XR8 idle hunt (video)

[pete r]

G'day,

I was wondering if you guys could watch this video for me.

You can hear what I think is the the cam synchroniser sqeualing. Forscan shows a P0340 error code so a new synchroniser with sensor is on its way.

Is idle hunt like this caused by a dodgy cam position sensor?



http://https://youtu.be/w1GExII37MI

[pete r]

Sorry, I can't get the bloody link thing to work. Here's a direct link -

https://youtu.be/w1GExII37MI

[lumen8]

Dodgy cam sensor will make them idle rough for sure, and given that its throwing a code and youve ordered one, install it and go from there.

There could be other things wrong given the way the rpms seem to float up, but they dont run smooth with the cam sensor playing up so eliminate that first.

Have you checked for vacuum leaks or dodgy PCV valve?

[baboon]

Originally Posted by pete r

Sorry, I can't get the bloody link thing to work. Here's a direct link -

https://youtu.be/w1GExII37MI

For future if you want to embed the youtube link, just paste the bit after the equals sign "="

so your link would be w1GExII37MI in between the youtube tags "[YT /YT]"

[pete r]

Originally Posted by baboon

For future if you want to embed the youtube link, just paste the bit after the equals sign "="

so your link would be w1GExII37MI in between the youtube tags "[YT /YT]"

Thank you!

[pete r]

Originally Posted by lumen8

Dodgy cam sensor will make them idle rough for sure, and given that its throwing a code and youve ordered one, install it and go from there.

There could be other things wrong given the way the rpms seem to float up, but they dont run smooth with the cam sensor playing up so eliminate that first.

Have you checked for vacuum leaks or dodgy PCV valve?

I have yes. I've cleaned the MAF sensor, made sure everything is grounded well. I've also got an IAC valve on the way, I have cleaned the old one but I'm pretty sure it's original

[pete r]

Sorry I forgot, it's also showing a P0350 fault, ignition coil primary circuit malfunction.

[lumen8]

Well ive got a few of these and the 3 things that stuff up seem to be leads, cam synch and coilpack, not much else goes wrong with them for me and I have some high k ones. And that code points to faulty coilpack obviously.

Make sure your spark plugs are ok also (I run NGK TR55 in my cars, I like em, cheap from rockauto.com)

[pete r]

Originally Posted by lumen8

Well ive got a few of these and the 3 things that stuff up seem to be leads, cam synch and coilpack, not much else goes wrong with them for me and I have some high k ones. And that code points to faulty coilpack obviously.

Make sure your spark plugs are ok also (I run NGK TR55 in my cars, I like em, cheap from rockauto.com)

Champion thanks mate. It’s a matter of giving the old girl some TLC and refreshing things bit by bit. Bloody thing goes like a shower of **** though, breaks traction in second when the revs reach a certain point!

[pete r]

An update - have replaced Cam Synchroniser and sensor, coil packs, IAC and TPS. Idle hunt is still there, however the car is running heaps better.

I will do leads and plugs next. However I am suss on the alternator/regulator. Sometimes the instruments voltmeter sits at 14v, other times just under 13v, or anywhere in between (this is with no A/C or lights). I might run some leads and monitor with a DMM, I don't really trust the cluster at the moment.

And as a curveball a tapping or knocking noise has now appeared, I've got it on video and will start another thread.

[Beastie]

Originally Posted by pete r

An update - have replaced Cam Synchroniser and sensor, coil packs, IAC and TPS. Idle hunt is still there, however the car is running heaps better.

I will do leads and plugs next. However I am suss on the alternator/regulator. Sometimes the instruments voltmeter sits at 14v, other times just under 13v, or anywhere in between (this is with no A/C or lights). I might run some leads and monitor with a DMM, I don't really trust the cluster at the moment.

And as a curveball a tapping or knocking noise has now appeared, I've got it on video and will start another thread.

The alternator is a know fault and I have seen engines stall because of them.

If you throw your DMM on it and it drops below 14v at idle, then it isn't charging properly.

