I'm stumped my 4R won't reve past 3 - 4000 rpm

[BCfish]

So I have a 2003 4 Runner sport with V6 an under WOT it seems to not to want to rev past 3,000 rpm. But under moderate throttle it seems fine. Now I had the fuel pump replaced in the last 2 years so I hope that's not it again was not cheap.

Could the 02 sensors cause a problem like this it's almost like it's in safe mode with in WOT the sensors have not been replaces since I have owned the the 4R in 5+ years. So as far as I know they might be the factory originals.

Thanx for any help or adivce!

Also new plugs and cleaned Throttle body and maf recently as well..

 

[scw1991]

I had an err... 87' El Camino years ago that experienced the same symptom. Turned out to be a plugged up catalytic converter.

 

[ARunner]

Check your physical hoses/clamps on the intake. I once left a clamp off one of my intake hoses on a motorcycle and when going WOT it would collapse the hose and big the engine. But a gentle rev would allow full rpm range.

 

[jow]

I experienced the same problem in my 1980 Jeep Wagoneer pulling a boat. I could not pass a tractor when we got to the occasional passing lanes or get a passing gear. With the Cat being restricted in mind, I had it cut out and a test pipe bolted in to replace it. I also remembered I added carpet on carpet under the accelerator.

With a layer of carpet removed and the test pipe bolted in vs the Cat I could jump down into a passing gear and blow you away. Looking in the cat you could see the restricted Honeycomb in it. The carpet was not letting my accelerator travel far enough. It might be a cable matter in your case, see if the accelerator give you full range at the throttle body.

Last, a Chevy 396? Had a double wall exhaust pipe to collapse inside that restricted the exhaust and RPM.

 

[Gdmeadors]

Make sure your exhaust system does not have any loose connections. The engine requires a certain amount of back pressure or it won't develop full power. I had a Volvo 740 on which the clamp came loose and I could barely back it up my driveway. Very simple fix in my case!

 

[BCfish]

So I had look around the intake everything seems hooked up and in good condition. Exhaust looks good as well nothing seems to be loose. Thanx for ideas I'll keep plugging away at it might have to take it to the shop and see what they can find.

 

[Velonici]

To see if its a clogged cat remove the O2 sensor in front of it and see if it runs any better.

 

[gm350reratliff]

Have you scanned the ECM for any codes? Is it running rough over 3k or is it basically just holding at 3k?

 

[K_Labs]

Any backfire how's the idle?

 

[BCfish]

The idles fine have not heard it backfire it's like the motor is starving for something fuel or air. As I said it revs fine as long as you don't give it more than about half throttle as soon as you step on it a bit harder it's like it's trying to go nowhere fast. Never had a CEL come one so I don't think there would be any codes

 

[badbasser98]

My cousin had a Nissan Maxima with this problem, ended up being a bad MAF sensor. Once that was replaced all was good.

 

[Tx9812valve]

X 7 on the clogged cat. I had my old 3.4L and my wife's civic do this exact same thing. They never threw any codes or anything so it was hard to diagnose until someone that knew better enlightened me. I took the cat off to literally find a 2in sheet of rust that would flip up and clog the cat and keep it from reving any higher than 3000-3500 rpm. Once that was removed it ran perfect. Good luck

 

[LOSTR4]

Clogged cat again...I've experienced the exact symptoms and once replaced, life was better...

 

[rich045]

could be:
clogged cat
bad maf (mass airflow sensor)
bad tps sensor
bad temp sensor (some cars wont rev past 4k if the temp is over 180~/190~ even though the display on the cluster is saying its at operating temp)

 

[jow]

Is the Cat bolted in? If so, some penetrating oil a day or two in advance might let you take a look in the “Front” of the Cat. I had carbon/Etc in the honeycomb in the 80 Jeep in TX. I can see Rust or etc depending on your area and use. We would have known from the exhaust output on the 70s Chevy 396 if we had known to check.

It was not a normal flow and luck saves the muffler from exploding IMO. 30-40 MPH was the best it would do. In the early 70s my advice was to, “Take It To The Oldest Mechanic You Can Find”! I knew we were dealing with something Rare But Someone Had Seen This.... Today An “Experienced Tech” Would Be My Advice. Hopefully, driving is not risking valve or etc damage.

 

[BCfish]

She rev's freely in P or N so I'm not so sure it's a cat. She's booked in next week to my mechanics.

 

[Ali0227]

She rev's freely in P or N so I'm not so sure it's a cat. She's booked in next week to my mechanics.

Ever find out what the problem was when you put it into the mechanic? I’m having the same issue now.

 

[AuSeeker]

Ever find out what the problem was when you put it into the mechanic? I’m having the same issue now.

The member you're asking this question of hasn't been on the forum for over 7 years, don't expect an answer.

 

[rdruss]

Don't you love it when someone posts a problem, gets all kinds of suggestions, tells us it's going to the shop, and then never heard from again! What a slug.

 

[zidaro]

and dont rule out the power (literal) of new plugs.