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Old 03-30-2016, 12:20 PM   #1
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s13 vert - 1jz vvti high idle and fuel cut issue - help?

Hi all, I have a few questions and maybe looking for some help or advice.I can’t seem to locate the source of these problems and neither can my JZ guru friends. I have a 1994 s13 vert with a JZZ30 1jz vvti with r154 MT. Recently completed at the start of March 2016. I am going to try to list out everything in as much detail, so I apologize for the long read. Overall issues with long story short, high idle & fuel cut/fuel smell at 12psi in higher gears. I don’t have any mods other than what is required to put this engine in my car. Intercooler, intake, downpipe back exhaust and a manual boost controller… factory ECU. We did the wiring ourselves instead of buying a harness (which I will buy one eventually sometime soon but the wiring was completed by a professional, not joe blow down at the corner).

High Idle Issue – So, the day we started my car up for the first time, it had a high idle. About 1200ish idle 99% of the time. YES, MY THROTTLE CONTROL SCREWS HAVE BEEN ADJUSTED. At this point in time, we removed the traction control sensor and the other sensor atthe front of the throttle body (I forget what it is) before we started the car for the first time. We milled it down on a lathe and cleaned it up really nice. The IACV was installed at this point in time. However, my IACV only had a breather on it. It was not hooked up to the Jpipe. The Jpipe essentially is blocked off with a cap but has a vacuum line that is hooked to the boost control solenoid. Eventually within a week, the car started having issues starting and staying on, misfiring… etc. I ended up getting a new igniter, solved the issue of it not starting every time. Once that was fixed, I was trouble shooting the misfiring and it starting and dying. It would rev up to about 2 grand and then die, or misfire and idle rough. I ended up swapping out my IACV for another one, same issue. I ended up unplugging my battery and hooking it back up, car ranfine for a few days. Then it started over again. I eventually ordered a IACV block off plate, and that solved my issue and now has got me to where I am now.

So, as of today my car starts and idles at 800 on a cold start. After about 2 minutes, it will bump up to anywhere from 1000 to 1500. I can’t find any reason that would cause the fluctuation to occur. I have the IACV blocked off, the Jpipe blocked off with a vacuum line going to the boost solenoid, throttle screws backed allllll the way out to where they aren’t touching the butterfly and the throttle cable is NOT too tight. I have sprayed the entire engine with carb cleaner twice and haven’t found any vacuum leaks. I also cleaned the throttle body when we milled it down. I do NOT know of any codes that the ECU is/could have been giving. I’m not sure if the stuff is hooked/wired up to read it to be honest, nor do I have a reader.

*NOTE* - I did notice that whoever owned this engine before me (ENGINE WAS IMPORTED FROM JAPAN) had a different MAF pigtail than the factory one. The factory pigtail was hacked off and rewired to a different MAF, just not sure which one. What I do know is that my MAF plug does fit with a little modifying f the MAF, but I am not 100% sure its wired right. I do know that my 12v switch power is wired correctly though. The car runs really well and feels strong, butI’m not sure if this MAF wiring could be an issue and maybe the wires aren’t going to the right areas with the stock MAF. Also, checked the capacitor in the ECU and it is fine.

***ANY ONE WITH A JZZ30 WITH STOCK WIRING, IF YOU COULD TAKE A PIC OF YOUR MAF PIGTAIL SO I CAN REWIRE IT WITH THE NEW MAF PIGTAIL I HAVE, THAT WOULD BE FANTASIC*** My wire colors are black with a red line, green with a black line (I think), red with a white line, brown, and then light green.

Fuel cut/fuelsmell issue – So I have read online and talked with a lot of people and from what I have been told, the factory ECU can push up to 15psi or so without anything tuning wise or running into fuel cut. I recently turned my boost up to12psi and the car ran great for a bit, then one day I attempted to race my buddies LS13 and I was in 3rd about 3 grand, about 3500 or so, I hit fuel cut harddddd for the 1st time. I then turned the boost down to 11psi tosee if anything was different, 3rd gear was fine now but instead it hit fuel cut in 4th at about 4000-4500. I have since turned the car down to 10psi and haven’t found out if it hits a fuel cut any more, only hit it twice and that was enough for me. I know 1st and 2nd are good though for sure haha I am running a Hallman PRO MBC and the factory boost solenoid. I am running NGK BKR7E’s and they are gapped at .028 or .28, whatever the measurement is… idk.

