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Check your alternator voltage when this happens. When its windings or diodes oxidise due to age,cycles,fluids it looses its ability to create sufficient voltage at low rpm.i had this happen to me but figured it out quick and replaced it
 

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Master Shit Fixer
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where is your vacuum port on bov connected? check that it does not leak on the threads there. looks kinda suspect. and please change your brake fluid ?
 

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It's hard to tell from your pictures, but it looks like your BOV is vented to atmosphere and since you are still on the MAF, you are losing metered air when letting off the throttle.
 

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Discussion Starter #30
Going to take a look at the BOV thread/hose for any leaks. Should I go with a recirculating BOV instead?

Also should any hoses go connected to intake piping? I see two connections capped off.

Thank you all.
 

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I was dealing with a similar issue with my 2jz-ge n/a. I had multiple issles that were causing my problem. One was the cats were clogged, replaced the manifold and was still having a kinda low idle (500-600). Did a injector and throttle cleaning service and it brought back all the power and idle speed. No more stumbling from a stop, throttle response is back to feeling like new. Carbon deposits build up on the intake valve, on top of the piston, and around the injector tips (carbon on the injectors will cause poor fuel atomization leading to incomplete combustion). I'd highly recommend doing a carbon cleaning service. Even if it doesn't fix the issue, your engine will appreciate it.
Also did you swap the MAF with a new one or used? If the hot wires on both MAF sensors were dirty, then both will read incorrectly. Cleaning the hot wire takes about 10 minutes with some MAF cleaner and will typically make a noticeable difference in engine performance. Also might be worth checking a scan tool to see IAT and CLT temps and verify they are reading fairly close to correctly. Vacuum leaks can also be a culprit, so smoke testing the intake to try to find any cracked vacuum hoses that are causing unmetered air to enter the engine is a wise idea too.
 

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handy with the steel
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Going to take a look at the BOV thread/hose for any leaks. Should I go with a recirculating BOV instead?

Also should any hoses go connected to intake piping? I see two connections capped off.

Thank you all.
The two large capped off parts on the cast aluminum intake & charge pipes on the left side are where the factory recirc valve was plumbed in - don't worry about those. I agree with Bitshiftr, it sounds like your BOV is venting to atmosphere. You still haven't clearly answered whether or not this is the case, so I am thinking you may not understand what he is asking.

The problem with an atmospheric vented BOV on a stock USDM 2jzgte is that the MAF meters all air coming in, then when you let off the throttle and the BOV makes those sexy BOV noises, it's letting the air escape which has already been metered, and therefore the engine runs very rich until the airflow can catch back up.

You need to verify where the BOV is venting. The hose you took a picture of is the manifold reference - this is just what activates the valve, not where the pressurized air is vented. If that's the only hose going to the BOV, then it's vented to atmosphere and most likely that is your issue. If it has been installed as recirculated, then there would be a larger hose (probably ~1" or so, possibly bigger) coming from the BOV and going to the intake somewhere after the MAF but before the turbos. There's only so many places on the factory setup that you could accomplish this, and I don't see this in your pics.

Now, if you determine it's vented to atmosphere and you want to have it recirculated, you don't need to buy a new BOV. Just run a hose from the large capped off port on the intake post-MAF to the exit flange on the BOV. I'm not familiar with the Blitz BOV so it may need an adapter or you may have to rig something up.
 

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Going to take a look at the BOV thread/hose for any leaks. Should I go with a recirculating BOV instead?
You should either use a recirculating BOV, or you should ditch the MAF for a MAP sensor, which means installing a VPC or using a standalone ECU. Right now, you are in the "in between" world...not good.
 

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From the land down under
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As above, its a very simple fix to swap in a recirculated BOV, and your problems should be solved.

There are plenty of recirculated BOV options to choose from, too. :)
 

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1987 Supra Turbo R154 Pearl White, Blue Velour
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On my 7M-GTE I had a very similar problem. Eventually I
  • replaced the TPS with OEM and adjusted it to spec
  • Took out and apart the IAC valve and cleaned and tested it
  • replaced my MAS
  • did the knock sensor rewire
  • new accordion hose, vacuum lines and clamps
  • timed it
The biggest change came after replacing the MAS, but the TPS, once adjusted completed the smooth rev.
 

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Discussion Starter #38
Thank you all for the replies.

Finally resolved the issue. Ordered & installed an Apexi power intake. No rev cut with this intake & no low idle issues/car turning off on me.
(Rookie mistake)

250248
 

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Bitshftr, CDSaints, and Mr Ree NZ, (and any others),
Why did changing the air filter solve this low idle trouble? I agreed with the thought of recirculating the BOV (i.e., bypass valve).
 

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Discussion Starter #40
I was told that not having the air filter was causing the hot air from the fan to go into intake and throw off the MAF reading.
 
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