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Running rich at idle

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I'm at a loss as to why this is happening, its been on going for along time and to be honest I'm considering changing ecu's alltogether if I carnt fix this problem.

I've got a wolf v500 ecu in an 80 series Landcruiser running a 2jzgte and the only problem it's got is running rich at idle.

What's happening...starts and runs fine, idles nicely, afr's are starting to come up as engine temp does the same, it reaches operating temp around 80°c and afr is hovering around 14.4 it will idle fine for a around 5 minutes the start to go rich to around 12.2 and increase revs to around 1100. It slowly goes richer from there to about 10.8 to 11.

Initaly I thought it was the sensor getting heat soak in the manifold so I moved the sensor on to the intake pipe after the intercooler.

I've checked all maps and compensation tables, the car runs fine while driving through all gears.

I have a suspicion it could be high air temps but if that's the case then how can I compensate for it when it dosent show up on the compensation table.

Can you log data while this happens? Is there a channel (ie. air temp, water temp, iac position, ignition timing, manifold pressure, battery voltage) that is changing as the mixture goes richer. Is there a compensation table for that channel? That's what you need to change.

If RPM is the only channel that is changing, perhaps the next highest RPM cell in the fuel table needs to have a little less fuel.

Idle is a tricky balancing act -- for the engine speed to remain steady, the torque produced by combustion must equal the load/drag on the engine. What could cause the idle speed to change over time -- probably not the torque (unless some startup compensation is still active), but most likely the load/drag is being reduced. Perhaps the engine oil heats up causing the viscosity to go down so the load from the oil pump is reduced. Or the alternator initially loaded to recharge the battery from the drain of starting, may complete the charge, and thus it's load is reduced. Do you have a way of monitoring oil temp?

So if it's idling for 5 mins is the ECT/IAT rising? Does it have ECT/IAT based Idle Air Control?

As David stated earlier it's moving into the 1100rpm cell area there must be a reason for it

The reason for the high idle is the over fueling, I'm not running a iacv, the shop/tuner that originaly worked on the car 7 years ago couldn't get it to operate properly, I and other people tried to no avail so I eventually pulled it off. The car operates ok without it.

The main fuel map is all sweet, all zones in the idle area are the same. I have compensation tables for all inputs, water/air temp, battery, ignition, manifold press. There's no werid stuff going on with those.

My next move was to data log, the only thing that won't be included in that is oil pressure, there's no way I can wire in the aem gauge into the ECU it dosent support it.

I'll come back to the forum with a data log and hopefuly a pic or two of the tune but keep the ideas coming.

Could it be the air intake heating up and my air temp compensation table not responding as it should or the air temp sensor calibration needing attention. Just hoping to bounce my ideas off of some more knowledgeable tuners out there.

Is it possible to zero out/ignore all compensation tables just to eliminate that being the problem? So just rely on the main fuel map and see if sustains idle just fine with minimal comp-table inputs? Idk if that makes sense.

New information, I've discovered the engine starts to run rich around 10 seconds before the thermo fans kick in. As the fans go through there temp cycle the idle slowly becomes richer. I've checked and rechecked all compensation tables, tried turning them off one by one and checked main fuel table.

I'm going to check the wiring and temp sensor, it could be possible that the engine temp sensor could be interfering with the injector voltage.

Have you checked to see if the ECU shown batt voltage drops when the alternator heats up from be stationary. Injector dead time maybe wrong.

what size injectors are you running? if they are too big, sometimes its hard to reach a leaner mixture at idle? just a thought

Running standard 440cc injectors, battery comp table is steady.

Wondering if it could be fuel heating up which means less dense so flows more easily through injectors

Fuel temperature variations usually only make 2-3% difference -- what you have described is more like 20+% error. Don't you have any way to log what is happening?

Yes I have data log which I've been using, the main problem apart from high idle is nothing shows up so I carnt find the problem, fuel, ignition delivery is the same at normal idle.

Something is overiding the main fuel map, I've managed to get closed loop idle working good but even that gets overridden after a while.

After a short time of the thermo fans going through their cycle, 80°c to 82°c operating temp the engine starts to run rich but will come back to 14.5 afr when the fans start up again then go rich when the fans stop

I'll try to share some pics of my fuel modifiers, air, engine temp, battery comp etc, etc.

Main fuel map, the highlighted zone is at idle.

Attached Files

Battery voltage normally sits around 13.8 at idle and dosent move around much when fans start up.

Attached Files

Air temp comp, as expected it heats up while stationary I have a feeling that this could be the problem or something related to this.

Attached Files

Engine temp comp,

Attached Files

Your battery voltage comp table is not anywhere close to reality. All injectors have a delay before they turn on. You have a delay of 0 ms at 12V and above, and that can't be right. You would be better off setting that entire table to 0.75 - 1 ms. But that will entail completely re-mapping your fuel table.

I think your engine temp compensation isn't correct for the operating conditions of your engine. You should only tune the idle (ie, reach your target AFR, set the idle speed, etc.) when fully warmed up. Once that is done, then the next time you start the engine cold, you will need to adjust the engine temp comp to keep the AFR to your target. I expect this will need an increase from the current values.

Good Luck!

BTW -- Here is a technique to determine the correct battery compensation value by changing the battery compensation and noting the resulting AFR changes:


and another I found:


I'm sure there are more, just google "injector dead times" and follow a few links...

Thanks for your help David but I'm not quite sure that the battery comp is the culprit.

Whats happening at the moment, it will idle fine to operating temp, around 80-82, the thermo fans will cycle in and out, AFR will hover around 14.5, battery volts are a steady 13.8v. Then after around 20min of constant running stationary it starts to slowly run rich (12.3 down to 11s) and high idle (1100s) at the same time.

If it was the battery compensation table causing this issue then wouldn't it be running rich straight away, I've checked the batt volts and they were the same when running good compared to running rich.

Also the wolf ECU has smart injector drivers with peak and hold and the injector dead times (0.85) are set in the ecu.

Thanks for the advice, I'll change the batt comp anyway and see what happens.

Leaky injector maybe? What are the fuel trims doing once it starts acting up @ idle?

I'm sorry I wasn't clear. You battery table comp isn't correct, and this can cause other compensations to not achieve the correction you expect (ie. a 10% change in fuel, does not produce a 10% change in AFR if the battery comp isn't correct). Yes you can tune around this (and this is probably the case here), but cases where the only thing changing (like engine temperature) will not work for all operating conditions -- likely all will be fine the higher the flow, but low-flow cases (like idle) will be affected the most by errors in battery comp, compounded by trim changes.

To fix your current problem -- Unless the coolant temps stays exactly the same (again, what does your LOG show?), I would say your problem could be adjusted with either the Engine Temp Trim table, or the actual fuel table cell tuning.

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