Fuel cut = check engine light? 1jz break up at 4500 rpm

[scottiedawg66]

Here is some info on my car
1jz
pt 61 turbo @ 9psi
crower 272 small core cams
550cc injectors
MKIV fuel pump
safcII
New copper NGKs gaped @ .024
AEM wideband with brand new sensor
No codes when jumpered.

The problem is a break up @ 4500 rpm. Which is right when I need to start adding serious fuel (+28% on SAFC compaired to + 8% at 4000 rpm)

Here are my questions

1. Does + 28% @ 4500 rpm seem like its adding an abnormal amount of fuel based on the larger 550 injectors?
2. Does fuel cut cause the CEL to come on?
3. Would a boost leak cause fuel cut given the 1j runs on a map sensor? My intuition says no?
4. My car idles @ about -12 HG. I figured this was due to the cams? can anyone else with 272s comment on that?


At this point I am thinking coil packs or ECU if it is not fuel cut. Hard to believe I would need to add + 28% fuel with 550s at 9 psi. But I suppose the cams and turbo could be that much more efficient at moving air than stock turbos and cams...

 

[IBoughtASupra]

Do you have the fuel dampener removed? It is on the feed line to the rail.

 

[scottiedawg66]

I believe that I do. But0c can you describe it?

 

[IBoughtASupra]

Look like a mushroom on the feed line that screws into the block.

I would say it could be the coils but if you say the car runs leaner in one spot than it does up top in the high RPM, I would look at the ECU since they are know to have a lean spot but that is usually around 3000-3500 RPM.

 

[scottiedawg66]

EDIT ** fuel dampener is on my car and it will not rev past 4500 in boost. at less than WOT it will rev high. AF does not get over 12:1 in boost

 

[IBoughtASupra]

Probably the ECU. When you check for code, what do you get?

Click the link on my signature about the JZ swap and you will have a list of codes and how to check them if you are not familiar on how to do that.

 

[scottiedawg66]

When I jumper in the diag. box the CEL just blinks with no pauses, I believe that means there are no codes.

After doing some searching it seems like the CEL would come on if I was hitting fuel cut, so I can rule that out.


I would really like to hear some other people chime in with their SAFC setting on the 550s so I can determine if I am having a fuel issue.

 

[te72]

When I jumper in the diag. box the CEL just blinks with no pauses, I believe that means there are no codes.

After doing some searching it seems like the CEL would come on if I was hitting fuel cut, so I can rule that out.

You are correct on the constant blinking meaning that there are no codes... that are stored. Fuel cut in my experience only causes a brief CEL, but it doesn't stay stored.


2. Does fuel cut cause the CEL to come on?
Yes, but only briefly.

4. My car idles @ about -12 HG. I figured this was due to the cams? can anyone else with 272s comment on that?
About normal, altitude also affects it. I have about the same in/hg measurement at idle on mine, but I'm on 264's, and at ~6500' elevation.

 

[scottiedawg66]

You are correct on the constant blinking meaning that there are no codes... that are stored. Fuel cut in my experience only causes a brief CEL, but it doesn't stay stored.


2. Does fuel cut cause the CEL to come on?
Yes, but only briefly.

4. My car idles @ about -12 HG. I figured this was due to the cams? can anyone else with 272s comment on that?
About normal, altitude also affects it. I have about the same in/hg measurement at idle on mine, but I'm on 264's, and at ~6500' elevation.

thank you!!! I was looking for the CEL when I was having the issue and it was not showing up. so I think its safe to say fuel cut is out.


can anyone on 550s and SAFC II comment on their fuel adjustments?

I am going to test coil packs this weekend with a known good set. If that fails to solve the issue then I'll make the trip to test the ecu and probably end up with the 1jz AEM V2 from Drift Motion.

Can anyone comment on the AEM V2 for the 1j that aaron sells? It seems to be a more simple version of AEM in regards to the available injector and plug mapping (6 vs 12 available inputs / outputs for plugs and injectors. last time I checked my surpa was not a 12 cyl!)

 

[JPsToyota]

Your fuel adjustment is way too high. I have to make negative adjustments at 18+ psi on a larger turbo with a Walbro 255 and 550ccs at 36-ish base pressure. I believe you need to check your base fuel pressure, do you have an adjustable regulator? You have some kind of fuel issue.

What are your AFRs when the cut happens? The car will also break up if you put too much fuel in it, under 10.0:1-ish AFR will break up in high RPM on my car.

You have to be careful with the SAFC and making large corrections, you should be (IMO) near 0% at WOT, as I'm pretty sure you are screwing with the ECUs timing and fueling maps A LOT with a 30% correction.

 

[scottiedawg66]

Your fuel adjustment is way too high. I have to make negative adjustments at 18+ psi on a larger turbo with a Walbro 255 and 550ccs at 36-ish base pressure. I believe you need to check your base fuel pressure, do you have an adjustable regulator? You have some kind of fuel issue.

