FIXED!.. I think ;) Need help chasing down sudden rough idle!

Hey guys. I wanted to post an update when I had a little more info, but I do have info to share.

1. Did a lot more reading (which leads to answers, or more to worry about
2. Bought, received, and installed (a couple of days ago) a used replacement OG Denso MAF sensor. (FYI, it was clearly dirty when I examined it upon arrival. I shot it clean with MAF CRC spray and let it dry in our local hot weather for about 4 hours before install. Cost on ebay was $17.85 shipped. Local salvage yards wanted $75 - $100 for a used one.) Ran fairly smooth for about a day... then noticed that rough idle was back... what gives? MAF sensor did make a difference for a bit.
3. Bought and used and Elm327 mini obd2. Bought Torque Pro app. Been driving and logging readings. Want to drive some more after re-checking some engine parts.

I want to see about doing a compression test tomorrow if I can. I already have the Pepboys loaner gauge. I'll post more soon. Still gathering evidence

 

awesome job on the elm327 + torque! now im more curious about your LTFT and STFT while idling cold and warmed up. keep in touch

 

Ok. Here are some photos and a little more info that I'd appreciate all of ya'll's input on. I pulled the #4 plug again. As I described in Post #1, plug #4 still isn't burning the same as the other plugs. I only pulled one of the other plugs (by the way, it was plug #1 which is the plug with Ignition Coil #1 - passing current over to plug #4.) When i've pulled all the plugs, they all are burning about the same, except #4, so I didn't check the rest since I just did about 2 weeks ago. You can see the photos the difference between the much more virgin plug #4 and the burning of plug #1.

I reset the ECU by discharging the system this morning early. (touched + and - cables together for about a minute, also connected + only and hit brake pedal about 15 times). I drove this evening for two driving cylcels totaling about 30 miles to see if possibly, the ECU still had memory from before I totally cleaned out the TB and IAC, replaced the MAF sensor, changed the wires and plugs.

As of a couple of days, the idle at stop in Drive wasn't too terrible, but still annoyingly noticeable. After purging the ECU today, and driving this evening, the idle seems a little bit more calm, but still not normal. It may be that I need to log more miles and time driving for the ECU to re-learn everything properly again, but the cleaner spark plug indicates something isn't normal. Unless, the ignition coil pack associated with plug #1 and plug #4 has been providing less current as dictated by the ECU because the ECU had adjusted for the previous plug in chamber #4 which had become totally loose inside there. I also show a photo of some oxidation on the ignition coil pack pin where wire #1 connects (the other end of wire #1 goes to plug #4 - I tried to clean that oxidation up as much as possible this morning before re-connecting wire #1 to it. The photo shows the oxidation before I cleaned it. Ignition coil pack #3 pin looks like new compared to this one - #1.

I didn't get around to do the compression test today.

My LTFT1 has been consistently high. Although while driving, it does reach 0 but the Torque app shows it constantly changing while driving. Photos below. What do u guys think?

 

6% is ok. its upwards towards 10-15% that raises a flag. the 6% is probably just from the computer running rich while the engine warms up. that's normal

the idle on my truck is around 650-750. you're engine being under 600 is the only indication of an issue that I can see from your pics.

it may be just something like the idle air control valve, cold start valve, or the idle screw isn't adjusted properly. see if the screw and it's nut are still tight.

let's see what other people say before you go further.

*edit*

after some quick research, when was the last time you changed your air filter or checked inside the housing? there may be something restricting airflow which may also cause this.

 

Thanks for the reply. The RPM in the screenshots above are actually showing the engine while I'm pulled over, stopped, but in Drive. The RPM's in Park are about 700 +/- (normal).

I've ran the engine for miles, and it still will show my LTFT1 hit 5%, 6%.

The Idle Screw has never been touched as far as I know (I've owned the truck since new).

The day before yesterday, I pulled the K&N filter again, washed it with the K&N detergent spray, dried for hours, even ran a low heat - low speed hair dryer about 12inches away to totally dry it, re-oiled K&N filter oil. Re-installed.

Any (yours or anybody elses) opinion on that plug #4 lack of burn???? In my opinion, for those that are familiar with the feeling, it almost feels like it has the wrong plugs installed - but

$18 K16TR11 Spark Plugs, Pack of 4

K16TR11 are obviously correct - all gaps checked/re-checked (.025 factory set from side electrodes to center electrode - don't ask me how that works with only official Toyota gap setting info that states it should be .044 ).

