Misfire With Burning Smell

Schiffer · November 1, 2015

Couple of months back my car started missfireing under load, then after sometime it got worse with a burning fuel smell.

took it to the mechanic and he did a engine tune up after plugging the diagnose tool (cleaned the throttle body, iac valve, inlet manifolds, and replaced new spark plugs) he checked the petrol filter and said its okay too

After that there still was a misfire but the burning smell was gone and it wasnt that violent as before but found out one of the plug wires was the culprit,

bought a new set of plug wires 2 months back and the misfire was compelete gone

aaand again 2 days ago the same issue started. now the car misfires again badly with that burning smell.

This is not present all the time.. It comes and goes.

Check the oil levels, seems to be okay, but dropped a tiny bit.

Davy · November 1, 2015

Assuming that your fuel injectors are fine, this might be due to a faulty ignition coil.

Is the miss sharp or is it like a momentary loss of power? And when you said "burning fuel smell", I assume you mean unburnt fuel smell?

Schiffer · November 1, 2015

Assuming that your fuel injectors are fine, this might be due to a faulty ignition coil.
Is the miss sharp or is it like a momentary loss of power? And when you said "burning fuel smell", I assume you mean unburnt fuel smell?

the injectors are fine. the ignition coils on the other hand i am not sure.

and the smell is more like something burning either fuel or oil. not a unburnt smell

Edit -: its sort of moderetly loss of power but sometimes becomes sharp as well.

Also have to mention that the miss usually occours once the car starts to warm up, as in initially when the car starts moving the misfire isnt there

Edited November 1, 2015 by Schiffer

Davy · November 1, 2015

the injectors are fine. the ignition coils on the other hand i am not sure.

and the smell is more like something burning either fuel or oil. not a unburnt smell

Edit -: its sort of moderetly loss of power but sometimes becomes sharp as well.

Also have to mention that the miss usually occours once the car starts to warm up, as in initially when the car starts moving the misfire isnt there

Well it does sound like one (or more, if available) ignition coils are going bad. If the engine has a "coil over plug" design, you can remove the mounting bolts of each coil pack and start the engine and then test each line as if you would test spark plugs. No change in RPM means the coil pack associated with that plug is bad. This might be harder to test if the miss is intermittent.

Is this the Liana?

Aquaman · November 2, 2015

Urgently check if your fuel line hose clips are tightly secured. If you are leaking fuel then it is dangerous.

Schiffer · November 2, 2015

Took it to the garage to check whether its the ignition coil. The Mechanic there checked and couldnt find anthing wrong

then i asked him to check all spark plugs just in case.

Found out one plug was burnt.

coudlnt figure out whether it was due to a injector issue or the ignition coil pack (which there are 2)

for now to diagnose the problem the mechanic cleaned off the plugs and swapped two injectors to confirm whether its the injector or the coil pack.

asked me to run a bit and see which plug will get burnt again.

oh and its the corona bro.

------------

Other Plugs

Burnt Plug

ignition coil (which seems like a recondition item)

Davy · November 2, 2015

Right. Since the plugs are new, it can still be an issue with the ignition or fuel system. Black carbon deposits on the plug is mostly due to a rich air fuel mixture. It can be due to a weak ignition current as well.

Since you have switched injectors, you can now determine if its a problem with one of them. If they seem to be fine (same plug failing again), you can try switching the coil packs to see if a different plug starts showing same symptoms.

Schiffer · November 2, 2015

Right. Since the plugs are new, it can still be an issue with the ignition or fuel system. Black carbon deposits on the plug is mostly due to a rich air fuel mixture. It can be due to a weak ignition current as well.
Since you have switched injectors, you can now determine if its a problem with one of them. If they seem to be fine (same plug failing again), you can try switching the coil packs to see if a different plug starts showing same symptoms.

Will do bro, Thanks for all the help.

will run the car like this for couple till i see any symptoms. after that will see if i need to replace the ignition coil

Will update the thread.

Schiffer · December 10, 2015

Update: After diognosing found out it is indeed the ignition coil.

The Corona comes with 2 seperate igntion coils the problem was in the 1 and 4 Coil.

TL quoted 25K for the coil so got a recon part for 10k Which weirdly for a toyota part was a bit hard to find and now the problem is gone.

Thanks Davy for your help.

Edited December 10, 2015 by Schiffer

Davy · December 10, 2015

Glad you got the issue sorted out Schiffer. 10k is pretty reasonable.

gayanath · December 12, 2015

Couple of months back my car started missfireing under load, then after sometime it got worse with a burning fuel smell.
took it to the mechanic and he did a engine tune up after plugging the diagnose tool (cleaned the throttle body, iac valve, inlet manifolds, and replaced new spark plugs) he checked the petrol filter and said its okay too

After that there still was a misfire but the burning smell was gone and it wasnt that violent as before but found out one of the plug wires was the culprit,

bought a new set of plug wires 2 months back and the misfire was compelete gone

One more example of incorrect diagnostic by the mechanic. Observed, most of the mechanics are recommending tune-ups (cleaning) without diagnosing the issue.

Davy · December 12, 2015

One more example of incorrect diagnostic by the mechanic. Observed, most of the mechanics are recommending tune-ups (cleaning) without diagnosing the issue.

A fuel system clean-up (commonly referred to as a tune-up) is a basic step of the diagnosis. Doing one helps eliminate possible causes for the issue. Therefore I don't think this was an incorrect thing to do.

In Schiffer's case we could safely exclude the fuel system because a tune-up had been done.

gayanath · December 12, 2015

A fuel system clean-up (commonly referred to as a tune-up) is a basic step of the diagnosis. Doing one helps eliminate possible causes for the issue. Therefore I don't think this was an incorrect thing to do.
In Schiffer's case we could safely exclude the fuel system because a tune-up had been done.

I mean it should not be the first step as it involves more dismantelling and cost. Considering misfire and burning smell, why didn't he inspected the wires at the frst instant ????

Edited December 12, 2015 by gayanath

Schiffer · December 12, 2015

That is true. most of these people without first inspecting the first thing they want to do is a cleanup

Schiffer · December 20, 2015

Update:

After running for few days with the new ignition coil. i felt theres still a small jerk once in a while

So i took it to my mechanic to check the Plugs and found out the same No.4 Cyl plug was burnt again. Swaped 2 Plugs (2,4) and ran for a half a day and then checked again. No.4 Plug was burnt again.

The mechanic Removed the ECU and said some transisters are weak or burnt. He repaired the ECU with new parts and i have been running for 3-4 days now.

Checked the Plug today and its not burnt and the engine seems to be running very smooth.

rskoora · March 26, 2016

Edited March 26, 2016 by rskoora

rskoora · March 26, 2016

I had the same issue recently, the issue was worn out ignition coil, replaced at TL and cost me 12k + labor 3k. Good deal I guess. No time waste at all. took around 2 hrs to repair.

Schiffer · March 26, 2016

I had the same issue recently, the issue was worn out ignition coil, replaced at TL and cost me 12k + labor 3k. Good deal I guess. No time waste at all. took around 2 hrs to repair.

12K from TL seems very reasonable since the asshats in TL quoted me 25K for one

NRX · March 29, 2016

I had the same issue recently, the issue was worn out ignition coil, replaced at TL and cost me 12k + labor 3k. Good deal I guess. No time waste at all. took around 2 hrs to repair.

But it took them 2 hours to replace a frigging ignition coil