Intermittent miss up to 2k and idle when warm NA-T

[Travis89Turbo]

The GE originally had two single wire narrow band o2 sensors from the factory. About 6 months ago I bought an na header that had screw type o2 instead of the 2 bolt so I bought two brand new bocsh screw type o2 sensors. Ran great with no problems.

When I put he turbo and downpipe on I ran the two new o2 sensors. When the problem started o2 sensors were ny first thought so I pulled those two off and exchanged them under warranty. Installed them both and same problem.

The wideband is strictly for my AEM AFR gauge.

The current set up just so u understand how I have it hooked up is my wideband hooked up in one of the banks and then 1 of the new o2 sensors with both o2 sensor wires ran to it. When I have the ecu o2 sensor hooked in the front bank and wideband in the rear the car runs flawlessly. It certainly doesn't feel like im down a cylinder.

When I switch locations of the wideband with the same ecu o2 sensor now in the rear bank still with both wires hooked to it goes lean as soon as I fire it up.

The single wire o2 sensors have less then 15 miles on it.

[Travis89Turbo]

Results= Bad News!

Compression test results done on warm engine. Done 3 times and averaged.

#1- 170
#2-171
#3-171
#4-172
#5- 168
#6- 140----- with oil in cylinder 192.

Lesson learned- never boost an na without thicker headgasket. Even under 5 psi!

[pwpanas]

Originally Posted by Travis89Turbo

Results= Bad News!

Compression test results done on warm engine. Done 3 times and averaged.

#1- 170
#2-171
#3-171
#4-172
#5- 168
#6- 140----- with oil in cylinder 192.

Lesson learned- never boost an na without thicker headgasket. Even under 5 psi!

Gosh sorry to hear that.

Y'know, there still might be a problem with the air:fuel tuning too. Since it actually ran great a few times for you, it's tough to explain that if #6 is broken. Maybe with some heavier weight oil and a new oil filter you could keep troubleshooting - just until you get your shortblock swap squared away? Just a thought - maybe a bad one. *shrug*

[warmkop]

I agree with pwpanas still might be a problem with air/fuel.
Is the car smoking.

[Travis89Turbo]

Originally Posted by pwpanas

Gosh sorry to hear that.

Y'know, there still might be a problem with the air:fuel tuning too. Since it actually ran great a few times for you, it's tough to explain that if #6 is broken. Maybe with some heavier weight oil and a new oil filter you could keep troubleshooting - just until you get your shortblock swap squared away? Just a thought - maybe a bad one. *shrug*

Well I have an update for everyone. Unfortunately this problem is not gone, however i do now have proper compression, and a TT headgasket giving me a more boost friendly compression ratio of 9.2-1.

So... the problem still is it runs rich at start up avg. 12.5+/- It will run in that range for a while approx 5 min. Then drop off carzy lean 17+ at times my AEM AF gauge wont even read it. I have only ran the car for few mins at a time and is not off jack stands so im not going to drive it and do damage with the 17 AFR. The time frame in which it starts to bog and miss (when it falls to anything more the 15 AFR) has gone down drastically from when the problem very first started. Im out of options other then swapping parts. Which luckilty have a friend with a 2jzge in his mk2 that is nice enough to let me use his good parts. Im hoping for a bad MAF

I have a friend coming by the house in a couple hrs to let me try his MAF. If that is not the problem what else would you reccomend swapping to try and troubleshoot??

NEW O2 sensors as well.

[interested!]

Hi! , Reading through the history chat , I noticed you mentioned that the spark plugs have been changed , - Question ? - was the engine misfiring before you changed the plugs ,or after ? .
My history , Years ago - my mate changed his spark plugs for new ones only to find he had misfires , I convinced him to put the old ones back in , misfires gone - the NEW plugs were the problem ! , recommend changing the plugs for KNOWN good ones , - just a suggestion! ,sometimes the simplest things cause the most problems , NEVER be convinced that new plugs are blameless .
An old test is to disconnect one plug lead at a time ( at the coil /cap if plugs are hidden ) and run the engine each time and see if there is a noticeable change , thereby highlighting the offending cylinder ( misfire problems ) .

[Travis89Turbo]

Originally Posted by interested!

Hi! , Reading through the history chat , I noticed you mentioned that the spark plugs have been changed , - Question ? - was the engine misfiring before you changed the plugs ,or after ? .
My history , Years ago - my mate changed his spark plugs for new ones only to find he had misfires , I convinced him to put the old ones back in , misfires gone - the NEW plugs were the problem ! , recommend changing the plugs for KNOWN good ones , - just a suggestion! ,sometimes the simplest things cause the most problems , NEVER be convinced that new plugs are blameless .
An old test is to disconnect one plug lead at a time ( at the coil /cap if plugs are hidden ) and run the engine each time and see if there is a noticeable change , thereby highlighting the offending cylinder ( misfire problems ) .

Yes the problem was present before the plug change. I changed them hoping they were the cause with no luck.

I do now have a Map.ecu that has a built in map sensor. I may just throw it on with a base map and hope it goes away. My good ol friend didnt show up yesterday to swap maf

[pwpanas]

Originally Posted by Travis89Turbo

Well I have an update for everyone. Unfortunately this problem is not gone, however i do now have proper compression, and a TT headgasket giving me a more boost friendly compression ratio of 9.2-1.

