No power when AC is on.

loke

NAXJA Forum User

Location

Round Rock, Texas

• Jul 6, 2006

• #1

I have an '85 XJ. 2.5 engine with a 5 speed manual. Lifted 3" and running 31" TrXus MT's.
When I'm accelerating with the AC off it feels ok, but with the AC on (it's really needed here in Texas) I am being passed by pedestrians and bicycles.

I know my exhaust manifold is leaking (broken bolt), but would this be the reason?
I'm not sure about my gearing as the labels are gone from both differentials.

 

cal

NAXJA Forum User

NAXJA Member

Location

Hammertown, USA

• Jul 6, 2006

• #2

"'85 XJ. 2.5 engine with a 5 speed manual. Lifted 3" and running 31" TrXus MT's"

Thats why. That 85 2.5L only nominally had enough power to get around with stock tires..

 

loke

NAXJA Forum User

Location

Round Rock, Texas

• Jul 6, 2006

• #3

I know it's not the most powerful engine in the world, but it pulls ok without the AC on. Does the AC really make that much of a difference?

 

cracker

NAXJA Forum User

Location

La Mierda

• Jul 6, 2006

• #4

loke said:

I know it's not the most powerful engine in the world, but it pulls ok without the AC on. Does the AC really make that much of a difference?

Click to expand...

Obviously it does

I'm surprised the AC still works

 

loke

NAXJA Forum User

Location

Round Rock, Texas

• Jul 6, 2006

• #5

cracker said:

Obviously it does

I'm surprised the AC still works

Click to expand...

Yeah, I guess I should have expected an answer like that. What I meant was: Is the AC supposed to make that much of a difference? :moon:

 

cal

NAXJA Forum User

NAXJA Member

Location

Hammertown, USA

• Jul 6, 2006

• #6

yes, thats pretty normal behavior. You don't notice it on most vehicles because there is at least /some/ power to spare, but your pushing that little 2.5 as hard as it can work just to go down the street.

 

9

90Pioneer

NAXJA Forum User

Location

USA

• Jul 6, 2006

• #7

Rev it up a few hundred extra rpm than normal before you release the clutch.

 

Lawn Cher'

NAXJA Forum User

Location

Westampton, NJ

• Jul 6, 2006

• #8

loke said:

Yeah, I guess I should have expected an answer like that. What I meant was: Is the AC supposed to make that much of a difference?

Click to expand...

The AC will drag a significant amount of power off the engine. I notice it in both my turbodiesel Suburban and my wife's '01 XJ, so with as anemic as your XJ is in stock form adding the 31's makes it even worse.

 

loke

NAXJA Forum User

Location

Round Rock, Texas

• Jul 6, 2006

• #9

So regear? (I don't even dare to ask what recommendation you might have:angel: )

 

M

muddshutter

NAXJA Forum User

Location

Fighting Giblet Burg, Va

• Jul 6, 2006

• #10

It makes that much difference. Even in my Volvo DD, if i am going up a big hill with AC on, it drags. Turn it off, it jets away.

I worked as a Tractor Truck designer for a while and most companies are switching their AC units over to a different sysytem. There would be a generator on or near the engine that would supply electricity to an AC unit w/o ANY load on the engine. Its a better way to get the same result.

You might try regearing, that puts less stress on the engine.

 

Lawn Cher'

NAXJA Forum User

Location

Westampton, NJ

• Jul 6, 2006

• #11

loke said:

So regear? (I don't even dare to ask what recommendation you might have:angel: )

Click to expand...

You probably already have 3.73 or 4.10

You could go to 4.56 or 4.88 if you put a D44 under the rear, but you'd be better off with repowering altogether. Which, in an '85 probably isn't worth the effort. Maybe just look for a newer one with a 4.0 liter engine.