MAP Sensor Voltage Low

gmctd · **Posted:** Sun Sep 28, 2008 10:16 am

Yes, but that's modulated\regulated by the ECM, and is dependent on required Boost levels, as sensed by the MAP and compared to throttle input and rpm - low voltage from the MAP results in reduced fuel\reduced power at all levels to prevent high emissions, such as black smoke produced at incident of reduced O2 levels - can also be caused by plugged\wet air filter or\and blocked inlet path, which should also give MAF DTC's - check to see if any furry varmits have taken up autumn residence in the intake path\airbox

jmoomaw · **Posted:** Sun Sep 28, 2008 10:41 am

sounds like I should still check the vacuum pressure before replacing the MAP. Can you describe where I plug in the gauge. I assume the 15 psi will occur at idle. Is there more I should look for by increasing rpms?

Jim

gmctd · **Posted:** Sun Sep 28, 2008 11:23 am

There are several articles with pics on this forum describing a Boost tap installation into the Boosted intake system, possibly even one by gmctd - neat thing about the jcwhitney.com guage is it is also a 30"HG vacuum guage, so may be used to take vacuum readings when required simply by disconnecting from the Boost tap, plug the tubing into a suspect vacuum circuit

jmoomaw · **Posted:** Sun Sep 28, 2008 6:36 pm

Glad to see the search works...

I will attached the gauge to the brake line vacuum to see if I get a solid 15 psi.

I also noted that I did not see a tension washer when I removed the map sensor. I read elsewhere that it will still function without the tension washer. Anyone loose their washer and had trouble afterward?

gmctd · **Posted:** Mon Sep 29, 2008 12:02 am

The brake booster hose will be full vacuum from the pump, to the tune of ~26"HG

You'll need to remove one of the pipe plugs at the front of the intake manifold to get to Boost pressures which can be up to 20psi at full Boost, or drilled and tapped, as seen here to the left rear of the Liquid Tape can lid, that brass fitting with the clear nylon tubing

jmoomaw · **Posted:** Mon Sep 29, 2008 7:34 am

I see. I thought about drilling. How do you keep any of the metal from getting into the manifold or doesn't that matter?

I can see several "pipe plugs" they have threads down the center and do not have any caps on them. There is one close to where you drilled and taped.

How do you prevent any metal shavings from getting into the manifold?

All I see are threaded pipes without anything covering the threads or holes. I hope there is not supposed to be a plug in the threads. I see the same in your photos.

gmctd · **Posted:** Mon Sep 29, 2008 1:11 pm

Those are all metric-tapped accessory\bracket mounting stand-offs - this engine is used all over the world in marine, stationary, commercial vehicle, etc configurations - I tapped that stand-off for 1/8"npt, blew that chaff out with shop air, then drilled a 1/8"dia hole thru into the intake plenum using shop air to clear the hole as I drilled - not enuff aluminum chips left when the drill worked thru to worry about, at only 1/8"dia

EDIT EDIT EDIT: my bad - there are no threaded plugs, only welch plugs - drill'n'tap is the method of choice..............

jmoomaw · **Posted:** Tue Sep 30, 2008 7:02 am

If I use a shop vacuum with a narrow end it would pick up the shavings as I drill. When you say drill and tap, ...would it be better to "tap" the existing threads on the stand off and then drill. Or will the stand off hold the brass vacuum fixture by just screwing it in tight...the threads are cone shaped in appearance..not straight down. (I may have just answered my own question.....nope, have to tap....

gmctd · **Posted:** Tue Sep 30, 2008 2:04 pm

Vacuum cleaner is prolly ok, tho you can plug the hose into the vac outlet port for pressurized air - just tap the existing metric threads, then use a 1/8"dia bit to drill thru into the manifold plenum - the hole was pre-drilled and tapped, so the previous bit-point angle at the bottom of the hole should center the smaller bit - hold the drill-motor as vertical as possible, don't hold your breath, and the deed is done.......................

jmoomaw · **Posted:** Mon Oct 13, 2008 9:17 am

I read over the thread regard the new Samco hoses. Talks about the hoses ballooning when the psi increases. That said, if I don't see any leaks, they could still be loosing pressure when they balloon. I drive pretty conservatively..but do notice the code faster when I drive more agressively after clearing the codes. Sometimes 4-5 driving cycles when mellow and then within minutes when I accelerate quickly after clearing the codes.

Looks like I should replaced the hoses in and out of the CAC first. Then look at the MAP Sensor if it still throws the code. The l

The low voltage doesn't sound like it is affecting the mileage by what I have read. Is that true.

thanks for all your input....

jmoomaw · **Posted:** Mon Oct 13, 2008 9:17 am

I read over the thread regard the new Samco hoses. Talks about the hoses ballooning when the psi increases. That said, if I don't see any leaks, they could still be loosing pressure when they balloon. I drive pretty conservatively..but do notice the code faster when I drive more aggressively after clearing the codes. Sometimes 4-5 driving cycles when mellow and then within minutes when I accelerate quickly after clearing the codes.

Looks like I should replaced the hoses in and out of the CAC first. Then look at the MAP Sensor if it still throws the code. The l

The low voltage doesn't sound like it is affecting the mileage by what I have read. Is that true.

thanks for all your input....

MAP Sensor Voltage Low

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