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  Soarer Central * Mechanical - V8 * New thread looking for help to solve a problem with full throttle miss on my 31. * Archive through December 09, 2013 Previous Previous    Next Next  

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John Stafford
DieHard
Qld.
Soarer UZZ31 GT-L V8 and a UZZ32 # 514

Posts: 682
Reg: 02-2010

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Friday, October 25, 2013 - 07:51 pm, by:  John Stafford (Johng12) Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

No backfires with vapour injection.

This problem seems to have gotten worse over time until now it is very restrictive.

It has probably been creeping up on me but seeing as I only just petrol to start off and every now and again on the highway to keep the injectors fresh, I haven't noticed it until it got bad on LPG. LPG has been what I call "zoomy" for a while. It surges forward in increments as you accelerate hard until finally that surge became a miss and then I realized after much tuning to fix the surging that it was actually a miss that I was covering up by injecting more LPG.
Tom Richards
Goo Roo
nsw
V8

Posts: 1724
Reg: 08-2005

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Friday, October 25, 2013 - 08:31 pm, by:  Tom Richards (Tomr) Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

do some research on EGR valve
John Stafford
DieHard
Qld.
Soarer UZZ31 GT-L V8 and a UZZ32 # 514

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Friday, October 25, 2013 - 10:10 pm, by:  John Stafford (Johng12) Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

Tom, to my understanding we don't have the EGR valve set up that the U.S. cars have. Their pictures of the SC400 have a whole system for emmissions that we do not have, at least on the early Soarers. Our emissions were much simpler than the U.S. in the early 90s.
Daniel Marshall
TryHard
QLD
V8 UZZ31 X6 jzz30x1

Posts: 498
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Saturday, October 26, 2013 - 12:15 am, by:  Daniel Marshall (Ydass) Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

Maybe it is the catalic converters?
Are they standard?
Should be upgraded for gas and there slowly collapsing.
John Stafford
DieHard
Qld.
Soarer UZZ31 GT-L V8 and a UZZ32 # 514

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Saturday, October 26, 2013 - 06:08 am, by:  John Stafford (Johng12) Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

You might be onto something there Dan. How do I test to see if it is the cats?
What is the cheapest route for replacement?
John Stafford
DieHard
Qld.
Soarer UZZ31 GT-L V8 and a UZZ32 # 514

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Saturday, October 26, 2013 - 07:53 am, by:  John Stafford (Johng12) Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

I just searched the web to see how to test my cats and found 3 or 4 sure ways to test it:
1. Using a vacuum gauge. Note vacuum at idle and then rev engine to a consistent 2000 revs and see if it is considerably lower. If so you have a cat blockage.
2. Check heat of front weld of cat, should be 300 to 500 degrees. Then check rear weld, it should be 150 degrees hotter. If colder or erratic your cat is bad.
3. Take out your O2 sensor/s and see if you accelerate better. If so, then your cat is bad.
4. Drill a 4 mil hole in the exhaust pipe just before the cat and one just after it. Put a pressure reading gauge on these points and if the pressure before is much greater than after you have a bad cat. If you front pressure is more than 5 psi, it is bad too.

What will I do?

1. First I will do the vacuum test with my vacuum gauge.
2. Next I will pull the O2 sensors out and see what happens.
3. Then I will ask a friend if he still has his infer red temp multimeter and measure the front and back welds of the cat but I am not sure if the heat shielding will allow this?

If my cats prove to be ok then I will move to the knock sensors I suppose. I thought that I would cut the wires at the ECU and if the problem is solved by eliminating the knock sensors I can then order new ones and get to work to pull the top of the motor, big job.