I have seen some drop as low as 11v will all the accessories on.

[pete r]

Originally Posted by Beastie

The alternator is a know fault and I have seen engines stall because of them.

If you throw your DMM on it and it drops below 14v at idle, then it isn't charging properly.

I have seen some drop as low as 11v will all the accessories on.

Cheers mate!

[pete r]

Originally Posted by Beastie

The alternator is a know fault and I have seen engines stall because of them.

If you throw your DMM on it and it drops below 14v at idle, then it isn't charging properly.

I have seen some drop as low as 11v will all the accessories on.

Geez the alternator output is all over the shop. When it’s doing it’s hunt thing the voltage is about 14v at 1200rpm and falls to 12.9 when the idle drops to 850rpm then bounces back to about 13.8 (with the idle still at 850).

On the road it sits around 13.7/13.9v no matter whether it’s spinning at 2000 or 5000 rpm.

Putting on the A/C and headlights sees it drop to about 12.9v.

Think I’d better go find a new one!

[pete r]

Alternator bearings are reasonably noisy too...

[pete r]

So, new alternator is in. Voltage about 14.4v and solid, stuff all voltage fluctuation…but…

The idle hunt is still there

Here’s an interesting thing, if I unplug the MAF it idles a lot better, quite smooth and no hunting. I’ve cleaned the MAF carefully and thoroughly with MAF cleaner. The sensor wires are now spotless. No bloody difference.

Looks like a new MAF is required (to go with the new alternator, cam synchroniser, coil packs, IAC and TFS!)

[Ben]

Hey mate,

Sounds like you will have it sorted soon. Also had a few issues with mine with the same codes but it was very hard to cold start.

Sorted plenty of small things out along the way but the 2 big ones affecting me were spun balancer and a faulty MAF.

[pete r]

G'day Ben.
I just did a scan for faults and it's still showing a P0340 fault for the cam sync even though there's a new fitted and timed.

A spun balancer would throw things out. I'll recheck that too...

Cheers mate

[Ben]

Is there any movement in the balancer while its idling? Dont just look at the pulley but the weight behind. Or any vibration through the rev range?

[pete r]

Originally Posted by Ben

Is there any movement in the balancer while its idling? Dont just look at the pulley but the weight behind. Or any vibration through the rev range?

No it looks pretty good. I’ll get out there tomorrow and take some close up photos of it, see if the rubber is failing

[pete r]

The balancer looks ok and the TDC mark is spot on.

So I thought I'd have a go at some data logging using forscan. The video is with the car parked and idling. I give it a blip and then hold it at 2300rpm for a while.

At idle the things that jump out are the short term fuel trims (SHTRTFT1,2) - they increase with rpm then drop back, but nothing else seems to move as dramatically. The MAF (MAF_V) seems to be stable, the O2 sensors (O2S11 and O2S21) are a bit weird but don't seem to correlate with the fuel trims. But when the revs are held at 2300 the fuel trims seem ok...

Does this indicate a vaccum leak at idle? Any advice or thoughts would be greatly appreciated

I'm yet to check fuel pressure regulation, a gauge is on its way.

[crakrz]

Fuel trims look weird. Have you replaced the o2 sensors. The voltages don’t seem to be switching enough.

[pete r]

Originally Posted by crakrz

Fuel trims look weird. Have you replaced the o2 sensors. The voltages don’t seem to be switching enough.

Good point the O2 sensors are slow. No I haven't changed them - yet!

[pete r]

Originally Posted by crakrz

Fuel trims look weird. Have you replaced the o2 sensors. The voltages don’t seem to be switching enough.

I think you've nailed it mate - this is from the NGK website...

"Using an appropriate connecting device, connect the sensor output to your oscilloscope; do not disconnect the sensor from the ECU. Run the engine at approximately 2000 rpm. A properly functioning oxygen sensor will show a rapidly fluctuating output voltage between approximately 0.1 and 1.0 volts. The time taken for the voltage to change from 0.1 V to 1.0 V (referred to as the lean to rich response time) should be about 300 milliseconds. A similar time should be measured when the voltage changes from 1.0 V to 0.1 V (rich to lean response time).

