Liana owners & fan club

[syedasadali21]

you have seen my car. They are 14 size rims.

[enthusiastic.learner]

You can compare your car's speed sensor with a sports version since the transmissions are exactly the same. There won't be huge difference. However you can measure the difference with a gps based speed check to identify what's the difference between your actual speed and what the speedo is showing and then remember that difference in speed limited areas.

[addeology]

Do u think the cng kit is the problem for RPM stalling? My car head is changed so it dnt have the cng injectors came in 2006 and mostly Liana got issues with them. I dnt feel any problem after 30kph. issues on lower speed and RPM only.

[MGK]

Do u think the cng kit is the problem for RPM stalling? My car head is changed so it dnt have the cng injectors came in 2006 and mostly Liana got issues with them. I dnt feel any problem after 30kph. issues on lower speed and RPM only.

Let's start with the little things first. Remove your battery terminals for about 5 mins and then attach them back, this will reset the car's ECU and see if this solves the issue. If not, report back then we shall guide you more.

[addeology]

I got this problem as soon as i activated the AC compressor back. Turning on AC rpm remain static at 1000, as i turn it off it comes to 500 n turnoff the car. Is it related to Ac or throttle issue?

[addeology]

My mechanic diagnosed that this AC sensor is main culprit. RPM fell down as i turnoff AC and on braking in speed is cz of it. Need ur opinion brothers.
@saboor73
@enthusiastic.learner
@MGK
@abid110

[abid110]

Have you serviced your IAC Valve attached to throttle body? That is responsible for air flow to keep idling possible..

[MGK]

But as you said this sensor is keeping it at 1k rpm when AC on, this is its job and its doing fine then how come this is the culprit? Did you reset the car's ECU as I suggested you earlier?

[enthusiastic.learner]

Low rpm are mainly caused by air or fuel restriction. See your air intake filter first. Then get rid of the cng packing that's put in place for running the car on cng. If that doesn't fix it then check the fuel pressure. It could be a dirty fuel filter or a weak fuel pump. It could even be cheap quality petrol that's causing it. Sometimes, high octane petrol also causes this problem when the engine is weak.

[welcome786]

You can compare your car's speed sensor with a sports version since the transmissions are exactly the same. There won't be huge difference. However you can measure the difference with a gps based speed check to identify what's the difference between your actual speed and what the speedo is showing and then remember that difference in speed limited areas.

http://www.tyresizecalculator.com/tyre-wheel-calculators/speedo-error-calculator

check this calibration tool found on internet.

[addeology]

@abid110 i got new Kabli throttle body with IAC Valve. That has been serviced.

@MGK i did reset as u directed. Nothing changed. This sensor supposed to keep RPM constant on both On & Off..Nahi??? Major issue as AC turned off, RPM comes almost 400x down and car turns off.

@enthusiastic.learner As per ur direction, I got rid of CNG. only running on petrol. I uninstalled all CNG setup. Overall everything seems fine when car touches above 30kph. On braking from speed, or in idle it drops to 500x.

[enthusiastic.learner]

Did you get rid of the air intake restriction packing at the mouth of the intake filter box? Also take one of the battery terminals off for about a minute afterwards to reset the ecu. Before connecting it back, unplug your car's throttle position sensor. After that, reconnect the battery and start the car. Ignore the check engine light and see how the rpms go. If they become better and more consistent then your tps is set to idle low. It can be readjusted or replaced in case it's bad. There are instructions about checking it in earlier comments in this thread.

[enthusiastic.learner]

Also, very important, check your car's fuel pressure. A clogged up fuel filter can cause low fuel pressure which often leads to low/rough idle. A bad chassis/block ground can also sometimes cause this. Even a dead/weak battery can cause your car to idle low by overloading the alternator. You can see there are many possible reasons. Shoot these down one at a time to make proper diagnosis.

[addeology]

There was a half cut pack on cng pipe end that positioned on throttle. Other thn than no packing. Cng setup totaly removed.
Throttle position sensor is the one in black color on throttle body. Right?

[enthusiastic.learner]

It's the one opposite to the butterfly wheel where throttle cable goes. It's connector position is vertically upright and positioned towards the front side of throttle body that is towards the fuel rail. The one on the left of the throttle body which is pointing towards the firewall is the iac valve, telling you just in case. Unplug that and your car will idle at 2-3k rpm

[enthusiastic.learner]

If the problem persists then open the filter box and take the filter out and then start the car to observe rpms. If it idles good then your air intake filter is clogged up. By the way, you mentioned earlier something about your air sensor. Are you referring to the one that's plugged into the side of the filter box? Could you share the error code that you cleared? If a different air temperature sensor is used in the car that has different voltage range for various temperatures as compared to the original one then that can also mess up your car's idle because ECU is depending upon the output of your air temperature sensor to control the pulse width of the fuel injectors which controls the amount of fuel delivered per stroke. Too less fuel can cause low idle and eventually the engine can die.

[MGK]

A car that idles poorly the first thing that comes in my mind after resetting ECU is the Throttle body and Idle air control valve (IAC) cleaning and diagnosis, in extreme cases cleaning of Mass Air flow sensor (MAF) can also be beneficial, moreover check for any air leaks around the joints (air flow system). If that doesn't works then its probably the throttle position sensor that has gone bad and needs replacement with a new one.

[MGK]

And I believe your air filter is not clogged with dirt too.

[enthusiastic.learner]

Air leak doesn't strictly cause low rpms rather it causes a surge/fluctuation in idle rpms instead. However in Liana the iac valve should compensate for that. What causes low rpms is primarily fuel restriction, air restriction, blocked cat converter or a dirty signal from the air temperature sensor. In the worst case scenario, low idle rpms can also be the reason of an awfully weak engine with massive compression loss.

[addeology]

Thanx @enthusiastic.learner and @MGK for ur guidance. I ll check this all n see wht kinda result i get. Revert accordingly