The MAP should never read zero since it is an absolute pressure. It KOEO, it should read the same as the Barometer (ie atmospheric pressure)

 

thanks for the info! i will check the map and the ICP sensor!

 

Hey guys, I really appreciate all the help. My daily driver car was smashed from a hit and run driver christmas eve so I am more motivated than ever to get my truck running right,

In case there are any new people chiming in, I will list the problem again. While cruising at highway speeds my RPM will randomly drop to 1200-1400. This makes the truck bog, if I give it more pedal it will just smoke. But if I take my foot off the petal and place it back on the RPM will go back up to where they should be and then drop again. The issue doesnt happen when accelerating, only when maintaing a highway speed. Also the issue does not happen when running in Tow Haul Mode, or when the truck first starts and is cold.

Today I unplugged the ICP, this made virtually no difference in the idle, however at highway speeds the ICP was able to reach higher PSI (2200) yet felt like it had less power. I only went about 2.5 miles with it unplugged so I am not sure if that was long enough to truly test ICP.
ICP values are ---- Cold: LI 772 HI 1153, Warm:LI 585 HI 992 (1400 max psi under hard acceleration) , Sensor unplugged and truck warm: LI 875 HI 1000 (2200 psi under hard acc.)

I also checked the rubber tube going to the MAP, no visable cracks or signs of a clogged nipple.

I did notice my oil pressure is a little low at idle (according to a pillar gauge) yet at HI it goes to 74 PSI. Im truly at a loss on what could be causing this issue, I also noticed that my truck has a little turbo bark is I accerlate hard then release the petal completely. Something I should also add is my truck has a SCT tune, however I have tried tuning back to stock and it still does the same shift issue. Any info or tips anyone can provide will be extremely appreciated. I do have a Scan gauge II so if there are any values you guys would like to see let me know!

 

When was the last time the fuel filters were replaced?

 

i just replaced them like 200 miles ago thinking maybe it was a clogged fuel filter no change.

 

So you going to correct the MAP sensor issue (assuming it actually is reading zero) or live with it?

 

The ICP when the sensor is unplugged is not a real reading.
It's the PCM wishing. Really it's an estimated number and
is really of no use. It's just where the PCM "thinks" it should be.

 

the map sensor only hit zero when it went over 35 PSI. i did some research and other people have the same deal with scan gauge. and now I started my truck to take it somewhere and map is reading 2.8 and wont move. My dash says my truck is not building boost but my pillar gauge says its building boost fine, and it now started throwing code P0237. Also it is now idling at 20psi oil pressure. What could I have done? I literally pulled the rubber hose off the map to inspect and put it right back

 

Gotcha. I have never heard of the MAP going to zero on a scangauge. Never seen it on mine. A hard acceleration of 35 psia is only 20 psig of boost. That part sounds normal anyway.

FYI on the low pressure oil pressure specs:
The minimum engine oil pressure specifications are:
12 psi at 700 rpm
24 psi at 1,200 rpm and
45 psi at 1,800 rpm with the engine at operating temperature.

Max ICP of only 1400 psig at hard acceleration is low. It would be good to see the ICP desired and also the IPR % duty cycle along with that ICP reading.

 

I have a new map sensor ordered. I suppose it wouldnt hurt to change the ICP when I get a chance as well although im not to sure that could be causing my low highway rpm drop. Am I supposed to change the wiring plug when I change the map? thanks

 

If your going to replace the MAP you may as well put a new hose on it too.
Just to take things a little sideways for a short ride. What are you using for
the air filter in this and when was the filter last changed?

Now back to your normal driving direction.

 

I have an S&B cold air intake. not sure last time it was changed. i have never cleaned it or changed since I owned the truck but I only put like 3k miles on the truck so far.

 

Looks to be an oiled gauze element type filter from a quick google search.
I think it would be a very good idea to check it.

 

Check the IPR screen too!