Misfire at Low RPMs Under Load

I think I posted my question in the wrong section. So here it is again hopefully in the correct forum.

Hey guys I've been searching for a little while and haven't found a great answer for my problem. First off I think it's my ignition coils but I wanted to check with people much smarter than I am before I load the parts cannon and start firing away.

The other day I was pulling a trailer up a hill, as I was climbing the hill it was almost like I lost a cylinder completely. I started losing power and my check engine light came on and was flashing at me. I dropped a gear, raised my RPMs, and slowed down and the cylinder came back and I got my power back. When I dropped below around 2700RPM I'd lose it. Above 3000 It was fine. I tried to pull the code but I couldn't because the light turned off as soon as I got the cylinder back and nothing was saved.

If I'm not pulling a trailer but lug it below 1,000RPM I get the miss but it's not nearly as bad as when I was pulling the trailer. It seems to idle just fine when I have it parked it's only when it's under load at lower RPMs that it has issues.

I was guessing fuel injectors or coils but when I was pulling the trailer on a start I got a backfire. That made me think that it was a spark problem and not an injector providing enough fuel.

Does anyone know a good way to test coils? I'm over 200k on my 1999 Tacoma and I think it still has the original coils. Should I replace them anyway because they are getting older, if it fixes it great if not I probably needed them anyway?

Just looking for some help and guidance to figure out what I should do.

TL;DR My 99 Tacoma with 3.4 was pulling a trailer up a hill and lost a significant amount of power, I think it's a coil but I'm not sure.

 

Definitely sounds like a secondary ignition problem, I would look closely at the coil boots and spark plug wires for oil contamination or carbon tracking as well as inspecting the spark plugs.
It's not very common for Toyota coils to go bad but it is possible.
It should have a code stored even if the light went off unless it's ran enough drive cycles without a problem that the code self cleared.

 

I changed the spark plugs less than a year ago and everything was ok at that point. I'll go out tomorrow and do a more thorough inspection though make sure I didn't miss something when I was replacing plugs.

I wasn't able to pull codes for a few days after this problem had occurred so I'm going to guess that's why there were no codes and without the trailer, I can't get it to re-trigger. Hopefully, in a couple of weeks I'll be able to get the trailer out and do some testing with it.

Maybe you'll know the answer to this, on the first-gen Tacoma can an OBD2 tell me what cylinder is having a misfire? Help me narrow it down then I can move the coil to a different cylinder and that will tell me for sure if it's a specific coil or if the problem is tied to a specific cylinder.

 

It's pretty common for wires and coil boots to arc to ground and burn or carbon track so that would be the first thing I would check.

I know they can set misfire codes I'm not sure if they will show live misfires or not, I believe they do but you would need a scan tool than can show manufacturer enhanced data not just generic OBD2 data.

 

Ok, more of a curiosity question, if it were a problem with the wires or boots shorting to ground why would it only be happening under load at low RPM and not all the time?

I have a bluedriver scan tool It's able to do some pretty cool things but I'll have to check to see if it can do that or not.

 

Had same problem the other day, starting swapping wires and it ended up that 2 of them were bad. It happened to me when it rained a shit ton in the day then it froze that night. I think that caused it. Idled fine but under load it was running on hybrid mode.

 

How did swapping wires help you get to the bottom of it? Like what was the method used? I've been trying to figure out a way to do something like that to help me figure out what's bad and what's not and I can't figure out how to do it in a way that would actually help.

I'm glad to hear someone else is has had a problem like this before! I've been looking for a while but I haven't found anyone.

 

Because high loads at low RPM require higher voltages for the spark to jump the spark plug gap so if there's an easier path to ground it will spark there instead of the spark plug.

 

I had some wires laying around so I scanned it, it said cylinder 2 and 4 misfire. Swapped them out and truck is fine. You can get a scanner for like $30 that you read w your phone or get one w a screen. Worth having w a 1st gen.

 

Some examples of what carbon tracking and a burned boot look like.

 

I have a wire that looks like that one.
If I'm understanding what all you've said I'm assuming that means coils are probably good and I should just have to replace the wires and be on my way. Please correct me if I'm wrong I'm still learning, but I shouldn't have to replace the plugs just the wire.

 

Yea that looks like the culprit, I would replace the wires and coil boots (I believe you can get them as a set) and the plug in the cylinder where that was.

 

Sounds good! I guess I'm off to autozone to spend some money. Thanks for your help man! I'll let you know how things turn out.

 

#sparkleak