Wife and I had the top down enjoying the weather today. Wound up in traffic and something wonky happened... After a good 30 minutes of slow stop and go, traffic picked up. When shifting from 1st to 2nd, car backfired and a few seconds later smoke. Not a lot, but enough to pull over and stop the car. Visually, nothing amiss. When it started, a second round of smoke that went away. I have a code reader in the car, no codes. Got the car back home and took a better looks...fluids, leaks, etc... Again, all good. I have headers, high-flow cats, and a Tubi...some popping is par for the course. What I called a backfire was different...think gunshot. Since this happened, and I could just be paranoid, the deceleration pops are more frequent ("gunshot" was only that one time). I'll add the smoke was oil, not coolant...smell has stuck with me. Will continue to dig through the forum...any tips or pointers would be awesome.
Sounds like unburnt fuel in the exhaust, how long since the injectors were looked at to see if dripping, will do no harm to pu some injector cleaner into a fairly empty fuel tank and give car an Italian tune up
1. Coils replace if it's been a few years. 2. Oil in intake plenum - check with a borescope 3. after backfire intake gaskets and injectors.
Thank you all. Car has 14000 miles. Original injectors and coils. Only see the plugs being changed in the service history. I’ll scope out the plenum this morning. Will have to read up in the intake gaskets.
Regarding the intake manifold gaskets…any reason to not use starting fluid to help check for a leak? There’s a Normal Guy Supercar video where he had to lift the top cassette out to gain clearance. Hopefully if the intake gaskets need replacing, that isn’t a hard requirement. He didn’t remove the plenum in the video. One of these days I’ll have to print the workshop manual. The PDF version I have is great, but a pain to use.
It has only happened once so don’t start ripping into it, if it was gaskets or coils it will happen again so drive it to see if you make it repeat . Otherwise throw some injector cleaner in the fuel tank
For sure, just first to come up with the morning coffee reading. My wife reminded me I had bought a smoke machine for troubleshooting another car project. Scary she keeps track of this stuff…even more so she remembers why lol.
Pulled the throttle bodies off the plenum. Surprising amount of oil in there. A project for next weekend… Here’s post cold start this morning. It did clear after 30 seconds or so. https://www.instagram.com/reel/C2qCCq8P5Sn/?igsh=emxvcHFyZWNmbGw5
The big question is why the backfire. Was it an excess fuel, lack of spark causign excess fuel? Was there too much oil in the air intake that built up, ultimately getting sucked in causing the backfire.. the question is why.
All good questions. Given I’ll be pulling the plenum off, anything proactive I should be thinking about while it’s apart? Ordered a set of plugs to have on hand. Worth having a coil or two as well?
In fact, one of the worst references. If you wanted to learn about clickbait titles and thumbnails, Dan's your man.
If he has a bad injector that is not atomising correctly and it drips, you end up with unburnt fuel in the exhaust, then speed up and it ignites.
Traffic - “stop and slow” for 30 min - that is the only variable that different in my ownership. Shouldn’t a ducky injector trigger a code? Smoking aside, car runs great.
I think the preferred method is to do a "smoke test" when checking for intake leaks. I know you say this only happened once but TBH, it should never happen. Check all the areas those here have mentioned. Something is amiss-- and may likely get worse. Probably an easy fix considering the low mileage. Typically not a mileage point where a lot could happen (or not have been done) over the years. Of course it can always be a freak incident but these engines when running great seldom have such hiccups. To add, don't always rely on fault codes. Bad misfiring coils often will not toss a fault code. But you will feel the engine isn't running as smooth as it did at idle.
Seems like some oil that was pooled in the intake might have got into a cylinder and resulted in incomplete combustion which caused a backfire when the unburned fuel got into the exhaust. Then the smoke would have been from the oil also burning off in the exhaust. I would clean the oil out of the intake, verify oil level is correct with the engine warm and running, and re-assess. Maybe do the smoke test while you're in there just for good measure since you already have the machine.
Overfilling. I think it's the PCV hoses at the top of the oil fill tank getting submerged when overfilled and either the intake vacuum and/or PCV pressure sends the oil into the intake tract.
Got the plenum off…front (toward cabin) passenger side bolt was a pita. Got it through the access panel. Prior to this, verified no intake leak with a smoke test. While I have everything apart, going to knock out belts, oil/trans/coolant swap. Also have a new set of plugs and coil packs. Did I mention that front bolt is a #@%*? Edit: Seems a catch can between the oil reservoir and throttle bodies would prevent oil from getting into the manifold.
A better method is to keep the oil level at the bottom of the stick. That way, if the oil is checked when it's not absolutely the hottest, you won't inadvertently add too much oil. It is likely that sometime in the past, somebody checked the oil with the engine off and filled it to the line. That is how so much oil gets into the manifold. If you wanted to install a catch can, it would be right before the throttle body, at the tube that enters the side of the throttle body. I made some tools to do the belt service that can be 3D printed: https://www.printables.com/@EastMemphis_905139/models I think you'll find them useful.
