Spark plugs or coil or what

[TrexRunnerGirl]

here we go. 99 Limited, just had the starter rebuilt and now....

I tried to go 60 mph and it shuddered and threw the check engine light. flashed on/off. Tried this maneuver several times and same thing.
Now the check engine light stayed on, couldn't go over 50 mph because it shudders so much.

Mechanic says code it for Cylinder 3 or coils. They swapped the spark plugs for Cyl. 3 and the other side. It does look like the plugs had been changed and looked good.
I tested it again and shudders still between 50 and 60 but NOT giving a check engine light.
They are saying they can't do much until it comes back on.

I ain't buying this line and I don't want my truck's engine to blow up over something that I know y'all can help me figure out. :cheer2:

What do you have for me? It runs fine under 50 mph but that shudder scares the crap out of me. I can't let my son drive it like this and I don't want to either.

 

[4Reak Show]

You need a better technician. Most scan tools give live data, one of which will show real time misfire counters for each cylinder. So after they swap a coil they can drive it to duplicate and immediately see which cylinder misfires. No need to wait for a hard code to set unless they are using a super basic autozone scanner. The tricky part of the waste spark system the 3.4 has is that the companion cylinder can be the problem cylinder and it could flag incorrectly if only looking at the code.

 

[Kanoe]

You could start with new plugs. They are cheap enough that you should never have to reinsert a used one. Old one out, new in. Regular changing will also prevent stuck plug disaster stories.

More likely coil or wire issue realistically.

 

[APhelps]

Use a ohmmeter / multimeter and measure the resistance of the coil pack and spark plug wiring. Verify if they are in spec but I'd verify all the coil packs and wiring because you're already there.

 

[Bad Luck]

You need a better technician. Most scan tools give live data, one of which will show real time misfire counters for each cylinder. So after they swap a coil they can drive it to duplicate and immediately see which cylinder misfires. No need to wait for a hard code to set unless they are using a super basic autozone scanner. The tricky part of the waste spark system the 3.4 has is that the companion cylinder can be the problem cylinder and it could flag incorrectly if only looking at the code.

3rd Gen 4Runner's don't show that much data. I'm in the same boat right now as the OP. I know it's misfiring, I can feel it misfiring, but the ecm will not set another misfire code. I've tried using a snap on scan tool and bluedriver, but neither show live data or a misfire counter.

 

[Bad Luck]

here we go. 99 Limited, just had the starter rebuilt and now....

I tried to go 60 mph and it shuddered and threw the check engine light. flashed on/off. Tried this maneuver several times and same thing.
Now the check engine light stayed on, couldn't go over 50 mph because it shudders so much.

Mechanic says code it for Cylinder 3 or coils. They swapped the spark plugs for Cyl. 3 and the other side. It does look like the plugs had been changed and looked good.
I tested it again and shudders still between 50 and 60 but NOT giving a check engine light.
They are saying they can't do much until it comes back on.

I ain't buying this line and I don't want my truck's engine to blow up over something that I know y'all can help me figure out. :cheer2:

What do you have for me? It runs fine under 50 mph but that shudder scares the crap out of me. I can't let my son drive it like this and I don't want to either.

I'm dealing with a misfire as well. Swapped my coil and have been waiting 2 weeks of driving with my misfire to hopefully get another code to set. In the mean time I used the FSM to test my spark plugs/wires/coil packs and they all test good. My misfire is intermittent but happens more under low rpms and higher loads (think 55 mph highway speeds but going up a slight grade). I tested all my injectors as well and they ohm out correctly but I'm going to replace them with re manufactured from LCE. I'm thinking one may be clogged or getting stuck. Good luck

 

[gamefreakgc]

Cheap easy things to do first:

1. Clean you MAF sensor with carb cleaner/MAF sensor cleaner. Helps a lot of idle and misfire issues by accurately reading air flow. Cost: $5

2. Put a couple of injector cleaners in the tank. If the misfire improves at all, suspect the injectors. I recommend Royal Purple's Max Atomizer. Cost: $7

3. New plugs won't hurt but not likely the issue if there's no visible damage to the insulator or electrode. Cost: $20

4. See if you can read Throttle Position Sensor data. It should track with the position of the throttle plate. If when it misfires the data is wrong, suspect the TPS. Cost: Free to diagnose.

5. Check all fluids for correct level & color. Check tailpipe for white smoke/head gasket. I have a 4Runner in the yard right now that has a blown gasket (and rod knock) and it shudders something terrible with absolutely no codes in the system.

 

[suncoug]

I would replace the spark plugs and spark plug wires first. This happened to me several years ago while driving to the beach in NC. I stopped at a auto parts store and swapped out the above. I would look at replacing coils as well. They are pretty cheap if you buy non-denso/toyota brand.

I would also start using Techron and see if that helps, which would point to the injectors.

 

[jkoni426]

I'm dealing with the same thing, same cylinder. About to throw some re-manufactured injectors from GB in this weekend after ruling out spark and compression. Mine only set a CEL and flashed once, although it will show a pending P0303 code when restarted warm and stumbling.

 

[jgue467]

...
the check engine light. flashed on/off. Tried this maneuver several times and same thing.
Now the check engine light stayed on, couldn't go over 50 mph because it shudders so much.
...

Flashing CEL is a Major No-No! Don't try to repeat it, once is enough.

When it flashes, the ECU is trying to to you really, really to let off the throttle! It's saying way to much unburnt fuel is getting past to the cats potentially causing harm in the medium to long run.

I'd go with plugs and wires for now, 98% that will take care of your shudder, its just a miss, only takes one on a six banger to feel bad.

Luck and enjoy the Runner. :cowboy:

 

[LittleCaesar]

The first question that should be asked is whether your 4Runner couldn’t go past 60 BEFORE the starter rebuild?

 

[19963.4lsr5]

I’ve said this many times before.

Toyota could have done a better job with their misfire detection. I had a dead coil on the 97 Puppy Hauler and never got a check engine light until 800ft before pulling into the garage.

That lack of quick detection is probably why the CATs go bad on these things. They melt down from burning off all the raw gas.

Antifreeze doesn’t kill them and is the other cause of the dreaded P0420 code.


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[dogtail]

Other than plugs and wires....coil boots will do that. People overlook them and don't replace when replacing the spark plug wires. They think you gotta replace the coil which very rarely if ever will go bad, either they work or they don't.
Pop off the coils, I'm thinking the boots are heat cracked. To check them, squeeze the bottom where it slides over the spark plug and it will probably have cracks in the rubber. You can buy a set of the 3 Denso coil boots for $37 from Rock Auto. Part #6716248. You'll surely use them anyway so you might as well buy them.
These things are super easy to swap out, takes like 20 minutes and a think just a 10mm socket.

 

[TrexRunnerGirl]

Thanks so much everyone for the help.

I will do plugs and coils and these boots. It's a place to start.

Hope this is the last thing before winter. Otherwise, it runs just fine and I miss my random country drives just to get her out and about.