[Radney]

G'day. I could really use some advice about a problem I've had for a couple of weeks. I have a 2017 Jimny, automatic. When I start the engine cold, everything works fine. However when I stop it, let it cool down for a few minutes and restart it, it's getting a constant misfire. The engine shakes like crazy, revs are very low (almost to the point of stalling) and the car has no power, it can barely accelerate to 30 kph. I try not to drive it in such state, but was forced to a few times and after driving like that for long enough - it just goes away. There are two other things, possibly related to the issue. Sometimes, even when working normally, when I try accelerate form stationary (e.g. at an intersection), the revs drop to almost stalling for half a second and then the car drives normally again. The other thing is that I think I sometimes hear a faint rattling from the back of the car when accelerating.

I did some basic research online and the symptoms are similar to what people write about a faulty fuel pump. My local mechanic however says that simple things like a fuel pump or an ignition coil either work or not and can't just work sometimes. He also said that a faulty oxygen probe would be recorded in the error log and the whole ting this is probably a computer issue. Which seems weird because there is a clear correlation with temperature, it only happens on a hot or warm engine. Why would a computer fault rely on temperature? Anyway, the mechanic told me to go to the Suzuki dealer because they have better diagnostic tools.

Now my question to the community: does that make sense? The dealer will charge me $400 for just looking at it so I'm seeking an advice here first. Does anyone have similar experiences? What could be causing such problems?

[fordem]

I think it's time to find a new mechanic.

Let's talk about simple things like a fuel pump or an ignition coil that either work or don't - fuel pump first - a fuel pump can pump fuel (so it's working), but unable to deliver the correct pressure (so it's not), or since flow & pressure are interrelated, unable to deliver the necessary flow at the correct pressure, in which case, as the engine's demand for fuel increases, which it does as the engine speed increases, the pressure drops and can be less than needed for the fuel injection system to work.

Moving on to ignition coils - I want to share my experience, not with a Suzuki, but with a Mitsubishi I once owned, the particular vehicle had "coil-on-plug" ignition and four ignition coils - in the ten or so years I owned it, I replaced maybe four or five coils, and I kept a spare coil in the back along with the tools needed to change it - that "spare" coil was actually a defective coil. It would cause a random misfire but only when the vehicle was cruising at 60~65 km/h, I could drive in the city all day long and never feel the slight hesitation of the misfire, or I could be foot to floor, hammering up hill at speeds in excess of 65 km/h and no hesitation - the misfire occurred only with light throttle openings. I kept it as a spare because it worked quite well as a "get-you-home" part.

Moving on to your heat related issue - I've no experience with the M13a engined Jimny, but, sensors can fail and the failure can be heat related - on the J20a engine used in the Grand Vitara, the cam position sensor is known to have "heat soak" related failures - the engine runs fine when cold, but will misfire, run rough & eventually die when warmed up, leave it to cool and it's fine again - a quick & dirty test for this is a bottle of water and a rag - wet the rag and place it on the sensor to cool it and then start the engine.

Back to your mechanic and the dealer has "better diagnostic tools" - generally speaking, dealerships have deeper pockets and can afford more expensive tools, but, there are affordable tools that are within the reach of anyone who is earning a living repairing motor vehicles and takes the job seriously. Your mechanic seems to be well behind the curve in this regard, and needs to up his game.