SOLVED/REPAIRED - Misfire Mayhem - P0301, P0302, P0300

Hello to you all!
First time poster, long time reader here, looking for some help with my 2007 Taco 2.7l 4-cyl with 93k miles.


About three months ago, even though the truck felt fine, I got a P0301 code light up on me and nothing else. I did the usual swap of plugs and coil pack first (plugs cyl 4 to 1, 1 to 4 / packs 3 to 1, 1 to 3) and cleared the code.

P0301 code came back 2-3 weeks. So I took out the fuel rail to swap injectors and noticed that the injector spacer for cyl 1 was very loose - it popped out with the injector. Figured this is slightly abnormal, so I got a new one from the dealer, installed it, swapped fuel injector 4 with 1, cleared the code.

P0301 code came back 2-3 weeks. Took out the old multimeter and tested all the spark plug and injector leads and everything was within range except for the battery (7 years old), so I replaced that and cleared the code.

P0301 code came back 2-3 weeks. I tried my hand at the compression test, but I think I may have not warmed up the engine enough because I could only get around 95psi max for all cylinders. Either way, I figured they're consistent, so I cleared the code.

P0301, P0302, AND P0300 codes popped up in 2-3 weeks. Took out the plugs to do a compression test again, and noticed plug 1 was a little carbon fouled. So even though I replaced all these plugs summer 2023 during my all car 85k maintenance - engine oil, air filter, transmission drain&fill, rear diff oil change, new plugs - I replaced the plugs again and cleared the codes.

2-3 weeks later (now): still P0301, P0302, AND P0300.


====I HAVE NOTICED====
The issue is always coming up UNDER ACCELERATION GOING UPHILL. The engine chokes out and I have to roll a bit with the car in neutral and cycle the ignition, then the car seems to operate fine with the MIL light on before I can plug in the obd reader back at home.


Is it possible I over-filled the rear differential summer 2023 and that is screwing up the crankshaft timing leading to misfires? Since the last tune-up, I've drained and filled the transmission again spot on to specifications, so I know it can't be the trany.
-I've tried pointing my finger to the cat because of fuel/foul odor at startup and the o2 b1s2 reading 0.000V in the last p0301 freeze frame, but I'm not getting any catalytic converter inefficiency codes and the o2 b1s2 responds after warmup in my obd2 reader's live data function
-Sometimes I think it could be fuel rail or fuel pump clogged or pump going bad, but why the problem on only two cylinders? Also, if it's a fuel issue, shouldn't I be getting a lean or rich fuel mixture code as well?
-Could this be a compression issue that has spread from cylinder 1 to include cylinders 1 and 2?


I'm lost and looking for any help from you wise gurus...

Thanks, Ed

 

The fact that the misfire codes only appear while accelerating uphill is a big clue here. When does it “choke out?” Before or after the tranny downshifts?

when vacuum drops away, like from a heavy load, the engine needs more fuel to deal with it. I thought that the 4 cylinder engines had a map sensor. Unsure if this is just for altitude compensation or is also used for accel enrichment. Most ecus use either throttle position or map for this, If the lack of fuel rapidly creates a misfire event, the o2 sensor cannot react fast enough and the ecu throws only the misfire codes. You cycled the engine off and on before it could see the lean spike.

might check coils again. I have had coils fail ONLY when under heavy load, like accelerating uphill.

compression seems very low. However, the consistency makes me think it was an operator error or instrument error. Not common to see all cylinders that low with such consistency. Even ice cold, compression should be well above 95.

 

Will your scanner do graphing?
If it will I would want to monitor upstream and downstream AFR and O2 activity and fuel trims when the event occurs.

Also may want to do a VE test. This is basically doing a WOT pull through first gear while recording IAT, BARO, Peak RPM and Peak MAF then entering the results along with your engine information in the calculator below.
This will tell us if we have an airflow issue (plugged exhaust, skewed MAF, etc), VE should be above 85% if everything is good there.

https://atgtraining.com/atg-volumetric-efficiency-calculator/

 

It chokes out and looses power while accelerating uphill, either from low-speed or from a stop, so reaching the rpm threshold to shift into 2nd, either successfully shifts into 2nd or just about when it's going to complete the shift, sputters and and looses nearly all power, basically stalling. Most times the engine was on for at least 25-30 seconds after the initial loss of power or the engine recovered by itself, so I'm assuming there was enough time to pick up more codes than the ones I'm getting.

I don't think the 2tr-fe has a MAP, but it does have a MAF sensor, but again, not getting any codes for the MAF sensor and obd freeze frame is showing 39% calculated load while ACC Pedal is 31%, so I'm assuming MAF is responding to vacuum correctly?

