[dhanushs]

Originally Posted by T1000

The latest news is, i found the pulse width in the scanner.
Im not sure if it has any role to play.

Hi T1000,

Like I have mentioned before, please check the O2 sensor. ~03 Zen's have this issue, and can result in very bad FE, like 5-6kmpl.

- Also, is there a hard smell of petrol on starting?

[VeyronSuperSprt]

Originally Posted by T1000

Well, the following things were checked till now and ruled out as a reason.
1. IAC value changed.(things got better after this, but the problem cropped up again)

2. Suspected Vacuum leak(idling used to be very high)
2a. brake vacuum pipe changed.
2b. all vacuum hoses checked.
2c. All packing in inlet manifold changed
2d. Inlet manifold gasket changed

3. Distributor cap changed
4. Spark plugs changed
5. Brakes are not dragging
6. Clutch is in good condition

7. Engine tune up done
7a.tappet settings checked
7b. timing adjusted

8. Injector cleaned.
9. TP Sensor was adjusted, it was at 0.9V..changed to 0.7V when the throttle is in fully closed position.
10. air filter changed.

The latest news is, i found the pulse width in the scanner.
Im not sure if it has any role to play.

In addition to what you have mentioned: (1) Check the compression (2) Replace the O2 sensor (3) Check for any exhaust restrictions - did you scrape your exhaust pipe anywhere ? (4) Check intake manifold for leaks (4) Very basic - Oil viscosity - Some MASS use a oil that isn't too great - check that too.

[T1000]

Originally Posted by Sutripta

What economy were you getting before, and what are you getting now? Was the change sudden?

Regards
Sutripta

PS. High idling speed: persists? Or if tackled, how?

Yes, It was a sudden change, that's another reason i believe its not because of wear n tear.

i gave my vehicle for servicing to a MASS at thane, i was referred to this workshop by a friend, he claimed they have won some award and stuff from maruti for good service.

It was my usual experience with MASS, whenever i send my car to them, it used to come back with new set of problems, but this one is refusing to go even after 6 months. :-(

[Rehaan]

Originally Posted by dhanushs

Also, is there a hard smell of petrol on starting?

What would this indicate?

Thanks,
R

[theMAG]

Since the fundamental issue seems to be lower mileage, you might want to run the standard "checklist" below:

1. Clogged intake manifold: have the service center manually clean the intake manifold(not spray)
2. Engine decarb: aftermarket treatments are standard
3. Replace/clean air filter
4. Spark plugs change
5. Coil packs change

Not sure if PW might play a primary role here.

[Sutripta]

Originally Posted by T1000

i gave my vehicle for servicing to a MASS at thane,

Routine service, or something specific?
What about idling? And the fuel consumption figures (before and after).

Regards
Sutripta

[T1000]

Originally Posted by Sutripta

Routine service, or something specific?
What about idling? And the fuel consumption figures (before and after).

Regards
Sutripta

It was a routine service. i was getting 16-17km in city. there was absolutely no issues before the service. I get 6-7 kms now in petrol.

I sent the vehicle from vashi to thane hoping that the service will be good.
i regret doing it now.

[Sutripta]

^^^
What do the plugs look like?
Scan shows no errors, PUC values within limits (I suppose) obvious things like air cleaner and leaks checked for (you still haven't answered about the high idling though) etc. Are you sure petrol is not leaking (or being pilfered).

BTW, this is an observation based on how many Kms of driving?

Regards
Sutripta

[PGA]

Phew! Drop of 65% in FE after a routine service, that too without any clear symptoms.

I think fuel consumption of 6-7km per litre in 2002 model zen will certainly have clear tell tale signs. Most of these have been discussed in the thread. I would recommend you revisit them.

Petrol is a precious commodity these days. Do look seriously at the advice of given above.

[T1000]

Originally Posted by PGA

Phew! Drop of 65% in FE after a routine service, that too without any clear symptoms.

