greencactus3

Hi guys,

I have a 90 3vze truck im having trouble diagnosing.

originally it began as a problem with lack of power noticable on the highway (struggled to get to 70) every once in a while. this problem went on and off multiple times during single trips.

I had a super high idle (2000 rpm) at the time, which may have had something to do with that issue, but the idle was taken care of with a new intake plenum gasket. I was able to drop the idle to 800 rpm with that, and it ran beautifully for several days.

Then all of a sudden one day I started it it and it stalled almost immediately.
several tries, and with gas I kept it alive, after which it stayed idleing, but super rough. on the road, it would jerk and buck at low rpms, and then as rpms rose over 2000, would run smooth. but only at low throttle inputs.
after about 25% throttle, it would lose all power and struggle to accelerate at all.
then I'd upshift, and it would be smooth at all throttle positions, until i shift again and then it would lack all power above 25% throttle.

then several minutes later it will have power at all throttle inputs and every gear, except be rough at idle.

then several minutes later it would stall at the light, or lose power, etc etc.

basically it's a very inconsistent problem.

I don't think its the Volume airflow meter because if its idling rough and I unplug the volume airflow plug, it will run worse, then stall (consistently) therefore I think that isnt the issue.


What all should I be looking at?
I should have a new fuel pressure regulator arriving at home tonight (after 2.5 weeks of waiting.... thanks autozone) which will go on as soon as i get it.

TNRabbit

1. Unmetered air entering the intake (vacuum leak in the hose)
2. Issues with the distributor
3. TPS is bad OR not adjusted properly
4. Shorts in the wiring harness

I'd try in that order. Do you have any stored codes from the ECU?

greencactus3

1.went through and redid the entire vacuum system when trying to find the vacuum leak (which was fixed via intake plenum gasket) so im pretty confident its not that

2. i'll pull the cap off and take a look, but I replaced the cap and rotor around 4 months ago, so shouldnt be that

3. just read up on TPS adjustments, will be measuring and setting that after work today.

4. Read about the COR and will be checking that too. I know it may have gotten water on it at some point from previous owners as I patched a foot sized hole in the firewall 2 weekends ago right in front of the ecu (ecu was caked with mud)

havent checked the codes yet (sorry, been lazy)
i'll get a paperclip tonight

jessed59

my guess would be tps or failing 02 sensor have u flashed the ecu?

greencactus3

what do you mean by flashed?
reset? I have not.


Also, forgot to mention, at idle (when rough) it's running very rich (black smoke, smells like fuel)

toyotacharles

cold start injector leaking? several of these on the v6 engine leak and will cause rich running and just unplugging it wont do. unplug injector, remove the 2 nuts DONOT LOOSEN OR REMOVE THE FUEL SUPPLY HOSE and put a finger or thumpb over the hole in intake have rag handy to asorb any fuel leakage and have a 2nd person start truck, if any fuel leaks out injector is bad and should be replaced.

greencactus3

sounds plausible. i'll try that later as well.thanks

greencactus3

had to do other stuff so only got around to swapping the fpr and resetting the (just barely off) tps, and checking the cold injector (which seemed to not be leaking, and firing fine at startup. and seafoamed it.

but its running beautifully now.... we'll see if it runs rough again, since its an inconsistent issue....

greencactus3

apparently nothing has changed.
on the way to work, stalled out a few seconds after the first start up, started it up again, its ran good for several miles, but then it got a CEL and ran ran rough after 25%ish throttle, which caused be to max out at 55mph on the highway.
after getting off the highway I was able to figure out a little more while driving the regular roads.

seems if I double clutch with a heavy 'blip' on every upshift, I can keep the CEL off and keep it from running rough at any throttle response.

but after letting off a bit to cruise at some speed, CEL would turn on and run super rough. clutching in and blipping the throttle a couple times will turn the CEL off, and run good.

This appeared to consistently work

I'll pull codes (if it retained any) over lunch break.

I'm thinking I didnt set the TPS correctly, does that make sense?

i followed http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml
... or so i thought. I will for sure try again tonight.

TNRabbit

I'd also unplug the vacuum hose going to the vacuum distribution "puck" located right above/behind the power steering pump. If that clears things up right away, the puck is ether bad or needs cleaning out. I had a TERRIBLE idle & power sucked --it ended up being this:

greencactus3

sadly not quite that simple as i've eliminated egr already so it cant be that.

went to tacobell for lunch, stalled immediately after starting up, started again, ran perfectly fine after that all through the drivethrough and back.

will be pulling codes after i finish eating.

greencactus3

codes:
24,31,41

24 is IAT. if the IAT is within the airflow meter, i unplugged this several times so i'll ignore it for now
31 is airflow meter. same as above.
41 is TPS. further making me think either the TPS is bad or I was not good at adjusting it correctly last night.

whats the easiest way to clear codes? I can disconnect the battery later, (forgot to bring tools today to work doh) or is there a fuse i can pull instead?

greencactus3

also quick question....

is the FPR vacuum line supposed to be a direct path to the intake plenum? or does it use a vsv?

93toyrunner2

Clear codes by pulling the EFI fuse out for a minute.
I had a similar problem, but no codes. At times, there was power, and at others, no power. Seemed to take a good jolt from a rut in the road, and power would come back. I first thought it was shorting wiring, and I tested all the harness in the engine compartment. I do not remember exactly how I noticed it, but the Intake Plenum was so clogged with carbon that it was clogging most of the vacuum ports and TB. I took the plenum off, removed all vacuum ports, etc., from it and had it boiled at the radiator shop, problem solved. Power back 100% plus.

greencactus3

thanks, ill clear codes before heading home.
ive looked in the TB and plenum, they arent bad looking ,and getting plenty good vacuum everywhere i need.

toyotacharles

there is a ground bolt on right head at back near valve cover, just check and see if it is tight.
you can see the ground from the top of engine but it does take a bit of effort to see. if its loose and 10 mm wabble and some extension can reach it with out pulling intake.

its been several years but i had one that took me a couple of weeks to find and the vaccum lines on the right side and that ground was loose.

greencactus3

after getting home i played with the adjustment for a good 2 hours without being able to set the tps to spec. close, but not quite. tried running it and got code 31 for airflow meter... and running ˟˟˟˟ty.
ill pull the tb off the engine tomorrow and work on it on a bench so i can work on it easier

ill look at the ground strap as well

greencactus3

got it within spec (barely) last night off engine, put it back on, ran great.
get up this morning, and it doesnt have the previous wont accelerate beyond X% Throttle issue, but wont idle right still.

idle is very low (400-500rpm), smells like fuel, and rough idle, if it even idles. stalls almost every stoplight. need to keep the revs up to keep it from dying.

so i think i fixed an issue, but still have others... does this sound like a volume airflow meter?
i'll check the specs on that later today along with pulling new engine codes...

93toyrunner2

Have you checked the timing by any chance?

greencactus3

i checked about a month ago and it was right on 10 degrees.
I can check again but id assume its still okay