If the sensor output is constant or the response time is too slow the sensor should be changed. It is a good idea to check the oxygen sensor function at every tune up and before submitting cars for emission tests. A slow sensor will affect fuel economy. A new sensor will pay for itself by cutting fuel costs."

[crakrz]

I hope that the o2 sensors are at fault, as they are an easy fix, and will cause the symptoms displayed in your video. IAC and MAF faults are not common and are usually very reliable on these engines. If I can make a suggestion, only use NTK o2 sensors. They are OEM and are super reliable for long life. No other manufacturer, including Bosch, can match them. Even though they will be accurate for many years, I replace mine with every spark plug change. Your fuel trims, and therefore fuel economy, are totally reliant on their accuracy. Just my 2c.

[pete r]

Have a go at the pic below, I did some more data logging focusing on the O2 sensors and fuel trims. Fuel trims are yellow and Orange, O2s are red and pink.

The O2s don’t do anything until I give it some throttle, they just flat line. When I give it some throttle one O2 does it’s thing but the other seems to ‘blip’ then flatline again.

At idle STFT are maxed out high, then when the O2s react to throttle they start to behave.

It’s almost like at idle the thing is in open loop, and goes to closed loop with some revs.

I’ve got O2 sensors on the way. Fingers crossed!

[Ben]

Would be a good idea to monitor whats going on with the MAF also. Mine went recently and would randomly throw up crazy numbers for a split second. In the workshop area there are some MAF numbers you should be seeing.

Also vac leaks are common and if the fuel trims improve with more throttle its a good chance. I found a home built smoke tester worked the best but there are a few methods(hose up to ear works good also). Make sure you check around the intake manifold, pcv valve(make sure its still secured in the grommet and sealing), and the hard plastic fittings around the coil pack area.

If you go down the smoke way I found disconnecting the brake booster vac and going straight to the manifold worked great.

Good luck.

[pete r]

Originally Posted by Ben

Would be a good idea to monitor whats going on with the MAF also. Mine went recently and would randomly throw up crazy numbers for a split second. In the workshop area there are some MAF numbers you should be seeing.

Also vac leaks are common and if the fuel trims improve with more throttle its a good chance. I found a home built smoke tester worked the best but there are a few methods(hose up to ear works good also). Make sure you check around the intake manifold, pcv valve(make sure its still secured in the grommet and sealing), and the hard plastic fittings around the coil pack area.

If you go down the smoke way I found disconnecting the brake booster vac and going straight to the manifold worked great.

Good luck.

I was wondering about the MAF. In the photo above its the blue line, seems the MAF is operating ok?

We're about to go into hard lockdown here so I nicked out to Bunnings and grabbed a small propane torch to help find vaccum leaks. I need it to do some plumbing too (at least that's what I told the minister for war and finance lol)

[pete r]

More weird stuff

The video below shows the engine in open loop after starting. Fuel trims look good.
When it goes to closed loop one fuelsys says “closed” and the other says “error”. I’m not sure if this is because the ecu isn’t designed to supply data of it is an actual error?

When in closed loop the fuel trims start to go high and the revs increase, 02s are flicking about (I will try to check the oscilloscope at this point)
The really weird thing is when I give the throttle a little blip the ecu switches back into open loop momentarily and fuel trims fuel trims fall. Then it goes back into closed loop and the whole thing repeats.

New O2 sensors should be here next week, I’ll have to wait and see if they make a difference. I’m feeling a bit nervous now…

Fuelsys open/closed loop is middle column at the bottom, fuel trims are left column 2 and 3 from the bottom, O2 sensors above them. Anybody got any thoughts?

[pete r]

The fuelsys switching to “error” is normal, apparently the ecu doesn’t supply info for that parameter when it goes to closed loop.

[pete r]

Bloody cars