Found my problem

[sonyman87]

Well again today my car took a shit on me. sputtering like a coil pack was bad. middle of rushhour traffice. i pull over check my plugwires all good, motor was ideling at 2k-3k rpms and smoothed out like coils were good, hit the throttle Bam 500rpm studder/choke. This is the 3rd time its done this to me couldnt figure it out. Seems to happen most when it rains. ideled in Drive to the closest auto shop and they ran codes.. 02 was off the chart and they couldnt get a reading. We took the Map sensor off and held the throttle and it reved easily. Took the Map out and it looked like it was near death. Cleaned it dried it pluged it in and problem GONE. so basily my Map sensor is borderline Dead. So this leave me no choise but to buy a new one.

 

So. Should i replace it with a Stock 3.4L one or use a chevy V8 one.

 

btw if anyone knows the correct V8 style to get for a 95 3.4dohc that will plug directly in please respond.

 

{edit} its MAF not MAP. sorry for all the confusion{/edit}

[sonyman87]

2votes? both units are basicly the same price. $94

[Prospeeder]

i wasnt aware that the 5.7 V8 and the 3.4 DOHC had the same Map Sensor

[HokemBokem]

Whats the point of putting the v8 map sensor on?

[Aaron]

Use a stock one, its not like a V8 one is going to add power. Unless it is a resistance, which it isn't, it won't do anything, so use the stock one.

[sonyman87]

i wasnt aware that the 5.7 V8 and the 3.4 DOHC had the same Map Sensor

 

they are not the same. one is ~2.5inches the other is 3.5-4 inches?

[GP1138]

I don't understand the advantage. All the MAP sensor does is adjust for vacuum at different altitudes and keep the manifold pressure steady. It's not like it's gonna add HP to put the Chevy V8 one in.

[terryk2003]

I don't understand the advantage. All the MAP sensor does is adjust for vacuum at different altitudes and keep the manifold pressure steady. It's not like it's gonna add HP to put the Chevy V8 one in.

 

thats what i'm trying to figure out...what kinda difference is this gonna make!?

[Aaron]

I don't understand the advantage. All the MAP sensor does is adjust for vacuum at different altitudes and keep the manifold pressure steady. It's not like it's gonna add HP to put the Chevy V8 one in.

 

First of all, he doesn't even have a MAP, he has a MAF. Secondly, that isn't at all what the MAP is for. Its purpose is to measure the amount of air that the engine gets so it can adjust fuel accordingly. But either way, a V8 MAP won't do an earlier engine any good.

[GP1138]

I don't understand the advantage. All the MAP sensor does is adjust for vacuum at different altitudes and keep the manifold pressure steady. It's not like it's gonna add HP to put the Chevy V8 one in.

 

First of all, he doesn't even have a MAP, he has a MAF. Secondly, that isn't at all what the MAP is for. Its purpose is to measure the amount of air that the engine gets so it can adjust fuel accordingly. But either way, a V8 MAP won't do an earlier engine any good.

 

What you described, is the MAF, the Mass Air Flow sensor. It measures the Mass Airflow of the intake of air, and adjusts fuel.

 

The Manifold Absolute Pressure sensor measures vacuum in the engine and adjusts for differences in vacuum, as I was told. I am probably off on the description a bit, but that's the gist of it.

[john99gtp]

From http://autorepair.about.com/cs/generalinfo/l/bldef_495.htm

 

 

http://autorepair.about.com/cs/generalinfo/l/bldef_495.htm" data-cite="\"http://autorepair.about.com/cs/generalinfo/l/bldef_495.htm" data-ipsquote-contentapp="forums" data-ipsquote-contenttype="forums" data-ipsquote-contentid="13682" data-ipsquote-contentclass="forums_Topic">

MAP SENSOR

 

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.

 

im going to go with John on this one.

[Aaron]

That is exactly correct, and that means that I am right, it is an instrument used for fuel/spark delivery, not for vacuum conservation or whatever.

 

The MAP sensor on the earlier cars does what the MAF does on later cars, it informs the ECU of how much air is in the manifold by measuring its vacuum.

[john99gtp]

but they take two totally different mesaurements.

 

one measures the actual flow of air, and one mesaures the vacuum. the way you worded your sentence makes it seem like your saying both use vacuum to measure.

 

 

 

and both are used for spark/fuel delivery.

 

either way, they both adjust fuel to compensate for something, whether its engine load/vacuum or the amount of air coming into the manifold.

 

If we were to get a bigger MAP, i think it would run rich. Same thing if he got a bigger MAF, it would run stupidly rich.

[Aaron]

A bigger MAF won't do anything, bad or good. It will not make it run rich. The same result would be for a bigger MAP, neither will make it run rich at all. It is just the bigger MAFs have the ability to measure more air, and are elss of a restriction.

 

Both units measure airflow, just in a different way.

[5speedz34]

Honestly, if there is no advantage and they are the same price, go w/the 3.4. If you get the one for the 5.7 who knows what could happen.

[sonyman87]

Honestly, if there is no advantage and they are the same price, go w/the 3.4. If you get the one for the 5.7 who knows what could happen.

 

well. take this in consideration. my entire intake system is 3inches or larger. the smallest part is the maf sensor at 2.5inches stock Maf. a 3.5inch Maf would open up that choke point a bit... There used to be a big deal about using larger maf sensors on our cars. apparently nobody remembers this.

Well, i havent bought one yet b/c the old one is somehow still working.

[Aaron]

It will not add power. The worst restriction ebfore your valves is that throttle body.

[john99gtp]

i believe if you opened the maf up, you will get something out of it

 

 

however, you might be required to tune it.

 

i know if i were to switch to LS1 body, we would have to tune the shit out of the car.

[Canada]

Everyone is correct in assuming that a MAP will not make a difference..as long as we are talking N/A. All it simply does it look at the absolute manifold air pressure (I wonder were the name came from.)

 

Now....a MAF.....Mass Air Flow sensor......WAY more accurate....it measures the incoming air.....the incoming air cools the three wires hanging out, which causes a change in voltage. Thus, the PCM is able to calculate the air entering. Very accurate, very effective.

 

The PCM and MAF are all calibrated to each other......the PCM understands that the MAF is a certain diameter and that a certain voltage drop will equal a certain amount of air. Now, if you where to enlarge that MAF...this means that the air velocity would be less.....which would cause the cooling effect of the wires to be less. This means the PCM would *think* that less air is actually entering the motor....which would cause a lean condition. This of course would be counter acted by the O2 sensor....but it still makes for a less than ideal situation.

 

Like Aaron said....the TB is a WAY worse restriction. If my measurements are correct....a 1996 LQ1 TB is 64 mm and MAF is 75 mm on the outside with a 70 mm inner. I have both in front of me.

 

I wonder what the bigger restriction is?

 

Another way to look at it.....I plan on turbocharging my LQ1.....around 10 psi. I am switching to a 1996 intake manifold....do you really think I am looking at the TB as a serious restriction?

[sonyman87]

just looking to cut corners..

 

a lean condition would probably hurt more then help thanks canada

[Aaron]

Yes running lean is very bad for engines and can cuase big problems.