[oldmarine]

A value of 4 is definitely incorrect. I included the latter information from the FSM to show that the MAP sensor signal is very important to the engine performing properly. With the wrong information from the MAP sensor, the PCM is not delivering the correct amount of fuel (injector pulse width) to the engine for the conditions, and causing drivability issues -- stumbling, hard starting, loss of power, etc.

 

[Branden.d]

A value of 4 is definitely incorrect. I included the latter information from the FSM to show that the MAP sensor signal is very important to the engine performing properly. With the wrong information from the MAP sensor, the PCM is not delivering the correct amount of fuel (injector pulse width) to the engine for the conditions, and causing drivability issues -- stumbling, hard starting, loss of power, etc.

Gotcha. Yeah i can understand that, I may be going to just buy it anyways as I'm sure it's probably needing to be replaced anyways. I have had the car for over 50k miles and I've not done or known if the last owner replaced it.

 

[Branden.d]

Think this is close enough of a match. Amazon said it fits. But it's slightly different

 

[Branden.d]

Okay sooo here goes.
Parts replaced as of March 1st.

-Spark plugs to the ones the truck calls for in the manual.

-New pully and tensionier pully (I kinda think I bought the wrong one because the smooth pully looks a little small compared to my original one.- but it works I think)

-New MAP sensor

-New Air intake temp(the one in the intake housing right before the throttle body)

- New hoses installed for the evap system (two main ones between the LDP and C.c)

- New oil and oil filter.

'Fixed a small hole in my muffler .( With some jb weld. (May end up cutting the muffler off anyways) 😳🤐🙏

If this doesn't make it run better or any problems from the minuet I start it, then I'm giving up.



🙏🤞

 

[oldmarine]

I'd be really interested what your fuel trims and MAP reading is after you changed the MAP sensor. If it was causing the problem, it may take a little while for the PCM to adjust down your fuel trims.

 

[Branden.d]

I'd be really interested what your fuel trims and MAP reading is after you changed the MAP sensor. If it was causing the problem, it may take a little while for the PCM to adjust down your fuel trims.

Well, so here's how it went. Started the car up sounded really really promising. Still a slight misfire or something but it felt 75% better. Let it idle for a minuet checked if there were any air coming from the cooling system no so took it up the block pulled over to shut my hood so I could diagnose more instead of hearing just the latch rattling.

So at this point I noticed my check engine light back on as well my car was throwing quite alot of white smoke out the tailpipe with the throttle input.. So I took it home and went to get my scanner and it said p0449 something to do with evap circut high. So that meant I forgot to plug the l d.p back in so I did that and tried again. Well the roughidle slowly getting worst once again. But the fuel numbers are all over the place atleast on the short term side 1. 0.0, 0.8,1.6,3.1,1.6. Also then 1500rpm I noticed the highest number was 20 let it idle and it started dropping into- 3.9, -4.7
Lt side1. 15.6 steady


spark advance 12.0, 11.0, 16.5 10.5 8.0 is this supposed to fluctuate?

I could post another video if you'd like to see first hand what the scanners reading live.

I wondor is the l.d.p to cause this rough idle? Cause when I plugged it back in it was running at 45% better than its worst. So not great but then the smoking stopped and I didn't get the check engine light popping back up but then it was like 20-25% better than when I started.

 

[Branden.d]

I'd be really interested what your fuel trims and MAP reading is after you changed the MAP sensor. If it was causing the problem, it may take a little while for the PCM to adjust down your fuel trims.

Well, so here's how it went. Started the car up sounded really really promising. Still a slight misfire or something but it felt 75% better. Let it idle for a minuet checked if there were any air coming from the cooling system no so took it up the block pulled over to shut my hood so I could diagnose more instead of hearing just the latch rattling.

So at this point I noticed my check engine light back on as well my car was throwing quite alot of white smoke out the tailpipe with the throttle input.. So I took it home and went to get my scanner and it said p0449 something to do with evap circut high. So that meant I forgot to plug the l d.p back in so I did that and tried again. Well the roughidle slowly getting worst once again. But the fuel numbers are all over the place atleast on the short term side 1 06,

 

[oldmarine]

Spark advance will vary a lot -- PCM regulates it based on RPM, throttle position, engine load, MAP sensor, and various other inputs. On (much) older cars, spark advance was based on RPM and vacuum, so you can see the similarity.

