Intermittent Power Loss - Not Full Limp Mode

V

VizFX

Member
Car
2013 FX37
Name
Tom
Hello iS! Reposting here, hoping you can help. 2013 FX37, 80K Miles. I previously drove a 35 so I know how beefy these V6s are. I'm experiencing a power loss along with RPM drop intermittently and can't figure it out. Happens mostly in scenarios with extra acceleration: going uphill, fast start from stop, freeway passing. No codes. Idles fine. No pinging or unusual noises.

--I tried cleaning, then decided to replaced the throttle bodies (great deal on Hitachi OEM)
--Cleaned MAF
--Replaced Air Filters and checked flows

Don't think it's my Cat or exhaust -- this is a California car. MPG is down, maybe something with fuel supply, mixture, electrical gremlin?

Thanks in advance!
 
I would look at fuel pump/pressure, spark plugs and ignition coils - seems like you are losing one of them when demand is put on the engine. My tuner said to replace the spark plugs every 30k miles, not whatever the manual says. Also due to the age of the car, it's probably running the original ignition coil packs. I have a 2015 with almost 80k miles as well. My valve body has gone out already, but you know that one as it throws a code and keeps you in 3rd gear and below.
 
Thanks LA! I would think if it were the plugs or coils you would hear and feel some uneven engine sound like coughing or sputtering with a misfire? I don't have that. I took it to the "stealership" and the tech was certain it was the valve body or TCM but again, no codes, and the limp/throttle loss is not a transmission slip. Since my first post, I also had a separate tech check the cam and crank sensors. I also got the multimeter out to check for any parasitic power drain, fuses, etc. All good/normal.

I just noticed a hole/tear in the under-hood insulation that lines up perfectly with the passenger side MAF. I put some duct tape over it so the insulation bits are touching the MAF.

I do suspect fuel pump/pressure or dirty fuel line? Maybe previous owner used low octane gas? Thinking of running some fuel cleaner before I pull out the back seat and mess around with the pump etc...Thanks again!
 
Great point about the coils/plugs! I'm still learning and it sounds like you have put a lot of effort into this already, sounds very frustrating. Now I did have my valve body fail last summer and it definitely throws a code (output speed sensor on mine) - plus it won't shift beyond 3rd gear. Weird they would tell you that without a code(s) to back it up. Known issue with the 7AT for sure. If it's not an issue with air or spark, it has to be fuel right? Where my knowledge ends sadly ... good luck!
 
Yeah, i’ve heard about the transmission output sensors going bad in the valve body causing the gears to malfunction. And the since the sensors are integrated into the valve body the whole part needs to be replaced! Another example of car manufacturers creating expensive car repairs by design.

I’ll keep this thread open until I find out what’s going on. Thanks again!
 
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