Cylinder #4 Misfire, Coolant Leak/ Head Gasket?

I took my 2005 Tacoma 4.0 V6 (154k miles) into the shop for a major tune up. The work they completed was:

-Replaced all air filters, and new spark plugs

-Change the oil, lube driveline, and serviced rear diff.

- Replaced upper hose, lower hose, and radiator cap. Plus flushed cooling system.

- Transmission flushed

A day after this work was completed the check engine light came on signaling a cylinder #4 misfire. I took it back to them and they said a spark plug was bad and replaced it. Around 2-3 days after, the check engine light came on again for the same thing (cylinder #4 misfire). I called them today and they said it could be the head gasket leaking into the cylinder.

I bought this truck about a month ago, and this problem only started happening after this work was done. Is there any way they could have messed something up or is it just a coincidence?

 

I hate to hijack your thread, but when the CEL code is "miss in cylinder 4" is it actually cylinder 4 or is it the 4th cylinder in the firing order?

 

Sorry, I'm not sure. I do not have the CEL code on me.

 

When I had a misfire in #6 I replaced the coil on that cylinder. #6 as in the physical location per the Haynes manual. No problems since and that was over 150,000 km ago.

Can you feel the miss? Rough idle?

 

A cheap check to see if it's the coil would be to swap the coils from 4 and 6 and wait.

 

Unfortunately likely the HG, went through this myself last fall, common on the 04/5 V6 4R and tacos, usually around 160k. Any wooshing sounds in the dash, eating coolant? Swap the packs as suggested, if it stays on the same cyllider, likely the HG. You can check my build for more details and DIY costs.

 

When I start up the idle is pretty rough at first.

Yes, I do hear some wooshing sounds in the dash...

 

I would be pretty confident it's the HG then. If you are mechanically inclined, not a terribly difficult job, just time consuming, ~$800 all in.

 

I figured... What a nightmare. Will know for sure tomorrow.

I do not trust myself enough to do it. Thanks for the help though.

 

No problem, try swapping the packs, then check for coolant disappearing. Those will pretty much nail it down. 3-4k at the dealer

 

We just had a 4Runner V6 in the shop here with the same symptoms, I'm curious what it was about those models and years specifically that caused that failure.

 

All signs point to a manufacturing issue, the part number changed in 2006 I believe. Much more common in the 4R than tacos for some reason, maybe has to do with Japan vs (US or Mexico for the tacos right?) manufacturing.

 

Does anyone know if this slowly develops overtime, or just abruptly? The check engine light came on a day after I got it serviced, and less than a week of owning the truck.

Do you think the previous owner knew about this? Could the mechanic have messed something up to cause this?

 

Mine was eating coolant for a month or so, and then noticed the dash noises. Finally threw the CEL. I don't see how the service could cause it, unfortunately likely just bad timing if it is the HG.

It is possible it had the codes and they were cleared, mine came back pretty frequently though and would have shown pretty quick.

 

- Replaced upper hose, lower hose, and radiator cap. Plus flushed cooling system.

This could be what pushed it over the edge. I have seen more than one engine that doesn't have a head gasket issue and the owner decides to Flush the coolant system. Then boom cylinder full of coolant the next day or so. My son had this issue for the same reason in his old MR2. Actually had coolant running out the exhaust pipe and hydrolocked.

Nothing that you could blame the shop for, not saying you have a blown head gasket. But it is a possibility.

I would do as others suggested swap coil packs and if it remains on cylinder 4 get it checked for the head gasket.

 

Start looking for another motor... just in case.

 

It's a blown head gasket. $1,600 to fix.

 

You can do it more cheaply if you have the tools and instructions.

 

And have a foampile experiance too.