Yet another *sigh* IDLE issue.
12-11-2009, 10:04 AM
#1
Yet another *sigh* IDLE issue.
From the searches I've done on this board it seems that everyone who starts a "help my idle is screwed up" thread has a unique problem that prior threads have not addressed. Here's my own version:
Quick background - engine was rebuilt 30k ago w/Engnbldr parts (and 268 cam), uses no oil, consistently gets between 18 and 22 mpg, and passes emissions with flying colors. The engine runs very well and the idle (i.e., no foot on gas pedal) is the only issue.
The idle on the 4Runner seems to have 3 distinct modes.
1) Low idle with occasional stalling. Will idle down to about 400rpm and sounds suspiciously like one cylinder is not firing. When this is the case I usually pull the e-brake and keep my foot on the gas a bit to keep it from stalling.
2) Correct idle at 750 rpm. This only accounts for 10% of all idling
3) High idle with occasional surging. Often finds a steady rpm between 1000 and 1400 rpm, or will rise slowly to 1400 and fall sharply back to 1000, repeating. At this point if I put the shifter in high gear, let out the clutch a bit to load the engine and drag the idle down, it will sometimes remain at mode 2 or simply keep surging. There is no correlation with the brake pedal in this mode.
This behavior has gotten more aggravated over the last 3 months. There seems to be little correlation with engine warm-up as the 3 modes can occur at any time. However, upon first start-up it usually idles correctly for 5 seconds and immediately refers to mode 1, stalling 10 seconds later. Sometimes if I negotiate a tight turn and push in the clutch to coast the engine will stall mid-turn, regardless of if it has been running for 5 minutes or an hour.
Yesterday I pulled the spark plugs (NGK iridiums, installed in 06) and they had moderate wear with some slight ash buildup. I cleaned them off and reinstalled with no apparent changes. I am planning to do the cap/rotor/wires though I doubt this is the issue since it runs so well. Throttle body was clean (all intake passages were cleaned during the rebuild).
I also pulled the auxiliary air valve yesterday. The sliding gate was operating correctly and there was no buildup or plugging. I do not know if the bi-metal part is working. I bought a used one on eBay (should be here next week) just to see if I might luck out and find that was the problem.
The TPS was checked/adjusted within the last 2 years but I will check again if it seems like it may be the culprit.
Please share any advice or troubleshooting tips. Sorry for the long-winded post but I know alot of you guys are great mystery solvers and can use all this information. Thanks!
Quick background - engine was rebuilt 30k ago w/Engnbldr parts (and 268 cam), uses no oil, consistently gets between 18 and 22 mpg, and passes emissions with flying colors. The engine runs very well and the idle (i.e., no foot on gas pedal) is the only issue.
The idle on the 4Runner seems to have 3 distinct modes.
1) Low idle with occasional stalling. Will idle down to about 400rpm and sounds suspiciously like one cylinder is not firing. When this is the case I usually pull the e-brake and keep my foot on the gas a bit to keep it from stalling.
2) Correct idle at 750 rpm. This only accounts for 10% of all idling
3) High idle with occasional surging. Often finds a steady rpm between 1000 and 1400 rpm, or will rise slowly to 1400 and fall sharply back to 1000, repeating. At this point if I put the shifter in high gear, let out the clutch a bit to load the engine and drag the idle down, it will sometimes remain at mode 2 or simply keep surging. There is no correlation with the brake pedal in this mode.
This behavior has gotten more aggravated over the last 3 months. There seems to be little correlation with engine warm-up as the 3 modes can occur at any time. However, upon first start-up it usually idles correctly for 5 seconds and immediately refers to mode 1, stalling 10 seconds later. Sometimes if I negotiate a tight turn and push in the clutch to coast the engine will stall mid-turn, regardless of if it has been running for 5 minutes or an hour.
Yesterday I pulled the spark plugs (NGK iridiums, installed in 06) and they had moderate wear with some slight ash buildup. I cleaned them off and reinstalled with no apparent changes. I am planning to do the cap/rotor/wires though I doubt this is the issue since it runs so well. Throttle body was clean (all intake passages were cleaned during the rebuild).
I also pulled the auxiliary air valve yesterday. The sliding gate was operating correctly and there was no buildup or plugging. I do not know if the bi-metal part is working. I bought a used one on eBay (should be here next week) just to see if I might luck out and find that was the problem.
The TPS was checked/adjusted within the last 2 years but I will check again if it seems like it may be the culprit.
Please share any advice or troubleshooting tips. Sorry for the long-winded post but I know alot of you guys are great mystery solvers and can use all this information. Thanks!
12-11-2009, 10:25 AM
#2
Check your cooling system for air pockets if you have yet to do so. Next yeah go ahead and check your tps as that may be the culprit. Then go ahead and check your afm as well. When you rebuilt the engine i'm also assuming you replaced the fuel filter, if not replace it. Another option that cleaned up my idle and made it run smooth is while your checking and or adjusting the tps go ahead and remove it and then thoroughly clean your throttle body if you haven't yet. Check for vaccum leaks obviously and also check your intake tube for cracks. Hope this helped good luck.
12-11-2009, 10:42 AM
#4
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one overlooked item is the actual throttle cable. I had one do some weird stuff like that once and did all checks and when I had the TB off to clean I for some reason checked the cable and found out it was rusted and would not move correctly, put a new one on and never had a problem after that. Worth a shot anyway.
12-11-2009, 12:22 PM
#5
What is the procedure for checking for air pockets? I didn't think the 22re needed the cooling system bled or anything.
Throttle cable is good - I actually just checked it a few weeks ago and took the 20 years of slack out of it!
