Author Topic: MAP sensor reporting boost under load/truck stalling  (Read 2692 times)

concealer404

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  • OH U MAF?
Re: MAP sensor reporting boost under load/truck stalling
« Reply #15 on: October 18, 2017, 05:47:43 AM »
Maybe not fuel pump.  Fuel pump was replaced (allegedly), wife picked it up from the shop (who also diagnosed "100% sure" without prompting from me that it was fuel pump), drove it to work with no problems.  And it stranded her again that night.

Currently en route back to me on a flatbed.  Reporting maxed out fuel trims through OBD2 at 25%.  In the 10 minutes i spent poking around it in the dark, i found a spark plug wire that wasn't seated, and the PCV hose to the intake wasn't connected.  Neither of which fixed the problem, but apparently i have to go through this with a fine tooth comb again, since someone else has been in the engine bay.

Yayyyyyyyy.

So far we've replaced:
Fuel pump
Fuel filter
MAF
MAP

I'm running to get a fuel pressure tester today i guess.  I have my doubts that the pump job was done properly, seeing some of the other stuff they did.  Or maybe at all, since the 15 years of dust/grime at hanger hat look pretty improbably undisturbed.  Still no CEL or codes of any kind being reported.

Real life footage captured of the ECU in this truck:



stupid montero by concealer404, on Flickr
1998 Montero Winter Package (For Sale)
1994 FZJ80 Land Cruiser (Wife's)
2006 V8 4Runner Sport Edition (Mine)

concealer404

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Re: MAP sensor reporting boost under load/truck stalling
« Reply #16 on: October 20, 2017, 06:11:01 PM »
Ok so after figuring out that 1) This thing doesn't prime when the key is turned to ON, because it's not supposed to (neat!), and that 2) it has TWO fuel pump relays (FML), i've discovered a few things.

A) Fuel pump turns on, has power
2) Still doesn't run for more than a few seconds at a time, and cranks for a LONNNGGGG time
iii) Does not make fuel pressure, after about 30 seconds of running the pump (jumped at relay #2) it generated a whopping 3-4psi.  Backed up by not much fuel spraying around when the test adapter was removed.
iii.5) still didn't make fuel pressure when the return line was clamped closed with some pliers.

Basically.... pump works (at least as far as i can tell so far), but isn't pressurizing the system.  I suspect a botched install.  Will pull the pump in the morning and investigate.  Good thing i paid a shop to do all this, right?  :unamused:
1998 Montero Winter Package (For Sale)
1994 FZJ80 Land Cruiser (Wife's)
2006 V8 4Runner Sport Edition (Mine)

concealer404

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  • Posts: 318
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Re: MAP sensor reporting boost under load/truck stalling
« Reply #17 on: October 21, 2017, 06:18:52 PM »
Today i learned that Gen3 Monteros run way better when they have gas in them.
1998 Montero Winter Package (For Sale)
1994 FZJ80 Land Cruiser (Wife's)
2006 V8 4Runner Sport Edition (Mine)

JohnnyBfromPeoria

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Re: MAP sensor reporting boost under load/truck stalling
« Reply #18 on: October 21, 2017, 11:21:02 PM »
Today i learned that Gen3 Monteros run way better when they have gas in them.

Uh oh...say it wasn't so...

John B.
AZ Crew/East Sider/Former 14th St Crew
95 SR, 35x12.5-15 on 8" steelies, 2" BL, stuff cut off, stuff welded on, lights, sound, front ARB pending
87 Raider, There's a turbo 2.6 under its hood, really
83 "Dodge" Power Ram 50, a bit lifted, way slow and gets more comments from random people than the other two put together
'95 Montero SR. Pretty much stock, Trail Gear Sliders, ADD skid plates, Stereo by Shovel, Timing maintenance by Pa_Jero

Monstero

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Re: MAP sensor reporting boost under load/truck stalling
« Reply #19 on: October 22, 2017, 03:45:29 PM »
I have had same issue with mine for over a year now and have thrown parts and have seen nothing positive happen. The one common denominator for me is the delayed start. I can crank and crank forever. The common denominator for me is that it will always be a hard start after 60degrees outside. and if its 35 degrees outside at night forget it starting. over the summer and warmer months it started just fine and had same symptoms as you had above....such as hesitation while running....blips here and there like it would cut off and on briefly...would stall at idle sometimes... I have replaced fuel pump relays, MAF, fuel pump and filter,brand new crank position sensor, new camshaft position sensor(a PITA to install BTW), a new Engine coolant temp sensor,  and all to no avail. NOTHING has worked. Just recently i thought forsure it was MAF and checked that and then it still delayed start.

I have a block heater on mine so I have plugged it in when temps drop to keep me going, but if i am anywhere too long and it sits in the cold i am screwed. VERY VERY Frustrating because i am usually a person that can troubleshoot and figure this out and havent been able to  for over a year now. Next thing I was thinking it could be was the Throttle body, but there is nothing temperature dependant in there. So I am not sure. Just following and googling and more googling and more scouring trying to find any bit of info that would pertain to it.