gaedbo

Anyone have experience with cleaning the MAP sensor on a 95 Z28

Injuneer

Do you have some sort of evidence that foreign material has entered the small tube that inserts into the manifold? Do you have a code for the sensor?

There's a fairly delicate silicon diaphragm inside, acting as a strain gauge, with conductors attached to it. It may not like harsh solvents or a pointy object.

The sensor is very easy to test, using a vacuum pump. Voltage should be near 1.5V with the engine at idle (~20"Hg vacuum), and close to 5V with the sensor exposed to the atmosphere at sea level(0"Hg). I can give you more detailed readings if you would like to try testing it.

gaedbo

Thank You for your quick reply. The car is stored in the garage, I live in Minnesota, and I am trying to get it set for spring. I have been doing a lot of things to it to make it the best it can be while leaving it basically stock.

I have taken the throttle body off and cleaned it, and also done the bypass with the coolant lines. I had read some one elses thread that they had all kinds of black particles come out of their MAP sensor, and they sprayed carb cleaner in it and it ran good afterwards. I wanted to make sure this was really the way to go, because sometimes there are so many different responses to the postings. Mine did have oil residue buildup on the end of the attached rod with the opening in the end. I wiped it clean along with inserting a thin rod to clean the inside of the rod opening. Do you think I may have damaged something internal ?

I would appreciate the additional information you offered in case I might have ruined something. I will document your info, because I won't be starting it up until spring. Do you know if replacement parts are available for the stock throttle body ?

JakeRobb

Are we maybe talking about the MAF (mass air flow) sensor and not the MAP (manifold air pressure) sensor? The one in the intake piping between the air filter and the throttle body is the MAF.

gaedbo

I am talking about the MAP not the MAF

Injuneer

With the key on, engine off, the MAP sensor is measuring the atmospheric pressure ("barometer") where the vehicle is sitting. Atmospheric pressure varies with elevation above sea level. And, it varies with atmospheric conditions.... stormy weather lowers the barometer.

If you are at sea level, barometer should be about 1 atmosphere, or 14.7psia. Your volt meter should read in the range of 4.9 - 5.0 volts. At 6,000-ft elevation in Denver, CO the reading will be significantly less, close to 4.0 volts.

As you pull a vacuum, voltage drops. At sea level:

5.0 "Hg = ~ 4.0 V

10.0 "Hg = ~ 3.1 V

15.0 "Hg = ~ 2.2 V

20 "Hg (this is typical idle vacuum, at sea level, with a healthy engine) = ~ 1.4 V

Don't get hung up on the decimal point. "Close" is goo enough.

gaedbo

Thanks again for a quick and detailed reply, I appreciate someone who knows what they are talking about.

gaedbo

Just wanted to let you know the MAP checked out according to the info you supplied. I was happy to see that I didn't damage it when cleaning and poking around. Next time I should investigate first to make sure I don't do something I might regret.

Thanks again for the info.

Injuneer

The MAP sensor itself is rarely a problem. The harness connector, on the other hand, tends to dry out and crumble, causing intermittent readings. Mine fell apart in 2000 at the age of 5.5 years. I new pigtail is a good idea.

Chimera96

^^^^

I replaced the MAP green plug. Also the small rubber sleeve that goes over the nipple can crack/break apart.

These cars are 20+ years old...