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

[Pin_Head]

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

If it was misfiring, it would set the MIL and show misfire codes. It is not misfiring. That is why replacing all those ignition parts had no effect. Look elsewhere, like the air/fuel mixture.

 

[sledge916]

If it was misfiring, it would set the MIL and show misfire codes. It is not misfiring. That is why replacing all those ignition parts had no effect. Look elsewhere, like the air/fuel mixture.

Like what? Any suggestions?

Thanks
Sethro

 

[sledge916]

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.

I will check the wiring too
Thanks
Sethro

 

[CJF]

Ok, progress report: Installed new spark plugs with no change, new coil and no change, new coil wire to dizzy and no change.

You didn't do the spark plug wires?

 

[sledge916]

You didn't do the spark plug wires?

They are not very old so I left them alone

Sethro

 

[SUMOTOY]

Looking at the old plugs, the only blaring thing that comes forth, is the antiseize compound. Why? NGK plugs (and a lot of others) use a zinc plating on their plugs that requires no Antiseize, it's in a TSB you can find easily. Secondly, A/S compounds alter the actual heat range of a given plug install. Enough to cause stumbling? I doubt it, but remember, 02 sensors will puke on A/S, so the thread sticking into the head can burn off and cause the 02 to fail.

I don't use A/S on plugs at all. If the engine is known to weld them in, use a good zinc coated thread-plug and/or increase the frequency of replacement (ala ford 4 and 8 cylinder engines). The 80 isn't known to be a plug-welder. If galling is your concern, run a chaser down the plug holes before installation.

Misfire codes don't always get registered as a CEL/MIL, OBDII can absolutely misfire without coding, btst many times. If you have a marginal ignitor, a spark leak can happen, with proper ECU 'fire confirmation' signal staying intact. FYI, Toyota coils and ignitors are matched, does the replacement coil have the same PN as the old one?

Do you have the ability to ck 02 values of LTFT and STFT with your OBD reader? If you reset EFI baseline does the hesitation go away or get worse?

Cheers

Scott J
94 FZJ80 Supercharged

 

[sledge916]

Looking at the old plugs, the only blaring thing that comes forth, is the antiseize compound. Why? NGK plugs (and a lot of others) use a zinc plating on their plugs that requires no Antiseize, it's in a TSB you can find easily. Secondly, A/S compounds alter the actual heat range of a given plug install. Enough to cause stumbling? I doubt it, but remember, 02 sensors will puke on A/S, so the thread sticking into the head can burn off and cause the 02 to fail.

I don't use A/S on plugs at all. If the engine is known to weld them in, use a good zinc coated thread-plug and/or increase the frequency of replacement (ala ford 4 and 8 cylinder engines). The 80 isn't known to be a plug-welder. If galling is your concern, run a chaser down the plug holes before installation.

Misfire codes don't always get registered as a CEL/MIL, OBDII can absolutely misfire without coding, btst many times. If you have a marginal ignitor, a spark leak can happen, with proper ECU 'fire confirmation' signal staying intact. FYI, Toyota coils and ignitors are matched, does the replacement coil have the same PN as the old one?

Do you have the ability to ck 02 values of LTFT and STFT with your OBD reader? If you reset EFI baseline does the hesitation go away or get worse?

Cheers

Scott J
94 FZJ80 Supercharged

What is LTFT and STFT ?

No reason for the AS, just old habbit I guess.

The coil had same part # as old one.

My Dad has a SnapOn OBD reader I could check and see if it has those features.

To reset the EFI baseline do I just unhook the batteries right?
Sethro

 

[Pin_Head]

Misfire codes don't always get registered as a CEL/MIL, OBDII can absolutely misfire without coding, btst many times.

That is not my experience. Do this experiment: Remove a spark plug wire and run it and see if you get a MIL and code. I will bet that you will always get a code because OBDII is very good at detecting misfires.

It is more likely a fuel delivery problem, especially since you have replaced nearly everything on the ignition side with no effect. If you rev it when it is parked does it still have the stumble or is it only when it is under load?

 

[sledge916]

That is not my experience. Do this experiment: Remove a spark plug wire and run it and see if you get a MIL and code. I will bet that you will always get a code because OBDII is very good at detecting misfires.

It is more likely a fuel delivery problem, especially since you have replaced nearly everything on the ignition side with no effect. If you rev it when it is parked does it still have the stumble or is it only when it is under load?

only under load, fine in neutral. Fuel pump/sock/relay are only a year old. Fuel filter is new.

Sethro

 

[Pin_Head]

That is consistent with a fuel problem, although ignition problems can be load sensitive as well. Do the fuel system trouble shooting guide in the FSM.

 

[SUMOTOY]

That is not my experience. Do this experiment: Remove a spark plug wire and run it and see if you get a MIL and code. I will bet that you will always get a code because OBDII is very good at detecting misfires.

It is more likely a fuel delivery problem, especially since you have replaced nearly everything on the ignition side with no effect. If you rev it when it is parked does it still have the stumble or is it only when it is under load?

OBDI or II can code, and usually does. However, when spark is blown out or weak, it usually doesn't code, especially with single coil OBDII. The ignitor sends the signal back to the ECU saying it fired the plug, but ECU can't detect whether or not the spark is proper (complete). Later OBDII coil over plug systems are more sensitive to misfire codes, because dwell is assigned to each coil. But I see bad plug fires without misfire codes regularly on turbocharged COP applications I work on.