 

Did you try just replacing that plug? It could be defective. Maybe even put the old wire back on to check the new one

 

Actually, in post #1 of this thread, I talk about that (and a million other facts, lol) I'm on my second set of brand new plug wires and second set of brand new plugs. Thanks for the input though.

 

Slim chance but have you tried a stock filter?

 

No. I thought about that. I know I have old unused one in a bin in the garage somewhere. I should dig it up and try it.

 

One other related clue I've mentioned before. Since all this started, I always see clear condensation accumulating and dripping out of the exhaust pipe. No matter what the temperature is outside. Here in my area of So Cal, daytime temps have been around 88° to 100° for the past few months. Nightime has been no less than 55°. Any opinion on that and the "clean" plug #4 situation? (see above on this page).
If you're new to viewing this thread - Hello! To avoid making this thread way too long with posts, I ask you to please read at least post #1 because I've been asked questions that are answered there. I appreciate everyone's help though

 

I wonder if you don't just have water in your fuel tank. are you using a shitty gas station who may be illegally adding water to the fuel?

try adding ISO-HEET to your tank and seeing if that works out. every parts store should sell it.

and even though you said you checked the air filter, did you check the rest of the housing? check for debris or puddles of water in there?

 

I usually only use ARCO 87. Although, because of the issues lately, I've been using Chevron 89, 91 for the last couple fill ups.

The air filter housing was clean and dry. Below is a picture of how I set it up. BTW, the configuration of how I set up the filter housing shouldn't be a factor since I modded it, as you see it, about 11-12 years ago. BTW, I always leave the top cover off the housing to get more air flow in. The filter was out, drying after cleaning it in the photo below.

I feel the sudden appearance of constant moisture/condensation has to do with how the engine is misbehaving. A poor mix of air to fuel or something like that caused by -????-. Which -???- is what is the main question I'm looking for the answer to.

I drove the truck earlier for about 10 miles. At first for the first 15 minutes or so, it ran fairly normal! But, after about 15 minutes, the obnoxious roughness of the idle came back. Although it came and went - came and went.. !..?. I now positively identified when it happens. While driving, the truck feels good. Come to a quick stop, the truck feels good. The roughness (not major mind you) is noticeable about 3 seconds after coming to a complete stop. I pulled over, and stopped in Drive for almost a minute many times to confirm.

 

here's an interesting thought. but just might be it. the intake gaskets also seal the intake manifold's water ports that go between the heads (see 4 corners of manifold in pic). it could have a pinhole leak seeping into the intake, or the manifold itself could have a leak internally. not enough of a leak to notice any missing water, just a few drops that cause condensation and a rough idle.

what got me thinking was realizing almost all intake gaskets also gasket the water ports between the heads, and that you said 1 of your plugs was burning differently. it would have made great sense if the #4 plug (as you've said) was right next to one of those water ports justifying the discoloration. but only 1, 2, 5, and 6 are near the water ports. im kinda hoping you mis counted your cylinders and it really is one of these



mainly because the only other solution that I could think of is....... you have a crack around the #4's combustion chamber... i've pressure tested a lot of heads at work and though I haven't found an aluminum head that had a crack leaking into the chamber, i have found 1 that had a crack leaking into the valve covers under the camshaft. and it is very possible for a crack to occur between the water jackets and the chamber or even just the intake ports where there is no pressure and always vacuum. you wouldn't be able to see this kind of leak on a leakdown test btw.

im really not sure how to test for this btw aside from removing the head with the misbehaving spark plug and taking it in to get pressure tested.

i hope it isn't this and good luck!

 

Lol, I hope it isn't either!!!! First, thanks for all the time you've dedicated to giving me good info based on real world knowledge. Well, I did happen to identify the plugs correctly, lol. Yes, 100% sure my plug #4 isn't burning like the rest. Along the idea that there could be some damage in plug #4's chamber, I had read about messed up threads by popped out plugs that seems to be not uncommon to Tacomas from what I've read. I neglected mine for years, otherwise I might have caught this plug in the process of loosening. The plug that's in there now screws in by hand fine and does tighten up after seating with the torque wrench (yes 13ft lbs), but as I've mentioned, it turns to 13ft lbs within about 1/8 turn after seating by hand.

What I had read about the damage made by loose plugs was irreparable damage to the threads, hence fixing the situation. What I found was the soundest solution was the use of Time Serts much more than Helicoil's. The way the plug actually does tighten up makes me feel I may be ok on the thread, but that's not to say that there may be a crack. I've read that condensation escaping the exhaust is not to be too concerned about, but in my case, it's obvious to me that it's happening much more frequently then I've ever seen it before. It has to be a by product of the reason for the idle.

