2001 2.7 won't rev past 2k RPM

hi all, first time here.

2001 regular cab 4x4, 2.7 Stick shift.

had to get towed home the other day. Right after i left the parking lot at work the truck would not REV above 2000 rpm's. actually at about 1900 rpm's its like it hit a REV limiter. if i hold the accelerator pedal down or slowly push is down, the RPM's steadily and smoothly rise like normal until it hit's about 1900 then it bounces down to 1200 or so and goes right back up to 1900 or 2000 RPM's. it starts and idle's perfect.

i've gone crazy and cross-eyed searching the interwebs. Most of the posts i've found referring to this has a CEL showing up. i don't have any check engine lights' coming on.

i have torque pro so i can look for codes or pending codes but there aren't any.

from what i'm seeing it could possibly be the MAF, TPS, engine coolant temp.
i've cleaned the MAF (iat) and no difference.

i've individually pulled each of the above sensors and the CEL comes on but the symptons that start from the sensors being pulled don't replicate the problem.

Right now the problem is not happening. it seems to come and go as it likes. When i do have the problem i get no CEL light. i'm able to disconnect the battery and the problem goes away for 1 to 5 minutes but always comes back. and sometimes even disconnecting the battery for ECU clear wont' fix it.

i don't think it's a plugged CAT because clearing the ECU shouldn't fix that problem.

I know without a CEL code this is tough to fix but has anyone seen or heard of this? any ideas on what else i can try? fuel regulator or anything like that? i have a new MAF and engine coolant temp sensor but i don't want to throw parts at it without knowing what went wrong.
thanks for any help

 

I'd putt around the block a little bit and try to get it to throw a code before I started trying to diagnose it. Could be many things at this point.

 

Subbing because I haven't heard of this before.
Next time it does it take a temperature reading in front of the cat and behind it (inlet-outlet). If it's hotter at inlet then it's plugged.
I'll put $10 on bad cat.
Glwf

 

i was wondering about that. if something is starting to fail, how long before it throws a CEL? for instance, if the MAF or IAT is failing, i guess i can either throw parts at it or drive it until it throws a code right?

 

I don't like to shotgun parts at a vehicle but it sucks to get towed home. I would drive it around the neighborhood this weekend so if something happens you are able to limp it home. Hopefully you get a code to point you in the right direction

 

i have a IR temp gun that i was using yesterday. I know these 2.7's have 2 temp sensors. one in front of engine for the gauge and one on the back of the block that the ECU uses. i wanted to see if the ECU temp sensor was reading correctly, ie, the sensor is sending the correct temp to the ECU.
the torque pro app i used showed the temp steadily climb to about 180. where on the engine could i verify that with my IR gun?
i tried the front upper RAD hose but it was cooler. so i aimed it at the port where the upper rad hose connects to block and it was about 170 when the ECU temp said 179.

it seems like it's in some kind of engine protection mode or 'limp' home mode but everything i'm reading about this, there should be a CEL on the dash.

i'll get a temp reading at the CAT next time like you said.. i wasn't focusing on the CAT because clearing the ECU seems to fix it temporary but i'll give it shot.

 

$50 says there is a squirrel stuck in the intake.

 

i had the front half of intake apart when i changed the air filter and cleaned the MAF.

but, when i did clean the air filter 3 weeks ago, it was the dirtiest filter i've even seen. the PO had the inner fender splash guards off because he got the truck painted. then he drove it all winter in Erie PA without the splash guards on. the air box and air tube above the passenger front wheel were FULL of dirt and sand.
i took it all apart and cleaned it. that's when i changed the air filter.
when i cleaned the MAF, it was clean looking but had a very, very tiny piece of lint/string from the new air filter hung up around one of the tiny wire's. i blew that out with air and MAF cleaner. the truck drove fine for about 2 weeks after that.

so, i know the MAF is suspect now but if it failed or was failing wouldn't i get a CEL? also, when i disconnect the MAF for testing purposes, the symptons don't replicate what i'm seeing when i have the 2000 RPM limit.

thanks again

 

Does it idle rough when it only revs up to 1900. Or us the idle smooth. If it's rough it can be a intake gasket. Had a few customers with that issue on the later 3.4.

 

How many miles on plugs?

 

idles perfect and smoothly climbs up to the 'limit' of 1900-2000 rpm's. even when it drops and climbs again it's smooth. i can use the gas pedal and hold it at 1600 RPM's for minutes and it's smooth. just as it climbs to 2000 it drops, pauses, then climbs again.

 

not sure about miles on plugs. truck has 205000 miles on it. a general tune up was on my list but then this problem occurs. i've read enough posts about toyota's and other cars in general seeing an issue like this and people would shot gun parts at it and plugs/wires was never a solution.

 

Plugged/blocked up Catalytic converter?

 

i was thinking about the CAT, but why would clearing the ECU make it work for a little while? 2 days ago i fired up the truck about 20 different times throughout the day, never moved it though. problem was present every single time. yesterday, i fired it up and no problem. REV's are smooth and climb as they should.
i know the honey comb material in the CAT's can become loose and move around but wouldn't they move around when the truck is moving? i just guessing here.

i'd like to be able to replicate the exact symptoms i've having with pulling a sensor or something.
if it is the CAT, could i slowly cover the exhaust to try and replicate the problem?

 

So when you disconnect the MAF, the truck does or doesn't limit out at 2k RPMs?

 

it does not Limp when MAF, TPS, or engine coolant temp sensor is unplugged. Unplugging those sensors makes it not want to start, idle terrible, and hesitate and stall.

Could a bad ground cause of this to happen?

 

loosen the exhaust before the Cat and see if she revs.

 

well, quick update. over the weekend i was looking at the ECT on the back of the block and i disconnected the rear ground to get at it. i disconnected the ECT and fired the truck up. thru an error for the ECT. then i didn't have time to work on it further. plugged it back in, cleared the CEL and left.
next day i walked out and tried to fire up the truck and nothing. the elec ODO wouldn't even turn on. i thought, dead battery. Checked it and it was fine. Then i saw the rear ground cable was disconnected. so i reattached it and tried to fire the truck up. tried to start but wouldn't. CEL came on. i forgot the codes but 2 different Crank sensor codes lit.
i thought i was finally making progress
So i cleared the codes and it turned on and idled and revv'ed just fine.
SO, i was staring at the engine and saw the ground on the battery wasn't hooked up. the little cable was laying behind the battery and i never even saw it. i also noticed my battery is 8 years old.... sheesh
so, after i attached the battery ground i went for several short drives and the 2k rev limit problem has not returned. i'm going to get a new battery for it this week.
i don't think i really 'fixed' anything. i didn't replace any sensors. i just added that 3rd ground.
hopefully the problem is resolved and maybe someone else down the road will benefit from this.
thanks all for the help

 

I feel lucky to get 4-5years out of a battery. Most new vehicles Ive had usually end up getting replaced in under 4yrs.

 

My original Toyota battery lasted just about 7 years, the replacement lasted a little less than 5. not too bad considering the cold winters.