92 940 turbo running rich, tried everything

[HELLOW]

I have a 92 940 turbo engine shaped into a LH2.4 240. Ive been trying to fix a running rich issue ever since doing the swap, i'm about ready to light this car on fire.

Wideband reads 14 on idle but when giving gas in any gear AFRs quickly drop to 8.5, the car makes no power and starts running rough. If you don't use the gas at all the car will drive and cruse at normal AFRs

Ive tried: new 02 sensor, 3 different junkyard MAFs, new coolant temp sensor, new knock sensor, new intake hose, new timing belt, spark plugs gapped at 0.028, checked to make sure FPR isn't leaking gas.

Im really pretty sure there are no vacuum leaks (unless the intercooler is leaking, I haven't done smoke test) and that the intake hose isn't collapsing. The boost gauge reads ~7psi when attempting to accelerate. Im using the 13c turbo with boost controller all the way turned down.

Timing at idle measured with timing light reads 12 but when revving in neutral jumps around 20, not sure if that is supposed to happen...

Video of the condition: https://vimeo.com/723906332

Please I need more ideas, next thing I was gonna try is new ECUs.

[bobxyz]

Are you running turbo injectors (and resistor pack) with a non-turbo ECU? What are the Bosch part numbers on your injectors, ECU, EZK?

Normal behavior is idle timing of 12deg, and jumping up to something with more power as soon as you start to rev it.

[HELLOW]

Im running the white top injectors with same impedance so no resistor pack. The ECU are from a turbo car the numbers are :0 280 000 560 and EZk: 0227400214.

[bobxyz]

OK, the white tops are a little bit bigger than original turbo injectors, but no where close to 8.5 AFRs. Something's dumping fuel into the engine off idle to get to the 8.5 AFRs. Air leaks, crud'd up MAF and misfire would all read as lean AFRs. Bad temperature, reading way colder than actual, could cause excess fueling.

I'd try pulling the fuel rail, with injectors still connected, and wrapping a baggie around each injector and then turn it on to prime, but don't try to start, and see if an injector keeps spraying. Do you have a cold start injector?

You could also swap back to the original injectors/ECU/EZK and see if it runs OK. The 13c isn't a big turbo so you should be OK if you don't romp on it -- keep an eye on the AFRs if you do since the NA setup may run out of fuel at max 13c boost.

Edit: It could also be a failing FPR. If you have the late-style fuel rail, there's schrader valve on the bottom that makes it easier to hook up a fuel pressure gauge to check. Otherwise, you need to splice into the fuel line, at which point it might be easier to swap back to the original rail.

[HELLOW]

OK so I tried swapping just the naturally aspirated fuel computer in keeping the white top injectors and turbo EZk and it actually runs significantly better at WOT (around 11 AFR) with this ECU. One weird thing was that with the turbo ECU, when you would start it up cold the AFRs would be at 16-17 then once it warmed up they would drop down to 14. With the NA ECU they start at 11 on cold start and go up to 14 like they are supposed to. Im thinking I somehow just got a broken turbo ECU.

[2manyturbos]

Originally Posted by HELLOW

OK so I tried swapping just the naturally aspirated fuel computer in keeping the white top injectors and turbo EZk and it actually runs significantly better at WOT (around 11 AFR) with this ECU. One weird thing was that with the turbo ECU, when you would start it up cold the AFRs would be at 16-17 then once it warmed up they would drop down to 14. With the NA ECU they start at 11 on cold start and go up to 14 like they are supposed to. Im thinking I somehow just got a broken turbo ECU.

Bingo, I was going to suggest exactly that this morning. The 560 ECU is notorious for failure. Don't bother with any of the 5XX ECUs. Get a 937, 939, 954 or 967 ECU. They have faster processors and are much more reliable than the 5XX ECUs.

[HELLOW]

I got a 937 ecu from a junkyard, $100. Installed it and it behaves the exact same as the other turbo ECU :(.

[dl242gt]

I know you posted that you replaced the coolant temp sensor. But you need to verify the wiring at the ecu connector. It's a dual sensor and you can measure the resistance of each circuit on the connectors on each computer. Because too high a resistance tells the computer that the engine is cold and that overrides closed loop operation. this keeps the engine mixture rich all the time.

Make sure you measure the sensor resistance with a cold engine, slightly warm, and fully warmed up engine.

