My truck (2000, 243K) has been suffering an intermittent misfire (I think) for about the past week. However, it has thrown no code. It tends to be worse in the morning or otherwise on a cold engine. Every couple of seconds, I get a small "bump" sensation (similar to the AC compressor kicking on). When cold, this will be followed by a noticeable pop in the exhaust, almost like a tiny backfire. This is worse when in gear with the brake depressed. I'll also have some roughness when first accelerating from a stop, or when transitioning from coast or light throttle to heavier throttle. At highway speeds, or with more aggressive throttle, it is not noticeable at all. When hot, it might idle for a minute or more perfectly normally, and then start bumping again.
I've no CEL and scanned it multiple times, confirming no code.
I did inspect all the coils and, based on physical condition alone, I have three suspects. One is a OE Toyota coil that might be original to the truck. The other two are no-name replacements, one of which also appears to be quite old. The other five are either newish Toyota coils or newish Denso coils (one of which I replaced myself in the last two months), so chances are those are not my problem. Plugs have all been changed within the last two months.
I don't like throwing money and parts at a problem without proper diagnosis, but I might just order four Densos from Amazon, replace all three, keep a spare, and chalk it up to preventative maintenance. However, I am wondering if there is a way to definitively test a possibly faulty coil if no CEL is present.
I've no CEL and scanned it multiple times, confirming no code.
I did inspect all the coils and, based on physical condition alone, I have three suspects. One is a OE Toyota coil that might be original to the truck. The other two are no-name replacements, one of which also appears to be quite old. The other five are either newish Toyota coils or newish Denso coils (one of which I replaced myself in the last two months), so chances are those are not my problem. Plugs have all been changed within the last two months.
I don't like throwing money and parts at a problem without proper diagnosis, but I might just order four Densos from Amazon, replace all three, keep a spare, and chalk it up to preventative maintenance. However, I am wondering if there is a way to definitively test a possibly faulty coil if no CEL is present.