Your short term fuel trim can vary a lot also. When things are stabilized - RPM, load, etc - it will vary only a little. You didn't say what the MAP sensor value was.

 

[Branden.d]

Also eas 4.1

 

[Branden.d]

Also eas 4.1

Spark advance will vary a lot -- PCM regulates it based on RPM, throttle position, engine load, MAP sensor, and various other inputs. On (much) older cars, spark advance was based on RPM and vacuum, so you can see the similarity.

Your short term fuel trim can vary a lot also. When things are stabilized - RPM, load, etc - it will vary only a little. You didn't say what the MAP sensor value was.

4.1

 

[99DakotaNate]

That's a vacuum reservoir, used to assist cruise control maintain a steady vacuum source. It's located under the cowl below the windshield on the passenger side. It has nothing to do with evaporative emission controls. I was looking in RockAuto under exhaust and emission to see if anything looked like this picture, and there it was, right under vacuum hose. I guess they couldn't find another category to put it in.

RockAuto is out of stock on that item, so you may want to hang on to it. It may become valuable.

I'm glad my 99 3.9 has no cruise control, this no vac res. Wish I had an EGR valve though...

 

[oldmarine]

I'm glad my 99 3.9 has no cruise control, this no vac res. Wish I had an EGR valve though...

I'm pretty sure you have vacuum powered actuators in your HVAC system though, so you have a vacuum reservoir.

 

[oldmarine]

4.1

Branden.d, if your MAP reading is still 4.1 (that's what it was on the video you posted), changing your MAP sensor didn't change anything. What is your MAP reading with the engine off and key on?

 

[Branden.d]

I will get that for you. And what eles numbers would you like to see or which Rev limit numbers? Cause I don't really want to push it too hard and right now 2500 rpm feels too much for the truck to handle.

 

[oldmarine]

Just the MAP numbers right now, key on/engine off, and then with the engine idling (which you stated was 4.1).

 

[Branden.d]

I just found out that it's 13.6 key in on position. And the map sensor reads at 5.4 as soon as you start the vehicle then a few seconds after levels out at 5.2.

Just the MAP numbers right now, key on/engine off, and then with the engine idling (which you stated was 4.1).

 

[oldmarine]

Something is wrong with how your PCM is reading (and reporting to your scan tool) the signal from the MAP. With key on, engine off, it should be reading the atmospheric pressure. In Las Vegas, your altitude is about 2000 ft above sea level. So your atmospheric pressure should be in the 27 to 28 range (mine shows 30, but I'm at sea level). Yours is showing 13.6. At idle, with normal vacuum, it should be in the 10 to 12 range. Yours is in the 4 to 5 range. You should also be getting a DTC in the P0105 to P0109 range because of the very low reading. My guess is you have a problem in the wiring or connector -- corrosion, bad wire, etc. -- or your PCM has issues.

 

[Branden.d]

Something is wrong with how your PCM is reading (and reporting to your scan tool) the signal from the MAP. With key on, engine off, it should be reading the atmospheric pressure. In Las Vegas, your altitude is about 2000 ft above sea level. So your atmospheric pressure should be in the 27 to 28 range (mine shows 30, but I'm at sea level). Yours is showing 13.6. At idle, with normal vacuum, it should be in the 10 to 12 range. Yours is in the 4 to 5 range. You should also be getting a DTC in the P0105 to P0109 range because of the very low reading. My guess is you have a problem in the wiring or connector -- corrosion, bad wire, etc. -- or your PCM has issues.

 

[Branden.d]

Idk what I'm talking about I did actually change the map sensor incase anyone saw this message before I edited it lol.

 

[Branden.d]

Something is wrong with how your PCM is reading (and reporting to your scan tool) the signal from the MAP. With key on, engine off, it should be reading the atmospheric pressure. In Las Vegas, your altitude is about 2000 ft above sea level. So your atmospheric pressure should be in the 27 to 28 range (mine shows 30, but I'm at sea level). Yours is showing 13.6. At idle, with normal vacuum, it should be in the 10 to 12 range. Yours is in the 4 to 5 range. You should also be getting a DTC in the P0105 to P0109 range because of the very low reading. My guess is you have a problem in the wiring or connector -- corrosion, bad wire, etc. -- or your PCM has issues.

Is there any oil that should be inside this area?! I just pulled the map sensor out and there appeared there was some oil or maybe some of the intake cleaner that I sprayed in the throttle body a few days ago.