What are your AFRs when the cut happens? The car will also break up if you put too much fuel in it, under 10.0:1-ish AFR will break up in high RPM on my car.

You have to be careful with the SAFC and making large corrections, you should be (IMO) near 0% at WOT, as I'm pretty sure you are screwing with the ECUs timing and fueling maps A LOT with a 30% correction.

thank you for an excellent post.

I have the stock fuel regulator. My only fuel mods are 550s, and MKIV pump. I will look into my base fuel pressure.

My AFs are in the high 11s right before break up. So I think the AF is not the source of my problems, but the fuel map (or lack there of) in the ECU is very suspect at this point.

 

[525gte]

I am running 440s. And a wlbro 255 in tank.. also stil running the fuel dampener.. and stock frp. And a sfac2.. at idle I'm pulling 9percent.. at 4500 pulling 15% and over 5k 18 to 24 percent.. I am adding fuel only one time like 1% at 25oo rpm on the low side.. are u sure that your wide ban is reading corrcetly? If itends up not being a fuel pressure issue maybe look into exhaust leaks pre wb.. I also have 264 cams

 

[scottiedawg66]

i just replaced the sensor in my wideband last week just to be sure it was accurate. It is mounted about a foot from the turbo (not my idea I like them much further away) so the only way an exhaust leak would occur would be at the V band. I just checked the V band, and its solid.

thank you for the commentary on your settings. that is extremely helpful. It seems now I am confident the ECU is bad. I wonder why I have had so many ECU failures?

Looks like I will need to go through my harness and double check that nothing is grounding out / shorting back to the ECU.

I have been away form these forums for years, but I am very glad I came back. Thanks to everyone for the help. Once I get this figured I will update this thread, if anyone else has suggestions I would love to hear them.

 

[525gte]

Could have a small leak at the turbo or even at the head. I coated all my gaskets and bolts with wheel bearing grease as it burns off it will turn to carbon and plug small holes or flange inperfections.. stinks like. Hell for a day or so. But helps out with exhaust leaks

 

[scottiedawg66]

right on I have never thought of that. I think im going to get out the soapy water just to be sure I don't have any exhaust leaks.

 

[te72]

Can anyone comment on the AEM V2 for the 1j that aaron sells? It seems to be a more simple version of AEM in regards to the available injector and plug mapping (6 vs 12 available inputs / outputs for plugs and injectors. last time I checked my surpa was not a 12 cyl!)

Just because your Supra isn't a 12 cylinder doesn't mean they're not out there.

Also, back in the day it wasn't horribly uncommon to run 2 injectors per cylinder for highly tuned motors. Not so much of a big deal with modern injectors though.

 

[mensrea]

You shouldn't be adding fuel with SAFC, your low throttle should be close to 0, ECU/O2 will auto correct. You might have to take lots of fuel away at idle, or it'll run pig rich. Adjust your BFP, I'm running ~23 PSI (BFP, that's with PT6265, not stock twins) and my idle (1k) is ~ -35%, and I still get 13.2-14.0 AFR. My High throttle is all 0% other than 5,6,7,8K (they are - 1 to -3 %), and I get a healthy 11.2 to 11.5 AFR @ 25 PSI.

 

[JPsToyota]

right on I have never thought of that. I think im going to get out the soapy water just to be sure I don't have any exhaust leaks.

How about this, have you re-wired your fuel pump? I dyno'd at 440whp 'maxing out' my Walbro and 550ccs on the stock wiring (My AFPR only goes to about 60-ish PSI max, that's probably about where it was set at).

I rewired it with beefy wire and a new relay (relay is turned on by the stock fuel relay setup) straight from my battery connection to the fuel pump (fused at 25 amps, Walbro should probably never pull more than 20.). I have a ridiculous amount of fuel over my stock wiring now, like I said I have to pull fuel out at 7600RPM at nearly 500whp well under base fuel pressure (which is 42ish I believe).

Your wiring could be especially tired or bad or stuck in that low-voltage mode that I hear about?

 

[scottiedawg66]

i will look into the voltage at the fuel pump I assume it should be ~ 12v?.

I just bought an AT jza70 ecu. hopefully that fixes my issue. I understand all I need to do to get this ecu workign is to jumper the neutral safety start wires?

 

[scottiedawg66]

the ECU did not solve my problems. so i ended up digging through my boxes of supra parts I have collected over the last 10 years and found a map sensor.

plugged it in, and had to totally re do my SAFC settings! this is good news. Went and drove the car end had to take out loads of fuel in the top end. The more fuel I take out the less it would break up. I am going to attempt to street tune the car next week once I have some more time but I am hopeful that my issue is solved. I am going to order up some new connectors for the coil packs since mine are all shot.