Any comments guys?
Tom Richards
Goo Roo
nsw
V8

Posts: 1725
Reg: 08-2005

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Saturday, October 26, 2013 - 08:03 am, by:  Tom Richards (Tomr) Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

cats are easy to remove and check. You can see if they are carboned up.For off road use put a crow bar through them and knock the "guts' out. (gut the cat)

This is not legal for road use??
Matthew Salkeld
Tinkerer
South Australia
1JZ powered 180sx

Posts: 88
Reg: 07-2008

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Saturday, October 26, 2013 - 08:26 am, by:  Matthew Salkeld (Munkymatt) Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

I've used decat before and I regretted it. The noise, smell and extra pollution for zero gains kinda made it a silly decision. Cost me $50 to get a high-flow cat installed in it's place :-)

I'd say check the cats, the knock sensor then take it to a dyno.
John Stafford
DieHard
Qld.
Soarer UZZ31 GT-L V8 and a UZZ32 # 514

Posts: 686
Reg: 02-2010

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Saturday, October 26, 2013 - 09:05 am, by:  John Stafford (Johng12) Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

I did the vacuum test and it was opposite to what would happen if the cat was blocked. Instead of the vacuum going down with the revs up, it went up, so no problems there.

Next is to cut the knock sensor wires at the ECU and see if that fixes it.

Matthew, how much was the hi flow cat?
Daniel Marshall
TryHard
QLD
V8 UZZ31 X6 jzz30x1

Posts: 499
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Saturday, October 26, 2013 - 09:08 am, by:  Daniel Marshall (Ydass) Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

The way I check because I'm in half rural is unbolt exhaust and then remove cats.
Tied exhaust up and go make some noise.
Haha
Decats stinks.
You might need to upgrade cats as the extra fuely gas may have started them to collapse.
May need to go stainless or something?
Matthew Salkeld
Tinkerer
South Australia
1JZ powered 180sx

Posts: 89
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Saturday, October 26, 2013 - 10:10 am, by:  Matthew Salkeld (Munkymatt) Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

Exhaust Technology in SA sold me a good cond (near new) hiflow cat (100 cell i think?) for $50... not sure how much it was to install on it's own because they did a whole lot of other work too... huge mid muffler and new rear muffler + install and new links was $700ish?

Either way, sounds like exhaust is not your problem... there was a thread like this on nissansilvia the other week... a guy was smoking under boost and getting some misfire... he checked pretty much everything on the engine.. took weeks, ended up being dead oil control rings, rebuild time :-)
John Stafford
DieHard
Qld.
Soarer UZZ31 GT-L V8 and a UZZ32 # 514

Posts: 687
Reg: 02-2010

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Saturday, October 26, 2013 - 04:26 pm, by:  John Stafford (Johng12) Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

That sounds like a good deal on the exhaust Matthew. If I need it one day, hope I can get something like that.

I have checked my crank angle sensor for good measure and it reads 1255 ohms - perfect, so it, like the cam angle sensors are fine.

That only leaves the knock sensors as far as sensors go. Can someone confirm that if I disconnect them that it will not just pull timing out, which is what may be happening now?
The manual does not say there is any other way to test them except to take them out and test for continuity. There should be none from top to bottom of sensor.

I have been told that the knock sensors will not be causing my problem, so don't want to do something there if it is not definitely the knock sensors.

Now I come to the point where I need to treat it one thing at a time, I mean, forget I have LPG, which makes the car driveable, and just diagnose it on petrol.

Ok, if I start looking at petrol, as if I did not have LPG, I need to connect a fuel pressure gauge up to the fuel "in" side and tape the gauge to the windscreen so I can see it when the problem shows itself and drive it and see what the gauge says when it misses.

Has anyone done this and if what kind of gauge and fittings did you use to connect to the V8 fuel lines.

If I prove that the fuel is right then my problem could be in the wiring up of the LPG system. Hey, that is my next challenge. But can someone give me some feedback on testing the fuel pressure, the easiest way.
Thanks for coming along with me on this guys. Pretty drawn out hey?
Tom Richards
Goo Roo
nsw
V8

Posts: 1726
Reg: 08-2005

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Monday, October 28, 2013 - 08:30 am, by:  Tom Richards (Tomr) Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

john, the wires for the knock sensor will be shielded?? , with the shield going to ground i would think. It would be better if you could just remove the plug from the sensor. If you cut the wire, you will need to rejoin the inner wire and outer shield.


(thats if my thought it is shielded is correct)
John Stafford
DieHard
Qld.
Soarer UZZ31 GT-L V8 and a UZZ32 # 514

Posts: 688
Reg: 02-2010

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Monday, October 28, 2013 - 01:45 pm, by:  John Stafford (Johng12) Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

Thanks for that Tom, that would be no good hey.
I have decided to take it slow in doing anything with the knock sensors due to how big the job is when I am not sure that that is the problem.