So I will:
- Follow the 4Crawler/FSM TPS and AFM check procedures
- Replace the fuel filter (good suggestion - I think I forgot to do this when rebuilding!)
- Clean TB with TPS removed, of course
- Check intake tube for cracks
Great. I'll do all this next week once my new AAV comes in the mail.
It would be great to compile an idle issue troubleshooter sticky for this board since it comes up so often. Maybe someone could come up with a system for pairing up symptoms and fixes. For instance, if 90% of people who have a certain problem find that it's a vaccuum leak, then it will help folks minimize their troubleshooting iterations if they have that symptom.
Keep the thoughts coming and I'll post up my findings as I get these things dealt with.
Throttle cable is good - I actually just checked it a few weeks ago and took the 20 years of slack out of it!
So I will:
- Follow the 4Crawler/FSM TPS and AFM check procedures
- Replace the fuel filter (good suggestion - I think I forgot to do this when rebuilding!)
- Clean TB with TPS removed, of course
- Check intake tube for cracks
Great. I'll do all this next week once my new AAV comes in the mail.
It would be great to compile an idle issue troubleshooter sticky for this board since it comes up so often. Maybe someone could come up with a system for pairing up symptoms and fixes. For instance, if 90% of people who have a certain problem find that it's a vaccuum leak, then it will help folks minimize their troubleshooting iterations if they have that symptom.
Keep the thoughts coming and I'll post up my findings as I get these things dealt with.
12-16-2009, 04:51 PM
#6
Time for an update. Here's what I've done so far:
I bought a used (and tested) auxiliary air valve and installed it. Removed throttle body, cleaned it and sprayed some cleaner into the upper plenum (with TPS removed). Tested and adjusted the TPS and it is perfect.
The truck runs the same way as it did before. Now that I am messing with it some more it looks like the actual throttle plate mechanism is sticking. For instance, if the truck is idling and I snap the throttle up with my hand, it will stay at 2000 rpm. I can move it back into position with a little force and it idles down correctly. Has anyone had good luck cleaning and/or servicing this part?
I bought a used (and tested) auxiliary air valve and installed it. Removed throttle body, cleaned it and sprayed some cleaner into the upper plenum (with TPS removed). Tested and adjusted the TPS and it is perfect.
The truck runs the same way as it did before. Now that I am messing with it some more it looks like the actual throttle plate mechanism is sticking. For instance, if the truck is idling and I snap the throttle up with my hand, it will stay at 2000 rpm. I can move it back into position with a little force and it idles down correctly. Has anyone had good luck cleaning and/or servicing this part?
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12-17-2009, 01:48 PM
#8
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Check my resolution and theory here. Mostly on the last page.
https://www.yotatech.com/forums/f116...others-196714/
I had a high idle and found my throttle stop screw being backed off caused the throttle to stick in the bore and eventually wear itself down, causing a huge gap in between the blade and bore.
https://www.yotatech.com/forums/f116...others-196714/
I had a high idle and found my throttle stop screw being backed off caused the throttle to stick in the bore and eventually wear itself down, causing a huge gap in between the blade and bore.
12-17-2009, 04:17 PM
#9
danned,
Thank you, you nailed it. Today I removed my throttle body, advanced the stop screw until the sticking ceased, reset the TPS position to match, and that was it. I also noted a substantial gap around the circumference of the throttle plate, which probably explains why my idle screw is only like 1/2 turn from dead bottom to get a good idle speed.
While I was in there I noted a huge crack in the rubber hose between the throttle body and the crossover tube. I expect good things from fixing that too!
I am also going to hunt for another throttle body that shows less gap when closed just so I can have more control over my idle speed. Although it's also possible that my "new" (aka eBay) idle air valve is faulty. Oh well.
Big thanks again to Danned - wish I had come across your thread before diving into all this nonsense. We probably need a stick that addresses idle problems with links to threads like yours.
Thank you, you nailed it. Today I removed my throttle body, advanced the stop screw until the sticking ceased, reset the TPS position to match, and that was it. I also noted a substantial gap around the circumference of the throttle plate, which probably explains why my idle screw is only like 1/2 turn from dead bottom to get a good idle speed.
While I was in there I noted a huge crack in the rubber hose between the throttle body and the crossover tube. I expect good things from fixing that too!
I am also going to hunt for another throttle body that shows less gap when closed just so I can have more control over my idle speed. Although it's also possible that my "new" (aka eBay) idle air valve is faulty. Oh well.
Big thanks again to Danned - wish I had come across your thread before diving into all this nonsense. We probably need a stick that addresses idle problems with links to threads like yours.
12-18-2009, 07:43 AM
#10
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No prob dude. I think we need a sticky about idle issues too, because as you said in your first post, a good chunk of the issues seem to be unique and not covered before in previous threads.
12-18-2009, 07:59 AM
#12
If you guys are interested, we could start a new thread and brainstorm how to categorize idle issues. Some sort of troubleshooting process with links to the necessary procedures. For instance - idle surging only when brakes are pressed = simply set idle speed correctly. Or, fora different symptom, a link to 4Crawler's TPS adjustment procedures, etc.
Who's in? We're writing the YT history books here!
Who's in? We're writing the YT history books here!
12-18-2009, 08:15 AM
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I think we should cover it all, even if it is a lot of ground to cover. A lot of the issues will cross over, just specifics will change between the 4/6cyls like timing and vacuum routing.
01-06-2010, 04:49 AM
#19
Just to wrap this up the issue turned out to be compound - a sticking throttle plate (fixed by turning in the stop screw) and a bad dashpot. The dashpot worked normally but would only intermittently drop the last millimeter or so of its throw. I removed the dashpot set screw and the symptoms are gone. I plan to clean the dashpot up and see if I can make it work properly.
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