zerohedspace

Just purchased a 1992 Toyota 4wd. Done lots of work to it so far and am now having an issue with the infamous power lag and some serious fuel consumption. I've searched this site and read lots of others issues, and am just looking for opinions!
What I've done:
-replaced head gasket
-valve lash
-timing
-adjusted TPS and cleaned throttle body.

I am still experiencing power loss at higher rpm range and after reading so many others I am wondering if my timing is off by a tooth or two?

As I recall the crank needs to be at TDC and the cam sprocket at the top mark correct? Thanks for any input. I've been at this thing for weeks now.

Thommo Thompson

ur cam timing wont be off, but ur belt could be stretched.
It is best to do the belt while the head is off. hehe isnt hindsight a wonderful thing.
Now please try to co firm through a roadtest, if the issue really is simply at higher rpm, or is it also influenced by engine load?
in other words, does a very gentle acceleration through this rpm range cause less problem than a hard acceleration?
or is the lack of power still there with a gentle increae in acceleration from this rpm range?


if the power is only lacking when u really kick it in the guts i would start suspecting a fuel or spark problem. this includes.
plugs, leads, dizzy cap, rotor and coil terminal
(check for leaking spark with mist spray over running engine at night)
coil (check it measures within spec and has a good 12 volts and engine has a good earth strap to chassis)
fuel pressure regulatir, fuel filter, fuel pump, injectors.


if it happens pretty much solely at a particular rpm regardless of power applied and engine load, look for
PCV leaks,
valvetrain issues (paper over the exhaust pipe and check for any back suction) (backfiring out intake)
sensors (fault codes??)
dirty air filter

wyoming9

iTrader: (1)

Chain not belt!
Then it also depends what your comparing it with

The 22re is not a power house at a little over a 100 horse power

Tires and gears can make a big difference

As well as weight I need to remove the extra 1000 pounds of stuff that ends up in my vehicle from time to time

What kind of fuel numbers are you getting

The middle of the plains or in the hills

Thommo Thompson

ah of course a chain haha. can rule that out then.
I guess spark timing could simply be off though. Uve purchased it sexond hand ao u habe no idea if timing was ever correct.

Co_94_PU

iTrader: (-1)

Cam dowel at twelve, crank keyway at twelve, cam dimple to the left of twelve

zerohedspace

Thanks Co_94_PU. I'm going to check my timing over the weekend and make sure its all lined up.

wyoming9, no comparison, she lags and I can feel it in the peddle. up hills or flat, there is a power loss on the throttle and it feels like its missing, tho it isnt. It also backfires off throttle and iirc that is a sign of bad timing, right? As for fuel mileage, I burned thru half a tank in less than 150KM (work is 18km away, there and back twice and maybe an extra 50km driving, MAYBE...)

Thommo, it has a new timing chain and guides and what looks to be an aftermarket (stamped USA) cam sprocket. engine load does not appear to affect the lag. It seems that if I am easy on the throttle it accelerates close to like it should, once I get to around 2200-2500 or so, is when its balky. plugs and leads are new, cap and rotor are good, spark is good, fuel injectors are good. Ive still got some diagnosing to do but at this point I think pulling the valve cover off and checking my timing marks is going to tell me right away. Failing that I will go thru the rest of your list, which by the way is much appreciated.

I am planning on checking my timing this weekend, then setting valve lash (again) and hopefully that solves it! Thanks everybody. Looking forward to getting the gremlins worked out of this ride. Ive owned 3 1st gen 4runners and this is my first truck. Looking forward to converting this girl over to a 22r. (I dig carburetors)

Thommo Thompson

ok im going to quote u and ask for details..
"Just purchased a 1992 Toyota 4wd. Done lots of work to it so far and am NOW having an issue with the infamous power lag and some serious fuel consumption. "
did u buy the truck and it had the issues, or did the issues start after u changed the HG and did the things u mentioned in ur first post, or was the motor not running on purchase so u dont know?

this is why the internet is so hard to help someone, its very hard to get ur situation across and understood by others.

zerohedspace

@Thommo, Yup makes it tough. waddaya mean you cant read my mind... lol. So I bought it, drove it home and it was puking oil from the timing chain cover and lagging power at that point. I changed the head gasket because the PO admitted to me that he had not had the head machined and I didnt want to take any chances. Glad I did it as he had altered the head gasket and cut the part that seals the top of the chain cover. so to answer your question, yup, engine was acting up to begin with. The reason I suspect the cam and crank are off is because I put it back the same way I took it off and seem to recall it looked a little not rite... I'm no mechanic tho and assumed that it was right because it ran but the symptoms I am having make it unbearable to drive. Needing to get to work tho forces me to. I am going to drink a bunch of Canadian Beer and crack that engine open again tonight. Cheers!

