2004 4.0L Post Engine Rebuild rough idle

[redninjazx11]

my2004, v6, 120K miles had started showing rough idling. from mile 1 to present, the engine has been glass smooth. I'll try and hand clean the carb.

BTW, for those who have experience a CEL with VTC/TRAC lights on. tighten the gas cap and disconnect the battery. This removed all warning lights. so simple.

 

[Nathana92]

I'm not sure what you're trying to say. Your thread title sounds like you rebuild a 1GR-FE but your post doesn't follow that at all. So basically your truck started having a rough idle? But then you said you're going to clean the carb to try to fix it? If you were looking for advice id say good luck finding a carburetor on a modern EFI engine. Also just to clarify there are more causes for a CEL and VSC lights than a loose gas cap, like almost any other trouble code. So basically what?

 

[Stuck CAPS]

I'm not sure what you're trying to say. Your thread title sounds like you rebuild a 1GR-FE but your post doesn't follow that at all. So basically your truck started having a rough idle? But then you said you're going to clean the carb to try to fix it? If you were looking for advice id say good luck finding a carburetor on a modern EFI engine. Also just to clarify there are more causes for a CEL and VSC lights than a loose gas cap, like almost any other trouble code. So basically what?

Maybe carbon? From the TB? I don't know, but since it was running fine before, with no real symptomatic foreshadowing, it could just be the intake needing some cleaning.
[MENTION=29133]redninjazx11[/MENTION]: Try pulling the MAF sensor and spraying it with some MAF sensor cleaner, but don't touch any of the inside piece -- i.e. wiping it down. Then pull the throttle body, spray some TB cleaner, and wipe the carbon buildup. Pull the battery leads for like 10 minutes, and reconnect to reset the ECM and see if that changes anything. If that doesn't do anything, try seafoaming like the others have said. If the seafoam doesn't work, try the PCV valve replacement. Really, I'm just trying to get you to do this medial, cheap stuff before you take it anywhere, so you could potentially save yourself a lot of $$$.

It could also be a number of other things. Does this "rough idle" come with any distinct sound? It could be the serpentine belt, one of the pulleys it's connected to, the fan clutch, etc. Just kind of check each thing that's visible and moving or has the potential to get dirty/clogged. Just try to cover all your bases.

 

[bgravy]

Same problem as OP

2004 4runner 4.0 v6. My issue is identical to OP. I got my 4runner back from the shop $4,200 later after repairing head gaskets, machining heads, a couple valve replacements, rebuild, water pump, etc. Has more power and drives great but it idles rough which was never an issue beforehand. Shop checked for vacuum leaks and found a warped plenum (not gasket but the entire plenum). They replaced it without charge and are stumped bc the rough idle is still there. At this point the shop offered to take it to dealer to see if toyota can figure it out. I have about 1500 miles on it since rebuild and I've started noticing a noise that sounds like a bad pulley but is intermittent not constant. This sucks haha. I'll keep everyone posted on outcome and if I get any answers.

UPDATE: Engine failed compression test at dealer.

 

[lordgeese]

Why not just check for the failing HG, I've been looking for a 4th Gen 4R for a bit now and so far I've found several that have a bad HG and the owners dont even know. I just went on amazon and bought UVIEW 560000 Combustion Leak Tester but there are others.

 

[PTPT2002]

2004 V6 4runner Low idle after head rebuild

BGravy, i have the same year model as your 4runner (04 4.0 V6) and had the head gasket replaced a couple of years ago. Had put on 20k miles since then. However, i am experiencing the same identical issue that you are having. I would occasionally have low idle when i am at a stop light (520-620 RPM). It got better when i put it in neutral or if the AC compressor is on.

Would you share with me the latest update with your truck? I want to see if you are still experiencing an issue with compression or whether it is caused by something else.

2004 4runner 4.0 v6. My issue is identical to OP. I got my 4runner back from the shop $4,200 later after repairing head gaskets, machining heads, a couple valve replacements, rebuild, water pump, etc. Has more power and drives great but it idles rough which was never an issue beforehand. Shop checked for vacuum leaks and found a warped plenum (not gasket but the entire plenum). They replaced it without charge and are stumped bc the rough idle is still there. At this point the shop offered to take it to dealer to see if toyota can figure it out. I have about 1500 miles on it since rebuild and I've started noticing a noise that sounds like a bad pulley but is intermittent not constant. This sucks haha. I'll keep everyone posted on outcome and if I get any answers.

UPDATE: Engine failed compression test at dealer.

 

[DanielMaat89]

Reset Short Term Memory

I had a similar problem when I cleaned the throttle body. I took the negative battery terminal off, went to bed, then reconnected it in the Moring. The computer relearned the idle after about 100 miles and ran smooth again. I would imagine some of the idle characteristics have changed with new heads and a good head gasket now.

 

[Danmac22]

Any more details on the compression failure and what how did you respond?

Any other updates?

My story is the same as op. I had the head gasket replaced 1000 miles ago and notice a very mild rough idle while being stationary in drive. The idle will fluctuate between 500-700 (with and without ac on). The power seems better post gasket work and mpg is average. I've done the following within the past 3 months (in order):

-new spark plugs
-cleaned MAF
-cleaned K&N air filter
-cleaned throttle body
-replaced head gasket and all associated gaskets with tearing out the heads
-replaced water pump
-replaced pcv valve (helped some)

I'm left scratching my head? Also I don't recall the idle issues before head gasket change.

(2005 v6 4wd sr5)

 

[Nevek08]

Hey did you ever figure out what was the cause?