Hunting ingnition timing at idle

I have a 2000 SR5 2.7 that has 261K on it. But got a cyl 1 misfire code a few weeks back along with a some what cruddy idle and have spent some time trying to track it down. What I've have done so far is swapped plugs and coils around. No difference. The plug wires were 90K old so put new in. No difference. Cleaned MAF checked EGR valve operation. No difference. There are no vacuum leaks (21HG at idle)or Exhaust system leaks. The cat and 02 sensors are working as they should. LTFT at idle is -12 and hovers around 2-3 at a steady 60 mph. STFT at idle moves up and down around 0.0.
At idle my ignition timing moves from 6 to 14. Most of the time it will stabilize 11-14 but then suddenly spike down to 6-7 then back up. It might do that every 3 seconds or so then then get tired of that and stabilizes until it decides to do other wise. At speed its almost rock steady. And there are no funny funky noises from the fr of the engine. I'm old school and my 68 Chevell SS 396 had an almost rock steady timing at idle. And that engine had never been touched. This timing hunting around bugs me..Should it??
I appreciate any suggestions. Thank you.

 

yes to the ignition hunt... my issue is with the negative fuel trim... sounds like there might be a leaky/weepy injector. If it was my truck I would put some fuel injector cleaner in and see what it shows in a few hundred miles, cheap and simple test.
Have the valve clearances ever been checked?

 

Injectors check out ok. valves never adjusted...
I did have the battery disconnected within the last few days and have less than 80 (?) miles on is since...I havent been far I know that much..ha!

 

She still might be learning...

 

Checked all my sensors the last few days and they are all within spec with no vacuum leaks. Then yesterday afternoon I'm reading an old thread with two guys arguing about the Idle screw on the side of the TB...One says you dont touch it the other says you do....The no no dont touch it guy did win the argument. And that made me realize something about my cruddy idle. The parameters of the sensors are set in stone within the ECU. And if you upset that balance the computer cant really deal with it. When I adjusted what I thought was the idle screw on the TB ,what I changed was some of the ECU's foundation. A good example....I think? When I turned that screw up that also changed my throttle position sensor reading as far as the ECU is concerned. So changing that screw changed the TPS reading that the ECU is expecting for Idle. Which might of changed how the timing is calculated or the injectors firing. And who know what else got a little out of whack. All I know is the truck idled crappy but ran beautifully. Disconnected the battery last night and reset that little screw back to the factory setting and today I got my nice idle when cold back. And once it warmed up it idles just like it used too. It still may not be as good as it could be though. Pulled the ICV yesterday gave it a check up and clean. It opens all the way but does not close all the way. There is still a sliver of an opening testing it with the battery. Every where I read its open or closed not somewhat maybe could be should be close to being completely closed. Maybe somebody reading this will know??
I'm hoping my pending cyl 1 misfire goes away now...............Fingers crossed.

 

Ok got some of the mystery solved. The LTFT of negative 12 is gone. I replaced the banjo bolt at the fuel rail with one that I could put a schrader valve in to finally check on my fuel pressure. It showed the pressure pegged at 45 ( service manual says 38-45) no matter the RPM...But more on that later. So when I got the Russell banjo bolt from Summit racing here in town I noticed it has a smaller inlet hole than the stock one. Put it in and right away (before checking the pressure)and my negative LTFT went from 12 down to 9.9 or so..Hmmmmm why????? Maybe less fuel flow could mean sorta the same thing as less operating pressure. Not sure about that but I was moving in the right direction even ifs not the right thing to do. A few days go by and it stays reduced. So I'm not imagining things.

Decided to try something. I cleared the computer by removing the negative cable. And hooked my old regulator to vacuum and with the ECU in closed loop it idled with a LTFT at 0.0. I let it idle for 10 min and the LTFT did not change. Ok, lets put the FPR rubber line back on where it belongs clear the ECU again and when it fired up the LTFT started out at 0.0 but very quickly started going negative.

That sold me!!...Rockauto.com and a new one is on the way..Saved almost $40 over the local Zone..ha! I installed the new FPR this morning and LTFT is solid at 0.8 at idle even after a test drive. STFT at idle moves over/under 0.0. The engine had a tiny hesitation just giving it throttle before and now thats gone and its definitely peppier. The timing I dont know? It looks calmer in idle in closed loop.

But it is still not idling as I think it should. It is around 700 but I believe it could be smoother. It may be, the IAC valve is also acting up?? I had it off a few weeks back for cleaning and testing. It was very clean and it opens completely, but does not close completely. There is a sliver of opening. Every where I look and what I hear is open/closed. I'm still not sure though.
One thing I will do is put the stock fuel rail banjo bolt back in. keep the Russell for future pressure testing. Maybe that will help my idle? I doubt it as I had a lower idle before swapping them. But if there is one thing I've learned is the ECU can compensate for a lot until the tipping point then most of us have multiple issues and that is what can make this emissions stuff so confusing.

I hope this helps somebody...

If I do figure out my slightly low idle.................................I will be back

 

The timing is supposed to fluctuate at idle. The 1996 repair manual says it should fluctuate between 7-18° BTDC @ idle and with TE1 and E1 jumped at the DLC1 it should be 3-7° BTDC @ idle. I'm guessing it's similar for the 2000. I'm not sure about any other problems.

 

I'm doing ok then..haha. Mine is only 6-14 degrees. There is very little too go by in either the Hayes or Chilton manuals. Its a little frustrating.
Thank you!

