Engine compression question

[ruralandalone]

Can anyone tell me what would be considered good compression on a 2.5 L engine?

[Pete M]

what numbers are you getting?  which technique are you using?

[ruralandalone]

cold and warm testing with compression guage. .  120 across the board, no change.

[eaglescout526]

120 is healthy for the 2.5L . Do you suspect something is wrong with your engine?

[ruralandalone]

Not particularly.  But it is an elderly vehicle with an unknown history (although I suspect it was used as a plow truck) and high mileage.  I assume it has the original engine, but I can't prove it either way

I just note the general lack of power and what I consider to be a low top speed,  and I thought it would be appropriate to check it.

I was doing my '92 volvo (190  lbs cold)  and since I have never done the jeep....

(I note the hopelessly optimistic speedometer.    This thing would not do 120 off a cliff with a tailwind....)

[eaglescout526]

I can break out my 2.5L engine rebuild book that can help decipher the date code on the block. Otherwise as far as these engines go and being made out of cast iron, some of them including my 84 XJ are going strong and well above 300k without a rebuild and 4.0's are doing the same. AMC made some really well built and stout engines that will keep going when properly maintained for years and miles. 

[Pete M]

59 minutes ago, ruralandalone said:

Not particularly.  But it is an elderly vehicle with an unknown history (although I suspect it was used as a plow truck) and high mileage.  I assume it has the original engine, but I can't prove it either way

I just note the general lack of power and what I consider to be a low top speed,  and I thought it would be appropriate to check it.

I was doing my '92 volvo (190  lbs cold)  and since I have never done the jeep....

(I note the hopelessly optimistic speedometer.    This thing would not do 120 off a cliff with a tailwind....)

 

 

I wish I had 120 across the board!  

 

what size tires?  what rear axle ratio?  how long since the last tuneup and fuel/air filters?  I'm assuming it's the original injector?

[ruralandalone]

I can only answer a few of those questions.

Drive train is stock.  I have no info on the ratio.

tires are 18"

plugs, ignition wires, oil and filter,  fuel and air filters are new. No tune up beyond that.

IS there more I should do as far a a tune up goes?

[Eagle]

18-inch tires? Stock tires are more like 28-inch. What size tire do you have?

 

More importantly, what vehicle do you normally drive? The Jeep 2.5 litre engine is a good, solid engine but it's not a modern, overhead cam pocket rocket. It will never be "fast."

 

 

[Pete M]

in stock form it's built for torque more than horsepower.  you could even get the Metric Ton package with the 2.5L!   I doubt your Volvo can carry 2200# in the back.

 

but it's 30 years old.  at least now we know the injector is a GM unit and so you can still get replacements. 

[Ωhm]

2 hours ago, ruralandalone said:

But it is an elderly vehicle with an unknown history (although I suspect it was used as a plow truck) and high mileage.

Hate to spend your money, but I believe the O2 sensor is a maintenance item. O2S response times can slow down. Replace at least once in a engine lifetime even if not needed.

[ruralandalone]

Good idea.  I'll do it.  Do I need  any special tooling to replace, or just a wrench?

I note a considerable range of prices for the sensor on rockauto.  I wonder if there is a quality issue that makes the bosch  worth twice as much? 

[Pete M]

if everything goes smoothly all you need is a socket or wrench.    but it's been baked into the exhaust for decades now so be prepared for a bit of a fight. 

[ruralandalone]

I checked the tires. they are 16 inches

[jdog]

11 minutes ago, ruralandalone said:

I checked the tires. they are 16 inches

Got the full size?

[Pete M]

1 hour ago, ruralandalone said:

I checked the tires. they are 16 inches

 

the rims might be, but what is the tire size?  225/70/r16? 

 

manual trans?  4spd or 5spd?

[ruralandalone]

the tires are 2255/70r16

[ruralandalone]

4 speed manual

[Pete M]

1 hour ago, ruralandalone said:

the tires are 2255/70r16

225 or 255?

 

the 4spd is likely the problem here.  not the trans itself, but the fact that a 4spd manual truck came with wimpy 3.55 gears instead of the 4.10s that a 2.5L/5spd would get.   

[ruralandalone]

that explains a lot.  Thank you