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Discussion Starter #1 (Edited)
So here is a little background on my problem(s). I have searched all these codes and tried many suggestions I found here on the board, some of which have helped.

First off, 01 Tacoma, 3.4 5 Sp. Manual. 212K miles

Symptoms: Poor gas mileage, shaking upon cold starts on slight up hill inclines.

Codes: P0303(Misfire cyl 3), P0300(Random Multiple cyl misfire), P0171(bank 1 lean), P1135(manufacturer control fuel air metering).

It all started with a P0303, misfire cyl. 3 So I started simple, replace plugs. The plug from cylinder 3 was missing the electrode so bingo that had to have been it. Shaking persisted so I checked wires and coil packs and they were ok.

P0300, multiple cylinder misfire showed up next. So my friend at the stealership suggested Fuel Pressure issues which made sense because it only happened on cold starts or on an incline and the P0171 showed up. Started with a fuel filter replacement because I saw a thread on here that pretty much had the same problem as mine and fixed with fuel filter. That helped with the shaking but it continued to persist. Replaced the MAF while I was at it because it was over due and could have been the issue, helped but did not solve running lean or eliminate all of the shaking.

Started to consider the problem being with my injectors as suggested in another P0171/P0300 thread. Replaced fuel rails and injectors with used (significantly less miles than mine) ones from a member here. This is where I noticed the most improvement, shaking upon cold start disappeared and temporarily was running well.

UNTILLLLL the p1135 showed up the other day, after searching I was sure it was the front-most 02 sensor, made the most sense, it regulates the air fuel mixture for the engine, causing bank 1 lean issues. Now after replacing the 02 sensor for a few pretty :2cents: P0171 lean bank 1 is gone but p1135 has come back.

Im running out of patience haha any suggestions?Another friend suggested the p1135 could be an ECM issue? I havent read anything here or anywhere else online suggesting that but I am sure I missed something. Maybe fuel pressure still or bad fuel pump? Anything stupid/obvious I've missed, feel free to direct me to more threads. I may have over looked a few but I'm getting tired of throwing money at my junk, sure it all is due to be replaced but I'm ready for this issue to be gone.

Thank you
 

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Does it still have a problem on inclines?

What would change on a hill? Fuel level and engine load is all I could think of now. How's your fuel pump? MAP sensor?

:dunno:
 

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Discussion Starter #4
Does it still have a problem on inclines?

What would change on a hill? Fuel level and engine load is all I could think of now. How's your fuel pump? MAP sensor?

:dunno:
Fuel pump I'm not sure, Ive been avoiding that cuz I'm being a lazy ass and dont want to drop the tank. :aahg:

FWIW P0300 and P0171 came back today, Im thinking my best bet is to get someone over here with the same engine and start swapping parts.

Could it be a PCV issue? :confused:
 

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Discussion Starter #5
Paid a visit to a friends house and swapped out coil packs and plug wires just for shits and giggles see if it helped any. While pulling the plug wires I noticed the ground strap next to my diagnostic comp was finger tight :banghead: Not sure if that had anything to do with the P1135 but it has not come back since. Also plug wires ended up being an issue so I replaced them. Also I replaced the PCV valve because it was cheap and easy, seemed to help some....

SOOO P0300 and P1135 have not returned, yet the ever illusive P0171 has returned.
 

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Paid a visit to a friends house and swapped out coil packs and plug wires just for shits and giggles see if it helped any. While pulling the plug wires I noticed the ground strap next to my diagnostic comp was finger tight :banghead: Not sure if that had anything to do with the P1135 but it has not come back since. Also plug wires ended up being an issue so I replaced them. Also I replaced the PCV valve because it was cheap and easy, seemed to help some....

SOOO P0300 and P1135 have not returned, yet the ever illusive P0171 has returned.
have a 01 auto 3.4 145K miles, same issue with the P0171. electrician said it was a bad ECM when i swapped out all the O2 sensors with new Denso OEM replacements. got a used ECM i just put in, after 100 miles of driving CEL came back. if it is in fact the 107 code again we need to swap stories because im out of ideas now too. i've done plugs, wires, O2's, fuel cleaner, PCV everything i could thinking of. Makes me wonder about a bad connection somewhere or a sensor that isn't an o2 thats causing it. i'll hit you up when im able to run the CEL code.
 

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ok so my P1135 is what won't go away. you mentioned a loose ground that might be the cause of your P1135? You said it hasn't come back but have you put 100-150 miles on the truck since that code was erased?
 

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Discussion Starter #9
ok so my P1135 is what won't go away. you mentioned a loose ground that might be the cause of your P1135? You said it hasn't come back but have you put 100-150 miles on the truck since that code was erased?
I have not gone 100 miles yet, about 70ish and the only code that continues to show is P0171 too lean...So a mechanic suggested an ECM issue and it did not solve your issue? Or did it and now you have the 1135 CEL?