 

You mentionned a bad cylinder..
Starting from the basics,...did you do a compression test....I know it sounds nutty..
Sometimes stuck rings,...or cruddy valves at this milage could do funky things.

The point being,...is the idle situation because of general wear accross all cylinders,...or just one? (lets prove it).
And then go from there.

Keep it simple...
Good spark?
Good compression?
Good fuel?..

Then work the diagnostics from that point on...

Just my $0.02

 

Compression test showed cyl 1 17lb of pressure lower than the others. A little oil bumped it up. looked at my ignition system a month ago. I swapped plugs and coils no difference. I did replace the plug wires as they had been installed 90K miles back. I have a tool that plugs into a plug wire and I can increase the distance between the points. The spark will jump 20MM or more so a nice hot spark. OHM checked my MAF. Its within spec and on my scan tool reports the correct air temp and flow at idle is .44. I assume the ECU is getting that same info. I cleaned my TB and IAC valve and EGR valve. Tomorrow I will disconnect the IAC and see if the idle changes in any way. If it doesn't I guess my next check is for power and signal. If it does then I'm almost at a loss as to what check. And did OHM check the TPS and on top of that.
Two days ago after a short drive I pulled into a parking lot................and it idled beautifully. Couldn't believe it!!! Luckily I had hooked the scan tool b4 leaving the house it was smooth at 750rpm. Lasted maybe 10-12 seconds than went back to its usual crappy idle. First time in 6 months it idled like that...I dunno? But not ready too give up.

I posted earlier today that I had replaced my FPR and finally had LTFT at 0.8 at idle after 14mile high speed run...Went out later and when I got to my destination, sadly the LTFT was negative again...But only 4.7 versus the 9.9 I have had for a short time now. If it stays improved I feel justified in spending $50 on a new regulator.

 

Check your valve clearances... as the clearances tighten between the follower and the cam the camshaft has a longer duration... think rumpity rump long duration cams on V8’s, poor idle, no low end vacuum. Is this what is happening on yours, dont know until you check clearnces. This is in only extreme cases.

 

My vacuum at idle is 19Hg and rock steady. I'm happy with that. But that doesn't mean I dont need some sort of valve adjustment. Soon I will be measuring them.

 

Ok finally got to checking valve clearances...Rear exhaust valve cyl 1 .000 clearance. Ok there's my cold misfire and crummy idle. Ordered Schley tool 88250 and dove in! Replaced that shim with the 2.500 from our friends at Toyota. Clearance ended up at a tight .008. Did a little sanding with a piece of glass and sandpaper and got the clearance too .010 Not optimum, but have a excellent smooth idle again...Ahhhhhhh so nice. Only needed one new shim for the intake side and ended up with 6 total new on the exhaust. Four get swapped around.

Ended up with warm engine compression 1-4 respectively 120-135-140-132 not corrected for my altitude. Leak down same order is 58-53-56-52% All in all just fine for an engine with 261K that idles nice runs great and burns no oil.

I have been doing almost all my own work for many many years. And I say now I'm truly sorry with my self for not checking the valves much sooner than this as I've owned this truck since it had 25K on it. So my advice too those who read this post and have never checked valve clearances. Do it! Do it now, so you know. Ya know?

The good thing about this whole 6 week process..Is I have learned quite a bit about my truck emissions system and fuel trims and its all good. The only bad part replaced was the Fuel pressure regulator.

I appreciate everybody's comments and suggestions.
Thank you!

JB

 

42 to 48% leakage? eeek. Well what are you gonna do beside drive it till she don't go anymore..

 

I see no reason why this engine wont go another 100K. Maybe more?
I've got a 2006 Honda Goldwing 1800cc motorcycle, checked the leak down on it just a few minutes ago. 1-3-5-4-6 are 40-46% # 2's the champ at 35%.....bought the bike brand new, it now has 197600K...And like the truck idles and runs beautiful and burns no oil.

Why are you so worried???

 

You did some great logical troubleshooting and diagnostic work here brother. I really appreciate you taking the time and typing it all up. Great info for peeps in the future.
Looks like @Glamisman nailed it with the valve clearance check. He's pretty darn good with this stuff.
I'm so glad people, in general, are so willing to help others out man. This forum helps show that the good still FAR outweighs the bad in the world

 

Yes Glamisman nailed it!!! And thank you for your kind words.
Happy Holidays!!

 

I'd be a little concerned that the bucket was damaged for the clearance to be that low (0.000). Did you take the exhaust camshaft off to get to the shims? Were other exhaust clearances very tight?

The low clearance could also mean the valve is worn down where it contacts the seat, so I wouldn't bank on 100k more miles, but keep driving and deal with that if/when the time comes.

 

The shim is higher than the edge of the bucket, so no worries there. .The remaining exhaust valves were all tightening up in the range of .006 to .010. Did not remove the cam, I used Schley products tool. So the one that was .000, now with the thinnest shim I could get ended up at .0075. Then after a little sanding with a piece of glass, oil and sandpaper ended up at almost .010. All others ended up hovering around .012. The intake side was better it only needed one new shim and I used two old from the exhaust to get them in order. The exhaust .009 one I will have to pop out and sand some more. But it can wait.

 

When I was searching for info a few years ago I found a few cases on other Toyota forums where the bottom side of the bucket got bent for some reason, so that it was sitting higher up on the top of the valve stem. I can't explain why or how this happens, but it's something you may not notice unless you remove the bucket to inspect it. I just don't understand how one valve was so much more out of spec than the others. Maybe once it got a little tighter than the others it caused a higher rate of wear on the valve causing it to tighten up the clearance faster than the others. (pure speculation)