Thommo Thompson

hahah canadian beer!
i recon ur timings right but ur dizzys off a tooth, simply because thats an easy mistake to make.
And that would fit well with the symptoms, if the dizzy was behind a tooth the timing would be way to retarded at about 2-3000 rpm as the electronic advance would be refferencing from a significantly wrong angle.
engines can idle with an incorrect dizzy timing, and can have lots of power down low, as the rich mixture and strong flow of air and fuel burns fast and doesnt need the advance.
but when the engine speed is up there, it needs that advance.
just try pulling the dizzy out gently and advancing it one tooth then stick it back in before u rip the entire engine out.
I o ow u said u did the timing, but im juat going to ignore that and suggest u recheck.

zerohedspace

Ok! rechecked the timing, was off but correcting it did not correct the issue. engine does run a little better but moderately. dashpot is wrecked (thats a non issue tho) and I have a fuel injector rebuild kit on the way, one of the pintle caps on mine is rough. I am seriously hoping that I just have an air flow leak. My check engine light finally came on yesterday and it gave me a 25 which is AIR/FUEL RATIO LEAN INDICATOR--LEAN SIGNAL SENT TO ECU FROM O2 SENSOR according to lce (http://www.lcengineering.com/LCNewsl..._TECHNOTE.html). I was checking the vacuum at the throttle body with my finger and two of the 4 ports I couldnt detect any vacuum. Should it be really noticeable?

Thommo Thompson

excellent we have a light!
Dont get fixated on trying to find vacuum. if the engine is running, there is vacuum. U can only feel it on ports after the throttle plate. so the PCV hose connection is one place or the connection to the fuel pressure regulator is another.
That code for lean by O2 sensor, can really indicate either
lean mix,
poor spark,
poor spark timing, or
poor compression.

your best checking compression and fuel pressure.

here are the specifications for u work on.
Compression test
HOT AND DRY
171 PSI maximum
142 PSI minimum
maximum variation between any cylinder 14 PSI

for testing fuel pressure, see this image for the relevant part of the manual.
https://ibb.co/cvJE9b

zerohedspace

Right on, thanks Thommo! Will get to it this weekend. just pulled a 16 hour shift today, ugh. On the way home from work today, colder evening here, getting colder... truck had bad power lag till it warmed up then back to the normal power lag lol. was way worse when a little cold than when fully warmed up. Going to purchase a compression tester this week and post back when I get everything checked. Cheers!

Thommo Thompson

the most important tools are compression tester and multimeter. gotta have em. even if u dont find anything anomalous, consider it a required purchase

zerohedspace

gonna buy a compression tester asap, and a fuel pressure tester too! Got my fuel injector rebuild kit and it runs so much better but still has a little bit of a lag in mid throttle. Thanks for your help, little rig is fun to drive! Got an exhaust leak before the o2 sensor, i think thats the reason for the lean code. gonna grab a new gasket over the weekend and get that sealed up. Merry Christmas!

Thommo Thompson

sweet as mate. hope u sort it, and be sure to keep us posted.

maco35

I did everything you're doing trying to fix my lack of power, replaced fuel filter, had my injectors reconditioned by witchhunter, replaced 02 sensor, swapped the intake and throttle body with a late model one, replaced the ignition system with new parts, etc....

Well, when i was adjusting the valves i looked at the cam shaft and bingo, 7 out of the 8 cam lobes were flat, replaced the camshaft with an 261C Engine Builder one and my truck has been running great with a lot of power, specially going uphill now i'm able to keep up with the rest of traffic on the freeway which i couldn't do before.

zerohedspace

dammit, thought i had it sorted out. sit fook dam piss ash. still way better but power lag persists. gonna do the fuel filter next and then fuel pump after that... its gotta be fuel related. reset my computer and just got my lean code back. I sealed the exhaust manifold flange ( y pipe?) with new gaskets (PO had nothing in there) and its nice and not stinky in the cab any more... (quiet lol).

on a side note, my cold start injector switch was dicked and i wanted to post my repair, maybe itll help some other cold weather sob. link with pics here

zerohedspace

@maco35, yeah when I did my valve lash i checked the lobes and they were still decent... didnt measure or anything just a visual. gonna try and get to the fuel filter this weekend and throw a pressure tester on there to check the pump. failing that, next step is a compression test and possibly a brand new loaded head from rockauto or another used engine and ill rebuild this one for late spring...

anybody know where i would source out some nice steely rims and skinny tires for climbing? (and highway...) PO has 33's on there and they are too big imo.

Cheers all, happy holidays!

maco35

If you decide to replace the head sometime down the road, Engine Builder has some of the best ones out there at a very good price, i got the rv head and the 261C cam and i'm very happy with the quality of the product.

http://www.engnbldr.com/toyota-heads.html

Co_94_PU

iTrader: (-1)

Have you done the sweep test on the vafm yet? Measure voltage and or resistance while moving the vane from closed to open SLOW, looking for dead spots/dropouts.

2000-2500 is where it spends most of its time, and where it will be most worn.