[kevz22]

Hope y'all are doing well.

Seeking some advice to get my old Suzuki Estilo F10D fixed. The car is strictly used as a beater and I have no intentions of selling/exchanging it since the running is minimal at about 150-200km a month as a city runabout. Barring this misfiring issue, the car has no other problems whatsoever.

Here's what's wrong. The car has done around 60,000 kilometres, maintained well and serviced in a timely manner with oil changes every year. All servicing has been done at Maruti's authorized service centers. Off late, the car's been giving trouble, as in it'll start to randomly stutter and buck under throttle input at low speeds/low RPMs. The check engine light does not come on.

So let's say I've slowed down at an intersection and the road ahead is clear for me to proceed, I give it gas and it just doesn't respond for a couple of seconds before suddenly surging ahead. This happens only after the car has run for 20-30 minutes in heavy traffic. Have had a couple of near miss scenarios due to this weird behavior. Doesn't happen at cold start, doesn't happen at higher RPMs. However, once it starts happening, the behavior persists, even when idling in neutral, until the car is shut off and allowed to cool for some time.

Here's what's been done till now in an attempt to fix it.
PCV valve, spark plugs, coils, air filter, fuel filter, fuel lines, O2 sensor- changed.
Fuel pump, sensors like TPS, MAF/MAP- checked by the authorized service center folks.

The fact that it throws up no error codes/CEL is making things difficult to diagnose. Asked the service center mechanics to check for vacuum leaks and they dismissed it by saying that wouldn't make the vehicle behave the way it does.

Any leads as to what I should be looking at next would be really appreciated!

[dhanushs]

Originally Posted by kevz22

...
Fuel pump...

Try changing the pump. To me, it looks like the pump isn't able to deliver enough pressure when required.

[asit.kulkarni93]

When the car is at operating temperatures, put up a scanner and do the actuation test for the fuel pump. Also check the pressure at the engine bay for incoming fuel. If it's adequate then it's mostly leakage from valves. A basic engine head overhaul should take care of things.

[kevz22]

Originally Posted by dhanushs

Try changing the pump. To me, it looks like the pump isn't able to deliver enough pressure when required.

Have left the car at the service center again. They've checked the fuel pump and pressure regulator and said all's well with those components. Also drained the fuel tank and cleaned it, post which, they took it on a long test drive in city traffic and the misfiring issue cropped up again. They're utterly clueless at this point.

Would it be wise to show the car to a FNG instead?

[narayanang76]

Originally Posted by kevz22

Have left the car at the service center again. They've checked the fuel pump and pressure regulator and said all's well with those components. Also drained the fuel tank and cleaned it, post which, they took it on a long test drive in city traffic and the misfiring issue cropped up again. They're utterly clueless at this point.

Would it be wise to show the car to a FNG instead?

I will first doubt the Fuel Pump or its relay (I had faced similar intermittent issues in my old Maruti Zen petrol). Secondly the sparkplugs, but since you said it was changed, hope its not a culprit.

Have you tried using System G for one/two full tank cycles and see any effect of it?

Cheers,
narayanang76

[CaptainBrijesh]

My doubt is on Ignition coils. These issues are hard to diagnose. When engine is cold there is less stress on ignition coils once engine starts to reach operating temperature then the issue starts.

Please try to swap coils and check if the issue resolves.

Hope it helps.

Cheers.

[ObsessedByFIAT]

Originally Posted by kevz22

So let's say I've slowed down at an intersection and the road ahead is clear for me to proceed, I give it gas and it just doesn't respond for a couple of seconds before suddenly surging ahead. This happens only after the car has run for 20-30 minutes in heavy traffic. Have had a couple of near miss scenarios due to this weird behavior. Doesn't happen at cold start, doesn't happen at higher RPMs. However, once it starts happening, the behavior persists, even when idling in neutral, until the car is shut off and allowed to cool for some time.

My doubt goes towards the a faulty TPS and a chocked throttle body. Also check for cracks, cuts in the hoses for air intake side.
Fuel pump maybe at its last stage, but then if that was the case, it should show issues at idle and high rpm alike.

Did Estilo come with a RPM gauge? If yes, does it maintain a constant RPM at idle or it keeps fluctuating?
What is the condition of engine? Does it rock when the issue occurs? As in, are there vibrations felt inside the cabin as well?

[arjab]

Change the ignitors. Located on top of the spark plugs.

To check whether they are at fault, as your friendly neighbourhood mechanic to get a used ignitor from any Zen, Wagon R, Alto etc. Fit that and check the performance. If it works then change all the ignitors in your car.
Get genuine one's as there are a lot of fake one's in the market.
Ignitors are common to Estilo, Wagon R(old), G13B Swift and Dzire.
A set will cost you around 2400 - 2800 rupees.

[kevz22]

Originally Posted by ObsessedByFIAT

My doubt goes towards the a faulty TPS and a chocked throttle body. Also check for cracks, cuts in the hoses for air intake side.
Fuel pump maybe at its last stage, but then if that was the case, it should show issues at idle and high rpm alike.

Did Estilo come with a RPM gauge? If yes, does it maintain a constant RPM at idle or it keeps fluctuating?
What is the condition of engine? Does it rock when the issue occurs? As in, are there vibrations felt inside the cabin as well?

