No power, no codes

1997 - 4x4 3.4 Liter - Manual transmission
I was having issues with acceleration going uphill. The RPMs were going up but no power. I read different things on the forum that could possibly cause it. I have:
- Cleaned the MAF sensor using MAF sensor cleaner - no change in performance
- Changed the spark plugs and new wires (needed it anyway)
- Checked the PVC valve - looks good and suction in the hose
- Changed the fuel filter
Still no change...
Engine runs fine, no rough idle
- Cleaned the MAF sensor again; This time i drove it around for 45 mins. At first it seamed like it may be a little better but got worse as i drove. Heading back home i had to stop at a light. When it was time to go i put it in first get and the truck would bearly move. I slowly rolled it into a parking lot. Let it sit for about 10 mins and started it again. Again a tremendous loss of power but was able to make it home at about 25-30 mph.

- I have a new MAF sensor being delivered and i'm also about to clean the catalytic converter.

Any other ideas? It shifts fine with no slipping so i don't think it's anything with the transmission.

 

I might be wrong but it sounds like a clutch issue? If your RPMs are going up but it's not accelerating accordingly it sounds like a slipping clutch to me. Which also would explain why there is no code or check engine light, since there isn't one for a bad clutch.

How many miles on the clutch?

 

Copied this from a google link on clutch issues..

1. My Car Moves Slowly but My Engine Races
This is known as clutch slippage. As you release the clutch pedal and accelerate, the vehicle moves slowly while the engine races, usually in high gear.

Slipping is common when a clutch disc is worn out. With the friction material almost worn away, the clutch disc has less surface with which to grip the flywheel and pressure plate, making it hard for the engine to transfer rotating power to the transmission.

Another symptom you'll notice is the clutch releasing sooner, without much pressure on the clutch pedal.

But there are other common causes for a slipping clutch, besides a worn-out disc:

• Clutch linkage in need of adjustment
• Clutch linkage or cable binding (cable housing filled with rust)
• Clutch linkage bent, misaligned, or damaged
• Blocked master cylinder compensation port
• Pressure plate weakened or warped
• Clutch assembly contaminated with oil (because an engine or transmission oil seal is leaking)
• Broken motor mount

 

As stated above, my money’s on clutch...

 

202k miles on clutch.

 

Definitely gotta be the clutch then, most people are lucky to get that many miles out of one. I think ~150k is usually the average, really depends on how the truck is used though (street only, offroading, towing, mostly highway, etc.)

But at 202k I would imagine it's nearing the end of it's life and that's why it's slipping now

 

I've had no issues changing gears.

 

That usually starts happening when it's really worn out, but not always. Slipping is generally the tell tale sign of a clutch going bad. If you have trouble going in-between gears but no slipping, then it's likely the shifter seat bushing. Or maybe bad synchros (not good). But just slipping = bad clutch unless there's another reason for it.

I've had a clutch start slipping before on me when I was offroading in the mud, got some mud up in there and caused it to slip but it went away after a short while.

 

It sounds like a clutch

 

If RPM is going up and speed is going up accordingly, then I don't think its the clutch.

Usually they slip more in the higher gears if indeed it is the clutch.

 

If I understand his original post correctly, he's saying the RPMs are going up but the truck speed isn't (feels like it has no power)

Sorta like it's stuck in neutral even though it isn't

 

He said no slipping. I read the first part as it was accelerating just a lot slower than normal. If the RPMs always stay proportional to speed in a given gear then there's no slipping.

If there are no codes it might be worth watching the live OBD data while driving to see if anything is unusual.

 

I read it as it's not slipping, but stepping on the gas doesn't give you any acceleration.

 

Would be weird to not have any codes if it's losing power that dramatically but I guess it's possible, might be a pending code stored

He mentioned something about the cats, when I had the P0420 code for a bad rear cat I had a similar issue where it eventually felt like the truck's performance was greatly hindered. Acceleration didn't really feel like the issue more just overall 'pep' if you will. But I definitely had the code for it

 

"...Sorta like it's stuck in neutral even though it isn't"

Right. And it's been gradual over the last 8-10k but got alot worse after i cleaned the MAF

 

Have you scanned for codes to see if maybe there's a pending code stored in the ECU?

 

No stored or pending codes

 

Codes are mostly emissions related, so if it doesn't sense an emissions issue, it won't send a check engine light.

If cleaning the MAF helped temporarily, that seems like a place to start. Make sure your air filter is good and if it's an oil type, that it's not over oiled.

 

I would clean the throttle body too, gets gunked up over time although it would be pretty severe to cause what you're describing. But I could see that not throwing any codes

Best way is to take it apart and clean it by hand, butterfly valve and all

 

A bad MAF, vacuum leak, or fuel pressure problem would eventually throw a lean code I would think.

Good point about restricted intake air flow. If it just couldn't get enough air the ECU could still keep the air/fuel ratio correct. You'd just have no power.