87 trouble code

[Skunksmash]

Hi all. The Service engine soon light came on in my 1987 half ton 5.7L 2WD 700R4. So I broke out the code scanner to see what it was. The code says this: "33 MAF / MAP sensor too high". I can only guess that means that its out of voltage specification. Meaning the voltage is too high? Also, just to see if anything might look wrong, I ran the realtime engine monitor and everything looked ok except that one meter said that the engine was running rich. Kinda hard to tell what it meant, cause all it said was "Rich/Lean Flag: Rich" so I take it that it was telling me that it was running rich. Thoughts? Opinions? Suggestions? Should I simply replace the mass airflow sensor and the manifold absolute pressure sensor? Perhaps if I did that, then the engine would not run rich and the service engine soon light would go off?

[Irish_Alley]

Lot of them sensors if you unplug them with the engine running and it doesn't change how its running usually means its bad

[VileZambonie]

You don't have a mass air flow sensor. Check the vacuum hose going to the MAP sensor for good connection and strong vacuum. If it has no leaks it should read about 1.25V at idle. If it's reading higher than that and the eleectrical connection is good then replace it.

[Skunksmash]

Ok I'll give that a try. But its weird though, cause sometimes the engine light comes on, and sometimes it don't. But I do know one thing, it only comes on when the truck sees highway use.

[DnStClr]

I've never had my map sensor go bad, but the erratic ses light is s'posed to be common with a bad one. As your engine works harder, the map sensor helps estimate airflow for the ecm. If the ecm sees bad signals from the map it doesn't know how much gas to feed the engine, and usually sends too much gas to the injectors. So you end up running rich. Make sure your vacuum line between the map sensor and the intake manifold is tight. Matter of fact- check all the vacuum lines before you take the voltage reading Vile described......(Oh, on edit, he already told ya that) lol