This sounds similar to the problems that Scuba had. He eventually traced it down to a bad fuel pump.
Haha NorCal VP kmillan and I were joking about how my truck was turning into Scubas. Next step is the fuel Pump, Im running out of other options aside from:xsmash:.
 

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I doubt it was that ground strap, I forgot to tighten mine down after we swapped all my shit back in, and it started up and ran for a while but then as soon as that ground strap lost contact it just died. No CEL or anything:2cents:
 

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Discussion Starter #11
I doubt it was that ground strap, I forgot to tighten mine down after we swapped all my shit back in, and it started up and ran for a while but then as soon as that ground strap lost contact it just died. No CEL or anything:2cents:
Yeah I seriously doubt it too. But so far no more 1135 code, just the P0171.
 

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I have not gone 100 miles yet, about 70ish and the only code that continues to show is P0171 too lean...So a mechanic suggested an ECM issue and it did not solve your issue? Or did it and now you have the 1135 CEL?



Haha NorCal VP kmillan and I were joking about how my truck was turning into Scubas. Next step is the fuel Pump, Im running out of other options aside from:xsmash:.
Naw, i was getting P0171 and P1135, got rid of the P0171 after the tune up, new O2's and a good seafoaming. but the P1135 is the one that keeps coming back even with a used ECM. the other weird thing is the kid that had the truck before me wired in some stupid fogs and weird shit for the towing package he added. im going to tare into the dash this weekend and see what all he did.

turning into scubas? might as well :flamethro that bitch :D
 

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Discussion Starter #14
Naw, i was getting P0171 and P1135, got rid of the P0171 after the tune up, new O2's and a good seafoaming. but the P1135 is the one that keeps coming back even with a used ECM. the other weird thing is the kid that had the truck before me wired in some stupid fogs and weird shit for the towing package he added. im going to tare into the dash this weekend and see what all he did.

turning into scubas? might as well :flamethro that bitch :D
hahah I have contemplated that ^.

I have only used a little seafoam before never done a full treatment or whatever its called, not sure if that will help me though.

Where did you get a used ECM? Online or at a junkyard and how much did that run ya?
 

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hahah I have contemplated that ^.

I have only used a little seafoam before never done a full treatment or whatever its called, not sure if that will help me though.

Where did you get a used ECM? Online or at a junkyard and how much did that run ya?
got one off ebay for $50 shipped. usually run from $80-$150+ shipping on there all day long. saw this one bought it right then. it runs the truck fine, no other issues. id let you try it out on your truck but mine is a 4x2 V6 auto...
 

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Discussion Starter #16
Figured I’d update this thread for anyone interested.

Finally found the issue causing the misfire.

After throwing parts at it for too long I got fed up and took it to a family friend’s shop to have them diagnose it. Essentially what is happening is cylinder 3 is filling with a little coolant causing the misfire on cold starts until the coolant is pushed and dried out. So most likely I have a cracked or blown head gasket allowing the coolant in. Not quite sure how the head gasket problem arose I’m generally not a “when in doubt throttle out” type of driver haha. It is a used engine from ATARCO and I received it with somewhere between 30 - 60k miles and I have put about 50k on it since.

The truck runs fine without any misfire once it is warmed up which led him to suspect a head gasket problem.

A recap of what I did before I threw in the towel

Checked compression All w/in spec
Spark plugs
Plug Wires
PCV
Injectors
MAF
02 Sensor
Fuel Filter
Checked for vac leaks
Swapped Coil packs with Kmillan, misfire still existed
Kicked my truck :xsmash::shiner:

So I suppose a head gasket replacement is in my near future. I’d like to do it before it gets worse, I havent had any over heating issues or noticeable losses of coolant (although occasionally I can smell it). I helped Kmillan do his head gasket work so I am confident it will be doable.

Wish I had known the head gasket was the issue about a month ago when I did my t-belt water pump replacement:doh::jack:
 

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That sucks to hear. I hope that isn't my problem. I have P0125 and P1135 also.
 

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Discussion Starter #18
I’d imagine its not. My p1135 code went away a month or more ago and hasnt returned after the 02 sensor replacement.

Seems like the head gasket issue is definitely causing the misfire. I wonder if it just had a little crack near cyl 3. I poked around in the engine bay today and there is definitely a little coolant seeping out. There isnt any detectable amounts in my oil so who knows.

I definitely need to get it done sooner than later, just really not looking forward to tearing my engine apart, happens too often haha

What is the p0125 code? I cant remember
 
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