96 FZJ80 missing at Bad at 2800-3500 RPM full throttle

[sledge916]

Hello all

I have a 96 LC and it has a super charger on it I installed last winter along with a new head gasket and fully refurbished head, fuel pump with sock and fuel pump relay with pressure regulator, injectors cleaned and balanced. I just put a fuel filter on it 5 days ago.
All has been fine until the last couple of weeks. Starts and purrs like a kitten, if you gently roll on the throttle it runs most of the time just fine even at the 2800 RPM, but if you stand on it full throttle it really craps out at 2800-3900 super bad, feels like 2 or more cylinders are just not firing or to rich to lean, something. Really shakes the whole truck bad.
Put a fuel pressure gauge on it and all is good.

EGR wire harness was wraped very good when we had the head off also.

Also ran several bottles of heat through the tank.

Anyone got any ideas??

The spark plugs were installed last winter with super charger, wires are not very old at all either.

Thanks
Sethro

 

[Wheelingnoob]

Any post MAF air leaks?

I would also check the plugs even though they are only a year old its something worth checking. Did you run the cooler plugs?

On my Supra before I went COP I would foul plugs every few weeks at it felt much the same as what you are describing.

 

[herbsfj80]

replace your 02 sensor even if it's not throwing any code. i had the same problem on my 96 s/c. mine stumbles or miss only on WOT

 

[sledge916]

replace your 02 sensor even if it's not throwing any code. i had the same problem on my 96 s/c. mine stumbles or miss only on WOT

so what was yours doing exactly? Was it as RPM specific as mine? Mine stumbles only when you push it all the way to floor fast, seems to be ok some times when you gently push the gas slowly WOT. Did yours do that?

Thanks
Seth

 

[bobm]

I, was having the same issue. I replaced filter sock in tank, fuel filter. Plugs were E3s and only a year old. Everthing helped but still had issues. Did plugs last weekend NGKs problem gone.

Thanks Bob.

 

[sledge916]

I, was having the same issue. I replaced filter sock in tank, fuel filter. Plugs were E3s and only a year old. Everthing helped but still had issues. Did plugs last weekend NGKs problem gone.

Thanks Bob.

Bob

Interesting, what NGK plug did you end up using?

Thanks
Sethro

 

[sledge916]

Any post MAF air leaks?

I would also check the plugs even though they are only a year old its something worth checking. Did you run the cooler plugs?

On my Supra before I went COP I would foul plugs every few weeks at it felt much the same as what you are describing.

Yes I ran the cooler plugs, I will check them out again.

Sethro

 

[bobm]

sledge916, NGK BPR5EY-11, I heard great things about E3s but after chasing this issue for a couple of months. The coughing and sputtering when accelarating (the other things needed to be done anyway.) I figured for a few bucks to do the plugs. And problem solved.

Thanks Bob.

 

[Tools R Us]

What codes?

 

[sledge916]

What codes?

no codes really, every once and a while I get the PO401 code but not very often.

What cha thinking Tools?

Sethro

 

[herbsfj80]

so what was yours doing exactly? Was it as RPM specific as mine? Mine stumbles only when you push it all the way to floor fast, seems to be ok some times when you gently push the gas slowly WOT. Did yours do that?

Thanks
Seth

my fzj stumbles @ wot between 2k-3500p rm but runs smooth after 3500 rpm. but if i step on it gradually it will be fine no stumbles or hesitations. i get no codes or stored codes with obd2

 

[CycloSteve]

I would also check all of the vacuum lines and be sure that the SC bypass valve is working properly (which bypasses when not needed).



Steve

Edit...also check that your PCV system is working correctly. Did you clean the TB and EGR? I am thinking inline with Pin Head that this may very well be a mechanical issue, instead of an electrical one.

 

[Pin_Head]

no codes really,

Probably not actually misfiring then.

 

[sledge916]

I would also check all of the vacuum lines and be sure that the SC bypass valve is working properly (which bypasses when not needed).



Steve

Edit...also check that your PCV system is working correctly. Did you clean the TB and EGR? I am thinking inline with Pin Head that this may very well be a mechanical issue, instead of an electrical one.

Thanks for the tip, I checked them and all is good with the vacuum lines. Cleaned the TB and EGR last winter and have hardly put any miles on it since.