Bad ignitors can cause spark leak of a coil fire, and cause the coil to fail. Just BTDT replacing a bad with a known good coil. When the problem didn't go away, I did an actual spark check and the spark at the plug was weak (more fires to ground than to electrode). Spark plugs themselves looked fine (BKR6EIX). New cap and rotor, wires ohmed out fine.

I replaced with new hotter copper plugs (Bosch FR7DC+ to do diagnostics), better, but not solved. Put it on a Sun Diagnostic Scope = weak spark on all 6. Replaced ignitor and coil, problem solved. Both bad factory coils BTW, passed the primary and secondary ohm tests. Just today, I put back the BKR6EIX in fact.

The best test for this is to use an older scope type diagnostic tool. It will show spark energy pulses. I personally think this is a weak spark, likely caused by coil, distributor cap, rotor, wires or plugs. Fuel MIL on OBDII will throw a code (especially with SC) faster and more consistently than ignition problems. Once you are out of Long Term Fuel Trim Value, it doesn't matter what caused it, the CEL is on. Because the danger of melting cats is really high. If fuel caused the running problems described, I'd expect Lean Mixture with Knock sensor codes, or rich mixture out of range + white plugs (lean) or fouled plugs (rich) respectively. The pics of the plugs don't show either.

LTFT = Long Term Fuel Trim (Rear 02 sensors)
STFT = Short Term Fuel Trim (Front 02 Sensors)

With the stock FJ80 Coil at 37kv, I would stick to the factory .8mm (.032) gap. Wider gaps make coils work harder.

Cheers and HTH

Scott J
94 FZJ80 Supercharged

 

[SUMOTOY]

Try this before you go any further

I see a 'disc' style gapper in pic #2 of your plugs. IME, those are notoriously inaccurate (I measured .040 on one @ indicated .030), and combined with the .035spec you used, you might be way off on the spark plug gap.

My suggestion is to go to your FLAPS and get a proper 'blade type' gap tool, and put the gap of the plugs down at .028-.030 and see if the stumble diminishes. For spark diagnostics I use NGK/Bosch Coppers of the stock heat range (5NGK = 7Bosch), but for daily-driving running boost, the NGK iridium (80 Supercharged app = BKR6EIX) will give the best performance for a given ignition system. The larger a gap, the more spark energy required to fire those plugs. Up to the limit of the coil, which is not that high on a 80 from the factory.

This test should run you about $5. Ditch the antiseize too.

HTH

Scott J
94 FZJ80 Supercharged - NGK iridiums

 

[sledge916]

I see a 'disc' style gapper in pic #2 of your plugs. IME, those are notoriously inaccurate (I measured .040 on one @ indicated .030), and combined with the .035spec you used, you might be way off on the spark plug gap.

My suggestion is to go to your FLAPS and get a proper 'blade type' gap tool, and put the gap of the plugs down at .028-.030 and see if the stumble diminishes. For spark diagnostics I use NGK/Bosch Coppers of the stock heat range (5NGK = 7Bosch), but for daily-driving running boost, the NGK iridium (80 Supercharged app = BKR6EIX) will give the best performance for a given ignition system. The larger a gap, the more spark energy required to fire those plugs. Up to the limit of the coil, which is not that high on a 80 from the factory.

This test should run you about $5. Ditch the antiseize too.

HTH

Scott J
94 FZJ80 Supercharged - NGK iridiums

thats some good pointers, I will check that disk gapper for accuracy or just buy a new one.

Thanks
Seth

 

[sledge916]

Problem solved

I have a Land Tank MAF on my truck with a #22204-21010 Toyota Denso sensor . So I swapped this out with a known to be good stock Toyota MAF sensor and rewired the plug to match and presto, runs perfect.

Who would have thought ???

Sethro

 

[Grench]

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

I think you may be getting chased down the wrong path.

If it were one or more poorly gaped plugs it would run rough at low RPM and get -better- at higher RPM - not limit the RPM like that.

IMHO you're more likely looking at either a disconnected vacuum line OR a bad O2 sensor OR much more likely, a clogged catalytic converter.

Watch out. If the catalytic converter is clogged you can wind up doing funky things to your EGR system.
https://forum.ih8mud.com/80-series-tech/245912-near-rth-vacuum-modulator-meltdown.html

Essentially if your cat/exhaust is clogged it acts like a restriction plate on the back end of your engine. When my cats were clogged I could get up to 75mph, but it took a long time. My gas mileage dropped to 4-6mpg too.

Has your catalytic converter ever been changed?

It's what prompted me to do a 3" over the frame rail custom stainless exhaust from new Y pipes all the way back. At $850 + muffler (I bought my own Stainlessworks one) it was considerably less expensive than a new Bosal unit - let alone the cost of a new Toyota one.

IMHO - YMMV

 

[sledge916]

Problem solved see post #34

Thanks all for the help, it good to replace some of the stuff I did anyway as good PM

Thanks
Sethro

 

[Grench]

I have a Land Tank MAF on my truck with a #22204-21010 Toyota Denso sensor . So I swapped this out with a known to be good stock Toyota MAF sensor and rewired the plug to match and presto, runs perfect.

Who would have thought ???

Sethro

Good to hear you got it sorted!

 

[clownmidget]

Did you know the history of the MAF sensor #22204-21010 Toyota Denso sensor.

 

[Pin_Head]

I have a Land Tank MAF on my truck with a #22204-21010 Toyota Denso sensor . So I swapped this out with a known to be good stock Toyota MAF sensor and rewired the plug to match and presto, runs perfect.

Who would have thought ???

Sethro

Me. See post #21.

 

[sledge916]

Me. See post #21.

your good, very good

Sethro