so been trying to find out why i have no top end on my rebuilt 3.0. i ported the intake and heads and did the halfshaft throttle body mod. it power is ok up to about 2500 then it flat lines.

i checked my fuel trims and at idle it usually fluctuates +/- 5 with occasional drop to -12. when i punch it WOT it will breifly drop to -10 or so then jump to 16.36 (i guess thats the max) and stays there the entire time its WOT.

ive replaced the MAF that idled at 4.4g/s with a good used that idles about 4.9g/s and no change. ive checked for vacuum leaks and didnt find any. i want to try the smoke test but need a good smoke source as blowing cigg/cigar smoke is exhausting and not very productive..


any ideas?
ill try and get my obd log loaded up in a video soon..

 

WOT doesn't use O2 sensor input it is "assumed" driver wants power not best MPG at WOT, so fuel trims are not a function of air fuel calculations they are max fuel based solely on RPM, so fuel trims won't be valid numbers in any real sense

Do you get WOT at the throttle plate?
Stretched throttle cable is common on Rangers
Key off
Put something against gas pedal so it is "floored"
Go the throttle plate and see if you can open it more, if so Google: Ranger throttle cable mod

3.0l gets max power/torque at 3,500RPMs so is considered a high RPM engine, i.e. 4.0l and 4 cyl get max torque at 2,500RPM
Specs here: The Ford Ranger 3.0L Vulcan V-6

So you shouldn't have much power until well above 3,000RPM
Max horse power is at 5,000RPM

What does it feel like above 3,000RPM, could you be running out of gas?

Fuel injected computers do have REV Limiters, these are only active if in Park or Clutch pedal is down, OR..................the Computer "thinks" vehicle is in Park or clutch pedal is down, this is a wire at the computer that usually has voltage when in Park or clutch pedal is down, and 0volts on that wire to disable REV limiter

 

i know that the absolute throttle position reads 17.6% closed and only 92% with pedal floored. ill physically check the throttle plate tonight.

theres next to no power above 3k and i wouldnt say it feels like running out of gas it doesnt sputter or hesitate or anything like that.. if feels like the ebrake got partially applied.. the rpms keep going up but the powers gone and stops accelerating... i feel like a horse jockey bouncin in the seat like faster faster come on you can do it keep going.. its difficult just to merge on the freeway because above 45mph it accels so slow

 

Exhaust blocked?
Partial blockage allows OK running until back pressure builds up then new air/fuel mix can't be pulled in so power just drops off

Vacuum gauge can show if that is happening
Raise RPMs and watch if vacuum starts to slowly drop at steady 2,500-3,000, just in driveway
Blipping throttle can also tell you, clear exhaust will show drop to 0 vacuum and quick return to 18" when you "blip" open the throttle
Clogged exhaust will slowly return to 18"

 

i checked with a vacuum gauge and it was quick to return to 15hg.. 15 seems a little low and logged some more data and bank 1 is running + fuel trims.. so im going to check bank 1 because also at higher rpm i get a what sounds like an exhaust leak or something knocking from bank 1.. hard to tell and i left my stethoscope at a neighbors.. but it sounds like an airy knock from a single cylinder.. maybe cracked manifold or something..

drove it to sears point today for a savemart 350 nascar race and it did ok.. still lacks top end but didnt seem like it was going to die like my last long drive..

heres a little graph of a scanxl log.. i figured out i can change the pids so this new pic has better info but the program crashes after about 20 seconds everytime i start logging data but here what i got.. a few pids arnt supported and are x'ed out

 

An exhaust leak will show a positive fuel trim but it's a false positive - exhaust exiting before o2 sensor(s) will read lean when it isn't actually. I figured out a cool way to test for and locate exhaust leaks a while back when I had a similar issue...find or make a hose that'll reach your egr valve and with the engine idling connect it to the top port. If the egr is functional applying vacuum at idle will nearly stall you - no worries. Then while applying a bit of throttle to keep from stalling, vacuum in some seafoam like you would for the o2 sensors at the brake booster line. If you have an exhaust leak it will start pouring out white smoke...it'll clean out your egr valve too [Bonus!]

My exhaust leak was at my flange joint between the manifold and cat caused by backpressure from a clogged/stuck egr.

Good luck =)
Allison

 

i already suspect an exhaust leak from the sound coming from bank 1 but cant use your method to check because i do not have an egr valve.

ill have to double check for a plugged cat.. about 2 years ago the bank 2 #1 cat plugged up the cat right behind it so i cut them out, beat crap on the inside out and welded them back in.. just passed smog last month no issues.. might do it to rest of them to solve this little issue

 

A low calc. load at 2500rpm is an indicator of a clogged catalytic converter...since you already have datastream frames ☺ also a heavy dose of seafoam will make it thru combustion enough to weed out even a small exhaust leak or you could try spraying sudsy water (or something a bit thicker that'll hold up to exhaust heat) at suspected leak points...it'll temporarily plug the leak - you should hear at least a slight change in sound.

 

dont really want to dump seafoam in a motor with 2k miles on it.. if it had 50k i would.. thinking about removing the belt and plugging up the tail pipe and give a 2 min inspection to see what i can find.. or what about blowing smoke up the tail pipe? hadnt thought of that yet but i dont see why it wouldnt work...

 

so i just noticed that theres a clicking sounds that starts about 5-10 seconds after i turn the key off for i dont know maybe 8 clicks about 2 seconds apart.. sounds like its #5 or #6 fuel injector.. is that a normal issue? just seems weird.. if theres no power hows it clicking?

noticed a little fluid around the #6 upper intake at the seam where 2 pieces are fused near the base by the lower intake. pulled it off and found a small crack on the back side.. cleaned it up with some carb cleaner to remove the oil, roughed up with some sand paper and epoxied the seam on the lower half of the manifold. hope that might help a bit andl hold up at least until i can get a new one...

 

does anyone know why i have fuel trim values for banks 3 &4? and why are they so extreme?

 

check out this site...it does a really good job making sense of fuel trim...may help =)

http://m.autoserviceprofessional.com/article/94982/Fuel-trim-How-it-works-and-how-to-make-it-work-for-you