Morning everyone. Haven't posted on here in a long time, but I thought I'd share a problem I've been having for a while in hopes it may help someone else and to see if I'm on the right track. First off my truck is a 93 runner with the 3.0. It's made it a long ways (342k) but for the last year it's had an intermittent problem of stalling, hesitating, and a huge loss in power. Up to date I've replaced the following;
Full tune up (plugs, wires, cap+rotor, air filter, fuel filter, oil+filter, radiator flush)
Fuel pump
Fuel injectors
O2 sensor
Tps
Maf
Thermostat
Coolant temp sensor
Alternator
Battery
Battery leads
Entire throttle body
Fuel damper
Fuel pressure regulator
Distributor
Cold air intake
Ignitor module


Along with deleting a few others;
Egr emission (kept fuel canistor only)
Cat (3" pipe and flow master from 02 sensor back, stock manifolds)
Ifs nonsense (SAS swap)

I'm sure I'm forgetting something but that's the gist of it. So replacing all this never fixed the issue. I've checked the timing to the best of my ability but I have an issue with the front of my crank. The bolt that holds the harmonic balancer on snapped half way off so I only have about 5 threads to use to tighten it. It came loose once and sheered off the key. I installed on the was close then used locktight to keep it tight. However it's not sitting at its proper position on the crank. When the plugs out and the pistons at the top, the cams are sitting where there suppose to even after 2 revolutions by hand.

I've taken my truck in to have it scanned. My engines throwing no codes, but is not firing on the number 1 cylinder. Compression test is 130 on that cylinder, the rest are between 145-155. I've checked and I'm getting spark. The injector is brand new and is getting power. Checked the wiring with a noid light and its getting power with the key forward, and flashes with the engine running. Still no go so I'm wondering if maybe it's a bad valve.

So now for what I found that was interesting.
My trucks been parked for two months since it cant get over 30mph. On a random car video some suggested if the engines running like crap to unplug the knock sensor. If the engine improves that's the problem and to replace the sensor. I gave that a try and to my surprise my motor ran great. Still missing on the number 1 but no more hesitation, stumbling and stalling.

My only concern thou is that everything online I can find regarding the 3vze and knock sensor, shows that if its faulty it will throw a code 52. It seems like my knock sensor is retarding my engine to point where it will hardly run even thou I don't hear any pinging or knocking. I'm going to replace it and see if it helps but was looking for all your thoughts. I've replaced everything and nothing has helped yet. Thanks for reading all this

 

I had an issue of where the noid light fired but the injectors would not fire. The injectors wiring is crimped to another wire and the crimp was so corroded that the voltage could not pass the corrosion. If you had a 50 strand wire and 49 of them were broken, it would still fire the noid light. It will even pass a resistance check but one wire or the corrosion just wont let the injector operate. Only suggestion I can make for now.

With your compression low on that cylinder, it does sound like a part of your problem.

 

Did the ECU generate code 52 when the knock sensor was unplugged? If it didn't your ECU is suspect, I think.

Code 52 means the ECU is getting no signal from the knock sensor. If you're not getting code 52, the ECU thinks the knock sensor is sending signals. That's no absolute guarantee that the KS is sending the correct signals, however.

I suppose it's theoretically possible that you have a hyperactive KS that is sending knock signals to the ECU even when the engine is not knocking. More likely is that defective wiring is causing noise that the ECU misinterprets as knocking. You might grab your ohm-meter and check the shield of the KS cable from the connector to the ECU and make sure it is grounded.

The other possibility is a defective ECU that is manufacturing bogus KS signals internally. Swapping in another ECU might be of interest.

 

Thanks for the idea. I have the pigtail to match up my flame thrower injectors. Would it be a bad idea to just eliminate that clip and connect the wires directly to the pigtail? Not sure how finicky the resistances are on the injectors.

 

Sorry I meant to include that bit of info in my write up. When I unplugged the knock sensor it did throw me a code. When it was plugged in it did not. I've questioned the ECU as well but was saving it til I was sure all the other sensors that feed it check out ok. Since the knock sensor is pretty much buried in the center of the engine, I spaced out on checking it til now. I intend on replacing it along with the pigtail. Just was curious on others thoughts thou cause I can't find anyone online saying they've had one get faulty signals. Just a code 52 no signal. Want to make sure I'm not over looking anything.