BUT, with that said, this last time it threw codes freeze frame is showing STFT -3.1% and LTFT 0%. >>>> If I'm gunning the engine for it to accelerate uphill onto the freeway, why would STFT be negative?

I've already swapped coils around a couple times and the problem remains with the first two cylinders.

I know for sure I did something wrong here or the tool was bad (a rental from the AZONE), even though I followed the steps. Either way, idk how it applies to this situation only because the original code was only for p0301 and then it spread to p0302 and random misfire.

 

95 psi compression?! Warmed up or not, that's not nearly enough. I'd retest that.

Is the converter clogged?

 

Yes it does graphing but I'm unfamiliar with recording functions. I'll look into this.

And your advice would be WOT fully through 1st gear and not just revving while stationary? Might have to connect the obd reader to a laptop while doing this, a little sketch, but doable.

 

Yes you would do it driving, I typically just run through 1st gear and let off after it shifts to 2nd.

 

95 psi, yes I know, I'm embarrassed. I did everything I could, even cut up a 3/4" copper pipe with slots at the end so I can tighten the adapter in the plug socket and still no dice. Either way, can I skip this for now assuming that the problem is elsewhere as it spread cylinders?

About the cat: given the mileage I dont think so. Again, no cat efficiency codes. It was my old man's truck before man and he took care of it. Could I be wrong?

 

Not sure how you can skip over 95 psi compression. The low compression is on all 4 cylinders and the misfire codes are spread out on all 4 cylinders

Fuel trims, injectors and spark plugs mean nothing without compression. Those numbers are trying to tell you something

The misfires show up under load because that's when the engine is being asked to do some work. A blockage could be anywhere, I've seen muffler insulation fall apart and block the exit of the exhaust. Can you get an exhaust backpressure tester? Poke around the air cleaner and intake duct, anything collapsed in there or causing a blockage? Shop rag? Mouse nest?

Really need to do that compression test again just to be sure. Maybe with a different kit and gauge if possible

 

I'll poke around the entire intake passage and the exhaust tomorrow checking for blockages. Just figured out my obd tool does live data recording so going to try and record the data and follow what Dm93 said above to check for obstruction somewhere I might not see.


I'm on board with eventually getting a proper compression test done, but I might have to take it to a shop for that because for the life of me I couldn't figure out what was doing wrong - plugs out, adapter tightened, gauge connected, CO relay out, pedal depressed, cranking 6-7 times on a brand new battery, nothing past 95psi...

 

Here to follow along.

 

Rockauto sells 8 different MAP sensors for the 2.7L engine and it is pretty rare for them to get that wrong, so I assume it has one. Problems like you are having were often due to the MAP sensors on the older GMs that relied on them for accel enrichment, but just don't know if the toyota 2.7 uses the MAP sensor for that. Maybe one of the experts can chime in. The MAF is only used in relatively static airflow. When you punch the accelerator, a different tool needs to tell the ECU that so it can add more fuel to deal with it. It is either the TP sensor showing a rapid movement of the throttle blade or a MAP sensor showing a rapid drop in vacuum. Your problems only appear under heavy load scenarios, so want to focus troubleshooting on things that would only occur during heavy load or heavy acceleration. You can observe MAP data on your scanner, so many want to see what it does when you accelerate uphill.

another thing to look at is the fuel pressure regulator, THese sense the drop in vacuum and up the fuel pressure to deal with load/accell. If they fail, the mixture can go lean under heavy load or accell, as the ecu was counting on an increased fuel pressure to deliver the extra fuel, but it didn't appear.

 

The 2.7L is not a speed density engine, it is a mass airflow engine.
What rock auto has listed as a map sesnor for the 2.7L is the pressure sensor for the Secondary Air Injection System, it looks just like a map sensor but isn't used for that purpose.

 

I'm leary of the whole spreading misfire situation. You had a misfire on cyl 1.. you never swapped anything from cyl 1 to cyl 2, correct?

 

So I did the same hill near me twice. Results:
Test 1:
1st Gear: RPMs 2448 to 4741, VE straight up from 89 to 97%
2nd gear frame drops to 72%

Test 2:
1st Gear: RPMs 2148 to 4613, VE straight up from 87 to 98%
2nd gear frame drops to 84%

So I'm assuming no blockage at peak WOT RPM.

So I actually recorded the data twice but I'm having trouble getting my Innova to NOT delete it, so I'm SOL for now until I can figure this unit out and run the test again.

One thing I did notice (have a screenshot of) is that LAMBDA was dropping as the WOT RPMs were going up during 1st gear. I know the ECU is throwing fuel into the furnace, but does it make sense to have the AFR shift that quickly to rich condition? From memory I think STFT s2 burn rate was 99.2%, STFT was +3.2% and LTFT was 0%.

