Whos got the lambda control module thingy that fixes idle hunt?

[artisticent]

Hey all, I have a bit of an idle hunt and im under the impression that someone (maybe David T?) has made a module or something that sorts this out.
Any ideas?

Thanks
Nathan

[NightFlyer]

Hey all, I have a bit of an idle hunt and im under the impression that someone (maybe David T?) has made a module or something that sorts this out.
Any ideas?

Thanks
Nathan

I believe you're referring to Dave McKeen's solid state Idle ECU, which allows for more precise control of the idle air/speed motor (ISM).

But this wouldn't correct idle hunts caused by a sticky ISM, vacuum leaks, fuel pressure leaks/bleed-off, incorrect AFR/CO adjustment, etc.

Are you hunting only when the engine temp is cold, as a small hunt is normal K-Jet operation during warmup. If you're hunting when the engine temp is hot, then you other issues that need to be identified and corrected.

IMHO, it's best to get the stock system working as good as you can before upgrading to Dave M's ECU. I'm sure that Dave M will have some more info you :smile:

Best luck :thumbup:

[Bitsyncmaster]

My idle ECU will not fix a bad hunting issue. It may help with some hunting but the problem is the Lambda running closed loop with the idle system running closed loop and the timing between the two just happens to run in sync.

If your idle hunt is very minor, just accept it. Sure you can stop it by running the lambda open loop but you will pay dearly for that gain with loss of MPG and other engine problems.

The idle motor has to be real clean to get a solid idle so that is the first place to play with your idle.

[David T]

Idle hunting is due to all of the cylinders not being balanced to each other within less than 5%. Anything that can affect the balance will cause or worsen hunting. That includes leaky or badly adjusted intake or exhaust valves, bad fuel injectors, vacuum leaks, worn spark plugs, old ignition wires, etc. Start with a compression test. If they are not all within 5% you will never get it to run smooth. Next is a smoke test for vacuum leaks. Then a tune-up and clean the fuel injectors. When you are all done it will still hunt because all of the systems function independently and each affects the other. You have Lambda cycling, the idle cycling, minor differences in each cylinder, etc. By the time one of the systems corrects it is already past that cylinder and has over-corrected anyway.

[artisticent]

Heres the short version of whats happening.
A year ago a take the D to DMC and Danny does a whole engine check up and gives it a clean bill of health. I pay 4k. (also included tires, stainless coolant bottle etc)
On the way home the car dies, I pull it in to a gas station and cant restart it for an hour or so. I also notice a coolant leak although it wasnt out of water when it died.
I had it towed home just in case.
It started once I was home and sounded just as good as when I had picked it up from DMC.
I immediately started working on the interior and removed the windshield rendering it not worthy for the street.
I have started almost daily since then and drive it around my block.
When I start it cold, it fires up immediately and runs smooth. Once it warms up it hunts.
If I disconnect the vacuum controller connector behind the console, it starts to idle smoothly.
A fellow member came over yesterday and thought that the reason why it smooths out after DISCONNECTING the vacuum controller thingy, is coz im creating such a major vacuum leak, that it stops the lambda(?) from hunting. Therefor needing this module thing that would fix this.

Thoughts?

[artisticent]

One quick thing, It does concern me why it died on the way home that day. In retrospect I should have had it towed right back to DMC after I called Danny right away. However it was after they had closed and I was so close to home. Im hoping that the car died for unimportant reason. Like I said it did have plenty of water. When I spoke with Danny while I was stranded, he had me disconnected some plug and reconnect in another spot. Maybe a blue plug? cant recall but the car still wouldnt start.

[David T]

One quick thing, It does concern me why it died on the way home that day. In retrospect I should have had it towed right back to DMC after I called Danny right away. However it was after they had closed and I was so close to home. Im hoping that the car died for unimportant reason. Like I said it did have plenty of water. When I spoke with Danny while I was stranded, he had me disconnected some plug and reconnect in another spot. Maybe a blue plug? cant recall but the car still wouldnt start.

After hearing the whole story you should call DMCA. If it didn't have this behavior prior to your bringing it to him we can only assume something he did caused this. There is no "adjustable" ECU to correct this. Sounds like you have 2 problems. The first is it dying as it's running and the other is hard hot restart. They could be related. You need to replicate the symptoms and see why it dies, it is losing fuel or spark. Try the plug swap.

[artisticent]

Unfortunately i never had the car running before taking it to them. I bought it with some engine pieces painted and in a box lol. Dmc put it all together.

[David T]

Unfortunately i never had the car running before taking it to them. I bought it with some engine pieces painted and in a box lol. Dmc put it all together.

Well then, you have a lot of "sorting out" to do! Part of this may be the original reason it wasn't running.

[NightFlyer]

When I spoke with Danny while I was stranded, he had me disconnected some plug and reconnect in another spot. Maybe a blue plug? cant recall but the car still wouldnt start.


Try the plug swap.

Sounds like Danny already had him try the plug swap to get it restarted after it had died while running - didn't work.