 

It is possible that your head(s) could be worn. On my 1990 4 runner, I could not go above 60 and it felt like it had no power. Also, do you have any air or vacuum leaks?

 

I replaced the headgaskets at 270k, but I never did any valve work. Compression test seems fine with the lowest being the number 1 cylinder. I'd think 130 would still be enough to at least make it fire intermittently but the hole is dead. With a vaccum gauge I checked all the lines and got 17-20lbs of vaccum in all the lines I could check. I've also tried spraying around the intake plenum and checking for increases in rpm. It doesn't seem to have a vaccum leak and I deleted most of the emissions and have triple checked all of my block off plates.

 

mmm, it is possible that your short block could be worn as well.
Any engine with 270K+, in addition to the HG it is recommend to rebuild it as the engine is already halfway apart and if something else goes out, you will have to take the engine apart again.

 

Where did you get your heads done? My fear is taking them to a shop that doesn't usually do this kind of setup with shims and getting them back and the thinnest shim available is too thick. I had that happen to a friend with his motorcycle head!



Fuel....whats up with the crank bolt again? Is it or is it not working as it should? You cannot check timing?

 

Could be. I really did want to have it rebuilt, but at the time it was my DD and I was limited to time and cash. I did the job myself for around 500 bucks including having the heads resurfaced. However the engines made it another 70K til it ran into this issue.

 

When I took the heads in I only had them resurfaced. I know I'm far overdue for a valve job.

As far as the crank goes, the main bolt that holds in the harmonic balancer snapped off half way in the crank. The balancer came loose one day and spun on the crank killing the key. I put a different key in but the slot on the balancer got deformed so its off a few degrees. I've been setting timing based on the cams and piston being at top dead center, then turning the dizzy a few degrees and setting it by ear. Been running higher octane gas as a precaution in case it's slightly over the 15 degree mark.

 

dr1553, I had my engine rebuild by a shop in Mesquite, TX called Town East Automotive. My friend's boss is a co-owner and he helped me out with a deal. As far as the work that was done, I had them rebuild the entire engine from March to May due to a blown HG that killed 2 rings in the process, top & bottom for $4200. As far as the machine shop where my heads went, I will have to ask my friend, if you want the name of the place where my heads were done, I can ask him.

Also, regarding this shop, the work they did so far is solid, however, in my opinion they need to work on there customer service. They were always busy, almost never answered the phone and they did not give me any updates on my rebuild unless I went in person.

 

Well I dug into the motor last night. Was a little surprised how much nonsense I found under the intake plenum. It was quite clean when I put it all together 70k ago, but I guess time will do that. Looks like I forgot a roll of electrical tape in there too lol. Oops.

Anyhow, I examined the pigtail for the knock sensor and it does have some damage. The shield wire is exposed about an inch or so above the knock sensor. The clip that goes into the knock sensor is also broken. Then theres a cracked wire that is by the clip that goes into the harness.

The truck never threw a code 52 while it was plugged in, so could these bare wires pick up extra signals or make it more sensitive?

I'm gonna replace both, along with a handful of other things I found defective while I was in there (upper timing tensioner, broken clips, new gaskets, dummy pump, ect).

Anything else I should check while its apart? Was thinking of popping off the passenger valve cover and checking the valve clearances and cam. Still haven't figured out why my number 1 cylinder is dead.

 

My vote is that you for sure pull the valve cover while everything is out of the way!

I'm not an expert...but I do own a few old Japanese bikes and have done valve clearances on them. From what I haven learned about my KZ1000 the valve clearances lessen as the engine warms up. The KZ has the same setup as these 3.0 engines, it uses a shim over bucket, exactly the same. But, the motorcycle is aluminum block and heads, these are cast block and aluminum heads correct? So could be completely different....but, if clearances do shrink, my guess would be that if your clearances are under minimum it might be ok when cold, but as the engine warms that clearance goes from barely to none. That would cause a dead cylinder....but you say you have good compression on #1 so I dunno man. Are you checking compression with the engine hot or cold?

But honestly, it's not going to hurt at all to pull the valve cover and eliminate out of spec valve clearance as the cause of the problem. Especially since all the hard work of removing the intake is done. What, 11 more bolts for the cover and off?

Are you replacing the KS with OEM? Where did you find the best deal on one? I think 1sttoyotaparts is the best price I found so far.

