cvriv.charles

I seriously need help. Here's the story. My truck has been bucking for a long time. I took it to a dealer and they said burnt valves and that compression was 30psi in Cyl#3. So I went ahead and bought a brand new head fully assembled, new water pump, new plugs, air filter etc, gaskets, and belts.

I pulled the head and didnt find burnt valves. I found WHITE cakey looking exhaust valves. i read that means the engine was running very lean. The cakey deposits i guess kept the valves from closing. The CEL codes pulled right before the work was:

P0171
P0125
P0141
P0420
P1130
P0141

I installed the new head, valve lash is fine, and I did a leak down. The leak down was done cold because the engine wasnt running. But the results were great.

Cyl#1 = 5%
Cyl#2 = 4%
Cyl#3 = 3%
Cyl#4 = 5%

The truck started right up. BUT! I still have this bucking! I mean the truck drives pretty good but under the right conditions the truck will smoothly and slowly start bucking. From very subtle to annoyingly strong. If I gas it some more it might go away. WOT usually kills it. Im afraid that this unknown problem is what cause the last head to fail. And what will cause the new head to fail if I dont fix it.

I read online that maybe clogged injectors? But I checked them. Using a 9v battery I open each and using a compressor and cleaner I flushed them. All of them work fine. A very nice mist from each. Whatelse?

Oh, my CEL came back on with a P0141. Which is post cat O2 sensor. I have to check it to make sure its working. I doubt that O2 sensor would be the cause of all this. My O2 sensors are actaully new too.

Now check this out. I also read that a clogged cat can cause this too? check it out. ALLLLLL this started after I installed a new muffler. the original was rusted through. open and loud. I bought a new one. It was for the 3RZFE engine which I have but for a extended cab. I cut cut the excess off and welded it back together. Once I had the muffler installed,... thats when the CEL's came on and I started experiencing the bucking. I got a P0125. When I took it to the dealer they got P0125 and P0171. I dont know what I didnt think of that before. But do you think that maybe theres something with the muffler causing this bucking? I mean because it happened pretty much right after the installation im thinking yes. But maybe its not the muffler and maybe the cats? But I wasnt abusive when I did that job.

What about the muffler could cause this to happen? anything? To restrictive? I dont know. Please help. all this is becoming very tiring mentally.

DeathCougar

iTrader: (23)

The bad cat and bad O2 sensor could also be a result of the lean condition in the engine.

I highly doubt its the muffler but if you have an question about it, cut it off and run straight pipe for a while. If it still bucks, that pretty well answers that.

cvriv.charles

How do I know if my cats are bad? I can test the O2 sensor but what about the cat? If I just took the muffler off and ran it without would it be way to loud to drive around?

DeathCougar

iTrader: (23)

Cats get plugged up, so the easiest way to tell is take them off and inspect them.

If you took the muffler off yes, it would be loud, but you would be able to figure out if it is causing the problem.

cvriv.charles

Starter? Didnt install a starter. Maybe you posted in the wrong thread.

Or maybe you meant "for starters"? The head is new and it is after market. Nothing is pinched.

How do I check sensors? By checking resistance? When a sensor fails do they all automatically close?

DeathCougar

iTrader: (23)

Dang it, yea I did. lawl.

Too many windows open!

Post edited, see above

cvriv.charles

How do I inspect a cat to see if its clogged? run a broom handle through it?

cvriv.charles

Ok I did another leak down while the engine was warm this time. To my suprise,... the results suck! But something doesnt seem right though. The results:

Cyl#1 = 13%
Cyl#2 = 60%
Cyl#3 = 10%
Cyl#4 = 60%

I think im doing something wrong. those 2 cylinders cant be doing 60%. When I did the first leakdown I didnt have the cams in. So I know that all valves were closed. Maybe I am doing the leakdown wrong.

This is what I did. I set removed all the plugs, oil fill cap, rad cap, dip stick, PCV hoses. I then turn the crank clockwise lining up the timing marks by the crank pulley to set cylinder one at TDC. I did cylinder 1 and got 13%. Normal. So then I did cylinder 4 because that cylinder is at TDC too with all valves closed. Right? I then get 60%! I then turn the crank and using a long screw driver feel for cylinder 2 at TDC. With the screw driver in cylinder 2 I did the leak for cylinder 3, 10%, normal. I did cylinder 2 and got 60% too!

Did I do this right? 60% is a huge leak! I couldnt even tell where it was coming from. I listen to the exhaust for cylinder 4 and could hear a little something from the exhaust. I couldnt hear anything from the dip stick tube and fill cap. Nothing from the radiator fill port either. I would imagine bubbles?!? i dont know.

When I did clyinder one I could hear a hissing from the dip stick tube and oil fill port. For cylinder 2 and 4 the leak was loud right from the spark plug tube area. Maybe I heard a little something coming from the throttle body. almost certain I did. And the leakdown tester itself was loud too. Hard to tell.

There weren't even the trouble cylinders initially. I was told the the dealer the cylinder 3 had the comp loss.

What do you think?

hross14

Start from the beginning and make sure everything is times properly on the motor.

Go through everything and make sure it is correct put together--have a buddy help you because sometimes familiarity breeds blindness.

Those numbers are way off--do you have a quality leakdown tester or is the pressure in the compressor consistent?

and i would test the original head also to see if it leaks--

cvriv.charles

I know the timing is correct. I spent a good almost 1.5 weeks working on the truck double checking and checking it again. I had the crank timing marks lined up so that Cyl#1 was at TDC. The timing marks on the cam gears were lined up and flush with the mating surface of the head. I turned the crank several times by hand clockwise checking that the timing marks realigned. They did. That was easy. Everything was easy actually.

