My Lexus has acted up....

Joined
Apr 24, 2007
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Location
WI.
Drove 600mi. over the Xmas holiday all on ice and snow, about half way through I notice a stumble once fuel
is applied say to climb a hill or increase my hiway speeds..that stumble became significant toward the trips end
I would not have left had it been like that from the start....was glad to be home.

In town here now few want to diagnose a Lexus but one guy ruled out the wheel/driveline bearings and u-joints
so it's probably fuel but not the quality (topped off 3 times), my check engine light came on for a moment
then quickly went out like half way through the trip but was still amiss.

Spose I'll remove the engine beauty covers and see if anything is out of sorts, I don't have much equipment
so anything I can check simple? this is the 4.7 V8 191k has always run perfect for me 4 years now.
 
Gas engine basics ... fuel, air, spark. Gotta be one of those three:
Starting with the obvious, easy stuff:
- Get the code(s) read. Even if the CEL is off now, it likely stored the code. If you don't have a reader, go to a place like AZ or ORs and they'll check it for you.
- When was the last time the fuel filter was changed? If the answer is "I don't know", then change it.
- When was the last time the air filter was checked/changed? If the answer is "I don't know, then change it.
- When was the last time the plugs and coils were changed? If the answer is "I dont know" ... you get the idea.
Some might say that changing these things is firing the "parts cannon" at the issue, and to a large degree, that is true. But it seems you intend to keep the truck, and so it's not a bad idea to refresh these things if you want to put another 50+k miles on it. It's not "cheap" to do all these, but it's a process of elimination. Do NOT buy knock-off cheap coils; spend some money to get quality replacement units.

If those things don't help fix it, then it's likely some manner of intermittent elecrical short or failing ignition control. Now you're into diagnosis that's probably above your head. I suspect you're going to be out of your repair-league, and you're going to have to find a reputable shop. I find it hard to believe that "few" places want to work on a 4.7L Toyota engine; by today's standards, those are simple engines.
 
In addition to what's been said, did you accidentally fill it with E85? If it ran fine until a fillup...could be bad gas.

Did you get into any real deep snow that could have piled up under the vehicle then melted away? If so, check any wiring down low.

Check air filter intake tube for any rodents.
 
Simple? you did check the oil level and get it scanned! If no scan tool, then visit the autopart stores(don't buy anything), and have them scan it and make their shotgun parts replacement recommendations.

Good to see someone request previous maintenance history. Can be anything if history is lacking.
 
Do as all others have said, those are cheap and easy things, and at this age, might not be money wasted even if not actually the issue.

My fear would be a cat getting plugged. But this sounds more like ignition to me. Misfire underload.
 
Every time I had that issue (in multiple Toyota/Lexus vehicles) - it was always the ignition coil. Flashing CEL also confirms this. Change them all at once. New spark plugs is a good idea too, if hasn't been done in a while.
+1
 
Need a code, but from what you described, it sure sounds like an ignition misfire. Check coils, coil boots and maybe plugs. IME, it's more likely to be a cool or boot than a plug.
 
The first step in diagnosing a problem is to scan the engine computer for codes.
 
Wow, many thanks, I'll plan on checking the coils...I do have a BlueDriver scan tool but it says no codes? maybe I didn't look for saved codes.
 
I replaced the plugs with OEM denso 30k ago. The engine starts and idles perfect, trouble starts under medium load. I use 91 fuel so doubt I could error to 85. Fuel mileage is usually like 15-16 and the new problem didn't kill it maybe only slightly (I didn't monitor).
 
All my car's beauty cover is on the shelf.
I removed them as soon as I got home from stealership.

I hate it when I cannot see the engine. LOL!!!
 
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I have a volt meter. any way to identify a bad coil with it? replacing all 8 myself is $200, that's no problem if I'm certain.
 
I have a volt meter. any way to identify a bad coil with it? replacing all 8 myself is $200, that's no problem if I'm certain.
Usually you hook up a code reader, find the cylinder that is misfiring. Swap coils around and see if it follows the misfire.

Do you have an Android phone? Now isn't the time to go get the Torq app, since you'd need the dongle to go into the ODBII port, but I want to say, you might be able to find misfire count in it... given the age of the vehicles, you may want to up your code reader game and get something more advanced.
 
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