VVT Problems!??!

[onnaj]

It shouldn't but if the valve a bit sticky i thought it might cause troubles...but that isn't true?

[BryceWSJ]

false alarm gentlemen! haven't drove it for about a week, i got in it yesterday to go to the liquor store and it bogged BADDDDDD. the mystery continues!!!!!! i'm gonna try to torch my o2 sensor today. see what happens. anyone else tried anything?

[yoshimitsuspeed]

It shouldn't but if the valve a bit sticky i thought it might cause troubles...but that isn't true?

Off idle it would barely be noticeable even if it was freaking out as much as it could. It definitely wouldn't cause bogging

[Sportmax]

false alarm gentlemen! haven't drove it for about a week, i got in it yesterday to go to the liquor store and it bogged BADDDDDD. the mystery continues!!!!!! i'm gonna try to torch my o2 sensor today. see what happens. anyone else tried anything?

Im not worring about it LOL. I can drive around it on the street and racing it does not bog so I really dont care right now HAHA

[onnaj]

Could a bad vsv evap sensor also cause such problems? Someone tipped me bout that

[BryceWSJ]

Could a bad vsv evap sensor also cause such problems? Someone tipped me bout that

i don't have mine connected at all. i torched my o2 sensor, helped quite a bit. i bought a new bosch today, gonna put that in and see what happens.

[The Bloody Panda]

I might as well just copy and paste what is happening to BryceWSJ, Sportmax, and BoostJunky because I have the exact same issue.

I'm running a Silvertop on a Blacktop ECU and if I unplug my VVT my engine runs perfect. With the VVT plugged in however I go off the scale lean on my wideband O2 whenever VVT engages and I'm at half throttle. The engine runs horribly and hesitates to the point that I'm afraid to pull out onto high speed roads when a car is coming from way off in the distance. I've been running my current setup for six years and this problem started occurring a year and a half ago.

I've swapped ECUs and inspected both for VVT chip damage with no luck. I've swapped MAP sensors three times. I've swapped TPS once and have the TPS calibrated exactly the way the FSM says to. I've swapped the VVT solenoid. I was about to pull the trigger on swapping the VVT gear but I'm confident that it won't fix the problem so I'm not even going to bother. I've swapped O2 sensors twice. I've swapped the coil and the ignitor. I've replaced plugs and wires. I've replaced the distributor cap, rotor, and set the air gap correctly on the distributor. I've checked for vacuum leaks. I don't know what to do at this point other than just drive my 86 without VVT since it runs just fine that way.

I concur with Sportmax that I'd really like to see someone go standalone who has this problem. I doubt it will fix it since I've swapped ECUs and so have others with no results, but still I guess it's worth a shot at this point.

Here's a big Lexus thread about some guys having similar issues to ours.

http://www.clublexus.com/forums/perform ... ilter.html

UPDATE:

I swapped O2 sensors today to a Denso 234-9011 since it doesn't require any wiring modification unlike my old Denso sensor but now the car runs lean at half throttle even with VVT disconnected. Granted it doesn't run super awful at half throttle, but it is still off the scale lean and will slowly come back down to a good AFR the longer I leave the pedal down. If I let off the pedal a little bit it will go down to something nice and rich like 11 or 12 AFR for just a split second before adjusting the AFR into the 14's. I feel like this problem would be simple for someone who knew their stuff but I just can't figure it out. If I go WOT the AFR goes into the 13's immediately and the engine feels terrific. But anything in between 1/4 throttle or WOT just sucks. I feel like the problem is just amplified when the VVT engages (when it's plugged in) and then the engine runs much much leaner and has lots of hesitation. So I can only imagine that I have too little fuel, but only at half throttle but not WOT which seems confusing. Or I've got a vacuum leak but I don't hear one anywhere and testing by spraying carburetor cleaner revealed nothing. I'm leaning towards a fuel problem even though it runs fine at WOT.

[The Bloody Panda]

Seems like I don't have a fuel problem since fuel pressure is slightly high if anything. Across the board my fuel pressure is about 6 psi higher than it should be for the FSM tests. I sent the fuel injectors off for a cleaning to eliminate the possibility of them being clogged or faulty but I doubt they are since all four looked flawless when I pulled them out.

After going through vacuum, spark, fuel, ECU, and sensors it looks like I'm going to have to start all over in my search for a solution. So I'm going to swap O2 sensors for the third time since that was my initial suspicion. I'd feel like it was pointless but I remembered that all these problems seem to slowly come on a year and a half ago after I swapped in the O2 sensor that Two R Us sells for the 20V. The first thing I did last month was replace that O2 sensor with yet another of the same model number (Denso 234-9011), but there was no change. Well yesterday I checked the resistance on it to find that it was 0.9 rather than the 11-16 that the FSM is calling for. So now I have a different O2 sensor that does meet that resistance requirement all wired up and installed, but I have to wait for my fuel injectors to get cleaned and mailed back before I can test it all out.

