Rough Idle and misfire after timing belt change

So long story short, just had my timing belt done on a recently purchased 06. Picked it up from the shop and everything seemed ok, drove a few miles and noticed the check engine light was on, again still seemed ok though. Short while later started noticing a rough idle. And then misfiring. So I took it right back to the shop. He ran the codes, misfires on 2, 4, and 6 and the camshaft sensor code. Left it with him to figure out. I’m admittedly pretty green with anything automotive, trying to learn little by little especially since buying this truck. After reading what I could find since leaving the truck at the shop the 2nd time, it’s becoming a little clearer that I could have a serious issue on my hands. I guess I’m just looking for opinions on what the chances are of physical damage to engine?

 

Best case sensor wire got pinched or chafed. Worst case engine was not timed correctly and piston struck valve and you need new engine. Please report what they find.

 

I’m gonna say low probability of engine damage based only on the evidence of misfire after timing belt change. Likely just needs a timing adjustment.

 

I'm guessing that the crankshaft position sensor wire was not installed correctly, and it was chafed or cut by the timing belt. Let us know what the problem was.

 

Did they do anything else, like the cam seals? If so, the truck would've slid out of time in about that succession if they failed to install the service bolt for the cams. We've seen it before.

If not, it's likely one of these few things:

• They didn't change the tensioner, as they should have (you need to do belt, tensioner, water pump, ideally pulleys too) and the tensioner or a pulley is tired/worn
• Timing skipped a tooth, which would absolutely cause these issues and is super easy to deduce (link to how to verify timing here)
• They mis-routed the crank position sensor wire (which is common) and it's gotten nicked by the belt pulley. Search THIS THREAD for the phrase: CORRECT ROUTING
• It's also possible the camshaft position sensor wire, which disappears into the driver's side camshaft cover (it's the wire going directly into the camshaft cover via rubber grommet, you can't miss it) has its connector loose, or the wire is being rubbed by the pulley BEHIND the cover.
• They broke a connector, didn't fully attach a connector, left a ground loose, or similar (I find this unlikely)

Given the misfires, I'm more likely to think it's bad-timing-related. But camshaft position sensor feeds the ECU in these trucks IIRC, and that's one way timing is calculated.

You have options. You can try to investigate yourself, which doesn't require major surgery, like, you could potentially try pulling the camshaft position wire toward you (out of the cover), then starting the truck to see if anything changes, and it's easy to verify the crankshaft position wire routing, it's a bit more work to pop off the timing covers and check timing, but totally doable for an inexperienced mechanic.

 

They didn’t do the cam seals or anything else, just the timing belt and water pump. Thanks for all the input, will report back when I find anything out.

 

Yeah, they should've done the belt tensioner too (and pulleys). Aisin sells the basic stuff you must replace in a kit for the 4.7L V8, Aisin is the OEM supplier. It takes zero extra time/effort to replace the other bits while you're in there, but if one of those pulleys sieze, or that tensioner fails, you're fucked, your engine is potentially toast if it happens under any wortwhile load (1,500rpm+). We've had some folks come here to share good news, they had their timing belt snap in a parking lot, in the driveway leaving the house, and a couple have put on a new belt and been fine. Others who snapped rolling on the highway, engine is now a boat anchor.

Note that when Toyota tells you, "Change the timing belt every 9yrs/90,000 miles, whichever comes first", those numbers are only valid if you're using OEM parts. Aftermarket part quality is garbage these days.

Why am I telling you this extra stuff? It's probably important you find out two things from the shop that did the work:

1. Did they replace only the timing belt and water pump? Or did they also do the two pulleys and tensioner?
2. What brand of parts did they use?

Knowing those two pieces of info will help you gauge when your next TB/WP service needs to be, in 50k miles, or in 100k miles.

 

Great info, thank you.

I believe they did the tensioner and pulleys as well because I was charged for a kit. I will confirm that though. And the brand of the parts.

 

Update: mechanic says the issue was a dirty valve on the camshaft actuator. Cleaned it out and it’s running fine now. The engine is good

 

That’s a new one I haven’t heard/seen before. Dirty with what, specifically? Did they say?

 

Since I don't have VVT on mine, I'm not familiar with how they're actuated. Is electronic, or hydraulic?

 

https://youtu.be/t9BlCQFaRJA?si=jpSPfcSOgsjL54Qy

 

He did not say specifically, basically just said it was “gunked up”

 

Need to revisit your oil choice and service interval.

 

got full synthetic a month ago when I purchased it, not entirely sure what the previous owner was using or how often. It’s in good shape, seems really well taken care of, but maybe they started to neglect it before selling.

Also, found out the timing kit the mechanic used was a gates. Lesson learned, I should’ve ensured it was OEM before the job.

 

The main thing that means is that the mechanic isn’t that well versed in these trucks if they think the gates is OK. I would also look into high mileage oils that have better cleaning properties.

 

My truck had roughly 60k on the clock when I got it back in 2018-2019 timeframe. You should see the plethora of varnish I found in the heads, along with some sludge. Not as much as others with similarly low mile trucks. But definitely sludge too.

I’ve been slowly working thru things after doing the valve cover gaskets and finding that nonsense. But … all this to say, it pays to have mechanics who know these engines, and these trucks, or just do the work yourself. On oil changes, use the OEM filters Toyota designed specifically for this engine with the filtration they prefer, and change your oil every 3.5-5k miles or 9-12 months, whichever comes first, unless synthetic, then 7k-9k miles or 12 months.

Gates is fine for drive belt, many of us use the green heavy duty belt. Timing belt, stick with the Aisin kit just don’t buy it on counterfeit-part-havens like fleaBay and scAmazon.

 

Ok another update here. I’m now noticing a noise that definitely wasn’t there pre timing belt change

https://youtube.com/shorts/EOI8WAqlup8?si=OLtuihxLip_CjnAW

https://youtube.com/shorts/duPS7EgTQic?si=H15Cb6TFJu7Ezoek


Also 99% sure it wasn’t there the first time I got back the truck before the rough idle and misfire. Any opinions out there on what this might be?

I believe it’s pretty similar to the sound going on here https://www.tundras.com/threads/noise-concern.149361/#post-3733385

A symptom of the gates bearings? Or could the drive belt have been misrouted in the same way that other thread describes on a 5.7?

 

Sounds like a bearing squeak.

 

You can very easily check the belt routing. Compare it to the sticker on the radiator support, usually. Toyota puts very few stickers in the engine bay, belt routing is one.

If I were you, I’d pop the drive belt off, which is super easy, then spin each pulley by hand. One is probably bad. But again, they should’ve used the Aisin kit, which includes the two main pulleys that typically go bad. And this is EXACTLY why those two pulleys are included, any reputable Toyota shop should know that.

That sound isn’t normal. It does sound like a bearing to me. IMHO, it’s their responsibility to fix due to failure to use the appropriate kit but the shop will probably fight that like bloody murder.

You really need to bail on that shop, it seems like they don’t know what the fuck they’re doing.