So I understand that these 4.0 motor are underpowered
But seems like mine got a bit weaker
Going over pass with 4 people seems it struggles a lot hardly gets up to 70mph
No fault codes or any thing like that
20k ago I replaced the hg and machined the heads replaced the spark plugs etc
Any suggestions on a service that may improve the power a bit
Other then that the disco is like a charm

 

I started driving mine in sport mode, seems to slightly disguise the lack of power. Of course now I am down to about 9.5 mpg gallon but I have 33"s, stock gears, heavy steel bumpers front and back and a full roof rack. Outside of a cam swap I am not sure there is much you can do for these tires old motors. I read tall tales here about mpgs in the high teens and low twenties but I am pretty sure those folks don't know how to properly calculate mpg.

I had a RRC a while back, I had a completely rebuilt 4.6 with a Cower 229 cam installed. That thing ran very strong. I mean it RAN. It also got around 10-11mpg.

 

I had a Subaru Forest XT and it had more hp and tq with far better MPG but NO character or charm. I will gladly trade a slight bump in speed for the overall great package the DiscoII is. (IMO)

 

You didn't mention but what kind and type of fuel are you using?

I know it can be controversial on the forums, but using top tier premium helps deliver more power and keeps the injector system clean. Speaking of which, did you have the rail soaked and cleaned when you did the HG's? Dirty injectors from using cheap fuel and a worn camshaft (from using thin oil and an oil pump fail) were the two issues I've had that showed up as loss of power.

I've also found that using non ethanol premium helps even more but is not widely available where we live.

 

My 4.0L in my Kalahari with 265/75R16's and all the off road goodies does great out on the highway. It's not gonna accelerate like an F1 car, but vs any of my 4.0L Jeep Wranglers or a 3.8L V6 JK/JKU it'll soar past em while they're to the floor barely able to top 65MPH on a flat road.

I'm normally at 2600-2800RPM going down the highway in my D1/D2's and I've sometimes used Sport Mode off the line or getting onto a freeway, but then I disable it. 93 octane is a MUST if you are pulling anything, loaded down, or in hilly/mountain terrain.

 

Non ethanol. Rail soaked, injectors cleaned.

 

Try cleaning your MAF. It helped mine alot! Also I replaced my TPS as it seemed like I had to push the pedal too far before it would downshift. It's much better now. These litle issues caused no check engine lights but it worked for me. If you have a scan gauge look and see what reading you get at WOT on your TPS. Mine used to top out at 70%. Not it goes from 0-90%

 

Thank you all
The amount of knowledge Is unbelievable

 

For my truck it feels underpowered off the line. Quite often I feel like I'm lugging the engine from a dead stop to about 80kph (I can rev it into the mid-2000s, but the translation to acceleration isn't great). It also struggles going uphill on anything greater than a mild incline. Once it's up to highway speed it does well and is happy.

I'm not sure what'd cause this sort of thing, but I'm going to research it a little. I suppose getting more air into the engine could help, or maybe doing something with the fuel delivery or the throttle plate/TPS. It'd be nice if there were a way to diagnose exactly what to do. I had a random lean condition code come up a while back – maybe I'll research that.

 

Also during the summer anything is gonna run with less HP as the air the engine is sucking in is hot (here in SETX I've seen my AI temps up in the 140F range. Cooler air will give you more power.

I am back in a Ford Transit Connect at work and in the cooler mornings it's fine. During the middle of the day it can't get out of it's own way lol.