Odd RPM hang on start
10-30-2016, 09:41 AM
#1
Odd RPM hang on start
Something I have observed:
When totally cold, for example sitting days, I start the truck, it starts idles up to like 1400-ish then settles down very short order, it's quiet.
When not totally cold, for example Let's say I ran it this AM and drove around and then parked for a few hours. Start truck, idles up to 2k RPM, and hangs here for a solid 20+ sec, then settles down where it should.
I figure it cannot be a vac leak, it should then do this each time, and it also runs smooth with either situation.
I have checked all seals in air inlet stream, these are good and again, it runs fine otherwise.
There are two pending codes because I recently removed my fan and went with an efan setup. It also did this prior to removing the fans.
In the past few months, this is what has been done though I don't think any of this is it:
Oil Change
New plugs
Clean MAF
Clean air filter
Replaced both o2
Fuel pump control module
New serp & blower belt
New idler for serp
Rear u-joint
Scrubbed all pulleys down, still chirpin'
New separator plate
New 1-2 accum piston
4.56's front and rear
Detroit Truetrac LSD
Fomoco efans w/ painless controller
True dual exhaust
Colder tstat
Evap canister
Ebrake cable
Installed airlift helper springs
Truck specs in sig.
This seems like a bad IAC but it simmers back down, my experience with bad IAC is the high revs persist 100% of the time, I didn't even see an IAC.
When totally cold, for example sitting days, I start the truck, it starts idles up to like 1400-ish then settles down very short order, it's quiet.
When not totally cold, for example Let's say I ran it this AM and drove around and then parked for a few hours. Start truck, idles up to 2k RPM, and hangs here for a solid 20+ sec, then settles down where it should.
I figure it cannot be a vac leak, it should then do this each time, and it also runs smooth with either situation.
I have checked all seals in air inlet stream, these are good and again, it runs fine otherwise.
There are two pending codes because I recently removed my fan and went with an efan setup. It also did this prior to removing the fans.
In the past few months, this is what has been done though I don't think any of this is it:
Oil Change
New plugs
Clean MAF
Clean air filter
Replaced both o2
Fuel pump control module
New serp & blower belt
New idler for serp
Rear u-joint
Scrubbed all pulleys down, still chirpin'
New separator plate
New 1-2 accum piston
4.56's front and rear
Detroit Truetrac LSD
Fomoco efans w/ painless controller
True dual exhaust
Colder tstat
Evap canister
Ebrake cable
Installed airlift helper springs
Truck specs in sig.
This seems like a bad IAC but it simmers back down, my experience with bad IAC is the high revs persist 100% of the time, I didn't even see an IAC.
Last edited by scobar; 10-30-2016 at 09:49 AM.
10-31-2016, 06:48 AM
#2
Mark
iTrader: (1)
Nothing about cleaning the throttle body ?
11-09-2016, 08:16 AM
#5
Some pics!
Here is the inlet plenum on the blower, it looks like some carbon schmutz on the right side of the gasket. Wish I had a borescope to peep in there better but it looks rather clean!
Inside of the TB, looks clean to me.
Here is the worst of it.
What it looks like clean.
Here is the inlet plenum on the blower, it looks like some carbon schmutz on the right side of the gasket. Wish I had a borescope to peep in there better but it looks rather clean!
Inside of the TB, looks clean to me.
Here is the worst of it.
What it looks like clean.