2000 3.4L V6 4WD will not rev past 2000 RPM no CEL.. HELP

Hello Everyone,

I have a 2000 3.4L V6 4WD that will not rev past 2000 RPM and it is not showing a CEL or any DTC codes on the ODB reader.

Let me start at the beginning. I bought the truck in October and a check engine light came on after an hour into my drive home. I checked the DTC but never wrote it down and cant remember it. From memory when I was researching the code I saw things like clean the MAF. So when I replaced the passenger side valve cover gasket in October because of an oil leak I cleaned the MAF Sensor thinking that would solve my problem but it did not so I assumed it was a faulty O2 sensor somewhere and went on with life. I am building a stereo system for the truck and while I was testing I saw I was not getting 12v constant to the wiring harness for the stereo. I started checking fuses and I ended up blowing fuse #25 7.5A Radio Fuse and fuse #12 15A Dome. I replaced the 7.5 A fuse. I did not have a 15A fuse only a 10A Fuse for the Dome and assumed this should be fine for testing. I then started the truck and found that it seems to be stuck in a limp mode of some sort and that It wont rev past 2k RPM. There is no CEL so I am not getting any DTC on the OBD reader to point me in a direction.

I assume the problem is correlated to the stereo blowing the fuses.

Things I have tried:

Disconnecting both battery terminals for 30 min to reset the system. - No CEL on start

Ground the battery with a jumper cable to the frame. Ground the engine block with a jumper cable thinking its a grounding issue.

I have unplugged the MAF and that throws a CEL and the problem persists after reconnection.

I unplugged the TPS sensor started the truck and tried to give some throttle and no throttle of course then plugged it back in and started and the truck revved fine with a CEL. I restarted the truck and cleared my TPS sensor codes with the assumption that the TPS sensor was faulty. I replaced the TPS sensor and started the truck but no avail and the problem persists.


I'm kind of stuck at this point and don't know where to go from here. From threads I've been researching I've read this problem can come from a multitude of things like: Clogged Cat, Fuses in wrong spot, bad plugs, and for bad fuses but checking my fuses none seem to be blown and I still think the problem is correlated with electrical.

Any help will be appreciated! I have attached some pictures of the fuse box and a video of the car revving up with the problem.

https://youtu.be/InuKeeFOHeM

 

Bump

 

https://youtu.be/UIUW5B4rzQI

Here is a video of the OBD sensor readings when I add throttle.

 

I’ve had 2 3.4 trucks now come in with not wanting to rev past xxxxrpm. Both were failed crank sensors. No codes from either. Only reason I found the issue was with graphing the engine rpm and noticing the signal dropping out


Can’t load the video out here in the boonies right now. But I’ll see what it sounds like when I’m home

 

I know my son's Ford Ranger has a rev limit without being in gear it won't go past 2500rpm. Does this happen driving your truck?

 

Yes, it does not matter what gear I'm in. I've puttered around my neighbor hood for 30 min to try and get it to throw a code but no luck.

 

Interesting, I usually assume MAF or plugged cat when I have a rpm limited 3.4

The crank sensor makes sense but is hard to diag without an o-scope.

 

Yea it’s a tricky one. Both trucks I had doing it were 99s. First one took a while to figure out. Second one was like... “ok I’ll check this first”

 

Thank you! I will definitely look into the crank sensor.

Here's a video of the engine RPM. When I hold the throttle is hovers around 2000 RPM and dips back down when I release. I can do this for any type of readings if anybody has any others that might help.



https://www.youtube.com/watch?v=xKWP8org90k&feature=youtu.be&ab_channel=notnup

 

Not as responsive as the graphs I can see at Toyota BUT. That does kind of look like what I was running into. Harder to say though with the slower response

 

I see what you mean. Those dips at 2000 RPM could be going to zero with a higher response rate from the sensor.

 

Exactly. Mine wasn’t a full 0 but it would dip from 2k to 1k.. looked like a mess.

 

Before throwing a sensor at it, checking for a clogged cat isn’t very hard. Thermal guns best, but a heat gun would give you an idea. Clogged cat would have super high temps before the cat, super low “comparatively” temps after cat.

also retrace your steps, did you mess with any ground wires? The one on the. Intake plenum can cause all kinds of engine issues if it’s a weak ground.

 

So I have not moved any grounds just added an alligator clip to make sure of connection. I also checked continuity with a volt meter and they seemed fine let me check again. And I assume I need to let the truck warm up for a little while to check the cat temps?

 

https://youtu.be/2Wob3Zeq1lI

Here's the grounding of the intake plenum. I'm gonna grab a temp gun to check the cat temps.

 

If your fuses aren't blown, it doesn't matter what fuses are the "right" ones, so take that off the table.
Take the pedal out of the equation too and hand-open the throttle plate, just for kicks.

There is no gear-selected RPM limit. You should be able to go to redline in park/neutral.

 

Your throttle position is only reading 15%.. if you replaced the TPS already and you're flat footing it, check the throttle cable

I'd also like to see fuel trims once your O2s heat up. Right now it's clear you recently unplugged power.

 

So I was hesitant to floor the throttle but I went for it and the truck will get over the 2K RPM but hesitates and then jumps past.

Here are the temps before and after the CAT, respectfully. I let the engine idle for 10 min before these readings.







Here's a video of my sensors after I floor it and pass the 2K RPM.
https://www.youtube.com/watch?v=rZYBllYmi48&ab_channel=notnup

Here's a video of the trim levels graphed against each other.
https://youtu.be/Sp-wEHo_SVY

 

FWIW that's about where the torque converter is supposed to lockup I think

 

Are you letting it hit closed loop? You have a lot of 0 trim regions.