Help, car has barely enough power to move itself.

Slow91z

Slow91z

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1st off I'm trying to figure out what the fuel pressure should be (i work on gm's, i kinda wish i had never bought this ford) i can't find an actual spec anywhere, but it's right at 30 at idle and goes up to 40 when you rev it in park or throttle it going down the road.

The car will barely maintain speed in high gear

A little background before i go to far, bought this car many years ago, has 174,000 miles on it now, i have never changed coils never had a valve cover leak either ...i have changed the upper chains and still don't have any valve cover leaks.

The car doesn't miss like coils and the plugs are fresh...i have no idea really where to start troubleshooting it any further. HELP PLEASE

Edit - the car is dead stock
 
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Start with the replacement of the coils.
 
I will not just throw parts at it without testing...as i said it doesn't miss it runs smooth just no power, i can unhooked each coil with the rpms held up and each is definitely working
 
Clogged cats crossed my mind, not really sure how to test for that, dont really wanna cut the exhaust up for no reason.
 
Slow91z said:
Clogged cats crossed my mind, not really sure how to test for that, dont really wanna cut the exhaust up for no reason.
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If they are clogged, it will be because of the marginal coils.
You can stress test them if you don't believe it. (That will cost more than replacing them.)
 
Slow91z said:
I will not just throw parts at it without testing...as i said it doesn't miss it runs smooth just no power, i can unhooked each coil with the rpms held up and each is definitely working
Click to expand...

Changing the coils is not throwing parts at it. It is part of regular maintenance. You said you have owned the car for many years and never changed the coils. It won't hurt. Joe's advice is respected on this forum and he is one of the most knowledgeable members on this forum when it comes to this car. Give his suggestions a chance, especially considering they are usually the less expensive more sensible options.
 
I had coil issues starting around 50K so it couldn'thurt replacing them. I swapped an ebay set in at about 60K snd all is good 130K miles.
 
Pulled o2's no change...i had 4 new coils sitting around, threw them on no way change, still going to order the other 4, but don't really think that's the problem...anyone know the fuel pressure specs? Any other ideas?
 
Slow91z said:
Pulled o2's no change...i had 4 new coils sitting around, threw them on no way change, still going to order the other 4, but don't really think that's the problem...anyone know the fuel pressure specs? Any other ideas?
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30/40 is in the right ballpark.
Disconnect your MAF sensor and see how it does. If it improves things, then your MAF is dirty or defective, or you have an air leak somewhere.
 
Well i did look at the maf and it's very clean inside but i didn't unplug and drive it.

Btw today was the 1st time i drove it completely cold, and while it definitely doesn't run correct cold it gets way worse as it gets warm.
 
Cats.

Start the car and go back and check to see if exhaust flow is uneven.
 
Robot said:
Cats.
Start the car and go back and check to see if exhaust flow is uneven.
Click to expand...
not likely any more, if the cats where clogged, removing the o2 sensors would give the exhaust gases a less restrictive way out and would restore power (at least some)

also the exhaust should still be even if only one of the cat where completely clogged as the third cat combines into one chamber and then splits back out.

Slow91z said:
Pulled o2's No change...
Click to expand...
 
Slow91z said:
Well i did look at the maf and it's very clean inside but i didn't unplug and drive it.
Click to expand...
well the problem is that looking at it is not the test suggested, at it looking clean wont rule out it being defective or having un-metered air leaking in

joegr said:
Disconnect your MAF sensor and see how it does. If it improves things, then your MAF is dirty or defective, or you have an air leak somewhere.
Click to expand...
 
Update, stuck a scope in the front o2 bung and looked at the inside of the cats...DS one was screwed, so new coils and 2 gutted cats later and we're back in business.

Mileage is much better than ever before, best I ever did on a highway trip was about 24...Saw 27 on the highway the other day...Used to average 17 with mixed city/highway, now about 20.
 
Acoording to Torrie at Fastpartsnetwork.com, the gen 1 3.9 fuel pressure should be 38psi. Just asked this very question to him about a month ago while trying to determine the best Hobbs switch for the n2O.
 
marcredd said:
Acoording to Torrie at Fastpartsnetwork.com, the gen 1 3.9 fuel pressure should be 38psi. Just asked this very question to him about a month ago while trying to determine the best Hobbs switch for the n2O.
Click to expand...

Yes, but 38psi at what condition? Fuel pressure is relative to manifold vacuum. Maybe that is for idle as sea level?
 
marcredd said:
Closed loop.
Click to expand...

Fuel pressure control is always a closed loop system (if it is working). The point is that fuel pressure is regulated relative to manifold vacuum. If you don't specify the exact manifold pressure, you can accurately specify the exact fuel pressure. That's why the manual give a range of pressures instead of one exact reading. I wouldn't want someone reading this thread later to think that they have a problem because their pressure is 35 or 45 PSI.
 
Perhaps my response was not as expanded as it should have been. I did mean closed loop as in making the assumption that the op's system was functioning properly(as you stated). I see your point Joe. Good call.
 
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