Neil Griffiths, who I wrote to personally, has suggested that something is causing a fuel cut to come on. I am waiting for his reply to my return email and will keep this thread posted.
Tom Richards
Goo Roo
nsw
V8

Posts: 1730
Reg: 08-2005

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Thursday, October 31, 2013 - 07:48 am, by:  Tom Richards (Tomr) Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

hi john, another thought from left field. Does this car have traction control? could a fault in the TRC system be the problem?
John Stafford
DieHard
Qld.
Soarer UZZ31 GT-L V8 and a UZZ32 # 514

Posts: 693
Reg: 02-2010

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Thursday, October 31, 2013 - 10:32 am, by:  John Stafford (Johng12) Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

No traction control Tom.
You asked previously if it made a difference to the revs when I moved the TPS and I said "No".
Well I went ahead and bought a new TPS and fitted it.

The following happened:
1. I could not get it to give me infinity ohms with E2 and IDL connected, with a 26 thou feeler gauge inserted at the throttle stop, unless I adjust it to the point where I loose my 4k ohms reading that I got when I inserted a 16 thou gauge at the throttle stop.
If I forget the 16 thou measurement and just get 4k ohms with no gap at the throttle stop that goes to an infinity reading there when I put a 26 thou gap a at the throttle stop and move the TPS to get in infinity there.

Do you follow me?
The gap at the throttle stop had to be quite wide, more than you could measure with a feeler gauge, before I get infinity there and still retain my 4k ohms at no gap. So, in the end I just had to leave it there.

The thing is I can not get a change in revs by moving the TPS even with the new one.

Any ideas?
Could this phenomena be a clue to the miss??

By the way, re the knock sensors being the problem, after having done so many other things, the idea of taking off all the top stuff from the motor to remove and test the knock sensors is a bit daunting, when it may not be the problem. Wish there was some other way to test these things without having to go to that extent and maybe find out that that is not the problem either.

The fact that there are no fault codes that come up tells us that it is something very basic, like fuel or basic spark and I have removed the possibility of it being plugs or coils or ingniters, so, I have been advised to forget that I have LPG at first and eliminate the possibility of petrol, which is what it most feels like. like it is not getting fuel when I floor the accelerator. The job then is to measure the fuel pressure when the problem occurs by connecting a fuel pressure gauge to the fuel rail and sticking it to my windscreen while I go for a run and give it a boot full.
Once the possibility of low fuel pressure has been eliminated I can move on to look for other things, like a problem with the wiring on the LPG system.

I have just taken off my fuel filter,it was totally clean as expected as it was relatively new. I also took the fuel pump out of the tank and looked in the tank for dirt or algae but it was spik and span, so now I need to test the pressure at the rail and see if there is a problem showing up there at all.
Nik Peacock
TryHard
Tasmania
V8 6 Speed Manual

Posts: 216
Reg: 05-2006

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Thursday, October 31, 2013 - 11:26 am, by:  Nik Peacock (Niko) Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

John there is a knock delete unit that can be fitted to the ecu loom, Greddy make them I think from memory, I have one fitted as when we were tuning the ultimate there was a dodgy sensor that was pulling lots of timing out at certain revs, not too expensive around $70?
Tom Richards
Goo Roo
nsw
V8

Posts: 1731
Reg: 08-2005

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Thursday, October 31, 2013 - 12:42 pm, by:  Tom Richards (Tomr) Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

hi john, i feel for you, if i get another left wing thought i will throw it up.
Daniel Marshall
DieHard
QLD
V8 UZZ31 X6 jzz30x1

Posts: 503
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Friday, November 01, 2013 - 01:13 am, by:  Daniel Marshall (Ydass) Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

Have you tried another ecu?
John Stafford
DieHard
Qld.
Soarer UZZ31 GT-L V8 and a UZZ32 # 514

Posts: 694
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Friday, November 01, 2013 - 06:29 am, by:  John Stafford (Johng12) Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

Hey guys, I have decided to bite the bullet and go for the knock sensors, seeing as they are the only thing I haven't replaced or verified as up to spec. in the ignition/sensor department. This seemed to be the cheapest way forward now.
I considered buying a fuel pressure gauge to test the pressure but by the time I did that just to test I could have nearly bought the knock sensors at the price I have gotten them for.

