CEL for cylinders 5 & 8, mechanic puzzled

Hi folks, Iv'e had my 2001 tundra in the shop for 2 months. I keep getting a check light, when I scan it reads that cyl. 5 & 8 have a miss. Well the mechanic could not find the engine missing,I have to say that its only under load that the light comes on. No loss of power, no cylinder shut off just the light. I've replaced everything except the fuel injectors, switched the plugs and coils but yet the light still comes on to those 2 cylinders. Can anybody help?

 

@ColoradoTJ can you move this to the 1st gen section where he'll get more help specific to his truck?

 

Time to swap the injectors around and see if the problem tracks.

 

Thanks. That was the last thing I was told from another friend. So I thought if I'm going to go through all that I might as well change all the injectors. So I bought a set of denzos, since the truck has over 250,000 miles and probably has never been changed.
Mahalo
Bill

 

You replaced the ignition coils? What brand did you go with? People have had issues with cheap Chinese coils.

What about spark plugs? I unknowingly bought counterfeit Denso spark plugs and almost destroyed our Rav4

 

Everything is Denso, just like the repair manual recommends. like I said, I changed all them around and so did the mechanic, changed all the hoses also, really the only thing I didn't
change are the injectors, He even checked for a short, besides driving with his laptop monitoring the engine. He finally gave up and gave my truck back, without a charge. The light only comes on under load which is when I drive it since I live on the side of a volcano, oh I also put fuel injector cleaner in the tank 3 day ago
many thanks
Bill

 

Verify the timing. When things either start to misfire OR stop misfiring when you apply load, that's a pretty solid symptom that the timing is off.

I take it you've changed the timing belt every 90k-100k miles (or 9yr/10yr whichever came first) as Toyota tells you, else your engine may become a boat anchor, right? At current mileage, you should be approaching your 3rd timing belt change soon.

 

shifty, thanks, I had it changed?. glad to see a sense of humor. I have only had it for maybe 15 000 / 20 000 miles and I do think I had it changed though, the mechanic looked and told me he didn't see it off,. your truck sounds awesome, I use mine only for work, and my 05 4.7 4 runner for 4 wheeling
Thanks

 

There always mechanically sound until there not

 

We're asking where the parts were purchased from because there are issues with fake parts from Scamazon and Ebay.

 

Bought them from eBay also bought for my 4Runner, no problem on the 4 Runner, it actually runs better. I thought that they might be the problem, so I replaced them twice. same outcome. ?

 

I like that Scamazon. we don't have as many choses as you do, it's either expensive or more expensive.

 

Shifty, I haven't changed the timing belt, wouldn't the truck surge or miss, or lose power if the timing is off? I've haven't had the truck all those miles less than 20000. I guess I'm getting signs that the owner wasn't a very good mechanic on his own vehicle for a mechanic.

 

We've had just misfires caused by timing jumping a tooth or two. You need to change that belt if you don't know when it was changed last or you run the risk of possibility turning your engine into a brick.

As for your spark plugs and coils and stuff I'd avoid ebay for those things. Risky choice. May get some spark plugs from a trusted source and verify operation. Local auto parts stores or rockauto could be a good choice.

 

Lost power? Possibly, but not always, depends on severity it’s off.

Surge? I wouldn’t expect it.

Miss? YES. A common symptom you’ll see with timing issues that’s unique: the engine runs perfect but only at a specific RPM range. Like, you’re either OK at idle and misfire when load is applied, OR you’re misfiring at idle, but when something kicks up RPM, like the A/C compressor kicks on, suddenly under the added RPM load, misfiring stops. This is NOT always the case, but I’ve seen it enough times in my lifetime to be able to say, “this is a real, legitimate thing”

You know the timing belt is due every 90k miles or 9 years, right? Leaks (oil, coolant) from either of those two pumps or cam seals onto the belt (which happens!) can cause belt stretch and failure. Failing/worn tensioner not putting proper tension on the belt can cause timing issues (saw an 2UZ-FE engine blown just last week from this exact problem in a video teardown this weekend!) Throwing the timing belt under any significant RPM can and will transform the V8 engines in these trucks into a boat anchor. This is one of the first things I would’ve checked after swapping the plugs and coil packs from cylinders 5 and 8 with some other cylinder that is NOT misfiring, to (1) confirm timing is NOT off, since it’s so critical to proper firing, and see if the cylinder misfiring changes (2) inspect for leaks and condition of the belt. I would do both of these steps, in that order, ASAP.

Granted, something as stupid as an intake manifold gasket breach at those cylinders - which we’ve seen before!! - could cause misfire, so you may want to proactively verify/replace that gasket AFTER swapping plug and coil, then after verifying the timing (but not before those two!)

do you have any record, any trace, any proof the timing belt was replaced in the last 9yr or 90k miles? If not, you may be ignoring a huge warning here…