So... the problem still is it runs rich at start up avg. 12.5+/- It will run in that range for a while approx 5 min. Then drop off carzy lean 17+ at times my AEM AF gauge wont even read it. I have only ran the car for few mins at a time and is not off jack stands so im not going to drive it and do damage with the 17 AFR. The time frame in which it starts to bog and miss (when it falls to anything more the 15 AFR) has gone down drastically from when the problem very first started. Im out of options other then swapping parts. Which luckilty have a friend with a 2jzge in his mk2 that is nice enough to let me use his good parts. Im hoping for a bad MAF

I have a friend coming by the house in a couple hrs to let me try his MAF. If that is not the problem what else would you reccomend swapping to try and troubleshoot??

NEW O2 sensors as well.

1) Thanks for the update - much appreciated!
2) For what it's worth, I wouldn't call 9.2:1 "boost-friendly". Oem 2jz-gte is 8.5:1, and even that is only good for 15psi or so on 93 octane pump gas.
3) Ime, 12.5:1 a/f isn't really all that rich for cold-start. *shrug* However, I agree with you that 17:1 is crazy-lean - I'm guessing that's where your problem is (i.e. not the 12.5:1 on cold-start).
4) If you can obtain some sort of fuel controller to modify the maf signal (eg. APEX'i S-AFC or MAP ECU), you could try richening the fuel curve that way (above idle) - just as a troubleshooting step.
5) Guesses: Test for vacuum leaks. Bad IAC. Dirty injectors. *shrug* - I'll ponder it some more and re-post if I think of anything else. In the meantime, please do keep us updated.

Note: You can pressurize the intake with an air compressor to test for vacuum/boost leaks.

[Travis89Turbo]

Originally Posted by pwpanas

1) Thanks for the update - much appreciated!
2) For what it's worth, I wouldn't call 9.2:1 "boost-friendly". Oem 2jz-gte is 8.5:1, and even that is only good for 15psi or so on 93 octane pump gas.
3) Ime, 12.5:1 a/f isn't really all that rich for cold-start. *shrug* However, I agree with you that 17:1 is crazy-lean - I'm guessing that's where your problem is (i.e. not the 12.5:1 on cold-start).
4) If you can obtain some sort of fuel controller to modify the maf signal (eg. APEX'i S-AFC or MAP ECU), you could try richening the fuel curve that way (above idle) - just as a troubleshooting step.
5) Guesses: Test for vacuum leaks. Bad IAC. Dirty injectors. *shrug* - I'll ponder it some more and re-post if I think of anything else. In the meantime, please do keep us updated.

Note: You can pressurize the intake with an air compressor to test for vacuum/boost leaks.

Okay have a few more updates. And they are not good news.

I pulled off my MAF, Coil, and igniter and tried them on another 2jzge together and individually and it ran great no miss or hesitation at all.

So I got thinkin about the compression again. I do know that the GTE is at 8.5 but there has been gray success running 9.2 on the ge at lower boost levels. I'm only shootig for 350hp with a t70. Anyways. I ran the car for a bit a couple different times to burn any oil from assembly out of he cylinder. Re dis compression test and wouldn't you know. 145 across the board until #6 which is 129. Now I know the compression would go down with the 1.3mm headgasket but everyone else says they are around 170 with the thicker gasket.

What I did to originally repair the compression is pulled the head off. Replaced rings in 6 cylinder all others were 170ish. I also replaced valve seals on all valves. However me not thinking did not pull the valves out to inspect them. I am wondering if I have slightly bent valves possibly?? I am almost to the point of pullin the motor and swapping to another GE. Or would u suggest just a head change? I really don't think its in the bottom end myself. But I am out of ideas.

I do have a map.ecu. But I would much rather get it running properly on factory ecu. Although I may try it. But the compression numbers are depressing. I am picking up a leak down tester to find out where i am loosing my pressure.

I have done the pressure test at 50psi. All checked out okay. I will wire up the map.ecu and try to play with it.

[pwpanas]

Originally Posted by Travis89Turbo

Okay have a few more updates. And they are not good news.

I pulled off my MAF, Coil, and igniter and tried them on another 2jzge together and individually and it ran great no miss or hesitation at all.

So I got thinkin about the compression again. I do know that the GTE is at 8.5 but there has been gray success running 9.2 on the ge at lower boost levels. I'm only shootig for 350hp with a t70. Anyways. I ran the car for a bit a couple different times to burn any oil from assembly out of he cylinder. Re dis compression test and wouldn't you know. 145 across the board until #6 which is 129. Now I know the compression would go down with the 1.3mm headgasket but everyone else says they are around 170 with the thicker gasket.

What I did to originally repair the compression is pulled the head off. Replaced rings in 6 cylinder all others were 170ish. I also replaced valve seals on all valves. However me not thinking did not pull the valves out to inspect them. I am wondering if I have slightly bent valves possibly?? I am almost to the point of pullin the motor and swapping to another GE. Or would u suggest just a head change? I really don't think its in the bottom end myself. But I am out of ideas.

I do have a map.ecu. But I would much rather get it running properly on factory ecu. Although I may try it. But the compression numbers are depressing. I am picking up a leak down tester to find out where i am loosing my pressure.

I have done the pressure test at 50psi. All checked out okay. I will wire up the map.ecu and try to play with it.

I'd assume you didn't notice any cracks in the #6 piston's ring lands (this is common when compression is low). A bent valve is unlikely, unless your previous config was interference? A bent valve on the top side almost never happens with the OHC+bucket config. A leak tester is an excellent next step. Good luck with it, and please keep us informed. If I were to just guess (which I don't like doing), consider replacing your #6 piston (i.e. not the head).