Maf sensor.

Tito · #1 08-29-2011, 11:20 PM

Ok guys so I've been trying nd trying to fix my truck. It stalls out all the time it won't stay on more than 1 min at most. I've changed lots if things and havnt made any difference over $700. X.x now I'm suspecting it's my maf sensor, at first I ignored it because when I disconnect it my truck would die. It only starts with maf plugged in. A few days ago I decided to test it throughly by checking the signal voltage. I noticed that it varies each time it's turned on. with engine warm It's usually either at .7-.9v or other times around 1.2v it varies idk why. But usually when it starts stalling the signal voltage gets too low less than .7v after that it jumps up or down then the truck dies.

So my question is if anyone knows or can anyone tell me their signal voltage at idle?

When I rev up to 1500rpm voltage is around 1.2v
At 2500rpm it is around 1.6v

1990 Ford Ranger XLT 2.3L inline4

sheltonfilms · #2 08-30-2011, 12:26 PM

Well this is not a graph of voltage to rpms but its to speed, but should give you a good idea. BTW this is from ALLDATA for your exact vehicle.

FireRanger · #3 08-30-2011, 01:08 PM

What have you done so far?

Tito · #4 08-30-2011, 10:22 PM

What I've done to the truck is:

Replaced the fuel pump and fuel filter, replaced fuel pump relay, replaced tps sensor, replaced evp sensor, cleaned egr valve, changed vacuum hoses, cleaned and replaced iac valve and sensor with 2 different ones, replaced fuel pressure regulator, checked all fuses, changed crankshaft position sensor, checked timing belt, changed battery and cables, replaced Coolant temperature sensor, cleaned out the intake air temperature sensor, cleaned throttle body, cleaned maf sensor with special liquid, replaced throttlebody gasket, added Lucas injector cleaner, and lastly checked wiring and voltage.

Tito · #5 08-30-2011, 10:41 PM

Quote:

Originally Posted by sheltonfilms

Well this is not a graph of voltage to rpms but its to speed, but should give you a good idea. BTW this is from ALLDATA for your exact vehicle.

Wow looks like my idle at normal operating temperature is too high. Thx for this graph

sheltonfilms · #6 08-30-2011, 10:51 PM

Compression test? How many miles?

It still may not be the MAF sensor. If it drops when its stalling it could just be the RPMS dropping causing the air volume to go down. So the voltage drop is the consequence of the engine stalling not the cause of the engine stalling.

FireRanger · #7 08-31-2011, 03:53 AM

Plugs? Wires?

Tito · #8 08-31-2011, 08:21 PM

Quote:

Originally Posted by FireRanger

Plugs? Wires?

Woops forgot to add:

Changed all spark plugs and spark plug wires, replaced both ignition coils, and also replaced the ignition control module.

FireRanger · #9 08-31-2011, 08:24 PM

hmm. Vacuum test? If you have a big vacuum leak somewhere, that could cause it too. Basically what we're getting at here is before you replace something expensive, rule out the cheap and free stuff. Like anthony said, the low reading could be simply because the RPM is dropping and the reading is correct.

Tito · #10 08-31-2011, 08:34 PM

Quote:

Originally Posted by sheltonfilms

Compression test? How many miles?

It still may not be the MAF sensor. If it drops when its stalling it could just be the RPMS dropping causing the air volume to go down. So the voltage drop is the consequence of the engine stalling not the cause of the engine stalling.

In my knowledge the Maf sensorl just sends information to the ECM or PCM it does not receive information from anything because it can't really control the amount of air going in so the signAl voltage drop shouldn't even b there when stalling I checked the 12v to it and it's always there even when stalling and that never changes. So I'm just saying that it shouldn't really b dropping cause of rpm, please correct me if I'm wrong. I understand what ur saying but the surging in voltage is a big difference for example from 1.2 to .6v nd back to 1.2v . What I think is happening is the Maf sensor is sending wrong info to the computer causing it to either inject more or less fuel. I also have a system lean code. Nd I replaced the o2 sensor as well and still get that code. I also checked for vacuum leaks.

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Quote:

Originally Posted by FireRanger

hmm. Vacuum test? If you have a big vacuum leak somewhere, that could cause it too. Basically what we're getting at here is before you replace something expensive, rule out the cheap and free stuff. Like anthony said, the low reading could be simply because the RPM is dropping and the reading is correct.

Vacuum leaks was also one of the first things that I checked doesnt seem to b any. What else could cause this problem?

sheltonfilms · #11 08-31-2011, 08:34 PM

What I meant was that when the engine stalls, the volume of air going into the engine decreases. This will cause less air to flow over the maf sensor, causing the REFERENCE voltage to drop.

Tito · #12 08-31-2011, 08:36 PM

Quote:

Originally Posted by sheltonfilms

What I meant was that when the engine stalls, the volume of air going into the engine decreases. This will cause less air to flow over the maf sensor, causing the REFERENCE voltage to drop.

Oh ok I understand now thanks for clearing it up

what else do u think could cause this problem??

FireRanger · #13 08-31-2011, 08:39 PM

I'm running out of things to test and replace here. You've practically replaced the entire engine. Alternator is working ok? 13.2-14 volts at idle?

Tito · #14 08-31-2011, 08:40 PM

What causing a system lean code??

Tito · #15 08-31-2011, 08:56 PM

Quote:

Originally Posted by FireRanger

I'm running out of things to test and replace here. You've practically replaced the entire engine. Alternator is working ok? 13.2-14 volts at idle?

Yea alternator is working properly good voltage, I'm thinking of doing the compression test maybe the problem is inside the engine x.x also another thing it's doing is that if u accelerate too fast or floor it either at idle or in gear it Boggs down instantly. I also thought it might b a clogged cat so I disconnected the exhaust line at the front before cat. Turns out not plugged...