[jondee86]

I see some familiar names in this thread, but worth a look for anyone
who has not read it before... http://forums.club4ag.com/zerothread?id=85825

Cheers... jondee86

[The Bloody Panda]

I checked both my ECUs and no luck, the chip and everything else looks perfect.

[The Bloody Panda]

Running a Toyota 4Runner O2 sensor now with proper resistances but still no luck. Initially I hooked it up so that the heater on it was always grounded and maybe it ran a little bit better than it does now with it hooked up like normal. I can't be sure though because I switched it to normal wiring pretty quickly since it was throwing a CEL. Either way, it shouldn't matter which way I wire the O2 sensor since I didn't have the O2 heater constantly on before this problem started. I do think though that it runs better with this O2 sensor than it did with the one that I got from Two R Us that doesn't have the correct resistance according to the FSM.

I also did a sweep test on my TPS and found that it was dropping resistance when it should have been increasing but only on quick throttle inputs. I swapped to a new TPS that I got from Toyota and that definitely helped even though the TPS doesn't have the proper resistance for the 0.8mm throttle opening test. I got yet another TPS from Toyota because of that and it has the exact same problem. I think it probably isn't an issue to be concerned about since Toyota has superseded part 89452-12080 with 89452-22080 so that's probably why it doesn't line up anymore with FSM specs on that one test.

All of this maintenance and troubleshooting has certainly made my engine run better than ever with the VVT disconnected, but it still goes lean (16ish) at half throttle and I have to wait 2 seconds for the AFR to come down and the power to really come on. If I go WOT the AFR is instantly 13ish and the power response is immediate. If I hook up the VVT then it goes crazy off the scale lean at half throttle and I stop accelerating completely. It will eventually bring the AFR down but it takes about 6 seconds.

I'm thinking about swapping the VVT cam pulley for no reason other than to fix the loud clicking sound it's making. I highly doubt it will help with my issue since everyone says that noise doesn't affect performance but I still wonder.

One weird thing that I noticed is that if I frequently go half throttle the leaness will be less and less each time. However if I drive for say a minute or two without going half throttle then the leaness will be back the next time I go half throttle. I don't know what this means... I keep thinking my ECU will learn around this issue but it never does, more than anything I want to go stand alone but I don't know of any tuners in the 45036 area that have 4age experience.

Does anyone else have any updates on their VVT dilemma? Or maybe I should call it a closed loop dilemma since things work fine in open loop but bad in closed loop and extra bad in closed loop with VVT.

[The Bloody Panda]

Finally found a solution to my problem, only took 3 months of suffering. It was totally worth it though, my 20V Silvertop sounds and runs excellent.

Checked the voltage on STA and E1 and came up with -0.05v while cranking. Strange since back in late May when I checked I was getting 5.5v. FSM calls for 6v or more but I glossed over it thinking that it was just my 6lb racing battery and that 5.5v should be enough. Previous owner had had an alarm system installed and the wiring was done poorly. I had to run a new wire for the starter years ago to address this problem because of intermittent failures to crank. I suspect this issue with the failing STA signal is related.

If you'd like to read about my suffering in greater detail go to the following link.

http://club4ag.com/forums/viewtopic.php?f=13&t=12497

[jondee86]

Awesomeness So now you have 12V (?) on the STA pin during cranking, and
all the drivability problems have gone ? No more leanness and no more having
to drive with the VVT solenoid unplugged ?

I always figured that the ECU just used the STA signal to adjust the fuel and
timing for easier starting, but maybe there is more to it than that. Perhaps
it stays in "start mode" if it doesn't see 12V come and go on the STA pin ?

Anyways... glad you got your car going right again.

Cheers... jondee86

[The Bloody Panda]

Yup, everything is working exactly as it should. Over 6 volts on the STA pin when cranking. All driveability problems are gone. No more leaness and VVT is plugged in and definitely making an audible difference along with a slight increase in acceleration.

[yoshimitsuspeed]

That is one I never could have guessed.
Now any time anyone has any problem at all with their car I'm gonna be like "Better test your STA signal" lol.
Now I'm going to have to try and gain a better understanding of this circuit and how it ties into or could affect these other systems.

[onnaj]

I'm going to test that also, though in my case the problems are not there always. Can drive 100% fine for 2 weeks and then suddenly it's hesitating. But I have another topic on that

Great that you've solved your problem!