[Mr. V]

Did you over-tighten the knock sensor?

It shouldn't be snug: about seven or so foot-pounds is correct torque.

If the torque is not correct it can cause the compuer to misadjust the ignition timing, resulting in poor engine performance.

[HELLOW]

I tested the voltages of the ECT by probing the connections on the inside of the ECU. Engine cold: 2v. Engine fully warmed up: 0.4v. This seems to be in spec.

I didn't use a torque wrench to tighten the knock sensor I might try renting one from auto zone. I don't think it being a few ftlbs off the spec would cause the computer to dump as much fuel as it is but its worth a shot

[OttoB]

Fuel pressure.

To measure FP I use this kind of t-fitting
Parker EL08LOMD

It is L8 Ernesto style din 24 fitting. Not actually same as Volvo ball fitting, so use only for testing.

[HELLOW]

I tested fuel pressure a few months ago and it did test a few PSI higher than spec but I wrote it off as the gauge being inaccurate. Is there anything other than the FPR that would cause higher than normal fuel pressure? Ive tried disconnecting the vacuum line on the FPR and plugging the hole on the intake side to see if the FPR is causing the rich condition, but it ran the exact same.

[dl242gt]

As the internal diaphragm in the regulator gets old. It can raise base pressure. That causes a rich engine that can get to the point where it's stalling and won't start warm. So, if fuel spec is too high that's a bad regulator. Even if there is no gas leaking from the vacuum fitting.

[bobxyz]

Originally Posted by HELLOW

OK so I tried swapping just the naturally aspirated fuel computer in keeping the white top injectors and turbo EZk and it actually runs significantly better at WOT (around 11 AFR) with this ECU. One weird thing was that with the turbo ECU, when you would start it up cold the AFRs would be at 16-17 then once it warmed up they would drop down to 14. With the NA ECU they start at 11 on cold start and go up to 14 like they are supposed to. Im thinking I somehow just got a broken turbo ECU.

I don't understand this behavior. Normally, a NA ECU with Turbo, or other higher flow, injectors would run much richer than a Turbo ECU. The NA ECU is expecting ~20lbs/hr injectors versus the ~30+lbs/hr Turbo injectors. If the NA ECU turns on the injectors for an hour (cumulative) you'll get ~20lbs of fuel with NA injectors and ~30lbs of fuel with Turbo injectors.

Originally Posted by HELLOW

I got a 937 ecu from a junkyard, $100. Installed it and it behaves the exact same as the other turbo ECU :(.

Originally Posted by Mr. V

Did you over-tighten the knock sensor?

That's an interesting question! If the EZK detects prolonged knock, it sends a signal to the ECU to enrichen the mixture to try to prevent the knock. You should be able to disconnect the knock sensor and run it at idle to see if the AFRs change. If you go over ~3K rpm, the lack of knock sensor will cause a CEL and may cause it to stick rich. Have you tried pulling the diag codes after running for a while?

Originally Posted by HELLOW

I tested the voltages of the ECT by probing the connections on the inside of the ECU. Engine cold: 2v. Engine fully warmed up: 0.4v. This seems to be in spec.

2v is ~75degF and 0.4v is ~195degF, so this seems OK.

Originally Posted by HELLOW

I tested fuel pressure a few months ago and it did test a few PSI higher than spec but I wrote it off as the gauge being inaccurate. Is there anything other than the FPR that would cause higher than normal fuel pressure? Ive tried disconnecting the vacuum line on the FPR and plugging the hole on the intake side to see if the FPR is causing the rich condition, but it ran the exact same.

If disconnecting the hose didn't change the AFRs, then the FPR isn't working. The FPR should adjust the fuel pressure to be 3bar / 45psi above the manifold pressure. If you're at idle with a ~20in-Hg vacuum, that's the same as -10psi, so the fuel pressure should be ~35psi. If you have a handheld vacuum pump, or a syringe, you can connect it to the FPR hose and pull a vacuum at idle. The AFRs and fuel pressure should change as you pull more vacuum.

[OttoB]

I have replaced fpr about five times on my LH cars in past 10 years. First I sourced used ones, but latest has been BeckArnley from Rockauto. Works fine, getting 25 mpg easily and no starting issues any more

[dl242gt]

I'm thinking the alcohol in the gas may harden the internal diaphragm faster than pure benzine flowing by.