I just ordered 2 Toyota OEM knock sensors, from the U.S. normally over $200 or even $300 each for $80 delivered for the 2!
I thought why not?

So I will let you all know if this is where the problem was, all the time?

Dan, yes, I have tried the ecu from the 32. here is what I swapped out from my 32 to see if they were the problem:
ECU
Igniters
Karmen Vortex
Coils
Spark Plugs}
Tom Richards
Goo Roo
nsw
V8

Posts: 1733
Reg: 08-2005

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Friday, November 01, 2013 - 07:09 am, by:  Tom Richards (Tomr) Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

hi john, have you cleaned all the earth points?

http://soarercentral.com/sc-forum/messages/51/103160.html?1167967823
John Stafford
DieHard
Qld.
Soarer UZZ31 GT-L V8 and a UZZ32 # 514

Posts: 696
Reg: 02-2010

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Friday, November 01, 2013 - 07:17 am, by:  John Stafford (Johng12) Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

thanks Tom, I will check them.
John Stafford
DieHard
Qld.
Soarer UZZ31 GT-L V8 and a UZZ32 # 514

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Wednesday, November 06, 2013 - 07:12 am, by:  John Stafford (Johng12) Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

Oh, I happened on the trick to adjusting the TPS and getting a response in revs when moving it.
I could not get any difference in revs when I moved it and then I thought that my movements could be being overridden by the fact that the air con was on.
So, I turned the air con off and voila, I got it to change from 700 up to about 1300 as I moved it back and forth, so set it at what seems to be the sweet spot, about half way on the adjustment slot, with the revs at 700. Did it on both cars with the new sensors.
John Stafford
DieHard
Qld.
Soarer UZZ31 GT-L V8 and a UZZ32 # 514

Posts: 744
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Monday, December 09, 2013 - 01:36 pm, by:  John Stafford (Johng12) Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

I have got the knock sensors and have the manifold gaskets coming tomorrow, so I can change the sensors to see if that is the cause of my miss, BUT
following Daniel's advice I thought that I should fully exhaust the possibility of it being the Catalytic converters, So:

I put a vacuum gauge on the PCV line and revved up to about 3500 revs and watched to see if the vacuum dropped off, it did not, it just went up a little, so assumed that the cats were fine. The vacuum should drop as you go up in revs if there is an exhaust blockage.

But to test further I took the temps at the front and back of the cats and the left one didn't seem to be much different but it was hard to get a consistent measurement. Maybe failed left had cat?

Next I took the 02 sensor out of the left hand pipe and took it for a run, giving it full throttle But the miss was still there. This should have relieved any blockage and given the exhaust an opportunity to go out through the 02 sensor hole. There was plenty of noise but still dies on full throttle.

The new cats are $128 each, delivered from ebay plus fitting so don't want to just change them to see if that is the problem.

The next test I could do is to drill holes before and after the cat and measure the pressure to see if it is higher at the front than the back. If the pressure at the front is more than 5 psi. The cat is bad anyway.
I would have to buy a pressure gauge to do this test. Maybe I could just go by the feeling of pressure by putting my gloved finger over the hole and seeing if I could tell the difference between front and back?
Daniel Marshall
DieHard
QLD
V8 UZZ31 X6 jzz30x1

Posts: 569
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Monday, December 09, 2013 - 11:23 pm, by:  Daniel Marshall (Ydass) Edit Post Delete Post Print Post   View Post/Check IP (Moderator/Admin Only) Move Post (Moderator/Admin Only)

When I had a gas system and the battery was disconnected it had to be started then revved to 1500rpm.
Then 15mins of driving afterwards.
Not sure if this is the case with yours?

With the cats it can give a similar symptoms.
Easiest way I found to test was unbolt from manifold and go for a noisy drive haha

It's as if fuel delivery is the problem

Do your injecters only do petrol?
And you have one of those rings infront of the throttle body?

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