I know that JZs like to over fuel, but when I get on the car now, I smell fuel for a few seconds after I let off, then it goes away. I have checked for leaks and the car does shoot fireballs here and there, so I am thinking I’m running rich. I don’t have a AFR gauge, so I cannot confirm. Once again, car runs fine as of right now and the smell only occurs on WOT. The fuel cut only occurs in higher gears in high RPMs after it is already at full boost (11psi and 12psi – unconfirmed at 10psi). Maybe it could just be left over fuel coming out of the exhaust.

Overall, I am starting to think Ieither have a bad sensor somewhere, or that MAF wiring is my issue (not surehow it should be wired exactly so I haven’t attempted to rewire it yet, need apic to be safe!!!). I can’t find a vacuum leak, it holds boost at whatever setting I have it at and doesn’t spike or fall off. I have a feeling that whether it’s one of the reasons just listed or not, but once I figure out myhigh idle issue, my fuel cut issue will also be solved.

Any help or ideas would be greatly appreciated. I am mechanically inclined and did 95% of this swap myself. I have owned several schassis’ over the past 12 years with different engines. I have checked majority of the easy testing that I can think of. Other than these issues, this car feels and runs great!

Also, if any one wants to follow me on IG, it’s @fubigemo_s13vert

Cheers and thanks for the help in advance!

Last edited by bdavis; 03-31-2016 at 07:20 AM..
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Old 03-30-2016, 08:35 PM   #2
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You ever figure this out?
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Old 03-31-2016, 07:13 AM   #3
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Nope, just posted it yesterday. I haven't figured out the issue. It was raining pretty good yesterday so I didn't get a chance to look anything over. Car runs great minus this stuff.
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Old 03-31-2016, 07:27 AM   #4
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any insight you have would be greatly appreciated!
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Old 03-31-2016, 07:58 AM   #5
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I'd snag an Wideband to see what the added boost has done to AFR and then I'd return to stock boost to see if things calm back down.
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Old 03-31-2016, 08:11 AM   #6
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Im going to play around with the car today. I still haven't ran into an issue with 10psi and fuel cut, but tomorrow will be the first drift event with this car so we will see how she does.


I have 2 questions...


1 - can you unplug the VVT-I sensor and then start the car? I know its REALLY bad to unplug while the car is on, but what about if it is off, then unplugged and then turned on? I read a few places of similar issues and one of them ended up being this sensor and filter were bad.


2 - Can you recalibrate the TPS or anything? I almost feel like the TPS could be misreading. The sensor itself is kinda beat imo.


I wish I could upload pics. I have a ton, but they are all way past 500kb.
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Old 03-31-2016, 09:10 AM   #7
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The vvti 1jz engines don't necessarily hit fuel cut under the conditions you are describing but they do have issues with the spark blowing out. Look on supra forums to see info about high boost misfires. My car did the same thing for a little while until I replaces the plug wires and coilpacks. Also of you still have the factory diverter valve in place they leak at anything over 12 psi and make tuning a pain as well as cause other problems. I have been running a vvti 1j with the Tomei arms setup on 20 lbs for over 5 years now without any real problems. Big thing that helped was going to a power fc djetro and getting rid of the maf
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Old 04-01-2016, 07:52 AM   #8
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Quote:
Originally Posted by landins13 View Post
The vvti 1jz engines don't necessarily hit fuel cut under the conditions you are describing but they do have issues with the spark blowing out. Look on supra forums to see info about high boost misfires. My car did the same thing for a little while until I replaces the plug wires and coilpacks. Also of you still have the factory diverter valve in place they leak at anything over 12 psi and make tuning a pain as well as cause other problems. I have been running a vvti 1j with the Tomei arms setup on 20 lbs for over 5 years now without any real problems. Big thing that helped was going to a power fc djetro and getting rid of the maf
Thanks for the info! my coil packs do look a little beat to be honest, so that's what I was wondering about too. Dumb question, but what is the diverter valve? I turned it up to 12 yesterday and didn't run into anything cutting out, so that's a plus I suppose. Cant figure out this idle issue though.
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Old 04-01-2016, 09:31 AM   #9
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what do you have your plugs gapped at? or did you leave them gapped as it was out of the box? i had a similar problem with my vvti where it would try to boost but kept breaking up
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Old 04-04-2016, 09:26 AM   #10
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I have my plugs gapped at .28 or .028. I cant remember what the actual measurement is... lol


so when we installed my engine, we found that the factory engine temp sensor plug wouldn't plug into the sensor itself. It looked like it would fit, but the alignment pins weren't in the right areas. So, we filed the one alignment pin on the sensor down and the plug fit and clipped in just fine. I am wondering if the sensor is reading backwards.


I was reading online that if the engine temp sensor doesn't read correctly, it will cause the idle to go up with the engine temp, and that's exactly what it is doing. Any one know?


