1998 3.0L has no power!

First, I would like to say I know these are no rocket ships. My Dad used to have a '98 3.0L 2WD and my last truck was a '94 3.0L 2WD which actually had more miles on it than this one. Both of those trucks had substantially more power than this thing does.

Here is what I'm working with:

• 1998 Ranger, extended cab 2-door
• 3.0L engine
• Manual transmission
• 3.73 axles
• 245/45-16 tires (original was 235/75-15)

I've had it since 2006 and 144k miles. It now has 292k miles on the clock. I realize the slightly bigger tires may slow it down a little, but it is ridiculous! I mean, it can't even maintain 65 MPH up a grade WITHOUT a headwind. Trying to drive on an expressway with a headwind is miserable.

I realize the engine has a fair number of miles on it, but it hardly uses any oil (less than a quart every 5k miles). I have already done the regular tune-up stuff (plugs, wires, fuel filter, cleaned MAF sensor, checked for codes and found none), but where else can I look for where I'd be losing power? Oxygen sensor codes did not show up, but should I replace the oxygen sensors anyway, or is that throwing money away? Yesterday I was thinking that maybe the fuel pressure is down. Should I check this out?

Of course I know that ignition supposedly isn't adjustable on these engines, but when I had my '94 truck with upper-200k mile range it seemed to have a similar loss of power. I checked the base timing on that truck, and it was ~2-degrees AFTER TDC. Once I adjusted it to 10-degrees BTDC it made power like a new truck. Is there some failure of the cam sensors on newer 3.0s that would cause a loss of power?

I'm sorry for the long-winded post, I'm just trying to provide as much information as I can and hopefully get some help. I'm new here, but not to forums in general. In my "spare time" I race my Mustang in SCCA's Solo II competition. I'm very familiar with working on cars in general, but this has me stumped.

Thanks a ton!

Compression check.

When I first noticed the power loss thing (about 30k miles ago) I did a compression check. It showed 125-130 psi in all six cylinders. When I get a chance I will do another one. Is 125-130 psi low? What should I be looking for?

I'm not sure what a 98 should have but I'm thinking your readings are quite low compared to factory new spec.

My own are up in the 185 to 195 range. Did you do the CC with a hot engine?

My dads truck is the same way but an auto and 4wd and it has no power. Its something that he is living with and wont mess with for some reason, plus has a miss of some kind going on.

What gears did the other trucks have?

Rearanger said:

I'm not sure what a 98 should have but I'm thinking your readings are quite low compared to factory new spec.

My own are up in the 185 to 195 range. Did you do the CC with a hot engine?

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Wow, I need to find the factory specification for cylinder pressure. If it is in the 185 psi range, I'm wayyyy off. That test was with a warm engine, but not quite operating temperature.

adsm08 said:

What gears did the other trucks have?

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The '94 had 3.45s, and I think the old '98 had 3.45s as well. They were both 2WD and had smaller diameter tires, but still.

kpgubert said:

That test was with a warm engine, but not quite operating temperature.

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It's hard with a just-been-run hot engine. I like to get everything ready, know how to cut the fuel pressure and wear my gloves to pull the plugs, take it for a good drive to full operating temp then do the test as quickly as possible. I have a pneumatic ratchet which speeds plug removal.

From warm to hot though I doubt you'll find much significant change.

kpgubert said:

Wow, I need to find the factory specification for cylinder pressure.

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Ford isn't great about publishing actual specs for cylinder pressure. They like to just tell you that if there isn't a 10% drop from high to low you are good.

I thought of that just after I posted. When I get a chance I'll still run the test again, post the numbers, and see what the reaction here is. Unfortunately, it may be a couple weeks before I can do this.

Here is the spec chart I did find.

My dad has 4.10 gears on his and is getting 12mpg on 30 inch BF Goodrich A/T tires, stock rims.

Alright, I wasn't kidding when I said it might be a while before I could do a compression test! I haven't forgotten (of course not, I drove the truck 525 miles back home yesterday - half highway), and I did a compression test tonight. Here are the results:

#1: 150 psi
#2: 125 psi
#3: 145 psi
#4: 115 psi
#5: 135 psi
#6: 125 psi

The spark plugs were removed with the engine at operation temperature and the test was done immediately. The engine was cranked until the gauge maxed out. The instrument used was a Milton S1251.

Any thoughts on these numbers? Thanks!

Other than cylinder 1, those seem pretty low. I remember 150-160 being pretty average, and the drop across all cylinders should be 10% as was already mentioned. Yours is clearly more than that. Seems like a rebuild might be in order.
Also, I'd check the condition of the throttle cable. They tend to loosen over time. Doing the "throttle cable mod", and taking the slack out of the cable can make a big difference in an older truck.

Thanks for the reply! I checked the throttle cable, and sure enough the throttle body wasn't opening all the way with a cinder block on the gas pedal (a one man show tonight!). I did the zip tie mod, so hopefully that will make some difference. I'll know tomorrow.

I figured I'd be up for a rebuild sooner or later. In order to minimize downtime, I would like to buy a second engine so I can rebuild it and just swap engines. Are there any Vulcan 3.0s I should avoid? Are Taurus engines acceptable? How about older 3.0s that were originally equipped with a distributor? I'm not worried about the oil pan, I need a new one anyway (current one is pretty rough).

Thanks again, and Merry Christmas!