MoJ
Moderator
You stated you cleaned the TB and replaced the gasket - you would’ve had to manipulate the main rubber giant black intake tube.
Terrible Idle After Major Service (2 Viewers)
- Thread starter TriaxialBulls
- Start date
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MoJ
Moderator
Look carefully in valleys between bellows and it’s not always obvious. In my case the crack only revealed itself when the motor was under load. It was super fun as the symptoms popped up while descending Black Bear.
- Thread starter
- #24
Alright, I’m back to report my findings.
Started the truck up today and it was idling better; however it was still low, sitting around 500RPM. I go to inspect the intake and use the propane method to look for vacuum leaks. Didn’t find any. Didn’t hear any hissing either. I took off several of the vacuum caps I had installed (like the ones for EGR or PAIR), just to make sure they were sealing. All seemed to be good; in fact, many of the ports I capped weren’t even pulling vacuum at idle, so I don’t think it’s a vacuum leak from one of them.
Then, I wanted to see what would happen if I CREATED a vacuum leak, just to see how the truck would react. I pulled this vacuum line:
and, as I predicted, the idle dropped a little bit, and there was a loud hissing from that port. Funny enough, when I put my thumb over it, the idle actually ROSE, up to exactly 650RPM, exactly where it needs to be. What is this vacuum line for? EVAP? I’m not sure if it’s actually the root of the problem, or if I’m just tricking it into running richer by momentarily capping it. That would be a roundabout way to raise the idle, but not actually address the root of the problem.
Started the truck up today and it was idling better; however it was still low, sitting around 500RPM. I go to inspect the intake and use the propane method to look for vacuum leaks. Didn’t find any. Didn’t hear any hissing either. I took off several of the vacuum caps I had installed (like the ones for EGR or PAIR), just to make sure they were sealing. All seemed to be good; in fact, many of the ports I capped weren’t even pulling vacuum at idle, so I don’t think it’s a vacuum leak from one of them.
Then, I wanted to see what would happen if I CREATED a vacuum leak, just to see how the truck would react. I pulled this vacuum line:
and, as I predicted, the idle dropped a little bit, and there was a loud hissing from that port. Funny enough, when I put my thumb over it, the idle actually ROSE, up to exactly 650RPM, exactly where it needs to be. What is this vacuum line for? EVAP? I’m not sure if it’s actually the root of the problem, or if I’m just tricking it into running richer by momentarily capping it. That would be a roundabout way to raise the idle, but not actually address the root of the problem.
- Thread starter
- #25
Oh, I should also add that I just pulled the EFI fuse and left it out for a few minutes. Now I’m going to put it back in, start the truck up, and try to let the computer re-learn, in the hopes that it will idle higher now.
That is known as the gas filter (not fuel filter) and yes, it is related to the EVAP system.
If you remove your oil fill cap while running, it should almost die due to the excessive amount of unmetered air suddenly entering the system. If you do it BEFORE you reset the computer, and it has little effect, then you have more vacuum leaks elsewhere (valve cover, spark plug tube seals, under intake manifold vacuum hoses)
Also, after you pull the EFI fuse, turn the key to run and let it sit for 10 seconds each time BEFORE you try to actually start. Do this (3) times.
This seems to help mine not go through the high/low RPM searching that they typically go through after it starts.
- Thread starter
- #27
So you’re saying that if I take off my oil cap with the engine running, it should die? Because I just did that and it didn’t do anything at all. I still suspect I have a vacuum leak somewhere, as it really seems characteristic of that and I did change a lot of things around the intake manifold. I also replaced the valve cover gasket and spark plug tube seals, although I didn’t touch anything underneath the intake.
If that had no effect or little, then it indicates your computer is already compensating for a large vacuum leak somewhere. Track it down.
Sounds like you may have found it. That gas filter (and its nipples) get brittle and is a great spot to lean on while doing other work.
Remove and inspect.
Remove and inspect.
- Thread starter
- #30
I agree that it’s a vacuum leak, but at this point I’ve put the propane to every place I can think of and it hasn’t had any effect. I know the method works because when I take off one of the hoses I know is pulling vacuum and put the propane to it (or even near it) it raises the idle significantly.
- Thread starter
- #31
Another thought that crossed my mind was that maybe the gas went bad over 4-5 months of sitting with no stabilizer in it, and that gummed up the fuel filter.
- Thread starter
- #32
Alright so I’ve begun disassembling the EVAP system. I took the canister out, the lines were old and cracked but didn’t appear to be leaking at first glance. Should there be vacuum on the line that goes from the canister to the intake? There is absolutely zero vacuum there.
I'm not positive on the system parameters. However, I believe the idle air control valve (IAC) is part of what controls whether there is a vacuum there and it is also temperature dependent.
You really need an FSM (not a Chilton's) to go through this in proper order.
- Thread starter
- #34
I have an FSM... maybe it would help if I read it huh
So I should look at the IAC valve next? It's an expensive part so I'd rather not replace it... my next step was going to be taking the plenum off and looking for vacuum leaks under there.
I think you can rebuild the IAC valve. (Not sure) Do a search here for it. There are a number of folks who have addressed it.I have an FSM... maybe it would help if I read it huh
So I should look at the IAC valve next? It's an expensive part so I'd rather not replace it... my next step was going to be taking the plenum off and looking for vacuum leaks under there.
I am facing if not similar problem. I just bought my FJ80- noticed issues with the idle right away. Weird thing the PO said he left the car sitting for most part of 2 years and the battery completely died and he replaced it with a new battery before selling it.
If I give it gas it drives fine- but when I slow down to stop the engine will completely stall out. I first noticed it when I tried to turn into a driveway and it just stalled out. If I leave it in P- it idles pretty good but could use a tune up. But when I get into D- the idle behavior changes.
BILT4ME suggested looking around with intake hose and/or vacuum leaks. That's where I've been looking at right now.
I also noticed I have alot of moisture underneath my Power Steering so I'm wondering if I may have a major vacuum leak with the power steering pump because when I turn, it takes alot load on the engine through power steering and that's where I'm stalling out.
I'm having a Toyota specialist look at everything in 2 weeks. If he can pinpoint what is going on with my FJ- I will pass the word along if we can find a solutions perhaps that could help you out as well.
Current suspicions -
Vacuum leak somewhere
Clogged/Dirty IAC Valve
Bad TPS
Bad MAF
Power Steering issues/leak
Electrical wiring issues somewhere? My VSS right now has a torn wire right on the tranny- not sure if could be relevant to how it idles/drives.
I will keep an eye on your thread to see if you figure it out as well.
Good luck!
- Thread starter
- #37
I was spraying the throttle body with CRC throttle body cleaner. Could that have damaged the IAC valve or something else?
As long as it was that and not Brakleen, then you're probably OK.
- Thread starter
- #39
That’s good to hear, please let me know if you find anything out. I don’t see how it could be a PS issue, the PS on these trucks is gear-driven off the front of the crank. It doesn’t run on vacuum AFAIK.
One thing I noticed when troubleshooting my idle issue was, with truck off I disconnected the IAC. When I started the revs went to about 1800. Shut off truck, hooked up IAC and when started revs went down. This told me the IAC was functioning.