But, the car is apparently running now - it just idle hunts a lot unless the OP pulls the spider plug off the mode switch and creates a vacuum leak.

The OP's friend has a theory that perhaps the created vacuum leak is causing such a lean condition that it forces the lambda out of closed loop and back into open loop, which then solves the problem by smoothing out the idle and thus indicating that there's something wrong with the lambda system when running closed loop.

Well, here's a really easy way that the OP can test that theory - leave the spider plug connected to the mode switch (no vacuum leak there), unplug the O2 sensor, and start and run the car. As the lambda ECU won't detect a signal from the O2 sensor because it's unplugged, it will stay with its static open loop program as opposed to switching to the dynamic closed loop program upon warm up. If the car runs as well it did when the OP was unplugging the spider plug, then the OP will know that there's a problem with his lambda system somewhere that will need to be identified and remedied should he wish to run closed loop in the future. But if the car continues to run crappy, then the OP will know that his problem lies elsewhere - ie CO/AFR adjustment, idle air/speed system (CIS), etc.

Best luck :thumbup:

[artisticent]

Ill try your suggestion with disconnecting the plug from the o2 sensor. I love the trouble shooting, just dont have enough of an understanding of this system yet to correctly troubleshoot on my own.
As to the condition when I bought it. Im not sure about how it was running or if it did. however the person I bought it from took off a lot from the top of the motor to clean up and paint. The engine currently sounds very nice and strong. I just gotta fix the hunt.

Thanks
Nathan

[NightFlyer]

Ill try your suggestion with disconnecting the plug from the o2 sensor. I love the trouble shooting, just dont have enough of an understanding of this system yet to correctly troubleshoot on my own.
As to the condition when I bought it. Im not sure about how it was running or if it did. however the person I bought it from took off a lot from the top of the motor to clean up and paint. The engine currently sounds very nice and strong. I just gotta fix the hunt.

Thanks
Nathan

It will either confirm or rule our your lambda system.

If Danny set the CO/AFR when he put everything together, then you could run your car open loop just fine indefinitely if you wished to - you'll likely see a slightly decreased fuel economy, but may feel a slight (very slight) increase in available power from doing so. Or if not, you could always set the CO/AFR by reading the O2 sensor's dwell.

Be sure to let us know the result from that test :)

My guess is that your problem doesn't lie in the lambda system, but as it's not hard/difficult to test it, why not do so and rule it :biggrin:

[artisticent]

Nightflyer should i run this test with the car warmed up first?

[NightFlyer]

Nightflyer should i run this test with the car warmed up first?

Up to you really.

Pulling the wire will just cause the ECU to default to static open loop operation, thus if you pull it before you start, the car will always be in open loop, and if you wait to pull it until only after the car has warmed up, then the car will have first entered into closed loop before reverting back to open loop.

Either way will allow you to test the theory that your friend advanced about the lamba system running in closed loop being the cause of your idle hunt problem.

BTW - Might be worth making a video of the car starting up (from cold), running up to temp, and posting that here, as it could help us with further diagnosis / trouble shooting, should such be required.

Best luck :thumbup:

[artisticent]

Good idea with the video. Ill get to this after work tomorrow. About how long till it gets to reg temp? and where is the best place to disconnect the O2 sensor? sometimes there is a connector at the sensor and another thats easier to get to

[ifelder]

Good idea with the video. Ill get to this after work tomorrow. About how long till it gets to reg temp? and where is the best place to disconnect the O2 sensor? sometimes there is a connector at the sensor and another thats easier to get to

Driver side rear wheel well. Towards the front of the car inside the well you can feel a single wire with a rubber boot over the connector. Slide back the boot and remove the spade connector from the terminal mounted to the body. This is the electrical connection of the O2 sensor to the Lambda ECU located above the cubby behind the driver seat.

You shouldn't need to remove the tire, I have stock suspension and can fit my arm in there to unplug the sensor.

[Bitsyncmaster]

FYI

I've found the Volvo idle motor runs much smoother than the OEM idle motor. Don't know why but running my ECU in idle motor test mode which slowly runs the idle motor open and closed and keep doing that, you just watch the valve open and shut. You will see the OEM unit will jump in some areas and the Volvo unit is smooth throughout the range.

The Volvo idle motor is much smaller and uses half the power. I don't use the bracket to bolt is down on mine, I just let the hose clamps hold it in place.

[Tillsy]

ou will see the OEM unit will jump in some areas and the Volvo unit is smooth throughout the range. The Volvo idle motor is much smaller and uses half the power. I don't use the bracket to bolt is down on mine, I just let the hose clamps hold it in place.

Oooh, what Volvo idle motor - where and how much?

[Flash66]

Ditto with Chris! I want one.

[Bitsyncmaster]

Oooh, what Volvo idle motor - where and how much?

I have to record that part number somewhere on my computer. I bought my used on Ebay but it's the same one they are selling new over the pond. Mine I painted so can't look for a part number on it.