2002 3.4 V6 - Pinging/detonation under load

Hello all,

I've got a 2002 Tacoma TRD, 3.4 V6, 339k miles. Previous owner (80something year old man) bought it new, likely drove it very gently. I have a 2-inch thick maintenance folder and he was pretty meticulous about things.

Over the summer, I noticed a rather prominent pinging/detonation noise when the engine was under load. nothing at idle/cruising -- only under heavy acceleration or going up a hill.

I do get CEL for P0171 (System too lean, Bank 1)

New OEM spec spark plugs didn't help.
Cleaning the MAF didn't help.
Also tried running through a full tank of fuel treated with Techron, and then a few weeks later, a full tank treated with

$24 BG44K BG 44K Fuel System Cleaner Power Enhancer 11oz.

BG44K. Neither helped. Normally I am not one to believe adding magic goo to a fuel tank will cure anything, but I thought I'd give it a shot after reading about the products here and elsewhere.

However, running 89 octane fuel (med grade in IL) does help greatly and the pinging/knocking goes away, even under heavy uphill acceleration. One thing I have not thought to try until right now is fuel without ethanol added.

I did clear the CEL after each step to see if my efforts would clear the light as well as resolve the knocking. No luck.

My question is: What are my next diagnostic steps?

My thought is maybe to pull and clean the fuel injectors. I don't hear evidence of a vacuum leak, but I should also try the starting fluid trick next time I'm tinkering.

Edit: It just occurred to me that this might be useful information. I seem to be getting unusually GOOD fuel economy -- the Fuelio app tells me I'm getting 18 city, 20 highway which makes me wonder if the problem IS fuel delivery. If one side of the engine isn't receiving fuel, it's not burning. However the other side IS getting enough fuel to do the work... am I onto something here or am I completely out of my tree? (Possibly the first person ever to suggest that a Toyota truck is getting too many MPG...)

 

I dunno, but that V8 4Runner Limited sounds awful nice

 

Well thank you sir! I've driven it since it was new and it's truly one of my favorite cars I've owned!

 

My money is on carbon buildup on the pistons from being too gently driven too long.

Another possibility is getting a bit hot under those loads due to a weak cooling system or restricted air flow

Make sure there is nothing constructing air flow especially between the condenser and radiator faces, and that things like the shroud are intact .

Once you feel the cooling system is ok Google Italian Tuneup. Fill it up with premium and let 'er rip.

 

Unmetered air causing it to run lean could certainly do it. Check for leaks after the MAF.

 

Any vacuum leaking will do it, if you have never done fuel injectors cleaned and serviced it’s definitely time and when did u do a fuel filter last?

 

The P0171 can be difficult to track down as it doesnt take much to set it off. What scan tool do you have?

The first thing I would do is to take the rubber air inlet off from the throttle body and the MAF and examine it for cracks. If it old and hard save yourself the time and just replace it with all of the updated tubes, your parts guy at Toyota will tell you if there are any additional hose(s) needed.

 

These are all great suggestions -- Now that I have the 4Runner put back together (leaky transmission cooling line replacement) I can dig into the Tacoma and try a bunch of these suggestions.

Regarding carbon buildup, I looked up the traditional "Italian Tune up" procedure and did that several times on a deserted stretch of highway after the engine was up to operating temperature. No luck. Years ago we used to do a little trick involving SeaFoam and a vacuum line on the intake manifold. How do we feel about that method?

Glamisman - My scan tool is a Nexpeak NX 501

Here's my checklist:

• Check the cooling department and make sure I've got good airflow. I don't think this is the problem because the temp gauge is consistently right in the middle, but I'll check just to be safe.
• Leaks after the MAF in the big rubber inlet tube. This sounds like a good bet too just because of age, but I'm skeptical because the code says the error is in Bank 1 (Cyls 1 3 5) and I'd think an intake vac leak would cause both halves of the engine to run lean.
• I'll do the starting fluid test in the whole area if the MAF/Intake tube seems solid.
• Fuel Filter: I'll check the service records -- I've not done it yet.

