Many problems/some answers?

[oneguyssky]

Here is the layout. 91 Ford Explorer Sport 4X4 auto w/4.0 V-6. Mods are as follows; home made and aftermarket suspension lift totaling 10 3/4" front/10 1/2" rear, 3" body lift, 33X12.50X15 tires on 12X15 rims, headers (Pacesetters-suck-bad fitment), free flow exhaust, kind of catalytic converter (made from an aftermarket for another vehicle), rebuilt top end about a year ago with new valve seals and such, 3:73 posi from a 97 Mustang in rear, adjustable vacumn modulator for tranny, shift kit in tranny-rv type, double platinum plugs, K-N cold air intake, class-3 hitch, billet window cranks, no power windows/seats/locks/cruise, new radiator, new coil pack, new wires, new fuel filter, new tranny filter/gasket/fluid, homemade radius arm brackets out of 1/4" steel box, 4" aftermarket track arm brackets w/6"X1/4" steel blocks, new radius arm bushings & track arm bushings, stainless steel extended brake lines front and rear, 4"over coils in front with 6 3/4" blocking (round under them), shock extensions front and rear above and below shocks, rear sway bar extensions 10", front sway bar end links after market for 6 to 8" lift with 3 3/4" blocks between sway bar and frame, dual steering stabilizers, new pump and gear box, new alternator, lighted visor, side steps, window visors (extra large type), rear hatch visor, custom flame gauge faces, grant signature series steering wheel, Jensen stereo cd/ipod/mp3/mp4/xm w/cd remote and extra amp plugins, 4 12" Lanzar comp d subs with 128 oz magnets, 1 or 2 Pyle Dryver amps comp. class d rated at 3,600 watts each, hybrid 24 volt 8,000 fahard cap, and some stuff I can't remember. Now here are the problems I have. Many. I read a lot of the forum and some of the answers for others might apply but I would like to make sure. The guys on here have some awesome knowledge and I hope I can tap some of that. The ride has 353,000 plus miles on it at current status. I have a constant problem lately when going against the wind or uphill (I know height has some part to do with this). Kicks down a lot, has loss of power, and no rpms. Taking off isn't bad up to 60 or 65 mph, then weakens after that when constant or like I said, going uphill or against the wind. I noticed comments about MAF unit having something to do with this(mine is original as far as I know), and fuel pump not putting the pressure out there in a constant 42 psi or more (mine is also original as far as I know). Maybe fuel injectors also?Motor seems slow to start, not cranking but firing. Seems like to have been that way for quite awhile. Also every once and awhile I slow down, stop, put in park, and idles up to 1,800 to 2,200 constant. Turn off and turn on again and settles down. Had the computer replaced once when it had done this with another used one. Maybe problem again? Another problem is a shimmy shake on the passenger side front tire. Tires were balanced, but it seems to feather all the way across it. The other front has no problem, or not hardly at all. New tie rod ends, ball joints, and inner tie rod ends as well as center link to. Adjusted and adjust caster/camber as best as can be done and just doesn't seem to help. Also need help-i.e. with wiring diagrams, drawings and or pics for to wire sound system properly for best results including air tubes in box and if the top of the box should be enclosed or open. I use to be able to spin the tires pretty easy when when taking off but now seems to not have the power for that as easy as it did. Cruising at 60, punch it, kicks down, and goes just about nowhere with your foot to the floor. Rpm's barely move as well as the speed. Motor doesn't smoke, compression is good, no air leaks, I'm at a lost. Also what would be the proper ring & pinion size for these tires and I do plan on going to 38's and what would the ring & pinion size be for them? It's not the greatest or fastest, but it was a lot better before. Power wise and such. Use to be able to squeal the heck out of the 33's.

 

[97sprt4x4]

I believe 3.73s are less then optimal for 33s however that wouldn't affect the drop down as much. I am curious because if I remener as far as what you posted you have an OHV. That motor had around 160 up from the factory and from looking around in the exhaust thread I know that the 4.0 needs back pressure. My truck had dumps in front of the axle and it ran like crap. I would say based on my minimal knowledge that it's a combination of low power to start combined with the free flowing exhaust lowering the back pressure combined with the fact your truck is 17 inches higher then it is supposed to be.

As far as what gearing when you move to 38s I think the general concesus is 4.88+.

Disclaimer: I'm sitting in class doing this on my iPod so I don't know if I caught everything but I will re read it when I get back to my dorm

Justin

 

[oneguyssky]

Thanks. I do seem to remember on prior posts that the question was brought up about not having proper back pressure. I located an aftermarket but still proper catalytic converter and will get that to see if it helps ease the power loss. Also the the gearing sounds right to. Thanks. Anything further will greatly help.

 

[Currency]

From my research to run 31's I found somewhere it recommended 3.55 gears. So I'm guessing your ok with your current setup. 38's I believe should be 4.88's also.

I do agree with the back pressure also. I thought about cutting my cats off just because at the time they junked for $150 together. But then I started reading up on removing them and decided it's best to leave them or at least one there.