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MAP SENSOR problem

12K views 8 replies 4 participants last post by  sevenmalards 
#1 ·
99 f550

No codes are being recorded and the check engine light is not on.

Every morning, when I start the truck up, the truck has no power. I push the accelerator all the way down and the rpms do not go up and the truck just crawls. After about a minute of holding down the accelerator, it seams that the fuel starts to flow and the truck takes off as usual. The truck has been doing this for a while.

I recently realized that if I disconnect the map sensor, the problem does not happen. And the truck starts up and drives as normal every time.

So, every morning, I disconnect the map sensor, start the truck, drive it a few miles, pull over, reconnect the map sensor, and every thing is normal.

I put in a new map sensor and I still have the problem.

Thanks,
Matt
 
#3 ·
Heres a bump for ya man. I had a hidden code on my truck that said something about a map sensor problem. Mine was in conjunction with my ebp sensor. I haven't been able to check for codes since i replaced my ebp sensor. Sorry i can't help you out more. My truck didn't "go slow" it just threw 2 codes and no CELs. I was just scanning it one day and found both of them.
 
#4 ·
Have you tried cleaning the EBP?
 
#5 ·
Thanks guys,

I replaced my exhaust backpressure sensor and I also replaced the tube.

I would love to just keep the Map sensor unplugged, I get much better performance when I do, but I think the fuel mileage goes down. I can't afford that at $4 per gallon.

Matt
 
#6 ·
Man I don't know. All the MAP sensor does is monitor your boost pressure, and defuels the injectors if you "over boost" it, after a few minutes of it not getting the "over boost" code anymore the fuel delievery returns to normal. That's why a lot of us run MAP FOOLERS. I don't think it would be a problem if you ran it unplugged.

So you have checked for codes?
 
#7 ·
I always hear the term: "defuel", I am not sure what it means, but I would imagine it would mean "take fuel away", in another words, take fuel away from my injectors.

It seems (I think), that the map sensor is getting an "over boost" when I first start it in the morning. It is defueling the injectors. After a few min, the map sensor is not getting an "over boost" and returns fuel to my injectors allowing me to drive normally.

I have no idea what i am talking about though, and still don't know what the problem is.

Thanks for the info though,
Matt
 
#8 ·
Go to ITPDIESEL.COM and look at their "overboost annihilator"
Nevermind, here it is.
Overboost Annihilator

It is the "MAP FOOLER". Yes "defuel" means to take fuel away. The Map Sensor is set at the factory at or around 19 PSI so if your turbo makes any more boost than that the map sensor senses it, and cuts the fuel to the injectors until it gets a clean code with no "overboost" and then it returns the fuel delievery to normal. All or mostly all the guys who run chips or programmers (I had an Edge Evo) will run the Map Fooler. It just allows the stock turbo to boost up to it's max potential, in the high 20's or even a low 30 psi with a really good tuner.
 
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