Ask Xulfiqar - An Automotive Encyclopedia

[k180233]

Sure.

Quick update though, I took it to the mechanic for just a quick look up on the things you mentioned, he checked the spark plugs and they looked pretty much fine, brownish electrode etc, so he said air/fuel mixture appears to be running fine.

I took him to a test drive, made him heard the noise, he said this sounds like too advanced ignition timing, retarded it a bit, and the tapping appears to have gone now.

I still have to test it under load i.e. going uphill etc, if it's still there then I am gonna ask him do a thorough check up on the things like you requested.

Anyway, can advanced timing cause that spark knock? And is retarding it gonna help?

Thanks

[Xulfiqar]

The spark timing is set with a timing light, do that so its set perfectly.

And yes advanced timing will cause spark knock and that can cause engine damage in the long run.

[k180233]

Sure, I will if I can find a mechanic who has it.

Also is there a dedicated thread here on forums for decent mechanics based in Karachi, people who diagnose with proper procedures and tools rather than "soongh k bata dena"?

Couldn't find it.

[genius.phoenix]

Salam! @Xulfiqar bhai I have a missing issue with my vehicle (Glory Pro 580, 1500cc Turbo engine) that the service centers haven't been able to diagnose. It's been there since 5k driven and now it's 25k driven. It's very intermittent.

Sometimes when you press the accelerator it starts missing and jerking. You leave the accelerator and press again it goes away. Sometime you have to go off the pedal one or two times for the missing to go away. The rest drive in fine.

Now I am trying to diagnose it myself. I recorded OBD data logs. And tried to match data with when it does missing. Below is the AFR data for the few seconds I think it does missing. Yellow being where I think it misfires.

Can you help me figure it out please?

[k180233]

Salam @Xulfiqar bhai, It's me with the Honda City 2001-2 again.

I have pretty much got all of the previously discussed issues fixed, only thing that I haven't been able to fix yet is proper idling.

With load and engine at operating temperature the idle goes way too down i.e. 575-600.

At cold starts the RPM numbers are:

1. 1500-1600 (No load)
2. 1100-1200 (AC on)
3. 850-900 (Gear engaged i.e. in D)

But once the engine comes at operating temperature:

1. 825-850 (No load - That's where I set my base idle)
2. 625-700 (AC on)
3. 550-600 (Gear engaged i.e in D)

I have verified ECU adjusting IACV duty cycle with load i.e. it goes from 20-22% to 40-42% with increasing load. What's the range though, how high can it go? Is ECU not adjusting enough.

Also did a compression test on engine to see if it's the low compression, numbers for cylinders 1 to 4 come out to be 165, 160, 160, 170 respectively. Also I haven't ever noticed oil reduction or anything that indicates low compression.

Also two weird things I noticed randomly:

1. Once at standstill when I was showing this shit to a mechanic, the engine reached high temperatures that the fan came on with the heat gauge at middle but still it was idling at 1500-1600 RPM. Doesn't make sense, in my driving I have always seen it adjusting RPM lower with rising coolant temperature.
2. Have noticed fluctuating RPM at idle at times in traffic i.e. erratic 50-60 RPMs fluctuations randomly for no apparent reason.

Can you please shed some light on how can I fix this, no one is able to understand what's going on here.

Thanks for the help, man.

[Xulfiqar]

is the iacv port blocked? and how are you setting base idle?

[Xulfiqar]

Yes that looks like very lean misfire - but this doesnt help, use your scan tool and pull up the PID that has the misfire counters per cylinder (should have it)

identify the cylinders, if its all random misfires then you have a fuelling issue, This is a GDI engine I presume, check the fuel pump data when it starts to mess up.

If this car is so new that its only 5000 kms old only then why are you fixing it, hand it to the dealership and ask them to fix it. Why should the owner be a beta tester for a new car?

[k180233]

Adjusting the flat head single lined screw with car at no load and hot engine i.e fan comes on.

