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Old 12-30-2009, 10:57 AM
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Maf?

Does the 4 cylinder have a MAF sensor? Found the TB but no MAF

Vehicle is a 95 YJ.

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Old 12-30-2009, 12:44 PM   #2
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look under the hood on the firewall almost dead center.

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Old 12-30-2009, 02:01 PM   #3
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thats the MAP sensor there, isnt it?
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Old 12-30-2009, 03:21 PM
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mod's delete this.
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Old 12-30-2009, 06:14 PM
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Is the MAF the sensor on the left of the TB? The one on the rear looks like a throttle position sensor?
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Old 12-30-2009, 08:22 PM   #6
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have found no mention of a maf sensor in haynes. they do mention a mat sensor.
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Old 12-30-2009, 11:17 PM
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have found no mention of a maf sensor in haynes. they do mention a mat sensor.
i searched for a good half hour. took the intake hose off and there is nothing that resembles a MAF down to the TB. I assume it's get it's A/F ratio readings from somewhere, but i can't find where that is.
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Old 12-30-2009, 11:18 PM
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MAT sensor measure manifold air temp.
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Old 12-30-2009, 11:44 PM   #9
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The MAP sensor is what you're looking for. Manifold Apsolute Pressure Sensor. There is no MAF sensor used in this vehicle. The MAP sensor is what meters the incoming air flow.
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Old 12-31-2009, 12:42 AM
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and would that be the sensor on the left side of the TB?
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Old 12-31-2009, 12:52 AM   #11
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TB holds the IAC (idle air control) and TPS (throttle position sensor) ... your MAP is on the firewall as mentioned above..

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Old 12-31-2009, 12:56 AM
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oh very good. thanks guys. i'm new to these motors and am just getting my feet wet. The reason for this thread is that i seem to lose power intermittently along with a rougher idle. i am thinking it is a fueling problem, and thought maybe the MAF was gunked up or bad. Now i can move on since the motor doesn't even have one.

any ideas?
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Old 12-31-2009, 01:04 AM   #13
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Always start with the basics.... Fuel pressure, ignition, etc,,,, have a few scans taken and see if all your sensors are within there parameters... Loss of power can be tricky to trace.... ive seen anything from a clogged cat, fuel pump, coil, etc cause it... wish you lived here, you'd be welcome to pop in my shop anytime for a few tests...
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Old 12-31-2009, 01:11 AM
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Always start with the basics.... Fuel pressure, ignition, etc,,,, have a few scans taken and see if all your sensors are within there parameters... Loss of power can be tricky to trace.... ive seen anything from a clogged cat, fuel pump, coil, etc cause it... wish you lived here, you'd be welcome to pop in my shop anytime for a few tests...
thanks for the help and offer. i was under the vehicle the other day and noticed that the exhaust piping after the muffler where it goes above the rear axle was somewhat crushed for some reason. no idea how it happened. was thinking this was the reason for the random power decrease but then wouldn't that cause a loss all the time?

in more detail, this event mainly happens in 5th gear on the highway. sometimes 5th gear is nonexistant, having to downshift to 4th to accelerate and other times to even keep a constant speed on an incline. other times 5th gear will gradually accelerate which appears to be normal power.
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Old 12-31-2009, 01:16 AM   #15
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Hmm,, try one thing... jeeps seem to be nortouious for ratttling cats (the ones i have seen anyway)... bang on your cat and see if it rattles.... if you have a lose chunk in there it can intermitently rattle sideways and block exhaust flow... just a thought as i have seen it many times before..... but you really should still do your checks... an overheated fuel pump could cause intermitent problems as well.... could be so many different things...
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Old 12-31-2009, 01:20 AM
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Hmm,, try one thing... jeeps seem to be nortouious for ratttling cats (the ones i have seen anyway)... bang on your cat and see if it rattles.... if you have a lose chunk in there it can intermitently rattle sideway and block exhaust flow... just a thought as i have seen it many times before..... but you really should still do your checks... an overheated fuel pump could cause intermitent problems as well.... could be so many different things...
yeah i know, that's what i don't want to here though. haha no CEL's though so i guess that is one good sign.

anyway, much appreciation for the help. i'll check out the cat tomorrow and report back.

how do i run said checks? with a scanner tool? don't think this jeep is obd2 no?
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Old 12-31-2009, 01:25 AM   #17
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95 should be OBD1 still.... yes if you have access to a scanner, go for it... if you can drive with it hooked up and grab readings when it's doing the lack of power issue.... poor idle could be as simple as a vaccum leak..... don't rule out a wacky crank sensor either.. just because it's running doesn't mean it's good...... i'm off to bed.. night bro
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Old 12-31-2009, 01:27 AM
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95 should be OBD1 still.... yes if you have access to a scanner, go for it... if you can drive with it hooked up and grab readings when it's doing the lack of power issue.... poor idle could be as simple as a vaccum leak... ...
I'll report my findings back tomorrow.
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Old 01-01-2010, 12:54 AM   #19
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There is no mass air flow sensor on a 4.0 that I have seen. A mass air flow sensor is usesd to alter thwe fuel map. As far as I know the ecu in the jeep uses a constant map. The tps sensor on the throttle body just let's the ecu know where the throttle is possitioned at. The map sensor just let's the computer know what pressure the intake manifold is at. I love the jeep 4.0 for the fact that it is an extreemely simple fuel injected design.
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Old 01-01-2010, 10:29 AM   #20
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the map sensor determines the amount of airflow by the amount of vacuum coming into the engine. The more the throttle is open the more vacuum there will be. the map sensor uses a 5 volt refrence voltage the amount of load on the engine determines the voltage that is sent back to the computer. higher voltage low vacuum, low voltage high vacuum.
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Old 01-01-2010, 05:07 PM
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thanks guys.
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Old 03-06-2011, 08:52 AM   #22
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I did a search and found this thread. I have a 95 jeep with the 2.5 engine. It misses at idle and cuts out when driving, especially when I get on it. Here is what I did to try to fix it. I did a compression test and all cylinders were at 135 pounds and above, replaced the spark plugs, cap, rotor, 02 sensor and the fuel pressure at idle is about 35psi.

I havent replaced the plug wires yet cause they had to order them. I took it for a drive and it still does it and I also have a check engine light on. I did the "key dance" trick and came up with a code 52 which says that its a rich contion. My chilton repair manual isnt here yet so I geuss my next thing is to test the coolant temp sensor but I dont know how until the manual gets here. I am going to check the cat today, also I might take off the fuel return line and blow air threw it for blockage. Any other ideas???????
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Old 03-06-2011, 10:02 AM   #23
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Well I fixed the problem, it was a plastic vacuum line that went to the map sensor. It had a small crack in it. I spiced in a piece of rubber vacuum line and it now runs like a top. Im going to unhook the battery and reset the check engine light and take her for a drive and see if it throws another code.
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Old 03-08-2011, 06:30 AM
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mine does the same thing when the motors cold. runs well after it heats up. can you take a picture of the vaccumm line.
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Old 03-08-2011, 07:16 AM   #25
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I dont have a camera at the moment to take the picture. If you look under the hood you will see the map sensor. Its about dead center of the engine and its bolted to the fire wall just above the engine. It will have a green connector and a hard plastic vacuum hose going in it. If you look at the map sensor you will see where the plastic line runs down about 3 inches and then bends over toward the drivers side of the engine compartment. Mine was broke rite at the bend, I didnt see it until I started moving the line and closely inspecting it. Once I got that sealed up it runs perfect and no more check engine light.

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