Bill54880

I have a stock 1991 manual toyota pickup 4x4 with the 22re and I'm getting 15-19 mpg mostly on the highway! Here is the series of events that led me to my poor mileage. I bought the truck in June and it was getting about 20 mpg with no muffler and the exhaust broken off at the bend just after the exhaust manifold. BTW no check engine light ever. Over about the next four tanks of gas the mileage went down one mpg per tank to about 15. It was also losing power (bogging out) from time to time usually once it was warm and turned off and restarted within a few minutes or when warm after sitting at a long stop light it would bog out on take off and then all the sudden bang! the power would come back and it would run fine. So I changed the plugs, wires, rotor, cap, air filter, oil, oil filter, fuel filter, had the cat checked, had the broken exhaust pipe welded back on, put a new muffler on, had the timing set checked with the valve cover off and nothing could be found wrong with it. So I changed the o2 sensor since it was time by the mileage and it ran great, no more bogging out! So I brought it down to my mechanic and had him look it over and he notice the timing had moved back from tdc by 4 degrees so he reset it.

Now is where the current problem begins, as soon as I left there is a complete lack of power. On flat level ground it does fine but as soon as I hit a hill it bogs out and loses all power and even once I get over the hill it will continue to be weak and refuse to go faster than about 50mph for a mile or two even in 4th gear, and then it will creep it's way back up and start to run better again and I can shift into 5th. It has a smooth idle and doesn't seem to ever miss at any rpm but two other things I noticed right away are that it doesn't start as easy as it did before changing the o2 sensor and its cold idle is lower and it's hot idle is lower and now it has even died a few times at idle. It seems to run better we it's first started and running cold. Within just a few minutes of starting it up it loses all power. I know it's running strong when cold because the cold injecter is running but as it warms up it gets weaker. Sometimes it runs just fine and others I have my foot on the floor the whole way just to go 50.

abecedarian

if he didn't set the timing correctly, jumpering the diagnostic test port TE1 and E1 terminals, the timing will seem alright at idle but step on the pedal and it's gonna be way off.

Bill54880

I've also ran a compression check that came out fine.

Bill54880

I have the chilton and I also have checked the timing while using a jumper wire and I get the same reading. At this point I'm thinking a sensor like either the IAC or the coolant temp sensor for the fuel mixture for the computer or maybe just that the O2 sensor I bought is junk because I've read of people on the net who got bad ones new out of the box but I'm hoping I'd get a check engine like if it were bad because I unplugged it and the light came on and it went off when I plugged it back in.

abecedarian

when you put the jumper in, did the idle speed change?
if not, the throttle position sensor needs checked / adjusted.

Bill54880

Yeah it slows and the timing rolls forward (closer to tdc) like 4 degrees as is normal. I need to also correct what I said earlier here, the timing didn't retard when I changed the O2 it advanced meaning moved further away from tdc by about 4 degrees. I'll correct it above as well. Sorry.

toyota4x4907

What is it idling at warm? should be between 750-800 rpm. Shouldn't the idle be checked/adjusted every time the timing is changed? I don't think that could affect the power at rpm, but that could be why it stalled at idle. Perhaps check the TPS? IAC valve?

abecedarian

what is the timing set at? should be about 5 BTDC, right?
and engine should be idling at approx 750-800 rpm warm.

Bill54880

It was idling cold at about 1750 now about 1500 and hot was 700ish and is now about 480. The correct timing is 5btdc you are correct. I'm currently running it at 8 with jumper and 12 without jumper so I have enough power to get around. It was my mechanics idea. I've also check the timing every week and it hasn't moved.

toyota4x4907

It doesn't sound like the mechanic adjusted the idle after he changed the timing!! 480 is LOW..no wonder you stalled! Take it to a diff mechanic and have them set the timing and tell them to adjust the idle accordingly!

abecedarian

another thing that may cause the issue is a partially clogged catalytic converter. I see that was checked, but possibly it was on the way out already and some other issue has caused it to become obstructed.

have you tried pulling trouble codes to see if the ecu has any stored?

Bill54880

I just had the cat checked and they said it had no restriction at all so I should look elsewhere for the problem. I also haven't had the codes read because I contacted my toyota dealer and they said if the check engine light isn't on it doesn't have anything to report. Could they be wrong?

1styota4X4

have a tempory cat pipe made i had to do that cause they saidmine was good and i went through everything you are...Cost me like 15 bux when i out it on truck ran better so i got a new cat and i wasgood...Just an idea though

Bill54880

I'm pretty sure it's not a restricted cat because it doesn't happen all the time. In general I do find a slight lack of power but the bogging out is probably only about 40% of the time I drive up big hills.

22mr2

Sounds pretty similar to a problem I have been hunting for months and still havent been able to find. Runs great when cold, then sometimes when its just getting into where it goes into closed loop, it has no throttle response off idle to 3/4 throttle. Floor it and it comes back alive. Mine happens either after it rains or a few days after. Starting to think its a ecm issue and noticed that its real wet under neath the floor by the ecm. You can checked for a plugged exhaust with a vacuum guage. Hook it up to direct manifold vacuum and zip tie the guage to your wiper. If its a restriction, youll have no vacuum. Try turning up the idle too.

Bill54880

I just drove my truck up the hill again and it didn't bog but once I pulled off the highway I found my idle has again lowered itself! Now it is idling at under 400!!! The idle has slowly been getting lower over time. It isn't that my mechanic didn't adjust it, its that it is deteriorating over time.

22mr2

I have heard on rare occasions of the throttle adjustment screw working its way loose, that might be a possibility. It could also be a vacuum leak thats growing. Take a peek at the throttle screw, it should have some resistance to it when it turns. Mark it and see if its moving. You can also try to move a unlit propane torch all around in your engine compartment where u might find a vacuum leak, air intake tube, throttle body, intake gasket and all around your vacuum lines. A sudden change in rpm will point out the leak if u have one

Bill54880

I also have read of that. I'll take a look at it. Can you help me find it? I'll also check my chilton. It's a little odd because it only dies when the rpms come down from like 3 grand after pulling off the highway. It doesn't do it any other time.

22mr2

look where your throttle cable hooks up, it should be right in front of it. It may have a small rubber cap to pull out to get to it. Its a regular head screw and points straight up toward the hood

Bill54880

Okay, I'll take a look. Any other theories on the main problem?