99 3.4L SC - High Idle, hesitation off idle, poor mpg and surging.

[davemw]

I'm having some issues with my 99 4runner with a supercharged 3.4L
The truck has 205k on it. the SC has been on it since 60k without issues. I'm pretty sure it's still stock fuel delivery system.

Symptoms:
Idle is about 1500-1700
Stabbing the throttle off idle causes it to stumble a bit, almost like it's getting too much fuel.
When depressing the clutch and letting off gas to shift at about 2200 rpm, the rpms momentarily jump by 100.
When coming to a stop and depressing the clutch and letting off the gas the rpms jump by 100 then drop to about 700 and "bounce" between 700 and 1500 before settling at about 1700.

What I've done so far. (Each time I pull the negative battery cable.)
cleaned MAF
tested with new MAF
cleaned throttle body
cleaned IAC
lubed throttle body
checked plugs
checked air filter (paper style, not oiled)
checked vacuum lines - just that they are all connected, no smoke/fog test.

This all started after I cleaned the throttle body (only) then the following day found that the neg battery cable was lose causing the truck to not start (hadn't touched it previously)

I'm pretty much stumped at this point. I'm going to try replacing the IAC next but 200 bucks is a tough pill to swallow.

Thoughts?

 

[nevada]

dont start throwing parts at it, that can get expensive.

have you tested the fuel pressure? the pump may be failing.
also, check for vacuum leaks.

and, double check the TB. maybe when you cleaned it, it dislogged something, and clogged a port somewhere, or you accidently disconnected something.

 

[Singtoe]

Sounds like a vacuum leak. Check your hoses for tears or fractures. Do you have a boost gauge? Does it read like it always does?

Do you have any CEL codes (check engine light on)?

 

[davemw]

No CEL but I'm going to scan it today.
I'm also thinking vacuum leak.
I don't have a boost gauge, I need to get one at some point.

 

[Mudtallica]

Maybe check the A/F ratio sensor.. Sounds like the same symptoms I had..

 

[davemw]

Update,
Finally threw a CEL. checking it tonight.

 

[davemw]

Just wanted to circle back around on this incase anyone is wondering.
The CEL was for the throttle position sensor. I swapped a new one in and still didn't have a difference in idle speed.
I re-lubed the trottle, put the old TPS in and still no change. I finally gave up and took it to a local guy. I was thinking it was something with a vacuum line or bad wire.

He ended up replacing the throttle body with a used unit. Problem solved.

For reference. Total cost of diag/work and parts was $370.00

 

[theizzardking]

Just wanted to circle back around on this incase anyone is wondering.
The CEL was for the throttle position sensor. I swapped a new one in and still didn't have a difference in idle speed.
I re-lubed the trottle, put the old TPS in and still no change. I finally gave up and took it to a local guy. I was thinking it was something with a vacuum line or bad wire.

He ended up replacing the throttle body with a used unit. Problem solved.

For reference. Total cost of diag/work and parts was $370.00

well that's odd, the actual throttle body was bad? that's a first for me , never heard that one before...

 

[davemw]

I didn't want to believe it, especially when he quoted me 1100 for a new one! Looking at it, I could see there was play in the butterfly shaft and signs of the flap scraping on the intake.

I almost want to think the IAC valve was the real problem and that he just swapped a TB wit IAC on it and it fixed it. Either way. It's fixed and I'm done effing with it.

 

[theizzardking]

I didn't want to believe it, especially when he quoted me 1100 for a new one! Looking at it, I could see there was play in the butterfly shaft and signs of the flap scraping on the intake.

I almost want to think the IAC valve was the real problem and that he just swapped a TB wit IAC on it and it fixed it. Either way. It's fixed and I'm done effing with it.

haha fair enough, i know exactly where your coming from, sometimes you just don't care and want your truck to run right, haha, well glad it got fixed, mind if i ask the mileage just for mental reference? and you saw the play for yourself?

that's just very strange unless you just sit at red light rev'ing your motor for drag races all day everyday since the truck was new, lol, anyone else ever hear of this ?

 

[davemw]

206k on it. I did see the play myself but I honestly don't think it was the problem... I just ran out of time to keep troubleshooting and needed it fixed. My next step would have been to replace the ICS.

I have herd of others having the same issues with idle not dropping, and replacing the TB was the final fix.

 

[nevada]

206k on it. I did see the play myself but I honestly don't think it was the problem... I just ran out of time to keep troubleshooting and needed it fixed. My next step would have been to replace the ICS.

I have herd of others having the same issues with idle not dropping, and replacing the TB was the final fix.

play in the butterfly can be a big problem.

some TB's have a replaceable bushing, just for when that happens.

 

[8sm]

I know what you mean by making the problem go away. After awhile, as long as the budget can handle the hit, just fix it.......RIGHT LOL. Been there done that a few thousand times.

Keep'in your guy honest, did get your old TB back with the IAC intact.

I'm sure you're glad it's over.

Regards.......8sm