I just talked to a friend of mine that lives and breathes 1uz's (owns a performance shop). He said there is a fuel pulsation dampner on the fuel rail's inlet and he's found them to be creating a restriction from time to time when some screw comes out of the top of it - i havent looked at mine yet but will do this afternoon sometime. He also said he thinks the problem (lack of power down low) will be a timing problem. So what you say about the knock sensors picking some up and pulling the timing way back is probably right.

We'll see how the next couple of days go with mine.

 

Well I hear 1UZs are very popular in NZ and AU, many people swap them into older Toyota trucks (mostly using aftermarket ECUs).

If you can, find out some information from your frend, maybe he can chime in on this thread, perhaps advice on how to diagnose?

 

P.S.

I'm actually planning on doing the diagnostics described here to see whether my computer is leaning out the mixture and what O2's are reading.

http://us.lexusownersclub.com/forums...&mode=threaded

 

Yea they're a pretty well tweaked engine down here, Geoff's 1uz is insane, crazy nitrous motor, ITB's, rev-limits at 9800rpm, massive cams

But because of the way 1uz's are used here (stripped down in custom conversions, Link ECU), often nobody ever gets the chance to actually work out the issues (like this) with the original car. They just go a whole lot better with a well tuned ECU that doesnt freak out at the first sign of something being out of place.

He'll probably end up helping with mine if i dont resolve it in the next week or so, if so ill definitely pass on any information.

 

See I just remember how, back a few years ago I disconnected an air line from the FPR and the car ran like a beast for 10-15 minutes, only to crap out and run even worse later, until I plugged the line back in.

I'll look into it more in the future, Im just burried with work right now, and gotta replace my valve cover gaskets that are now leaking.

 

OK i'm just checking it out again. I'm not too familiar with the 1uz so forgive me. I can see the fuel pulsation dampner, and its nothing like the one i pulled off my supra. Its just like a sealed diaphragm that sits at the rail's intake, i can see the screw Geoff talked about and how it could affect what the diaphragm is doing but mine looks fine. It seems that the fuel doesnt necessarily flow thru it so it shouldn't be restricting anything. It should be pretty easy to remove this dampener and replace with a bolt of some sort if i decide to (not likely).

There is a solenoid on the FPR's vacuum line... what the hell for? So the ecu can play with the fuel pressure if it see's fit? Goddammit lexus, how much control does an ECU need?!?!

Im gonna bypass it and go for a burn...

 

Seems like I have something that is called Fuel Pressure Control Solenoid on my car to and according to alldatadiy;

"PURPOSE
The vacuum switching valve for fuel pressure control is used to raise fuel pressure during hot restart conditions.

OPERATION
During a hot restart, the engine control module energizes the vacuum switching valve which redirects the vacuum supply for the fuel pressure regulator to the atmosphere. When the vacuum is vented, the fuel pressure regulator raises fuel pressure accordingly."

If I understand that information right is that the only thing that will do is to raise the fuel pressure, not lower it

 

Well thats weird...

A couple of days ago, when i took the car for a few runs to test its 0-100km speed, it could only manage 9.4 seconds best after a few consistent runs (worst was 9.8). This was stalling it up to about 2000rpm just on the brakes in D, jumping off the brake and flooring it, letting it shift by itself. Traction control off, ECT in PWR.

Just now i bypassed the "Fuel Pressure Control Solenoid" (thanks JAnderson), left it plugged into the loom. I took it to the same stretch of dry road, same half tank of gas, similar ambient temp (within a couple of degrees). Did the test in exactly the same manner, letting the trans shift itself, first run was 8.6 seconds! It had a lot more power off the line, would often step out sideways and would quite easily fry the tyres (245/40/19) I got it as low as 8.4 letting the trans shift, and 8.01 manually shifting it at redline. I could probably get it around 7.8 with better tyres. This is at 300m above sea level.

After this, i thought i'd shut the engine off, hook the solenoid back up, and try again... No change! It ran the same as it just did with the solenoid unhooked, i tried a few times. Totally consistant.

So...... i've got no idea what happened but my car's going a whole lot better right now. I wonder if its possible that the solenoid was altering the fuel pressure, and with it unhooked, the ecu was forced to re-tune? Dont take my word for it tho, it's got me stumped.

I'm going to leave the solenoid unhooked and see how it runs over the next few weeks. I did notice it starting different, but it actually seemed better if anything.

 

With that line unplugged, im pretty sure the o2 sensor feedback will keep it running fine at part throttle and idle. Put if you stood on it, the maps would run it very lean. I think i've got that right.

 

Can you post a pic of that solenoid? I'm not sure where it is.

 

Here is a picture on the solenoids location. It's called VSV in this picture

 

Different place on my UCF20, round the back of the manifold:

 

I'm a bit lost. I'm not quite getting the purpose of this solenoid or how it works. I inspected it on my car earlier today, it seems that it has an air hose going from the throttle body to this said solenoid, and then from the solenoid to the intake manifold. What the hell could that possibly accomplish?

 

Wait, I think I might be wrong on the routing of the air lines, I think it goes from the FPR to the VSC then to the manifold. In any case, heres a description of what that solenoid does from the manual.

"The ECM turns on a VSV (Vacuum Switching Valve) to
draw the air into the diaphragm chamber of the pressure
regulator if it detects that the temperature of the
engine coolant is too high during engine starting.
The air drawn into the camber increases the fuel pressure
to prevent fuel vapor lock at high engine temperature
in order to help the engine start when it is warm.
Fuel pressure control ends approx. 100 secs. after the
engine is started."

So that means if I bypass it, it will continuously increase fuel pressure.

 

Only during warm starting. During normal running conditions that VSV shouldn't be doing anything to the fuel pressure at all, if we're to believe that is ALL the ecu uses it for.

Edit: ooops no, read that wrong, it will DECREASE fuel pressure if you bypass it. I like the way my car's been starting with it bypassed, it fires up the same but the idle drops back to 650 faster.