Causes of over fueling/running rich

I recently fitted a 1jz engine in the supra and thought everything was fine but have recently noticed the strong smell of petrol, I have no leaks but when starting from cold you can actually see petrol (like mist) from the exhaust and it smells very strong, I have the second N/A cat in place (not for long though) exhaust wise and I have also noticed the bumper above the exhaust is getting "sooty". I have searched on here and tomorrow I will be fitting a new ECU temp sensor and then resetting the ECU but something I read made me check my oil and it also smells strongly of petrol, any ideas on what could be causing this?

Vac pipes? Mine came off once raising the revs slightly but the smell of petrol was everywhere and it was running rich.

If the oil has suffered fuel contamination it must be crazy rich. Check the injector duty cycle and compare with a known good similar engine. The map itself, the mass air pressure sensor, the throttle pot and the water temp sensor for the ecu are the dominant signals and sensors in how the engine instructs the injector duty time. If the duty time is sensible suspect leaking or otherwise malfunctioning injectors, or very excessive fuel rail pressure, perhaps due to a faulty or incorrectly plumbed fuel pressure regulator. If it's none stock, and not a Bosch one, be very wary of its operation. HTH.

If the oil has suffered fuel contamination it must be crazy rich. Check the injector duty cycle and compare with a known good similar engine. The map itself, the mass air pressure sensor, the throttle pot and the water temp sensor for the ecu are the dominant signals and sensors in how the engine instructs the injector duty time. If the duty time is sensible suspect leaking or otherwise malfunctioning injectors, or very excessive fuel rail pressure, perhaps due to a faulty or incorrectly plumbed fuel pressure regulator. If it's none stock, and not a Bosch one, be very wary of its operation. HTH.

Thanks for your reply Chris but a lot of what you've written I don't understand I know that the FPR is stock but checking the correct function of the other parts is, at this time, beyond me.

What sort of pressure should a fuel pressure regulator be seeing and can an aftermarket one be set to that pressure? I'm not sure how these work exactly (pressure wise).

And while I'm here asking silly questions ....what on earth does WOT mean?

Whats the set up, stock 1J, stock turbos, fuelling etc?

Yes mate, all stock.

Whats the set up, stock 1J, stock turbos, fuelling etc?

if its all stock, the Lambda Probe could be goosed, that would cause a massive overfuel if the car has no idea how much fuel its using? Also a dirty maf? Easily sorted with a spray of brake cleaner round the element in the maf, obvious one is boost leak especially if it is on a MAF, and all stock, intercoooler may have had it and be cracked in a non obvious way. Could benefit from a pressure test, I like to use tuna tins for IC pipework block offs

if its all stock, the Lambda Probe could be goosed, that would cause a massive overfuel if the car has no idea how much fuel its using? Also a dirty maf? Easily sorted with a spray of brake cleaner round the element in the maf, obvious one is boost leak especially if it is on a MAF, and all stock, intercoooler may have had it and be cracked in a non obvious way. Could benefit from a pressure test, I like to use tuna tins for IC pipework block offs

More stuff to check .......I wish I hadn't just bought shocks, springs and exhaust, not sure where to start now. I have just replaced the ECU temp sensor and reset the ECU and (I know its not a proper test but) all the injectors sound as though they're functioning correctly. I need cheap ways of diagnosing the possible problems, I wonder if I should start by replacing the FPR with a new adjustable aftermarket one .....

It won't be the O2 sensor, even if none working it won't go that rich, it just runs off a safe default map. Don't just buy bits willy nilly. Spend the money with a pro who can check things more scientifically.

Does it give any fault codes for a start?

If it's overfuelling to the point of contaminating the oil I'd have thought it runs rough with low RPMs on starting and idle as well?

O2 sensor only comes in once it's warmed up some, so prob not that. One leaky injector would probably knock it down to 5 cylinders. Multiple leaky injectors? Not so plausible.

The wrong duty cycle on a stock system would really only be affected by the coolant temp sensor circuit being dodgy and convincing the ECU it's -20degC outside. That'd be my go-to check. Second guess would be the fuel return might be blocked causing excessive fuel rail pressure. Third was a report once of the starter signal to the ECU being on constantly so it put in cranking fuel enrichment as well, but that's way out there as a theory.

Checking the fuel rail pressure and the injector duty cycle is really the first thing to do. One of them will be wrong and that'll dictate your next diagnostic step.

It won't be the O2 sensor, even if none working it won't go that rich, it just runs off a safe default map. Don't just buy bits willy nilly. Spend the money with a pro who can check things more scientifically.

Does it give any fault codes for a start?

Not looked for any, does the paperclip thingy work the same on the 1j as the 2j? never done that before so will have a look for the "how to".

P.S. I now don't have any money to spend on a pro ......

