcv valve to pull the gasses out of the crankcase and a breather tube to the air filter housing so it is pulling filtered air into the crankcase The valve cover has a baffle in it where the pcv is so it dont pull oil just the gasses. somtimes the breather tube where it takes air in has a filter media so the oil dont get into the air filter it just drains back into the block. If the breather filter gets plugged you will pull a neg pressure in the crankcase that sounds to be your problem. The crankcase needs to breath filtered air as the PCV clears out the gasses.

 

[kimcrwbr1]

Also did you reset the computer. Do the KOEO test and when it starts giving codes stop the test. That will erase the memory then disconnect the battery for at least 1/2 an hour to reset the computer. Then start it and run it for 20 mins or so to reset the new values once it it up to operating temp run the codes again KOER and write down the results. Whenever you clean or change a sensor or run it with one disconnected you must reset the computer or it will run on false values.

 

[tomw]

Given the location of the PCV, inline between the separator and the intake manifold, could it be installed backwards? The flow should be clean air, from 'behind' the air cleaner, drawn through the flex tube and l-fitting into the cam cover through the oil filler cap. Crankcase vapors will combine with the incoming air, travel through to the oil separator under the intake manifold, trapping oil particles in the 'maze' for drainback into the sump, and through the PCV, as metered, into the intake manifold.
If the separator drain were clogged, you could pull oil through the PCV. If the PCV were upside down, you could have full manifold vacuum on the crankcase all the time. I think.
If you have flow back through the filler cap, your crankcase is not being ventilated properly.
tom

 

[kimcrwbr1]

If you see someone with the same truck and engine year maybe you could pop the hood and see how it is set up. sounds like someone didnt put it together correct that mistery vacuum line into the cab goes to the heater hvac control for the heater valve and the air flow doors in the cab in most cases.