Misfire issue

I replaced my headgasket on my 2.7 Tacoma. Now I have a bad miss. It’s throwing the p0300,p0301,p0302,p0303,p0304 codes. Not sure what the culprit is. The engine ran perfect minus the head gasket before. Anyone have any advice where to start? I have verified the timing several times.

 

Are you sure you you have the timing set right?

 

My guess would also be timing as it is effecting all 4 cylinders... Either that or your wiring harness got pinched somewhere.

 

I set cylinder one TDC verified the crankshaft timing mark and the cam timing marks lined up with the marks in the cam cap marks. I may have missed something. But I feel confident I have it set correctly. But it also makes since since it is all four cylinders having a misfire to be a timing issue. I suppose I will re verify everything again in the morning

 

You didn't happen to replace the injectors with some junk off Amazon/ebay did you? Just asking because it seems so common for people to do that "while they are there" even though the OEM injectors rarely have issues and the 4/6 for less than the price of 1 injectors are total garbage.

 

Unfortunately I wish it was that.this was a straight forward head gasket job. Nothing changed. Minus the head gasket and reassembly

 

Just checking before we got too deep just to find out we had shit injectors.

Do you have a scanner that can show live misfire counts so we can see if indeed all cylinder are misfiring? What about fuel trims?

Have you verified all vacuum lines are connected? I know there's on on the 4cyl under the intake that is easy to miss.

 

p0300,p0301,p0302,p0303,p0304 codes Are the only codes showing. On my one reader. I know the 301,302,303,304 are individual cylinder misfires… P0300 shows a ignition system misfire

 

I mean't in the data stream, I know the codes are there but I have seen single cylinder misfires set codes for multiple cylinders. I'd like to see the live misfire count on each cylinder.

 

Yeah I was thinking the same. Op the vaccum hose is between the firewall and intake did you make sure it's on.

 

Couple questions for you.
Are the intake and throttle body gaskets new?
Did you use ngk or denso spark plugs?
Did you clean the throttle body good when you had it off?
Did you have to have the head machined down flat? How much did they take-off of it?

 

I verified the vaccum hoses were connected. Intake & throttle body gaskets were replaced. The head was pretty flat they took .006 off for a clean up pass. I’ve checked for pinched wires. Loose connections to the wiring harness. Ngk plugs were used.

 

Do you have a scanner that does live data. Maybe try looking at that. See if the throttle position or tps% matches what ever input you have and the coolant temp matches what you think it should be.

When the truck runs does it backfire out the exhaust or intake?
How rough does it run, like a little rough or it seems like it might die at any moment?

 

I don’t have scanner that does live data.. it doesn’t want to run. It stumbles and stutters like it’s starving for fuel or air. It’s not really backfiring. Just really rough idle very low rpm senario

 

Have you checked / cleaned the MAF Sensor and checked the connection?

 

Sounds like a timing issue to me......

Compression check and/or timing verification is in order at this point.

 

Clean throttle body and maf.

Check wiring connections at throttle body. Maf

Check that you hooked up the fuel lines to the throttle body in the right spots

Check that all the vaccum ports are hooked up or at least plugged

Make sure the 2 ground wires at the back of the head are on and tight. Or you could make a temporary jumper from the head to the negative on the battery.

I just got done doing a headgasket on my 2.7 a few weeks ago and the pcv hoses were cracked and I needed to replace them.

I would think if your cams were out of time it would backfire either through the intake or exhaust.

If your going to dig this deep into a motor I'd definitely get a scanner that can do live data. You might even be able to get one that plugs into your phone for super cheap.

With live data you could see engine temp, throttle % and other things to help diagnose

 

Uneducated question here, does the 2.7 have the buckets on the valves? Were they reinstalled on the same ones from which they came? Is there a possibility some of the valves aren't fully closing if the clearances are too tight?

 

If it's a 2trfe in a 2nd gen then it has hydraulic lash adjusters

 

Hi,
A friend and I just did the timing cover on my 2tr two weeks ago, We had the same thing happen as you did, wicked misfire across all cylinders. Engine would start up, rev high ( like 2500 rpm ) try to settle down to normal but just could not do it. The whole engine was shaking violently anytime it was below 1000 rpm. Another thing we noticed is that I just **could not** keep it revved up to 1500 rpm, it was so touchy / sensitive I could not hold it there.

Our culprit was "un-metered air". We had a vacuum leak in the form of an un-plugged hose. The little bugger that's on the back of the air intake on the right hand side of the engine. The one that goes from the PCV check valve to the hardline that's bolted on the back of the head, and then goes back into a rubber line that connects to a nipple on the intake.

I know you said you already checked all hoses, but I thought I did as well. I had my hand on that damn hose and swore it was connected. My buddy was the one who triple checked it and found that was the culprit.

We started to head down your path as well. Checking Timing, checking injectors, electrical connections, checking the Cam and Crank sensors etc...



So that's the air line, It was disconnected from the intake right at the last hose clamp ( # 12263A ). Its hard to see/reach, and I found the hardline its connected to gave me a "false positive" of it being connected since I would have bet my life on it being connected. I remember trying to wiggle it, but that stiff line made me think the other end of that little elbow was connected when it wasn't

Hope this helps, and that you get your truck back on the road.