I just made a run from northern CA to southern Oregon. All was good on the way up but on the way back I noticed some surging, especially when at light throttle on flat road or off the throttle going down hill (coasting but still running 2000 rpm) . I switched tunes from my MoparMan mileage tune to the tow tune and no difference. I also hit the overdrive button and no difference. Fuel pressure was always 15lbs or more. By the time I got home I had a check engine light and it was 0236, Map sensor. I have cleared the codes numerous times and I might get away with driving a hundred miles or so with no code but the surging continues. A day or so later, the code comes back. 

 

I don't have boost shown in the Quad display since I have a separate boost gauge directly off of the intake elbow.  I can't remember, does the Quad boost value come from a fitting I don't have installed in the intake/head or off the computer data?

 

Any help before I start replacing parts!  I read somewhere that the Quad has some known boost value issues and some guys run a separate boost fooler connected to the stock wiring harness and disconnect the Quad completely from the map sensor circuit, is this a way to start troubleshooting?

 

Thanks!

First off try removing the Quadzilla and seeing if you can reproduce the problem. If the problem goes away then the boost fooler in the Quadzilla is to blame. Now if the P0236 code returns there might be a wiring issue or a bad MAP sensor. Typically the P0236 is a boost too high for too long. Typically this is a boost fooler issue where the boost fooler is misreporting boost values. Like back in my Edge Comp days if you unhooked the MAP sensor and then ran the truck it would report max boost all the time and would set off the P0236 code because boost values wouldn't fall at idle or coasting. 

Can I just unplug the Quad module or do I have to unhook all the Quad wiring at the engine and restore to factory?

MAP Sensor at the least. The rest can remain.

I had recently received a DAP map sensor that I had ordered so I swapped that out tonight. On the Quad display, the factory /original map sensor read 54 at idle and up to 56 when accelerating. After installing the new map sensor, idle boost was reading 35 and went up to 39 when accelerating. The truck seems like it has a lot more power than it did prior, is that because it was defueling based on the 54psi reading? Mike, I'm running either your eco or tow tune here, is there anything within your turn that would have been affected with the boost indicating that high? 

 

So the boost reading 35 at idle is obviously not correct, what do I check into next? I'll try pulling the map sensor plug and see what that does for the surging. 

Boost fooler and/or boost circuit is having issues. Double check by ohm testing the wires. Check for your 5V signal and signal ground.