I may start another thread just to ask about the clean plug vs. the other plugs. Seems that the other contributors to this thread are done with it. Multi page threads tend to turn people off. I failed to share that I did a smoke test to check for vacuum leaks, but that didn't show anything. I was tempted to do the carb cleaner spray test for vacuum leaks, but that test scares me to be honest, lol (see Eric the Car Guys' vid on youtube). For now, I'll keep driving and see if it develops into something more obvious. I hope not, but time will tell.

 

I wanted to come back to the websites where I posted my rough idle problem as a courtesy to those that helped me and to those that might have a similar issue.

So after purchasing items that I didn't need in trying to fix this problem (another MAFS, 2nd set of new plug wires, 2nd set of new spark plugs, fuel filter, 3 bottles of fuel injector cleaner, thread chaser, 1 vacuum hose, and other stuff) It looks like the culprit was either the No.1 Ignition Coil Pack, or it's boot.

I bought the used ICP on ebay for $25/$5 shipping. When I got it and went to install, I pulled the suspect: ICP No.1 (suspect because No.1 ICP was providing the spark for plug No.4, the plug that had been boppin around loose in it's chamber for a while along with loose plug boot.) When I pulled the boot just for curiosity sake on the original No.1 ICP, I noticed the thin coil/spring inside the boot was very "jittery". It wasn't on the used replacement ICP. I also had already noticed the pin on the ICP where plug wire connects was very oxidized compared to No.3 ICP, which was clean.

At any rate, I've been driving it around for the past week and noticed the rough idle dramatically, yet not immediately, subside. I really wouldn't complain about my idle now, other than so far, once in a while, it does idle a little rough, kind of like a small vibration while stopped in traffic. It's only about 15% of the time though, and could be either the ECU re-learning or just the natural engine wear. I do notice that my STFT1 and LTFT1 are showing larger numbers. STFT1 as low as -6% and up to +5%. LTFT1 ranging from 0% to +9% while driving. The last bottle of LUCAS is probably just exiting the fuel system as I just filled up 2 days ago after being near empty with LUCAS in the tank.

There's been one occasion since changing the ICP where the idle/rpm's did drop to a noticeable shake, but not crazy harsh. Still, it caught my attention. Hasn't happened since. Could be adjusting, even though I purged/discharged the ECU system again.

Anyway, hopefully this is behind me. My next to do's will be changing the original timing belt, water pump, thermostat, and belts. :wink

 

I suggested that about 1000 post ago.. Almost wanted to say poss. burnt exhaust valve.

 

I was starting to think I had a bad valve. That's why I used the Lucas as a long shot for a band aid fix. The Lucas lubricates valves, not that this would have necessarily alleviated the issue. I still see a bit more clean condensation coming out of the exhaust pipe then I'm comfortable with. More than I remember before this whole deal.

 

since there is still a little "something something" there pull the other two coil packs and inspect very very carefully for any sign of "anything" and that might be where that little "something" still exists.

glad I came across this post as I have an unexplained "random" rough idle on mine as well after doing most of the common things you did on yours.

I just bought a new set of plug wires but haven't installed them yet but after reading this thread, I will be looking hard at the coil pack condition when I do.

 

Yeah, earlier in this thread I mention the other coil packs, and why this particular coil pack was suspect, although based on the clues I gave, this coil pack wasn't picked out as the possible cause in this thread. Lot's of other good advice which is why we come to these forums, but sometimes we find the obvious on our own by sheer trial and error/re-try.

I suspected the coil packs from the beginning, but because I thought they'd be expensive to replace, I focused on all the other things I mention that I tried. That was dumb, and not dumb at the same time. It "could of" been one of the things I tried, but as we see, it looks like it was none of those things (hopefully :| ). Wasn't until I realized that used parts can be good that I decided to look for a used coil and found they go for about $20 to $25 bucks on ebay for oem.

I'll probably throw in my original MAFS back in since it actually looked cleaner than the used replacement I installed (which didn't make a difference anyway).

The correct way to check the coil pack is to measure it's resistance as compared to factory specs and/or put the engine on an oscilloscope and run tests for individual measurements/performance including ignition components like the coil packs. I didn't have the means to do either.

 

I've had a similar problem with mine and I assumed I needed to replace the coil packs. Good to see that was your solution.

Did you leave your spark plugs at .025 gap? Mine were all gapped that way from the dealer too, but I widened it to .040. My guess is those plugs may be used in another Toyota engine and they don't come gapped for the Tacoma... maybe