Another PO301

Tacoma 2008 w/ 4 cyl. I have a cheapo (Fixd) code reader that says misfire on cylinder 1. No other info. About 2 years ago I had the same symptoms: sudden loss of power, inability to accelerate much past 25 mph, real rough running, hardly make it up any gentle hill, or get out of second gear. An important aside is it was intermittent.. sometimes it would run fine..then do it. I took it to our very capable mechanic and they had trouble diagnosing because it wouldn't act up on them during test drives.. though it finally did. They diagnosed it with the cylinder 1 ignition coil connector being bad. Replaced it and all was well. If I look at the ignition coil connectors.. all have colored wires except cylinder 1's, which has all black wires.. so I know they swapped it.

About a month ago the truck started running rough again, but not real rough - would still drive up to speed - and it turned out that one of the ignition coils was broken. So they replaced all ignition coils, plus all new spark plugs. Ran pretty good after that, but wasn't long before I noticed a bit of hesitation every now and then. Then last week the big problem hit as I've described in my first paragraph - loss of acceleration, lost of ability to get out of second gear.. and the code PO301.

I swapped ignition coils between cylinder 1 and 2, the the Fixd still reports PO301. So I don't think it is the new ignition coil. The mechanic is pretty thorough so I'm hesitant to think it is a head gasket issue, especially with the recent history. Unfortunately the mechanic has gone off for a couple weeks so the truck sits. Wondering if there is any thing I can do without more than a multimeter and full set of tools (though I don't know how you get the damned spark plugs out of that hole -- magnet?). I've built a '73 CJ5 jeep from top to bottom - rebuilt the engine myself, replace the chassis, all that.. but new vehicles are beyond my knowledge. (I'm an old man).

I had ordered a better code reader - an Innova 5610 (or about that.. not looking it up) for a couple hundred bucks from Amazon, but shipping to Alaska takes weeks sometimes. Right now it is touring the western states. Not sure it would help me though.. the mechanic might get back before I see it.

Is there suggested tests? - maybe a way to test the connector to see if their repair failed?

Sorry for long post, but wanted to give the history.. /jim

 

Coolant in cylinder #1 should be easy enough to see by pulling the plug and using an endoscope, can be gotten cheap on jungle site.

Swap the plug, maybe the porcelin is leaking spark or is otherwise damaged? A magnet or piece of fuel hose will grab the end of the plug to pull it up out.

If you have a traditional spark tester you should be able to use it if it will reach down the hole to the plug, the coil doesn't care it's orientation as long as it's plugged in.

Have you/the mechanic checked fuel pressure?

 

Thanks for the reply. I have not checked fuel pressure, and mechanic hasn't looked at it since this cropped up. He is out of town. I'll check that plug as you suggest.

 

What kind of coil packs did they install? OEM or aftermarket?

 

Don't know if OEM but he sure charged a pretty penny for 'em... $400 for a 4-pack, labor extra.

 

Denso is factory Toyota. Those are some Autozone duralast Chinese ones.

https://www.autozone.com/ignition-t...uralast-direct-ignition-coil-c1452/827752_0_0

 

Yup, and they're famous for not lasting very long.

 

But moving the coil and the problem not following rules that out, at least for now.

 

True

 

My next move would be to get the spark plug out and take a look.

 

Haven't rounded up any spark tester.. I did get the plug out and visually it looks brand new. Didn't see any cracks. Suppose I could swap it with another cylinder to see if the code follows. A friend is lending his code reader - a Foxwell NT630 - which I'll have to read the manual to see if it will help. Should be better than mine, anyway.

 

Couldn't figure out the Foxwell.. looked like the only apps loaded on it were for ABS/SAS or somesuch, as well as reading codes. It gave me the same code. But my Innova 5610 showed up today and that also proved a bit over my head.. not sure it would be of much help.. definitely showed the code. It also gave a PO171 System too lean (bank 1) which was new to me. Haven't googled that yet. I didn't have the air hoses properly hooked up at the time, but maybe that wouldn't matter.

 

Air hoses not connected could be a vacuum leak which would induce lean conditions. I would not focus on that after you hook them back up it should clear

Sometimes the fancy computer tools are just more headache than they're worth, but the innova should be able to show you misfire counts which would let you know how bad the misfire is.
https://youtube.com/shorts/6dPvcD9S_MU?si=XJ3hYji0biTGJPDf

 

You say the connector for coil #1 was previously repaired/replaced

My next move would be undoing the tape for the connector on cylinder #1 and looking to see if previous repair has failed.

 

I suppose there's a way to trace those wires for continuity.. but they sure are buried. I'll search a bit for wiring diagrams to see if easier than I think.. however the mechanic is back in town in 3 days.. so maybe I'll have to throw in the towel and let him at it, provided he can get to it quick.

 

All you can really do is check for power and ground.
Black/Red is Power with key on.
White/Black is Ground.

Pin 1 is Power
Pin 4 is Ground.

Pin 2 is the IGF it should have 5V Key on.
(But you'd likely have a IGF code - P035x if it were the IGF wire) - Basically...might as well check it since you are there.

Or just wait until your mechanic comes back.

 

Exellent.. Thanks much - saved me some time. I'll check those.

 

Well the pin 1 registered at 11.99 volts (maybe the fan was on), pin 4 had continuity to ground, and pin 2 had 5.04 volts. So seems to check out. Wife is gone for the weekend so at least I have her car for now. Might be time just to wait for the mechanic.

 

At least you tried.
You still have fuel and air.

But waiting for the mechanic might be a good idea at this point.
Fuel and air aren't exactly easy to check with out "other tools".

Please do come back and update us when you find out the issue.