If it's overfuelling to the point of contaminating the oil I'd have thought it runs rough with low RPMs on starting and idle as well?

 

O2 sensor only comes in once it's warmed up some, so prob not that. One leaky injector would probably knock it down to 5 cylinders. Multiple leaky injectors? Not so plausible.

 

The wrong duty cycle on a stock system would really only be affected by the coolant temp sensor circuit being dodgy and convincing the ECU it's -20degC outside. That'd be my go-to check. Second guess would be the fuel return might be blocked causing excessive fuel rail pressure. Third was a report once of the starter signal to the ECU being on constantly so it put in cranking fuel enrichment as well, but that's way out there as a theory.

 

Checking the fuel rail pressure and the injector duty cycle is really the first thing to do. One of them will be wrong and that'll dictate your next diagnostic step.

It ticks over fine and runs fine too, no miss firing whatsoever. Have replaced both the dash temp and the ECU temp sensors for new and when the ECU coolant sensor is unplugged the engine management light stays on which tells me that the circuit is good? The fuel return pipe had to be lengthened when I fitted the engine as it was slightly short but I used an 8" piece of air con metal tubing as a sleeve as it fitted perfectly and is certainly not interfering with the flow.

How exactly do I check the fuel rail pressure and duty cycle and what "figures" do I compare them to?

Have you done dozens of cold starts , never letting the engine get to temp ( not unusual if playing around fitting things / testing/ chasing leaks/ ) hence fuel in oil ?

What mpg are you getting? 28-30 O2 sensor is ok ,18-20 O2 is fubar (car still runs well) - adds to over fuel problem

Check hose lines and correct routing - lots of them!

Try another map sensor ( there is no MAF) they can vary quite a lot - used one is ok

Have you done dozens of cold starts , never letting the engine get to temp ( not unusual if playing around fitting things / testing/ chasing leaks/ ) hence fuel in oil ?

What mpg are you getting? 28-30 O2 sensor is ok ,18-20 O2 is fubar (car still runs well) - adds to over fuel problem

Check hose lines and correct routing - lots of them!

Try another map sensor ( there is no MAF) they can vary quite a lot - used one is ok

Hey Adam,

Only regular cold starts are every morning for work, mpg is probably in between those two but still slightly better than when it was N/A, had a bloody good look today for anything obvious like hoses and vac lines but looks ok, did disconnect the map to see what it would do and it just started missing but fine again now reconnected (running wise).....don't want to drop the oil and put fresh in if it's going to ruin that too but I know it needs it :-(

Be careful of borewash, oil contamination from overfueling removing the oil film on the cylinder wall, causing accelerated piston ring / cylinder bore wear.

Be careful of borewash, oil contamination from overfueling removing the oil film on the cylinder wall, causing accelerated piston ring / cylinder bore wear.

I hear ya

Check pin 13 on ecu - black wire , should be 12v only during cranking .

Have you messed around with the looms ? What's NA and what's 1jz loom wise ?

Check pin 13 on ecu - black wire , should be 12v only during cranking .

Have you messed around with the looms ? What's NA and what's 1jz loom wise ?

Hey mate,

Engine loom is 1jz, ecu plugs untouched, 1jz engine loom plugs= grey 14pin, white 25pin, white 12pin, grey 17pin and orange 23pin all reduced and connected to Supra plugs= orange 38pin, grey 20pin and white 16pin. ECU is 1jz obviously and body loom is N/A.

Only thing noticeable that is not working correctly is the dash temp gauge ....and the overfuelling of course.

Fresh oil added today to maintain correct lubrication.

The engine was originally paired with the soarer dash - this is a digital dash and totally different to the supra one , the self test diagnosis is similar but the soarer displays in alpha numerical display and you step through the various systems , suspension, gear box , abs , efi and so on using a button on the dash - it shows OK or NG (no good ) and a code .

The supra flashes the red light and you count .

You will get neither .

The car starts / runs so looms must be pretty close for compatibility , but there only needs to be one wire that isn't compatible and it will cause you issues - something like a stray 12v on the cranking input to the ECU , maybe a difference in the park/ neutral switch wiring

so what was the problem? My stock 1jz non vvti manual harness and motor, auto ecu with fmic, walbro 255 runs stupid rich always and has a surging idle once the car is warmed up

ive tried different injectors, O2, water temp sensor, fpr, coils,map and its on its like 5th set of plugs. no vaccum leaks. ohm tested my 5v circuit, recalibrated my tps 10x. cleaned iacv and air intake sensor. im lost

It sorted itself out .....I did change both the coolant sensors (the one for the dash and the one for the ECU) I had also been running it with the timing out (not purposely) and the engine had been stood for 4 years prior to me fitting it but after changing the oil and driving some decent distances it was fine. I do think the ECU coolant sensor had something to do with it.