Toyota 4Runner misfire and odd smell from exhaust

I’m not a car expert by a long shot, but this one has my Mechanic confused too.

The problem:
My Toyota 4Runner 1999 model has all of a sudden started misfiring when Idle. It acts like it wants to die. It also has an odd smell coming from the exhaust too. It throws error codes about cylinder misfiring.

What’s been tried:
The mechanic changes the coil pack it said had the error, but the problem remained. He checked, the MAF, spark plugs, vacuum hoses, and wires. No dice. He is confused as to what could be left as well.

When you drive down the road it runs just fine until you idle at a stop light or so. The only thing left I can find on the internet to try is the catalytic converter. They say the misfire code and the bad smell can be caused by this.

I’m told the dealer could tell me the exact problem with a diagnostic test? Is that true? Or will it still be a needle in a haystack?

Any help is greatly appreciated!

  • Confused in Louisiana :\

Can you describe the smell? It could just be you’re smelling unburnt fuel that’s coming out of the exhaust, it could be a bad catalytic converter (or you could be smelling the converter overheating because of processing too much unburnt fuel), it could be a bad head gasket. Is there any visible smoke? Does the stored code indicate a single cylinder misfiring, or a random misfire?

And yes, a competent mechanic should be able to tell what the problem is with a diagnostic test–that is the whole point of one. However, this is assuming that this is some actual troubleshooting and not just reading the code that’s turning on your check engine light.

Could be something as simple as a vacuum leak.

Thanks for the responses! The smell is that of unburned fuel. I’ve been told by several people it sounds like it could be lean misfire.

Mechanic told me he checked the vacuum and all the hoses too which is what leaves me stumped.

I don’t know how it works at the dealer. I assumed they would charge me $90 an hour (Their rate) to find the problem, but my friend tells me that is not how it works. He said, They price you for the project and the total hours it will take to fix the problem after diagnosis. I’ve never had to take it into a dealer after warranty.



I don't know how it works at the dealer. I assumed they would charge me $90 an hour

Depends on where you live. Here in NH it’s $140/hr. The local good independents charge $90/hr.

I called them and they said $90/hr. I suppose I need to call and see if that is $90/hr while they are searching for the problem or 90/hr while they are fixing it. I know diagnostics is a flat fee, but I’m not sure if that included diagnosis.

Well, at least problem is constant. Mechanics hate hit or miss issues. So, take mechanic for ride and show him your poor idle situation. Maybe he can take it from there

it sounds like the misfiring due to injector stuck open

At this age I would get a compression test.