As said before,... with the cams off I got great leakdown readings with the engine cold. I am using a leakdown tester I got from harbor frieght. A "US General":

http://www.harborfreight.com/cpi/cta...emnumber=94190

I dont know whatelse could cause the 2 and 4 cylinders to leak at 60%. Should I check valve lash again?

When I took the head off I noticed these ring grooves at TDC for each cylinder. I just just barely feel them. I was told its no big deal that its kind of normal for this engine. Each cylinder had them. Im thinking maybe it could be that. But then I am totally doubting it. Because the leakdown was great right after I installed the new head. Now I have 2 cylinders at 60%. Thats a huge difference.

Im runniing the output prssesure on the comp at 80psi. same as i did for the first test. even if the pressure from the comp was wonky it wouldnt matter. The cylinder should pressure to some extent and read out a % of leak.

Maybe the head gasket isnt sealing for those 2 cylinders? I clean the mating surface real good and the head was brand spanking new.

Kiroshu

Well i will tell you one thing you can't do a leak down test on a cylinder on the exhaust stroke or intake valve is open thus leakage.... I sounds alot like Mass Air flow sensor prob, try cleaning it. Egr? When you did the first test with no cams you had all the cyl sealed. Even a brand new engine does not perfectly seal it never will. 5% is very good and about right for a healthy engine and new engines off the lot have this. Check MAF, Vac leaks? EGR? If that cat was bad you would smell rotten eggs out the exhast if not its good.

cvriv.charles

I know you cant do a leakdown on the exhaust stroke or intake stroke. If I set TDC for C1 then it would be the same for C4 right? All valves closed for C4?

Wait a sec,.... the firing order is 1342. Thats means if C4 is at TDC of the exhaust stroke. which means the exhaust valve is closing and the intake valve is opening. I have to do it again. I did it wrong.

Plus I just pulled another code: P1130?!?! Whats that? I got that the first time.

cvriv.charles

Ok I got it. I did it right. I set all the cylinders to a true TDC(valves closed) and got 10% exact for each. Which is perfect.

But I still have something going on. I cleaned my MAF sensor a little under a year ago. Its clean I checked it. How can I check it with a meter?

My exhaust doesnt smell like eggs. But I do have a strong fumey gasey smell though. What sensors should I test and how to test them? Im goignt o try and test the rear O2 sensor now.

Im probably just going to take it to a toyo dealer and pay them to figure it out. I did a lot myself so I narrowed it down for them a bit.

cvriv.charles

I went under the pass seat and disconnected the rear O2 sensor. I check the voltage of the heater pins or slots of the connector going to the truck with ignition on. i got 12.14v. good. I also check its ohm's too. I got,.... damn cant remember. Either 3.2ohms with ignition on and nothing with ignition off or the other way around. Anyways,... i checked the ohms for the heater pins going to the O2 sensor and only got 1.94ohms. I am not savvy with checking ohms and such. I have my ohm meter set to 20k?!?! is that right? anyways,... 1.94 is low right? i was told from 11 - 16ohms? Does this mean the O2 sensor is bad? Do I do this right?

cvriv.charles

I just noticed that a bolt is missing from the rear O2 sensor. the exhuast is leaking from it.

Kiroshu

The<--(this i mean) issue is prob out of your home garage exp. When you take it to the dealer they should hook a smoke machine up to it and check for Exhaust leaks and vac leaks and also get te codes out and see what they are saying. Any haynes manual or w/e will prob tell you the specs for the MAF checks.

cvriv.charles

Your probably right. I am going to go through the FSM and look for any sensor check that I can do. Im also going to make an appointment to take the truck in for them to take a crack at it.

cvriv.charles

I read through the FSM. I amd going to check all the VSV's. Im also going to use the propane technique for checking for vac leaks. Im still going to bring the truck in. I just want to keep cracking at this myself too.

IUEC'rnr

Maybe completely off topic or you have ckd it.. but since you didnt say if it was bucking at certain rpm's and have poured over so much of your engine...

Did you ever check to see if your coil packs were good.. Often can cause it to buck

cvriv.charles

I never checked them. Does the FSM say how to? Well,... the bucking is not as bad as before. Its hard to pin point when its the worst. Going up hills at just the right rpm,... seems to be the worst maybe?

But when I feel it the most is when on the highway because I do a lto of highway time. Its not super bad but its definietly not right. I'll be cruising around 75 maybe in 5th gear and about a bit under 3000rpm. If I gas it to go faster,... it feels kind of liek the engine is constantly cutting out. not very bad but its definitely doing it. Its not in a steady rythmic pattern either. very random mixed feeling. its like a rough drive. If I WOT,... it doesnt do it.

Weird. I checked my MAF and its fine. I did a quick propane vac leak test and nothing. Truck idles fine.

One thing I want to ask. the O2 sensors sense O2 in the exhuast and sends signals to the computer. The computer reads these signals and adjust gas intake accordingly right? Whats happens at WOT? Does the computer ignore the O2 sensors and justs pours in as much gas as possible? I think my porsche 951 does this. I dont know if the same applies to this truck. My rear O2 sensor is bad. Plus one of the bolts came out. I think one of them was stripped. I got a new one and will get it in soon. But I am thinking that the computer isnt or is getting wrong signals so its feeding the engine wrong. WOT, the truck is ignoring the bad O2 sensor and is just feeding as much as possible. right?