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Quick recap of the engine
Toyota 4AGE 16 valve DOHC
264 degree cams
Haltech Elite 550 ecu
Denso coil on plugs
Miata 1.8 injectors (tan) 230cc cleaned and bench tested 3000 km ago
BMW TPS

The car was running great. Plugs were tan colored. The only issue was a high rpm misfire (only on the track)
All of a sudden, it started running really rich, struggling to run at part throttle between 1500 and 2500 rpm in first and second gear. Clears up at 3000 rpm and pulls like a freight train.
I am reluctant to remap the fuel until I find out the cause of the problem. Plus, the soot has clogged up the O2 sensor and I don't want to waste money replacing it until the problem is rectified.
The ecu says there are no trigger issues with the cam angle sensor in the distributor or the hall effect sensor on the crank trigger wheel.
fuel pressure is normal. I replaced the fuel filter.
Suggestions????
thanks
Doug

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book 4AGE build, Supra W58 transmission, Corolla GTS live axle

I would start with looking at sensors values (TPS, CLT, MAP and IAT) while its misbehaving and see if one of them is reporting abnormally. I would be especially suspicious of the MAP sensor.

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Peace, Ron

Agreed. I'd start by checking what the ECM thinks the IAT sensor and possibly the MAP sensor reads. It could be bad sensors, or bad wiring. See how long the fuel pressure remains high after shutting off the engine. Possibly a leaking injector?

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Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

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Awesome feedback Ron and Chuck.
TPS works perfectly.
I'm not using a MAP sensor as I am using motorcycle ITBs and they don't give a good enough signal.
The load is purely by the Throttle Position Sensor.
All four cylinders seem to foul the plug the same, so I can't see how four injectors would fail at the same time. I could pull them and get them bench tested anyways, my guy only charges $100.
The intake air sensor reads normal, as does the coolant temp sensor.

The pissoff is that it was running fine, now something is causing it not to. The challenge is to figure out what.

Grrrr

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book 4AGE build, Supra W58 transmission, Corolla GTS live axle

Alpha-N then. Good choice for an ITB NA car. I assume you are using barometric compensation? Has the local barometric pressure changed much since this happened? When you say it ran well before, how long are you talking about? days, months years? Is there any chance the map got corrupted? Have an older version you can try? Can you share a data log? You said fuel pressure is fine, are you checking it real time when this is happening? Vacuum line to FP regulator not leaking/disconnected? For what it's worth I've personally seen an OEM FP regulator stick and be fine one moment and runaway pressure the next, back and forth.

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Peace, Ron

Thanks Ron
I can't say that I know anything about barometric compensation....
The car ran fine for two years. I did reinstall an old map, no difference. I don't have a datalog, (hard to do without a copilot). Datalog won't show my air fuel ratio since the O2 sensor is plugged. I did a testdrive with my computer on the seat. The fuel pressure varies between 40 and 45 psi depending on the load (goes up wlith full throttle). 45 with ignition on and not running. Fuel pressure regulator is connected to my vacuum manifold. Vacuum reads -10" at idle, drops during acceleration, raised to -18" when decellerating. Fuel pump is a fairly new AEM unit, 340 lph.

I think I'm going to pull the fuel injectors today and get them bench tested.
Any other ideas?

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book 4AGE build, Supra W58 transmission, Corolla GTS live axle

-10" at idle sounds pretty low to me. I don't know much about what a highly modified engine would normally run. On a DD, I expect in the range of -17" to -20". Unless you are saying -10" is what you get when things are running right, I'd check for vacuum leaks before pulling the injectors. Maybe a vacuum port plug has gone on vacation?

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Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

Or my Wankel powered Locost log : over HERE

And don't forget my Cushman Truckster resto Locostusa.com/forums/viewtopic.php?f=36&t=17766

Yes, your vacuum seems low, but your cams sounds like they might be pretty aggressive? For reference my Miata engine has a torque peak at almost 5k rpm but still manages to pull 21-22" at idle. What's the possibility of jumped cam timing? That would throw your vacuum and your tune off.

When running Alpha-N the typical arrangement would be to sample the current atmospheric pressure when the key is first switched on and before the engine starts. Knowing the atmospheric pressure and the air temperature, the ECU can compensate for changes in air density reasonably well. Since you've been running well for an extended period that's probably not the issue. Since you're older tune produced the same results I would guess it's something external.

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Peace, Ron

FWIW, my 5.0l Ford 7 starting running very rich 4 years ago while we were in Palm Springs, to the point where the exhaust fumes burn't your eyes.
The culprit was a bad intake manifold temp sensor.

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Perry

'If man built it, man can fix it'
"No one ever told me I couldn't do it."
"If you can't build it safe, don't build it."

Perry's Locost Super Che7enette Build
Perry's TBird Based 5.0L Super 7 L.S.O
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Perry's Final Build the 1929 Mercedes Gazelle

FWIW, my 5.0l Ford 7 starting running very rich 4 years ago while we were in Palm Springs, to the point where the exhaust fumes burn't your eyes.
The culprit was a bad intake manifold temp sensor.

_________________
Perry

'If man built it, man can fix it'
"No one ever told me I couldn't do it."
"If you can't build it safe, don't build it."

Perry's Locost Super Che7enette Build
Perry's TBird Based 5.0L Super 7 L.S.O
Perry's S10 Super 7 The 3rd
Perry's 4th Build The Topolino 500 (Little Mouse) Altered
Perry's 5th Build the Super Slant 6 Super 7
Perry's Final Build the 1929 Mercedes Gazelle

Okay, I got my injectors serviced and bench tested.
They are supposed to be 230cc injectors for a 1.8 litre Miata. When I had them serviced two years ago, they had an average max. flow of 226.5 cc/Minute, perfect. This time they have an average flow of 297.6 cc/minute. That's and increase of over 30%
I'm going to consult the oneline Haltech gurus and see if they are okay with me just doing an overall fuel map correction. I want to make sure that what I do is safe. I don't want to blow up the engine. I also don't want to pay a tuner $1200 to retune it and risk blowing the diff again like the last time.
Do you guys think that I should replace the injectors with ones that are more stable? These ones might continue to have more and more flow.

thanks in advance!

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book 4AGE build, Supra W58 transmission, Corolla GTS live axle

Thanks for getting back with that interesting tidbit. 30% is quite a lot - I’m skeptical they are OEM injectors. I wouldn’t recommend re-scaling without exercising your diligence and verifying with a wide-band or dyno. It’s not a risk worth taking over a relatively inexpensive tool that will likely come in handy again in the future. If you’re budgeting new injectors have a look at EV14’s.

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Peace, Ron

It’s very odd that all of them are failing in the same manner and by the same amount. I’d almost suspect the testing equipment if it wasn’t for your car’s operation apparently confirming the findings

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Look at the fuel pressure regulator. At idle a stock 4AGE should be around 30-32 psi and max pressure should be about 38 psi. Also check the vacuum line to the FPR and for vacuum leaks. My 4AGE with 264 cam has an idle vacuum around 14, and run slightly rich at idle, with an after-market reg set higher than stock psi for WOT.

His pressure is notably higher than that. Did this happen after installing the new fuel pump? It's possible the larger pump is overwhelming the regulator.

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Peace, Ron