Hey guys,

I have an 01 Supercrew with a 5.4L and about 95k miles. I noticed last summer that the truck was really down on power. It seemed to get better in the winter but now that we're back in the throws of an AZ summer the truck is really weak again. The motor seems to run smooth, no miss, no rough idle, it just doesnt have any power, especially on the low end. I've replaced the plugs about 8k ago but other than that, the truck hasn't had anything done to it.

Any ideas where I should start looking for the culprit?

Thanks

 

how hot exactly is it there? what brand plugs did you get? how olds the fuel filter? what kind of air filter do you have in the truck? has the maf ever been cleaned? cel on? are you saying that the engine has always been down on power? or that its not as strong as it use to be?

 

Sounds like a cry for boost to me

 

Do you have an aftermarket intake? If so, the intake air temperature is too high.

 

Most likley a combination. Needs to be updated with the CORRECT parts.

A Dirty MAF sensor can really screw things up as well.

jas.az -

What mods are you running ?

What's been updated as far as maintenance parts and when ?

What Spark Plugs are you using ? (that can make a big difference as well)

At those miles, -it's time to go thru her and update/clean.

 

It might have something to do with your exhaust. I was told that a plug up of any kind in your exhaust can cause a significant loss of power. I dont know if that explains why it would go away in the winter though.

 

Doubt it, might not hurt to check.

VacSync -

Testing for blocked exhaust

Just "T" into your vac system and guage it -

When reading gauge ~

Idle speed reading slowly dropping toward zero indicates exhaust restriction.

Excessive back-pressure in exhaust, then indicated by reading not increasing quickly to about 16 Hg (in's of mercury) when engine speed slowly increased to 2000 rpm.

Back-pressure also indicated by reading not dropping as quickly when throttle quickly released and remaining 5 Hg higher or more than normal.

Disconnect exhaust manifold from engine and retest. If problem disappears exhaust system is blocked.

To locate restriction reconnect exhaust system one unit at a time testing after each until problem reappears.
___________________

That's the book ^^^

All you need is a spec sheet with the numbers for your engine model = Ford Service. There's other ways to get these, but if the guage reads lower than spec @ 2000 rpms, - you should definitely look more into an exhaust prob/ over restriction.

 

Clogged cats?

 

Hey guys, thanks for all of the input. Here are some responses to your questions.

Mods: K&N in the stock box, 35's with 4.10 gears, 4" lift, Flowmaster (went on at about 65k miles). Other than that, stock.

Fuel filter and plugs were done around 85k miles. I don't remember what brand plugs went in but I'm pretty sure they were factory replacements...Autolite??

No CEL, MAS hasn't ever been cleaned. I've always felt that the truck was down on power (I bought it brand new), but this problem is a big time drop in power that started last summer. Its bad..real bad. Today I pulled out into traffic and with normal throttle tip in the truck wouldn't get up to speed. I had to stand on it to get it to downshift and then it would run. The truck will make some power with higher RPM's but the low end is gone.

I suspect that you all might be onto something with either a vaccuum leak or blocked exhaust. My dad has the same truck with similar mileage and it seems to have a vaccuum leak also. His runs ok but the A/C keeps changing from vent to defrost when he accelerates (clearly a vaccuum leak)

Anyway, I'm all ears so please let me know what you all think.

 

Boost doesnt help, my truck is a dog in the summer. It was suppose to be 114 today? When I got in my truck after work it said it was 146 after sitting in the sun all day lol. IAT will be 100-150s even if the truck is cold. Its Arizona.


Your dad has a vac leak, follow the vac lines that come out of the firewall and see if you have a leak there or behind the dash.

Clean your MAF with non chlorinated brake cleaner. It will take all the nasty crap off. Especially if it has never ever been cleaned. That will for sure make your truck a dog. Guarentee that your K&N oil from your filter has gotten on your MAF. Clean it, could be your whole problem. Ive seen it fix alot of problems over the years.

 

as said above clean the maf.
what brand plugs did you use?