4.0 sluggish after swap

[kunar]

so last fall/winter i swapped a 4.0 into my 87 ranger. the engine was from a 93 navajo, wiring from a 90 ranger, injectors from the same 90 ranger, and computer from a 91-92 explorer (x2x2) engine was completely disassembled and hot tanked, cylinders honed and new rings, new main bearings and rod bearings, the only thing that wasnt done was cam bearings.

ever since the swap ive been disappointed with the power that this thing makes, on top of that i get really crappy mileage. im running 31" bfg's with 4.10 gears and average like 12-14 mpg. up until now ive pretty much just dealt with it since i dont drive it much but now im getting kinda fed up and i have time off this week so im gonna start looking to see if i can figure anything out. im gonna check timing and spark, compression and also fuel pressure if i have a gauge, i dont remember if i do or not. i've tried pulling codes but couldnt get it to show anything at all, so i dunno whats the problem there.

i used all of the sensors on the engine from the navajo, are all of these compatable with the older wiring and computer? i know that the injectors had to be switched so i pulled the red ones out of there and put in the ones from the older engine (black i think) now i guess im just hoping that i missed something. anybody have any other ideas or suggestions?

 

[Big Jim M]

The word

so last fall/winter i swapped a 4.0 into my 87 ranger. the engine was from a 93 navajo, wiring from a 90 ranger, injectors from the same 90 ranger, and computer from a 91-92 explorer (x2x2) engine was completely disassembled and hot tanked, cylinders honed and new rings, new main bearings and rod bearings, the only thing that wasnt done was cam bearings.

ever since the swap ive been disappointed with the power that this thing makes, on top of that i get really crappy mileage. im running 31" bfg's with 4.10 gears and average like 12-14 mpg. up until now ive pretty much just dealt with it since i dont drive it much but now im getting kinda fed up and i have time off this week so im gonna start looking to see if i can figure anything out. im gonna check timing and spark, compression and also fuel pressure if i have a gauge, i dont remember if i do or not. i've tried pulling codes but couldnt get it to show anything at all, so i dunno whats the problem there.

i used all of the sensors on the engine from the navajo, are all of these compatable with the older wiring and computer? i know that the injectors had to be switched so i pulled the red ones out of there and put in the ones from the older engine (black i think) now i guess im just hoping that i missed something. anybody have any other ideas or suggestions?

SLUGGISH usually means ... runs good, no missing just not enough horses... Right?
If that is the case then we first look at the tire size and gear ratio. Then we ask if it runs well in 4th gear and not in 5th.. If the answer is yes then we need to put smaller tires in it or change the gears.
If, however, the thing is sluggish in all gears we look at the timing. Then we look at cat and muffler for stoppage.
A look at the sparks will tell you if it is running too rich.
Big JIm

 

[kunar]

SLUGGISH usually means ... runs good, no missing just not enough horses... Right?
If that is the case then we first look at the tire size and gear ratio. Then we ask if it runs well in 4th gear and not in 5th.. If the answer is yes then we need to put smaller tires in it or change the gears.
If, however, the thing is sluggish in all gears we look at the timing. Then we look at cat and muffler for stoppage.
A look at the sparks will tell you if it is running too rich.
Big JIm

doesnt miss, just awfully weak. its the first 4.0 ive ever owned but its not much of a step up from my 2.9 and it doesnt seem to perform up to the hype that i've read here. it runs fine in any gear, i can cruise on the highway in 5th without trouble, and with my 4.10 gears and 31's it shouldnt be any different than 3.73's with 235's. i drove my dad's b2 with 3.73's and 235's and it was noticeably quicker than my truck.

as far as exhaust goes, i have a cut out right behind the cat and it doesnt make any difference in power weather its open or closed. i suppose that could still mean the cat is plugged though. i havent pulled the plugs yet but i plan on it so i can check compression as well. they were brand new autolites that went in when the engine went in, so it should be easy to determine any abnormal conditions once i pull them. i do know for sure that all 6 plugs are firing with a good spark, if i pull a wire off of the coil pack, it will ark a good inch and still fire the plug. i did just read in the tech library that the plug spec'd for the 4.0 is a platinum, im running a copper. same plug otherwise.

i have just checked timing though, looks right as long as the marks mean what i think they do, kinda hard to tell for sure. 10* advance with spout pulled, somewhere around 15-20 with it in, at idle. i've looked for vacuum leaks and cant find any. i have noticed though that the engine doesnt seem to care if i unplug the mass air sensor. should it stall if i pull that plug, or does it revert to some default? it doesnt really seem to make any difference in the speed or tone of the engine.

btw, sorry for the long posts. just trying to provide as much detailed info as i can.

 

[kunar]

compression checked out good, cyl 4 and 5 checked low the first test, but i retested them, and re-retested them and the numbers looked good

1- 150
2- 145
3- 145
4- 130, 155, 145
5- 105, 150, 155
6- 150

the plugs all look good, number 5 was a little lighter than the rest but still didnt look that bad.

 

[Bird]

All of the 4.0's that I've checked / put together with stock compression have always tested out at around 160-165 psi compression, so your's does seem somewhat low. Without knowing your testing procedure, I can't verify that though - need to spin it over with the throttle wide open when you test. Low compression could be from retarded cam timing also.