One more odd thing is my gas milage has gotten waaay worse than normal too.

Sethro

 

[sledge916]

my fzj stumbles @ wot between 2k-3500p rm but runs smooth after 3500 rpm. but if i step on it gradually it will be fine no stumbles or hesitations. i get no codes or stored codes with obd2

yup, thats what mine is doing too, installing spark plugs right now and if that don't fix it I will have to try the o2 sensors next

Sethro

 

[pmcbrier]

I have an MR2 turbo that had a similar problem a few years back. For the life of me I could not figure it out. Ended up being a cracked distributor. Not really visible to the naked eye, but when getting on the throttle hard, it would sputter once the revs got above 2500 and run REALLY rich. The crack would widen under heavy load, and cause the engine to misfire and sputter. Replaced it and haven't had the problem again since.
Boost leak somewhere? Not sure on the layout you have. Are you running an external intercooler? Check the piping to and from that. Make sure no boost leaks. Those will also provide stumbles under boost that are not evident at light throttle.

 

[jfz80]

Also might wanna check the IAC and TPS bundles that required extending for the SC install.
About a year after my install the connection on the 6'' harness extension had failed. You could pinch and roll the two bundles heading over the VC to the TB and it would replicate the stumble while idling. Mine was the same, get on it hard and it stumbled, ease into it and it was ok. I think the motor torque was tugging just enought to break connection.

could check the O2's and the knock sensors, both can contribute to poor mileage and performance but both should be throwing a code for you.

 

[sledge916]

Ok, progress report: Installed new spark plugs with no change, new coil and no change, new coil wire to dizzy and no change.
Today I will start checking wiring and look for something there. Still no codes showing.


Sethro

 

[SUMOTOY]

Ok, progress report: Installed new spark plugs with no change, new coil and no change, new coil wire to dizzy and no change.
Today I will start checking wiring and look for something there. Still no codes showing.
Sethro

Gas mileage going down the tubes tends to point at the 02 sensor/s. WOT tables are a calculated values from Closed Loop operation. Without any other symptoms, my initial bet would have been the spark getting blown out. What spark plug did you use and what gap? IME, the 80 coils are good for longevity, but they top at 37kv. This dictates that the NGK reference to xxxxx-11 plugs are not the best. You want the tighter 8mm gap, and the iridium plug will do better at this gap than even the coppers. I use BKR6EIX in my SC rig for the last few years, and it's exactly my plug of choice for Audi turbos running 26psi too. Expensive (Autozone 8ea), but they last forever comparatively speaking.

What did the 'old' plugs look like?

Try pulling a plug and cranking the engine with the plug grounded to make sure you have a strong spark jumping the electrode. Baseline timing setting? Do you have a known-good ignitor to try swapping in?

Cheers

Scott J
94 FZJ80 Supercharged

 

[sledge916]

Gas mileage going down the tubes tends to point at the 02 sensor/s. WOT tables are a calculated values from Closed Loop operation. Without any other symptoms, my initial bet would have been the spark getting blown out. What spark plug did you use and what gap? IME, the 80 coils are good for longevity, but they top at 37kv. This dictates that the NGK reference to xxxxx-11 plugs are not the best. You want the tighter 8mm gap, and the iridium plug will do better at this gap than even the coppers. I use BKR6EIX in my SC rig for the last few years, and it's exactly my plug of choice for Audi turbos running 26psi too. Expensive (Autozone 8ea), but they last forever comparatively speaking.

What did the 'old' plugs look like?

Try pulling a plug and cranking the engine with the plug grounded to make sure you have a strong spark jumping the electrode. Baseline timing setting? Do you have a known-good ignitor to try swapping in?

Cheers

Scott J
94 FZJ80 Supercharged

Scott

Here are photos of the Toyota spark plugs, they sure look rich around the edges for sure. The new ones are Auto Lite # 3923 cheepos purchased just to trouble shoot. The Toyota plugs shown are 1 step cooler. The new Auto Lights are supposed to be one step cooler as well. I set the gap at .035
The timing was set to stock settings when I installed the new head and super charger, I would not think it could have changed but I will have to check that. Have not tried the igniter yet either

Knock sensors were changed last summer with new ones, the O2 sensors might be 2 years old.
Sethro