Please let us know how it runs with the new KS and wire. But don't give up if that doesn't fix it, you might end up running a new wire all the way to the ECU. That should eliminate the KS and wire as the problem. Still could be the ECU, I guess at that point the best thing to do would be to find another from a good running 3.0 to swap in and see if the problem goes away.

I've been checking out Supra and MR2 forums and those guys are rewiring their KS all the way to the ECU and report very good results. Even guys that were not getting a KS code report that the car runs much better after the rewire. Stuff like "It went from fast to, holy crap hang on here we go fast" and "it will easily go over 125mph now"

Stuff like that.

My guess is that the ECU is getting bad signal from the KS, or wire, and is causing the engine to run like poop. But it doesn't throw a code because it's getting a signal and is doing what it thinks it needs to do. But ya, like you say, maybe it thinks it's knocking when it's not so it retards the timing so much it barely runs.

It's interesting you unplugged your KS and it ran better. That means that even in limp mode it had more power than whatever it's doing with the KS plugged in.

I might have to try that myself. I'll report what happens. But I am getting the code 52 sometimes. Not always. I drove it yesterday and wow....I could only get to 65 in 4th gear, shift into 5th and 55ish was about it. If I kept it in 2nd or 3rd when it hit about 4K rpm the engine would bog down and rpm's drop to about 3k before picking back up. The longer I drove it the less and less power it felt like it had. It never threw the code 52 during all this.

 

I haven't ordered the part yet, but I was going to go with the Toyota knock sensor and tail. I've read a lot of people having problems with the over the counter ones at O'Reillys, autozone, ect. I like the idea of rewiring it back to the ECU, my only question is how important is the wire gauge when doing this. Would running a larger wire be beneficial? If in the end this doesn't fix the retard issue I think the ECU will be the only thing left I haven't changed

I am gonna pull the cover as well. I'm still trying to understand how the valve assembly wears thou. From what I hear the shims lose there gap and need to be replaced with thinner shims once worn correct? How exactly does this gap disappear? If the cam lobes are rolling on the shim caps, and a spring is what brings the valve and shim back up, wouldnt the gap increase over time instead of shrink? Still confused about that one.

When I had the engine checked for compression it was still warm. I drove it for about 15 mins to get it to the mechanics shop for a diagnostic check. I still haven't done a leak down test thou, so maybe that will give me some more clarity if I'm having a valve leak.

 

The wear isn't at the shims, valve stems, or the cam lobes. Those areas are well lubricated and wear is negligible. The real wear occurs at the valve face where it contacts the seat. As the hot exhaust gases flow out of the combustion chamber over millions of cycles, they abrade the valve face such that the valve settles deeper and deeper into the valve seat, reducing the clearance at the cam. Eventually the clearance goes to zero, and a small gap begins to form between the valve face and the seat even when the valve is "closed". At that point the valve cools poorly, the gases leak past while at their peak temperature, and a burned exhaust valve and poor compression is the end result.

 

Thank you, that's exactly what I wanted to know. So how does one go about measuring to find the right size shim?

 

So in addition to trying to get my 3vz going again, I want to add its not going to be staying in there forever. I'm currently rebuilding a 5vz to do a swap with.



I'm replacing everything on the 5vz. So my other question is, is there a difference in knock sensors between the 3vz and the 5vz? They look identical but they are stamped with different numbers. Any one know a way to see if there interchangeable? Would save me some money to throw towards the 5vz.

 

So I went ahead and bought a new knock sensor and wire along with a few other parts and gaskets.




Got everything together but no luck. The longer the truck runs the worse the throttle response seems to get.






So now I'm trying to figure out if I should redo the wiring all the way to the knock sensor from the computer, or look into why I have a dead #1 cylinder. Could the dead hole be giving off a sound that the knock sensors thinking is a ping? As I've stated before, as soon as I unplug the knock sensor the engine runs fine on 5 cylinders. When I plug it in, it studders when the gas is pressed and won't rev over 2-2.5k unless I feather the fuel.

Any advice would be greatly appreciated. Thanks.

 

Well after more digging I finally found the issue. My fuel pump was faulty and I have a bad valve. The exhaust is sucking in air so I'm gonna have to adjust or rebuild my heads. Replaced the fuel pump thou and my engine runs a lot better. I was getting 20 psi at idle and it dropped to 10 when I applied throttle.