If you're running the 92 pcm, you need to run the injectors from the 92 engine (19#) - running the earlier injectors(14#) will cause it to run with higher fuel trims and a higher injector duty cycle with less capacity for power at increased throttle opening.

I installed basically the same setup in a 88 Ranger GT with the same wiring setup that you have and it flat out screamed with a factory 92 Explorer PCM.

Bird

 

[kunar]

All of the 4.0's that I've checked / put together with stock compression have always tested out at around 160-165 psi compression, so your's does seem somewhat low. Without knowing your testing procedure, I can't verify that though - need to spin it over with the throttle wide open when you test. Low compression could be from retarded cam timing also.

If you're running the 92 pcm, you need to run the injectors from the 92 engine (19#) - running the earlier injectors(14#) will cause it to run with higher fuel trims and a higher injector duty cycle with less capacity for power at increased throttle opening.

I installed basically the same setup in a 88 Ranger GT with the same wiring setup that you have and it flat out screamed with a factory 92 Explorer PCM.

Bird

well i didnt realize the throttle should be full open, i guess it makes since but i tested it with the throttle closed. now, about the injectors. i have run the engine on the 90 computer, but it was for an automatic. there really didnt seem to be any switch when i changed to the explorer computer, which i think i read should use the same injectors as the 90? i think it changed from 92-93. if however they are the wrong injectors, ill do what i have to do to get the right ones in there. that might be the problem.

cam timing is somewhat in question at this point as well. my stock timing set failed very shortly after the engine was installed. the harmonic balancer bolt worked its way loose which let the key shear off of the crank sprocket. i pulled the timing gear, drilled where the key was, and pressed in a pin. im sure it should be within a few degrees or better. how much difference would cause an issue? are there any aftermarket replacements available or am i stuck with a OEM equivalent?

also, the engine is a fairly fresh rebuild, maybe 5,000 miles? any chance that its just not 'broken in' yet? a friend of mine is saying that it might not be up to potential yet because the bearings are still tight or the rings havent seated. i'd think that with the miles that are on it, it would be past that new engine stage.

 

[Big Jim M]

also, the engine is a fairly fresh rebuild, maybe 5,000 miles? any chance that its just not 'broken in' yet? a friend of mine is saying that it might not be up to potential yet because the bearings are still tight or the rings havent seated. i'd think that with the miles that are on it, it would be past that new engine stage.

Not one chance in this world! If new engines are TIGHT the quick result will be extreme failure.. New engines are LOOSE. They may burn a bit of oil but they are FAST! As they "break in" they slicken up and get faster. But TIGHT isn't in the cards..
Big JIm

 

[kunar]

anybody else have any input on the fuel injector situation? i looked up the part numbers and a 90 ranger and a 92 explorer both use the same injector. i dont think thats an issue....

are there any aftermarket timing sets available? im thinking about replacing the timing chain and sprockets, should i just use (another) stock replacement?

 

[feellnfroggy]

The engine may be new, but its an older refurbished block right? Means the cylinders arent to new specs they are slighlty bigger, if this wasnt taken into consideration when pistons were chosen it could explain the compresison issue, but shouldnt have been noticable. 4.0's are very horsepowery, they are more torquey than anything, does it pull well? I think you should borrow a friends 4.0 and drive it for an hour to compare so you have a reference point when your trying to fix this thing. How you break them in is how they will perform best btw, watch some honda or saleen break in procedures on youtube.

 

[kunar]

The engine may be new, but its an older refurbished block right? Means the cylinders arent to new specs they are slighlty bigger, if this wasnt taken into consideration when pistons were chosen it could explain the compresison issue, but shouldnt have been noticable. 4.0's are very horsepowery, they are more torquey than anything, does it pull well? I think you should borrow a friends 4.0 and drive it for an hour to compare so you have a reference point when your trying to fix this thing. How you break them in is how they will perform best btw, watch some honda or saleen break in procedures on youtube.

its a used block that was cleaned and honed, everything was within spec. it doesnt pull well at all, not nearly like my dad's b2 with a 4.0, thats why im trying to find something wrong. it runs fine, just doesnt seem to move like it should. btw, during "break in" i was tough on it. full throttle pulls and closed throttle coasting, back and forth. changed the oil after like 20 miles and again after like 100, then 1,000 or so.

i need to get a fuel pressure gauge on it and a vac gauge and see what they say...

 

[kunar]

pulled the exhaust apart at the flange between the wye pipe and the catalytic converter and took it for a drive. it felt like it might have made a little difference, but not much. mostly it was just loud. so i took it back home and put a vacuum gauge on it, recorded about 21.5 in Hg @ idle. after that i cracked the throttle and let it spin back down to idle. at wot, it fell to zero, then went to 25 until it reached idle. after i put the exhaust back on, i did the same test and got about 20.5 in Hg @ idle, and nearly identical readings in response to the throttle. anybody have any thoughts on this? according to the tech library, it should only drop to about 2 with the throttle open. lower than that may mean bad rings?