Also, I have the factory FPR still. I also read that you should adjust your fuel pressure about 4psi per pound of boost raised from factory.


So, what does the factory fuel pressure usually sit at? and what should I run at 12-13psi? I think that's why I am hitting fuel cut. Everything else seems to be in order.
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Old 04-06-2016, 08:01 AM   #11
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BOV Issue - so my BOV doesn't work, I just have compressor surge. The BOV is hooked up as so from the factory with the electrical solenoid. I tried to by pass the solenoid and just run it off of vacuum the other day. Car started just fine, ran great but I found that it didn't have the normal boost and power it should. The BOV worked now, but when I was in low gears at high RPM, it would boost about 6 PSI, and then drop down to like 3. In high gears at low rpms, It would eventually build 10psi, but realllly slowly. So I hooked everything back up to factory and now I just have surge again. Sounds cool, but it would be nice to have this working properly. would this be an issue with the BOV or solenoid? or both?
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Old 04-06-2016, 08:47 AM   #12
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Quote:
Originally Posted by bdavis View Post
I have my plugs gapped at .28 or .028. I cant remember what the actual measurement is... lol


so when we installed my engine, we found that the factory engine temp sensor plug wouldn't plug into the sensor itself. It looked like it would fit, but the alignment pins weren't in the right areas. So, we filed the one alignment pin on the sensor down and the plug fit and clipped in just fine. I am wondering if the sensor is reading backwards.


I was reading online that if the engine temp sensor doesn't read correctly, it will cause the idle to go up with the engine temp, and that's exactly what it is doing. Any one know?


Also, I have the factory FPR still. I also read that you should adjust your fuel pressure about 4psi per pound of boost raised from factory.


So, what does the factory fuel pressure usually sit at? and what should I run at 12-13psi? I think that's why I am hitting fuel cut. Everything else seems to be in order.
from what I read online, you don't want to have your gap that close unless you're throwing big boost at it. I happened to have mine gapped the same as your's and it stopped it from breaking up but it was also mentioned that if we h ave to gap it that close to keep it from breaking up, there's a problem elsewhere (most likely coil packs are about done for).

The engine temp sensor for the ecu can only on one way so I can't imagine you plugging it in wrong.
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Old 04-06-2016, 09:02 AM   #13
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from what I read online, you don't want to have your gap that close unless you're throwing big boost at it. I happened to have mine gapped the same as your's and it stopped it from breaking up but it was also mentioned that if we h ave to gap it that close to keep it from breaking up, there's a problem elsewhere (most likely coil packs are about done for).

The engine temp sensor for the ecu can only on one way so I can't imagine you plugging it in wrong.
yeah, my coil packs don't look the best to be honest. Im wondering if that could be one of my issues. Do you think having a factory FPR instead of an adjustable aftermarket one to compensate for the extra boost could be causing the issue too?
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Old 04-07-2016, 01:47 PM   #14
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Still no resolution!!!!!!
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Old 04-12-2016, 03:19 PM   #15
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yeah, my coil packs don't look the best to be honest. Im wondering if that could be one of my issues. Do you think having a factory FPR instead of an adjustable aftermarket one to compensate for the extra boost could be causing the issue too?
i'd say on a mostly stock set up, an aftermarket/adjustable FPR shouldn't be necessary. A wideband wouldn't be a bad investment to give you an idea of whats going on up there in boost.
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Old 04-15-2016, 12:12 PM   #16
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I turned it back up to 12lbs yesterday, hit fuel cut in 3rd gear about 4500 again. Im wondering if my plugs need a little more gap maybe?
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Old 04-17-2016, 07:41 PM   #17
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Definitely not blowing spark out at 28 on 12psi, I had a similar issue when I initially swapped my 2jz and it was a mixture of bad grounds and 2-3 dead coilpacks. Can you email me a picture of your MAF connector though? [email protected]
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Old 04-17-2016, 09:30 PM   #18
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I am not that smart but my friend runs into boost cut at about that psi in high rpm stock ecu. non vvti though. He said he needs to get the boost cut defender My 1jz runs off a map sensor and safc2 on 16psi with 440cc injectors no fuel or boost issues. I hope that helps somehow.
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Old 04-17-2016, 09:34 PM   #19
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you can test your coil packs pretty easily too if you just pick one up and see if there is a change in the way it runs at all. I would try that before replacing look for cracks and such
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Old 04-19-2016, 06:02 PM   #20
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if you did the timing belt, i'd go back and check it. first time i did mine, i thought i had everything lined up but it ended up being off by a few degrees.
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