I know you mentioned looking at AFR, O2, and fuel trims: any specific PIDs I should try and superimpose their graphs? Like O2: from memory I know that o2s1 and o2s2 sensors were showing normal range voltages, but should I be comparing those to the MAF readings or MAF to something else?

 

Not the first few times, no. I can guarantee you though, whatever combinations there were, any of the 4 coil packs have been tried in cyl 1, and the plugs are new twice over in less than a year. P0301 has ALWAYS popped up. P0302 and p0300 have joined the party recently.

 

So VE appears good, unless it's a converter coming apart and intermittently blocking something which is unlikely and you would hear it rattling if that was the case.

Pretty normal for Lambda to go to around 0.8 when it goes into WOT enrichment, a lambda of 1 is normal stoich (14.7:1). Higher numbers are leaner and lower numbers are richer.
So it looks like we have plenty fuel.

It looks like we have plenty fuel and the exhaust doesn't appear to be restricted, we're down to secondary ignition, an injector dropping out, or engine mechanical.

When the event happens does it feel like 2 cylinders are dropping out at the same time?
Does it idle smooth with not misfires?

 

Never played musical chairs with the injectors, right?
Eh. What I'm wondering is if you have a wiring issue with cylinder 1, and then if there was any possibility you spread damaged parts (result of the wiring issue) around to cyl 2. you've got a 4 banger, so the cylinders are right next to each other.
Here's a thing that changes when you go up-hill -- the engine rocks backards toward the cab (and fuel goes back, too)

But all the stuff I'm pitching is low-tech diagnostics, and you've got a scanner that's working you toward the fault. My treeshade ways may be of little use.

One thing I'd consider doing is.. Probably the least likely to be desired. I put together some jumpers with mini quick disconnects to fit onto injector male terminals. I take em out, pour a little fuel cleaner into their holes (one at a time) jump them from the battery and bloowwww. Its tricky being they cant hold much fuel, but after a few attempts I can usually see a spray pattern and compare the bunch to each other to check for drips, etc.
You can get at their spray holes with a toothbrush, too... then later, with a new toothbrush, try to get the fuel cleaner outta your mouth. really, just off the lips.

 

Tough to tell from this pic without axis reference data, but it appears that it spikes quite lean at 5 seconds into the pull and that is right where accell enrichment should be active to eliminate that spike. I can't see the RPM or the afr so cant say how good or bad that is. However, a major lean spike will start a cascade of misfires once it crosses the threshold of too lean. Again, you only get these misfires while accelerating under heavy load and that points to accel enrichment.

 

Under WOT (even from a stop sign sometimes and not gunning it uphill) the engine feels tired. Like trying to ride a street bicycle on a sandy beach. Can't tell if cyl 1 drops or not, just feels tired.
Idle is okay, a little rougher than I expect, but I've read theses 4-cyls idle a little rough. It was my dad's truck before, so my baseline is a little sparse on engine performance history. So was surprised when I got the first cyl-1 misfire because I thought everything was A-okay after my 85k maintenance summer 2023.

Injector dropping out:
-I have carefully swapped injectors and problems have remained consistent
-I've multimeter tested all the injector leads and they are in normal voltage range (tested the coil pack leads too)

Secondary ignition: Are you talking about the contact between coil and plug and engine block, like if there is a short somewhere making the cyl not fire correctly?
If you are, I'm thinking why would have the short started in cyl 1 and then spread to cyl 2? So let's skip this for a second.


===NOW THIS IS WERE I LOSE SLEEP: MECHANICAL===
Oh man did my dad try and keep maintenance up on this truck. But with his age going up he forget things (it scares me the things he was able to do all by himself and what has happened to him over the years). Few examples: drove around without the gas cap off leading to MIL codes I had to diagnose and realize the gas cap was in the truck bed. I've found empty and spare 5w-30 quarts in the cabin when the truck takes 0w-20/5w-20. I have found empty coolant bottles in the cabin when he swears there never was a leak.

Makes me wonder: can any of my problems be because of 1) incorrect engine oil 2) over-fill/under-fill engine oil 3) over-fill/under-fill transmission fluid 4)engine overheating because of lack of or incorrect coolant
What are some symptoms I can look for or test for any problems related to the above?
I'm thinking valve cover gasket possibly?
Is it time for me to take it to a shop and get a proper compression test? (oh man if it's the o-rings)

Right now, all fluids are correct and nothing leaks from the truck - no oil, no trans fluid, no coolant - and oil consumption is normal. Engine operates at perfect temperature - warms up nicely and doesn't overheat. And besides a little fuel odor on cold startup, no smoke or anything else out of the tail-pipe. I'm worried something happened/he did something and forgot about it, why I wanted to eliminated anything related to me possibly overfilling the rear-diff at 85k miles and shift some focus to potential history.