Mine's a LXI variant and doesn't come with a tachometer. However, when the misfiring issue crops up, the gear level starts vibrating, so does the exhaust.

I brought up the topic of changing the MAF/TPS which was dismissed by the service center folks, since they claim that a faulty sensor should have thrown an error code/CEL. Throttle body is as clean and shiny as it can possibly be after multiple rounds of cleaning by them.:

Originally Posted by arjab

Change the ignitors. Located on top of the spark plugs.

When this first started happening, I had bought a pair of aftermarket ignitors(Assia make) and swapped them in, but that made no difference whatsoever. Have tried troubleshooting by pulling out each coil when the engine misfires and all of them seem to be producing a healthy spark. The service center has informed me that that they'd test it again by installing coils from another car and test it for some time.

[kevz22]

So here's a detailed rundown of the messy situation.

I start my car on a warm, sunny day, drive it around in city traffic; all's well for the first 10-15 minutes. Low RPM, high RPM, idling, everything seems alright. Now at some point, I have slowed down to cross a speed breaker or at a traffic signal, and as I downshift and give it gas, there's no response for 2-3 seconds. It's as if the car doesn't know that I'm giving it gas. And then, there's a sudden surge. Now, if I keep the RPMs high enough, the car runs fine
(while guzzling petrol of course).

At this point, the car becomes undrivable in bumper to bumper traffic with the constant lag-surge behavior. Even if I pull over and let the car idle, the car continues to misfire. The exhaust is inconsistent and has a fuel vapor smell to it when it misfires. Shut it off for 30-40 minutes and start it again, it's back to normal until it warms up enough and the cycle repeats.

Here's the work carried out at the authorized service center(Mandovi Motors):
-Throttle body has been cleaned.
-Injectors have been cleaned.
-Spark plugs replaced multiple times in the past year.
-Ignition coils have been checked.
-Fuel tank cleaned, fuel pump checked, fuel filter and fuel lines checked/replaced.
-Air filter replaced.
-TPS/MAF sensors are fine as per the service center. O2 sensor had been replaced 5,000 kilometers back.

The main problem with the authorized service center is that they don't(or can't?) work on the car immediately when the problem occurs. I got a call from them a couple days back after I had left the car with them, asking me what exactly the problem was since they couldn't find anything wrong with it. Well, obviously, they wouldn't since their test drives were on a cold engine, cruising on a 4-laned highway with sparse traffic. They tagged along for a test drive as I drove through city traffic and demonstrated the issue which they acknowledged, but by the time the car gets to the servicing bay, the engine has cooled down enough and the mechanics are clueless again.

[kevz22]

Update:
It's been a week since I left the car at the service center but no luck on pinpointing the culprit that's causing the misfire yet. Saw the car parked outside the service center while passing by the place and the rear seat covers were removed. Guess they're testing the fuel pump again. Ignitors were swapped with another car's and they seem to be fine. Hopefully, the issue should be sorted out by this week.

[kevz22]

Update:
Been two weeks, so called the SA for an update. They tried swapping ignition coils but the problem wasn't rectified. Next step will be to swap the throttle body since a senior technician from their head office has suggested them to do so and drive around with their scan tool connected, and if it isn't rectified even then, they'll hand the car over to their main branch(Mandovi Motors, Hampankatta, Mangalore).

[abhi9044]

Here's what I'll suggest,

1) Check the MAF Sensor.
2) Then the IAC Valve.
3) Try changing the fuel regulator.

If the problem doesn't get solved, try to replace the ECU.

If the problem still persists, I'm 80% sure it's the head that has gone bad due to short city driving conditions.

But before opening the head, verify the Crank Position sensor, the Cam Position Sensor and the Engine Timing.

By the way, is the car fitted with CNG?

[kevz22]

Originally Posted by abhi9044

Here's what I'll suggest,

1) Check the MAF Sensor.
2) Then the IAC Valve.
3) Try changing the fuel regulator.

If the problem doesn't get solved, try to replace the ECU.

If the problem still persists, I'm 80% sure it's the head that has gone bad due to short city driving conditions.

But before opening the head, verify the Crank Position sensor, the Cam Position Sensor and the Engine Timing.

By the way, is the car fitted with CNG?

MAF sensor has been checked. IAC valve: throttle body has been cleaned and checked multiple times by the authorized service center. Fuel regulator has been checked.

Head is fine. All sensors are fine as per service center. Timing is alright as well.

No the car is not fitted with CNG.

It's been 16 days since I dropped it off at the authorized service center. I wonder how difficult it is for an authorized service center to diagnose a fault in a simple engine as the F10D, more so, when it has been exclusively serviced by them for the last decade and a half!

[jeeva]

Originally Posted by kevz22

This happens only after the car has run for 20-30 minutes in heavy traffic. Have had a couple of near miss scenarios due to this weird behavior. Doesn't happen at cold start, doesn't happen at higher RPMs. However, once it starts happening, the behavior persists, even when idling in neutral, until the car is shut off and allowed to cool for some time.

Since almost everything else has been checked, the ones that are left out are the fuel lines and the accelerator potentiometer. Minute pinholes in the fuel lines can cause all kind of issues.
Since this happens only when the car is getting warmed up, I think its a good idea to get the coolant temperature sensor checked.