My 98 Ranger has no power on take off most noticeable with a/c on. It's just generally not even comfortable driving because it is such a pig. I know it's a 2.5L 4cyl but even being that this is definitely not right. I never remembered it being this low on power except when the coil was bad. The engine was replaced at 228,000 with a used 2.5 from a 2000 model year Ranger with 48,000 miles. So now it has roughly 84,000 miles on the engine. It died in Kentucky and when we got it back home I changed the plugs, wires, fuel filter, air filter, and pcv with Motorcraft parts. So now the tune-up has about 36,000 miles on it. I didn't think the fuel injectors came with the used engine so I finally got those changed last week with new Motorcraft injectors. That did help some on the power loss. There is no Check Engine Light on but the catalytic converter was replaced at 223,048 with a universal fit listed for a 98 Ranger 2.5L regular cab because no one around had a direct fit in stock that day. The O2 sensors were also replaced shortly after that. I thought the coils were bad so I checked the resistance on them, Primary was .9 ohms and secondary was 15.25 ohms on Motorcraft coils. The test procedure I was following said the Primary resistance should be between .5-1.0 ohms and secondary between 6500-11500 ohms. So according to that both are bad. But I checked the resistance on two over the counter parts store brand coils and they were .8 and 14.25 ohms right out of the box. Is there another way to tell for sure if the coil is causing a problem? I know when I did the tune up I didn't adjust the gap. I used the Motorcraft sp-432 and I remember the gap being at like .050 right out of the box but I didn't know if it made a difference. Could that cause such a power loss? I was going to try a tune-up again but I'm thinking it's something more than plugs and wires.

 

Many auto parts stores will check your coils for you at no charge. It might be worth having them check the coils for you. Their tester may be more extensive than just checking resistance. It would at least be worth a try. I hate to see you throwing more parts at your truck. The store may be able to do other testing as well that may pinpoint the problem.

Also, if you are thinking of changing plugs again, use Motorcraft double platinum plugs.

 

the primary resistance should be less than 5 ohms and the secondary resistance should be 13,000-15,000
you might want to do a fuel pressure test

 

It seemed to be the ignition coils. I replaced them tonight and it appears that its back to the correct amount of power it should be with all my performance add-ons removed. I'm sure once the plugs and wires are changed it should be as good as it gets. Now I'm on to figure out the a/c vacuum problem. I will check the reserve canister tomorrow.