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2 Different Boost Readings - Bad MAP Sensor?


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My Stewart Warner pillar gauge and I-Quad aren't reading boost the same.

 

When I'm on the throttle, the pillar gauge says 35+ and Quad says 5-6.

At cruise, mech says 4-5, Quad says 0

No doubt the mechanical gauge is right and Quad is wrong.

 

I hardly use the Quad gauge on my phone so I don't know how long there's been a difference.

No codes. Map sensor is clean - no soot.

 

Is the Quad reading directly from the MAP sensor or thru the ECM?

Can a MAP sensor be sick and not throw a code?

 

 

 

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  • Administrator

Yeah. Boost shows right for me up to about 25 PSI then after that it starts to skew. When I hit roughly 45 to 47 PSI the Quad shows me maxed out at 67 PSI

 

You might talk to @dripley about the MAP sensor ground and where the crimp is you might look over the MAP sensor circuit.

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14 hours ago, IBMobile said:

Thanks for the links.

That gives me some insight to what might be happening.

What has me stumped is the spread between the two gauges..

1 hour ago, Mopar1973Man said:

Yeah. Boost shows right for me up to about 25 PSI then after that it starts to skew. When I hit roughly 45 to 47 PSI the Quad shows me maxed out at 67 PSI

 

You might talk to @dripley about the MAP sensor ground and where the crimp is you might look over the MAP sensor circuit.

Thanks Michael.

No codes and the truck running  good has me wondering.

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As for MAP sensors you should try a second one of quality. (Cummins or NAPA). Then ohm out the wires between the ECM and MAP sensor. Might be a bad Quadzilla module and/or wiring too.

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Posted (edited)

"Might be a bad Quadzilla module and/or wiring too" I started getting the dreaded P0237 low boost code a while back. I had a spare MAP sensor and swapped it out. That seemed to take care of the issue but it wasn't long before the eng light popped back on with the same code. After going over the wiring and cleaning the connectors I decided to pull the Quadzilla XZT+. That was about a month ago with no further problems. 

I bought that XZT+ when they first came out (2002'ish). Back then we were online with the company and they would email us a new tune to try out. Kinda fun but I rarely used the 'High Power" setting and ran it mostly in the "Fuel Mileage" mode (timing advanced only). Now that I'm back to somewhat stock power I think I'll sleep OK without the Quad. 

Edited by MikeH
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Posted (edited)

Quad XZT is like the Edge EZ model. Way different when you have the Adrenaline. Way more control of everything including timing and fuel mapping. 

 

Still best to have a tuner module that allows for custom timing. This is where the High MPG comes from. Fuel map you can custom out like I've done. 

0 to 5 PSI from 80% to 100%, then from 5 to 15 PSI is all STOCK fuel at 100%. Then at 15 PSI and up both my wire tap and the CANBus fuel will rise together for strong passing power. My timing is currently 20 degrees at 2k RPM's in cruise state.

 

 

Edited by Mopar1973Man
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"Quad XZT is like the Edge EZ model. Way different when you have the Adrenaline. Way more control of everything including timing and fuel mapping"

Right...just making the point that it was the Quadzilla throwing the code. My OEM system worked fine once I pulled the XZT from the mix.

 

BTW...now that the Quadzill XZT is gone, along with it's Boost Fooling, what's the max boost the ECM can see before de-fueling? I was getting ~32psi with the XZT in place.

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Be best to have a tuner and gain back the boost fooler. Like the 2006 I've got any time it has any engine code the boost is limited to barely 20 PSI which the EGTs are much higher. When all codes cleared it will run  30 to 35 PSI and EGTs are much lower. Always best to have good boost while towing or climbing grades.

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I haven't actually pulled the XZT yet, just have it disconnected. Might just go over the wiring and connectors to see if I can find anything obvious. If it's in the circuit board I'm screwed. Losing the XZT didn't bother me that much as I just ran it in Fuel Economy mode (slight timing increase) 95% of the time. It just occurred to me that boost fooling also went along with the other stuff. 

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4 hours ago, MikeH said:

I haven't actually pulled the XZT yet, just have it disconnected. Might just go over the wiring and connectors to see if I can find anything obvious. If it's in the circuit board I'm screwed. Losing the XZT didn't bother me that much as I just ran it in Fuel Economy mode (slight timing increase) 95% of the time. It just occurred to me that boost fooling also went along with the other stuff. 

Sooo...just went over the Quad XZT+ and found I can squirt some electrical contact cleaner right into the circuit board. Pulled and cleaned all the other plugs associated with it and may have found the problem. One of the OEM connectors was missing the little red locking tab. Don't know how I missed that before but that right there would cause an intermittent fault.

I shouldn't have been so quick to blame Quadzilla as it's looking like pilot error now!!!

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  • 2 weeks later...

Update:

 

Replaced the MAP sensor and all is good.

Now both gauges are just a few pounds different.

The truck never threw a code on this one.

Oh well...

 

Everyone, thanks for your help.

 

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Some time you need to rely on live data. Then remove any add on like tuners to see if the tuner is at fault, which sometimes happens. Then at least you know what is at fault sensor, boost fooler or wiring. Like @dripley has been fighting the MAP sensor issue for awhile.

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8 hours ago, Mopar1973Man said:

Some time you need to rely on live data. Then remove any add on like tuners to see if the tuner is at fault, which sometimes happens. Then at least you know what is at fault sensor, boost fooler or wiring. Like @dripley has been fighting the MAP sensor issue for awhile.

I lost two in just over a year and then thought I lost another but turned out it was fine. Not sure what caused the others to fail but we will see how long this goes. 

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