Thanks again everyone for the suggestions. I'll report back with what I've learned.

 

What is your scan tool showing for short and long term fuel trims?

One thing that hasn't been mentioned yet is the ECUs propensity for learning driving patterns to try to achieve 'fuel efficiency". It is always chasing the elusive 14.7 afr number. In reality, what this tends to do is to lean out the system as much as possible. In some driving situations the result can be pre-detonation or pinging.

Have you tried disconnecting the battery (removing power to the ECU) to reset all those "learned" patterns. I have always disconnected one of the battery posts for 30 minutes to attain this. This is the number I have read on here and other Toyota forums that is supposed to cause a full reset.

 

Lots to repsond to and in no particular order. The idea of the air tube not being a source because the affected cylinders are only on one side is a valid one but it is misleading. I just had to replace a fuel pump on an 05 F150 and it showed the same thing, lean on bank one. Now you know damn well that the poor fuel pressure affected all injectors the same so why did it only show lean bank 1... dont know. I checked the fuel trims on this 200k mile truck after and trims were +- 1%

Your scan tool, it is ok at best. I downloaded and read parts of the manual and in section 4.1.6 it tells you that the readings you are looking at are not live data, you need to look elsewhere for that data. I am telling you this because you will be looking at the tool and thinking that everything is OK so why arnt my fixes, fixing this? It is because you are looking at interpreted data. Am I saying go out and buy a zoomerama scan tool, no, alternate between enhanced readings (year, make, model) and generic OBDII on the scan tool.

I did not see where there was a MAF airflow test. I am sure there is I just didnt see it. You want to set your tool up to read in g/sec of airflow. The general go-no go is 1 g/sec of airflow for every liter of displacement so your 3.4 at idle should show between 3 and 4 g/sec. This isnt a hard number it is a range... if it shows 1.5, you have a problem if it shows 6, you have a problem. This coupled with your fuel trims is an indicator of whats happening. FWIW, a + number on fuel trims is it is adding fuel and a - is it is taking away fuel. This adding or taking away of fuel is calculated in the PCM by inputs from ALL the sensors, not just the front 02 sensors so look at all your sesnsor readings, IAT, ECT etc etc.

One other always overlooked source of false air is the brake booster / master cylinder seal. There is a seal on the snout of the master cylinder inside the recess of the booster that can be torn if the tech that is putting in the replacement brake master does no know it is there and they just jamb the master in place. Squeeze off the line from the booster to the intake and see if the fuel trims at idle change.

If you need to replace a part after you have diagnosed a fault, use Toytota parts. There are too many posts of guys are chasing thier tails because of aftermarket parts not working right. There is a point where you have diagnosed the hell out of it and cant find the problem and it is usually something you cant test like injector flow and pattern. This is where you will have to make a choice... do I put $800 worth of injectors in her as a test?

Fuel pressure testing isnt easy on these trucks and this is where I would start as EVERYTHING depends on the correct amount of fuel getting into the cylinders at the right time.

Thinking about the old guy who owned her before you... he probably never really drove her too far or too fast and there is a slight possibility that the intake valves are coated with carbon deposits. If so, the injectors spray onto the valves and if there is carbon it soaks up some the fuel and she runs lean. A visual inspection is all that is required of this... this is a last resort type of thing.

 

Replace your Intake gaskets. The sealing material gets old and brittle causing it to break loose.

 

Adding that I got this on my tacoma but switching to 91 octane made it go away. Never found a good reason for the cause. I did find it interesting that the manual has this to say about it (emphasis mine):

OCTANE RATING Select Octane Rating 87 (Research Octane Number 91) or higher. Use of unleaded gasoline with an octane rating or research octane number lower than stated above will cause persistent heavy knocking. If it is severe, this will lead to engine damage. If your engine knocks... If you detect heavy knocking even when using the recommended fuel, or if you hear steady knocking while holding a steady speed on level roads, consult your Toyota dealer. However, now and then, you may notice light knocking for a short time while accelerating or driving up hills. This is no need of concern.​