Breaking up around 3000rpm

[GotTurbos?]

A new problem popped up with the car now that I have my ecu fixed, it kind of did this before but I just attributed it to the ecu and figured once I got that fixed it would go away. I read a thread by another person that seemed to be having the exact same problem as me, but I can't find it by searching for the life of me.

When driving, if I get up to the 3000rpm range, it will break up really really bad, wideband is showing it going lean, but if I just stay on the throttle it will slowly accelerate and around 300rpm later I will be smooth sailing.

Any ideas?

Jon

 

[aphxero]

try o2. What's plug gap?

 

[GotTurbos?]

o2 sensor is a known good mustang sensor off of a friends car. Gap is a .025. My fuel pressure is at 38psi, I'm going to try raising it up to 43 and see what that does.

 

[suprahero]

Make sure and check your coil packs for cracks also. You can wrap them in electrical tape, or shrink wrap to help eliminate small cracks.

 

[Satan]

...I still have the sputter and was finally able to get a code... 14.

Swapped the ignitor and still the same. I checked the 1st 3 coilpacks, according to page EG-522 of the '95 TRSM and while hot ~200F, am getting 1.3 to 1.5 resistance.

Supposed to be between .68 to .98

Would love to borrow a set of known-good ones to rule them out for sure. Sounded like you did already swap yours though, right?

 

[GotTurbos?]

Well I did swap the coil packs, but my 2jz ones aren't in known good condition either. However... if I'm understanding it correctly, a faulty coilpack would leave unburned fuel, which would give me a rich reading on my wideband right? It is showing lean.

Jon

 

[91T breezen']

My car is(was) doing this also! I too, swapped out the ecu, and it still broke up, almost the same rpm as yours, (2700-3200ish) I've had some issues with wiring on my old school Tomei wb, so I don't know if it was going lean. I raised the fuel pressure to 42psi today, and it seems to have taken most of the problem away. By weeks end, the wb should be operational, and I will also have the fcd, and Safc II hooked up. Real tuning should be just around the corner.:x:

 

[Satan]

Well I did swap the coil packs, but my 2jz ones aren't in known good condition either. However... if I'm understanding it correctly, a faulty coilpack would leave unburned fuel, which would give me a rich reading on my wideband right? It is showing lean.

Jon

All of my plugs showed the goop of running rich. Will mess with it some more this evening.

 

[Andre]

I had the same problem with my 1.5 JZ

swapped ecu did not solve the problem

I change plugs
O2 sensor
Fuel presure at 43 psi
Ciol packs

Strange is that some people get it at the same rpm range

My was also at 2700 to 3000 RPM the car jus go lean without any load on the engine

After that rpm range is goes to 14.7 back (cruisen)

I thinks that is the spot from close loop to open loop (somebody correct me iff i wrong)

In that rpm range i ad more fuel like 30 % in the greddy emanage map so the car wil run fine at 14.7 also is that rpm range

With data loging i could see were i am runing lean so at that spot i ad more fuel

Strange is i get NO erros codes

BTW i am using an MINES ecu and runing 550 CC

There are now a few peoples with the same problem so it must be something

What i want to do next is plug my ecu in somebody else car to see iff that car aslo go lean at that rpm range

 

[sctwinturbo]

i have the same problem
(i change back to the stock injectors to try to fix the problem)
when i am at idle and rev it runs fine but when i drive it 3000rpm it breaks up and then at 4000rpm it run's strong all the way up to 8500
i increased the fuel pressure and it got worst when driving but at idle still runs fine ????
i am running 36psi fuel pressure am i running to low ????

also did any of you guys check to see if you had aftermarket cam gears (i did and returned it back to 0) (now i wonder if i have after market cams)

 

[Bigzavs]

we took his car out yesterday, like he said it goes full lean at 3K, then pulls out of it back to normal. we boosted it and once in boost (albeit he was untuned) hed go 10.0 and it would completely cut on him, at 6300rpms, i went into his afc and pulled 15% fuel out from 4K-7K but we werent able to test it, as he needs an alignment something fierce and it was wet outside and we went sideways gettin on it in third.

after he drives it today hell post up how its doing with that little bit of fuel work.

o and we found out that his timing was off, we readjusted the tps sensor to where the timing was correct according to how BigAaron said to set it

 

[GotTurbos?]

Alright guys, turning up the fuel pressure up to 42psi seemed to do the trick. It still wants to go lean around the area but I added 20% fuel from 2500-3500 and it keeps everything in check and drives normal. Also by taking out 15% up top I was able to keep it from drowning itself in fuel, I'm still 10:1 afr but I hit 7300rpm Haha yes ben, sideways in 3rd is no fun!


Jon

 

[Satan]

I am using US cams w/JDM gears.... Did not think it'd be an issue since it seems that's been done many times before. Should we find some US cam gears and see if there are any differences?

 

[Bigzavs]

i dont believe the cam gears are different between the 1JZ, JDM 2JZ, or the USDM 2JZ. with the timing, you have to use a timing light and adjust the TPS on the throttle body

 

[YotaRob]

Has anybody gotten an ociliscope out the checked signals when this happens? I wonder if the crank sensor signal (N E) is being lost due to harmonics like a faulty crank pully or in the harness somewhere its not shielded. Just my 2¢.

 

[GotTurbos?]

This is still bothering me a tad, I just don't feel right adding 30-35% fuel for 1 small rpm range, that effects my whole map in the 2500-3500 range, which is pretty much the only range I end up cruising in on the freeway. I'd like to figure out what is causing this as I know on a friends car with an almost identical setup it doesn't have the same problem.

 

[YotaRob]

When I stretched my harness, I noticed that the cam and crank sensor wires were twisted for noise reduction. I did the same with my extensions and I have not had this happen to me.

 

[Bigzavs]

When I stretched my harness, I noticed that the cam and crank sensor wires were twisted for noise reduction. I did the same with my extensions and I have not had this happen to me.

his harness isnt stretched tho, its routed through the firewall, repinned and all

 

[Satan]

I did undo mine when removing all of the unecessary wiring/connections. I did "twist" it back up to make it slimmer. May not have put in the right number of twists (like you would measure with twisted pair, etc).

 

[tissimo]

obd1 lean spot maybe?

obd1 2jz ecus run mid 14 a/f till ~4k then switch to an open loop mode. Maybe your low rpm closed loop tune is sooooo far out that the ecu is running an extreme negative fuel trim trying to get the tune correct then in that range, its tooo lean and misses?