How to test MAP sensor

STEVE57

MEMBER
1994 FORD F-250
15,000 MILES

I had a cold start idle problem, I replaced the MAP sensor. It solved the problem for 2 days, now the rough idle is back.

Tuesday, February 7th, 2012 AT 3:49 PM

3 Replies

ASEMASTER6371

MECHANIC
52,797 POSTS

In open loop cold, the computer relies in RAM till it hits closed loop. Then the computer takes over.
I would start by looking for vacuum leaks, fuel pressure and anything not connected. Beyond that, you need to look at the o2 trims to determine if the injectors may be clogged or failing.

Also, start with the basics and do a compression test to verify the motor is capable of working correctly.

Roy

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Tuesday, February 7th, 2012 AT 3:53 PM

STEVE57

MEMBER
11 POSTS

It only runs rough at start up, after it warms up it runs fine. There are not any check engine lights.

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Tuesday, February 7th, 2012 AT 8:18 PM

ASEMASTER6371

MECHANIC
52,797 POSTS

Too old for any help from codes. I suggest a shop with a scan tool monitor the sensor readings when it is cold to see which sensor is not reading correctly. Otherwise, you may be looking at a computer issue with the PROM failure.

Roy

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Tuesday, February 7th, 2012 AT 8:21 PM