Also if the port is blocked shouldn't it be not able to achieve such higher RPMs at cold, they sometimes go so high on colder/rainy mornings that it starts doing that typical Honda idle surge until I put some load.

Also does the duty cycle range look fine? Is 40-42% supposed to be the max?

[Xulfiqar]

The biss should be adjusted with the idle disconnected, also make sure its o ring is good so the screw doesnt self adjust.

The %age is a bit too high, but redo the biss and recheck.

[k180233]

Ohhhh, yeah, I messed up there, didn't do it with the connector disconnected. Just for my understanding, what's the catch here, what is actually happening If I don't disconnect it.

Also I am assuming the %age is going so high due to such low RPMs and ECU trying dead best to bring 'em up somehow?

Thanks a lot, man!

[Xulfiqar]

The idea is fhat you first set the idle mechanically and then let the idle control do the control.

Adjusting it with it connected would give you a bad result as the idle motor has opened up a lot already to maintain idle rpm (it will be out of range very quick)

[k180233]

Did it the way you said and it's fix now.

Also found out the radiator fan switch was faulty, it was triggering the fan at around 84° and was switching it off around 80°, so I kinda set base idle below operating temperature previously.

Replaced the fan switch, reset the base idle after properly warming the engine up and setting it mechanically first around 800-850. Now it compensates for the whatever load comes.

Transmission load is too much tho, I can see it adjusting the RPMs up in between the minor lag of switching gear and transmission engaging, but after that it kinda falls (to 650-700) due to load, should I set base higher (900ish), or just let it run a bit rough.

Anyways, thanks a lot, man. Finally it's fixed after trying for a long time.

[Xulfiqar]

You're welcome!!

the transmission load behaviour is interesting here, so you are saying the idle compensates first then allows the rpm to drop to 600?

[k180233]

Yes.

Also one more weird thing that I noticed is after driving it for a while 20-25 mins, it stops compensating load entirely, in traffic and at traffic lights it idles as low as 550-600. And base idle i.e. when I park it at home after above, it idles at 750-800, then jumps to 1000, then comes back to 750. And this fluctuating is erratic, irregular, not like the one happens in idle surge in a specific pattern.

But if it's warmed up at standstill i.e. multiple times fan come on and off, and then I put load it compensates fine.

What's going on here?

[Xulfiqar]

put some oil into the air port of the idle control valve, the thing is getting stuck.

If its really dirty, clean it out first then add some oil and leave it alone to soak it up for about 2 hours (use cheapest engine oil not fancy synthetic stuff). then pack it up.

The thing is a porous bearing

[k180233]

Hmm, sure, will do it tomorrow morning.

Why does it happen only after driving though? Vibrations due to driving or the heat is different in engine bay when driven vs brought to operating temperature at standstill?

[Xulfiqar]

The valve is held at certain positions by the two directional controls, when it gets dirty it can jam,

When driving spritely the throttle body cools down a lot, (this is why there is a heating system) and can cause the valve to jam a bit.

[abdulraffay502]

Recently bought, Liana RXI 08’ with M15A. It’s been giving me 6-7kmpl within city which is driving me crazy.
- Data Stream Values are exactly like stated in manual except air intake temperature (46C) which i think is due to hot weather in KHI
- Replaced TB and IACV along with it.
- Turning steering wheel completely changes engine sound it becomes unusually louder with some whirring sound and increases RPM
- Engine compression is around 150+ psi
- replaced spark plugs with NGK BKR6EY-11
- No catalytic converter is found. And no CEL. If CAT is installed could it increase economy to its usual approx. 12kmpl? Or something else is wrong?
- Upstream O2 sensor values are varying btw 0.1-.09v which is I think is due to absent CAT.

[Xulfiqar]

Your upstream sensor is reading 0.09 to 0.1v?

You sure?

[abdulraffay502]

Yes, checked twice upstream O2 sensor readying is varies between 0-1-0.9V when idle. Not sure about in motion.