I think fuel consumption of 6-7km per litre in 2002 model zen will certainly have clear tell tale signs. Most of these have been discussed in the thread. I would recommend you revisit them.

Petrol is a precious commodity these days. Do look seriously at the advice of given above.

PGA, i dont know you, but you make me cry with your post.:-(
i used to evaluate everything in life in terms of litres of petrol.hehehe
everything has been done, and till now no answers.Btw baby is 2005 model

if you want to know more about the sad story you should read this one
http://www.team-bhp.com/forum/techni...aining-21.html

i fixed the mileage problem in feb 2012, with help from teambhp, but then it got worse with the service in march2012 :-(

i have spend about 12k since then to rectify the problem, with no use..
im stranded at home inspite of CNG :-(

my drive is mostly on highways and city driving is relatively less

[PGA]

Originally Posted by T1000

PGA, i dont know you, but you make me cry with your post.:-(

Was wondering if you have been able to resolve the issue of FE. If we could know the outcome or the prognosis.
Hope this time my post is able to cheer you up.

[T1000]

Originally Posted by PGA

Was wondering if you have been able to resolve the issue of FE. If we could know the outcome or the prognosis.
Hope this time my post is able to cheer you up.

Hi PGA,
Well, here is the latest update. Things are slightly better. FE has improved, its around 10km/litre, but im yet to get 15km/litre which i was getting earlier.

Things improved after i did the following with a new mechanic(he didnt charge me much after listening to my full story :-) ).

1. Engine tuneup,
2. Tappet setting
3. Cleaned injector
4. Cleaned inlet manifold.
5. All hoses checked, vaccum leaks ruled out
6. Distributor cap changed again.
7. Airfilter/Engine oil changed.

All engine parameters checked with a scanner.
All sensor values(rpm, o2, throttle pos, map, idle value)seems to be correct as per the scanner

the latest in the suspect list,

1. The rate at which O2 sensor values change or the response time.
For eg, When the engine is in idle. the O2 sensor value is around 0.3V.
When i accelerate a bit and leave the throttle, the O2 value takes sometime to come back to 0.3V, till that time the engine rpm is high. it takes about 5-10 secs for the idling to settle down to 800.
This was observed using the scanner.
Does this mean more fuel consumed? What should be the response time for an O2 sensor?

2. the resistance of spark plug cables, As per the service manual there are two types

High-tension cord resistance
Z – 7E type : 7 k/m (2.3 k/ft)
Z – 16E type: 16 k/m (5.2 k/ft)

I measured a resistance of 5.2k/ft in my vehicle.
Question1: Can someone say which type of cable is used in zen?
Question2: the difference in resistance value is almost 100%, Will such a difference have an impact on FE?

Im not going to give up, i may accidently end up doing a phd on zen..but im not giving up. :-)

PGA, thanks for your interest.

[jeeva]

Originally Posted by T1000

1. The rate at which O2 sensor values change or the response time.

How many wires does the O2 sensor have right now?

[T1000]

Originally Posted by jeeva

How many wires does the O2 sensor have right now?

The sensor has two wires(red & black) coming out of exhaust.
Red gives a voltage reading of 0.3v @ idle, if checked with a multimeter.

[jeeva]

Originally Posted by T1000

The sensor has two wires(red & black) coming out of exhaust.
Red gives a voltage reading of 0.3v @ idle, if checked with a multimeter.

The problem with these 2 wire O2 sensors is that they are very slow to respond. (they don't have an inbuilt heater).
It needs to heat up pretty good inorder to work accurately (change over from rich to lean and vice-versa). So, there is a high chance that the sensor doesnt work accurately in lower rpms or at idle.
Check the voltage, when you idle the car and then when you revv it. The change in voltage (from ~0 to 1 volt) should happen reasonably fast, if not instantly. If not, then I guess its time to change the sensor. And, when you are at it, replace it with a 4 wire sensor.