Diagnose My Tacoma Misfire

So to clarify, you took the plugs and wires apart but didn't replace anything..and the misfire is better but not gone? It still sounds like you'd benefit from some plugs and wires to me. Get good quality wires and some NGK plugs. Also, I don't know about that particular setup but usually the COP setups still need a boot between the coil and plug, don't assume that just because there's no wire there, there's no failure point...they're supposed to be replaced with the spark plug wires. Rock Auto shows an AC Delco plug wire set for $25, the boots are a lot more so I'd look around on some forums to see if there's a cheaper place to get them (straight from Toyota?), and obviously plugs are cheap.

This doesn't sound like plugged fuel filter because that would tend to get worse with higher flow rates (in other words, as you revved it higher under load it would hesitate worse). Of course, if you've never done the filter that wouldn't hurt either.

Bryce

OBD II won't always set a fault code for misfires. Way back in the early days of OBD II (like 1996-up), if you accelerated down a rough road and the drive tires 'chattered', you'd get a MIL which said random/multiple misfire. The way it works: the crank actually stops momentarily when the engine misfires and the crank picks that up from the crank position sensor. Tire chatter on acceleration on a rough road can do the same thing. So, the mfgs. 'dumbed down' the misfire monitor to keep the light from coming on all the time. So it's entirely possible to have a random/multiple misfire yet not have a CEL on the older OBD II's.

Since the earlier R&R of the original parts helped temporarily, I'd trashcan those Bosch Platinums immediately and check the plug wires and coils very carefully for carbon tracking.

First, the OBDII update:

The check engine light finally came on, oddly enough when I used my turn signals. I figured, a-ha, it must be electrical. The CEL was pretty insistant, flashing at me occasionally.

I sprung $90 for new plug wires and NGK platinum plugs from NAPA. The install was simple, especially since I had just been in there. The truck immediately ran better. I pulled the EFI fuse to reset the CEL and the truck runs great again. It's too soon to know for sure but I think my mileage has improved, as well.

Thanks again to the GRM crowd for helping a complete noob get his truck running right again!

David

Glad it's running better!

The OBD II check engine light has two modes, BTW.

If the CEL glows steadily, there's a problem which will cause the vehicle to not meet Federal emissions standards. That's the 'loose gas cap' syndrome. Whatever it is shouldn't cause any driveability issues, at least not immediately. There's probably 140 different codes, some common across all manufacturers and some manufacturer specific, that can cause the PCM to illuminate the CEL this way.

If the CEL flashes, there's something more nefarious afoot which can damage the catalytic converters. That's generally a 'hard' (steadily occurring) misfire which dumps a lot of raw fuel in the exhaust. That can lead to the converter overheating and melting internally! There are only a handful of codes involved with this mode and generally the engine will run like crap.

I love it when a plan comes together!

Bryce

That's what you get when you buy a POS Toyota....

Well, that's what you would all say if it were an F-150 or a GMC....

Think about it.

Nice that you got it fixed- and I'll second what Jensen said about flashing MIL light. It's flashing to catch your attention so that you'll immediately stop and prevent further damage.

The solution is the primary reason that you see pretty much all engines now with COP- the num-cyl of coils isn't much more expensive than the coil packs, but removes one of the most common long term ignition hardware problems. And since emissions warrantees are now 80k+ miles (for the 120K federal standard and the 150k PZEV standard), it's important to remove as many failure points as possible.

Congrats on finding and fixing the problem!

Eric

OK now The big Mistake is the plugs used Bosch are not for toyota! they themselves will cause a misfire! Use Either NGK or DENSO dual ground strap plugs!!! otherwise you will have issues for the rest of the time you own the truck! Yes they use an exhaust waste spark system this means that both cyl.s attached to the Coil will spark! and what ever exhausting fuel there is will detonate no they dont back fire!

TTORA is a toyota forum Along with Customtacos there we are very knowledgeable about the Tacomas so please do some research there about your truck and find that there is a Tech/FAQ section where you can find the Factory Service Manual for use in all steps of maintenance and repair!

I have a 95 Toyota Tacoma and have been having problems..check engine light came on and truck has been i guess what you call skipping? My dad changed the wires and plugs and still is running bad..not sure what to do

Pull the codes and see what the ECU is telling you is wrong. You can get a "code reader" that plugs into the diagnostic terminal under the hood, then when you turn on the ignition, you count the flashing check engine light. You can use a paperclip also, but you have to know which 2 terminals to short. Have your dad google it up so that he understands it.