Supra sputtering when building boost

[DJ6ta]

Car: 95 Supra
Engine: Aristo 2jzgte
Miles on chasis: 147000
Miles on engine: ?
ECU: stock JDM ECU
Tranny: 4 speed auto
Mods: straight pipe exhaust, brand new Iradium laser NGK plugs pre gapped

Problem : the car sputters really bad as it builds boost. The boost will top out at around 10.5 psi. The car will accelerate but the sputtering is bad. It shakes the car really bad too. When the car is under vacuum it will pull fine.

Problem 2: when the car is nice and warmed up it will run fine over 1000 rpm but as soon as it goes below 1k the car will shake and die. I restart the car by pushing the gas and starting at the same time and it will idle fine until I put it into
Drive and it will die. The only to remedy the problem is to shut the car off, disconnect the battery, wait 30 min and then restart the car.

Problem 3: I'm sure this is a stuck valve or something but there is a noticeable tapping noise coming from my valve train. The car runs royal purple sythetic and the oil only has like 500 miles on it.

 

[hvyman]

Id first check your codes.

Second i wouldnt boost until the engine is warm.

3rd. id check for boost leaks.

4th id check the isc valve.

 

[DJ6ta]

No codes. Boost shutter happened cold or warm. Two small vacuum leaks on the valve cover. Will check iscv.

 

[hvyman]

vac leaks are no good.

Its not good for the pistons to be boosted on when cold. Pressure cause heat and if you heat up alum to quick it will crack. Cracking a piston cause the motor didnt warm up would suck. That was the point i was getting at.

 

[DJ6ta]

I get what your saying. Your absolutely right, but Im sure the two very small vac leaks on my valve cover aren't the culporate to all my problems.

 

[te72]

Make sure your plugs are gapped correctly as well. I had a similar problem with the 1j after the y-pipe swap. Gapped the plugs evenly and at a bit tighter spec, and the problem went away.

 

[DJ6ta]

What's the suggested gap? The plugs I just bought are pre gapped iridium for my car.

 

[hvyman]

Coppers are better for boost.

iridiums are hard to gap.

But the gap should be around like .028 or so.

 

[te72]

Believe I gapped mine to .028, have yet to have that issue again. Wouldn't believe how far off "pre-gapped" plugs can actually be.

 

[hvyman]

There also pregapped for other vehicles as well.

 

[DJ6ta]

I will buy some coppers today and gap them to your suggestion. I hope your right because I want this shit to go away.

 

[Flateric]

I find the lifecycle of the coppers just way too short is my issue with them. I agree Iridiums are both hard to gap and way off of what our cars like in turbo trim.

When I first did my 2jz swap I left the plugs unchecked and ungapped (the way they came out of the box) and my car hardly ran at all. I also second the vote to check the isc valve. Make sure it is not filled with gunk and also the little flappy disc under it is sealing up correctly.

 

[89turbotoy]

check the coil wires and connectors, they get hot and crack nad they can short to one another causing a mis fire.. Also be sure you have the correct spark plugs. If you have the ones from an n/a they will blowout spark under boost. here are some part numbers for you

NGK - BCPR6EP-11
NGK - BKR6E (2756)
NGK Iridium - BKR6EIX-11 (3764)
Denso Platinum - PK20R11
Denso Iridium - IK20

 

[DJ6ta]

I bought some coppers, gapped them to .030, pulled the coil packs, examined them for damage and found small to
Medium cracks, I electrical tapped them as a temp fix, changed the order in which the coil packs were in, fixed the exposed wires of the harness and checked the resistance for all coil packs (all within spec from TSRM). Car will now idle much better, pulls very hard and smooth when warmed up but still sporadically sputters at about 5psi. I guess I fixed the problem kind of. I'm not sure if I need to replace the coil packs to make the problem fully go away.

 

[Flateric]

The JZ coils are very prone to tiny cracks and well...they are also old at this point. If you have seen some improvements then I suspect you are correct and coils are still at the root of your problem. The electrical tape solution is as you do appear to realize and bandaid solution at the very best.

You may try finding some larger size shrink tube to put over the lower part of the coils, but this again is only slightly better than electrical tape and not a proper solution. The only way to really correct this is to buy some new coils. Even if you do find used coils that are not cracked. They are still likely to crack on you within the near future. It's just so damn hot in that valley and hard on the plastic.

 

[DJ6ta]

I'm pricing new coils, but I don't think that is the whole problem. I think I just fixed part of it.

 

[DJ6ta]

Now the damn car is dying at stops and sputtering just as much as they were before. I have no idea what to do. I think the IAC might be an issue because I can unplug it while the engine is running and there is no change in the engine. It does make the clicking noise and the rubber valve on the inside has just been cleaned. The only way I can get the car to turn back on is to disconnect the battery, wait 10 minutes and then the car will start. As soon as I drop it into drive it will die unless I'm on the gas. It will run fine above 1k with breaking up in boost. Any ideas?