2006 Seqouia.. I am baffled

so my buddy is having some problems with his 06 sequoia.  It'll stumble on startup, and then stumble when taking off from a stop.  Not down on power.  It throws the random misfire code and then a misfire for all cylinders.   

2006 Seqouia with a 180K miles.  T-Belt was done about 1500-2000 miles ago.  Issue happened shortly after getting a load of gas from costco.  No obvious leaks, cracked hoses etc..  idle is rock solid steady.  Plugged in my OBD2 scanner and used dash commander... nothing looks odd while driving.  etc.   My thoughts were, run a bunch of seafoam to eliminate bad gas issue, and potentially clean a clogged fuel filter..  

interwebs says... clean the MAF and then it's a coil problem, but if a coil problem, it wouldn't set it a fault for all?

What am I missing?

I'm going with the fuel thing. 

Well, the "it started after getting gas from Costco" doesn't mean anything on its own - I mean, car problems always start after getting gas from somewhere. Now, if you mean it started acting up within minutes of leaving the station, okay, because otherwise it probably has nothing to do with Costco.

In reply to kb58 :

He drove home. Shut it off at the mailboxes  then when he started it up it did the stumble.

Could be gas, though I've found that the 4.7 in the Sequioa will basically burn anything. When I bought my Porsche it had 15 gallons of 4-5 year old gas in it that I drained. For the Sequioa's next three tanks I just mixed 5 gallons of it with the rest of the tank of fresh fuel and it burned it up no problem, with no observable effects. This truck has refueled at so many backwoods gas stations towing to rallies, with God knows how old fuel or rusty tanks. Never an issue. 

I'd bet on a bad coil. I think I've replaced one or two over the years for an occasional stumble that threw a code but otherwise the truck drove normally (mine has 125k miles on it, and is an '05). That's all I got. 

tried replacing the fuel filter?  or preemptively replacing the fuel pump?

In reply to irish44j :

I'd agree with this but all cylinders are throwing codes. 

Fueled by Caffeine said:

In reply to irish44j :

I'd agree with this but all cylinders are throwing codes. 

doesn't always matter. I've found that OBD2 is amazingly nonspecific when it comes to individual misfire codes. May not be the case here, but just saying that in my experience on various cars a single coil going bad can cause a general "all cylinder" misfire code in some cases. 

In reply to irish44j :

Yeah its throwing the random misfire code and also misfires on every cylinder. All individual codes  

Stumble from stop sounds vaccum related

I would look again at doing all 8 coil packs.  

I dont see them all failing all at the same time. Very weird. 

random misfire combined with multiple cylinder misfires always sends me looking for unmetered air, ie the engine sucking air somewhere between the MAF and the TB.   anectodal, i know, but i'm 5 of 6 with this being the root cause.   on the 6th, it was a split vacuum hose to the brake booster.

I know you said no broken hoses but my first suspicion here is a cracked intake tube between the maf and throttle body. At rest it won't leak much but when the engine shakes or torques over to one side it'll pull on the hose in a way that opens the crack and lets it suck a gulp of unmetered air. Have you taken it off and looked at it?

In reply to Vigo :

I checked all the small vac lines but did not check the intake tract   

Antihero said:

Stumble from stop sounds vaccum related

I'll +1 that, had a car do that with random/multiple misfires at idle/pulling away from a stop and threw a bunch of parts at it until a shop finally did a smoke test.

Vigo said:

I know you said no broken hoses but my first suspicion here is a cracked intake tube between the maf and throttle body. At rest it won't leak much but when the engine shakes or torques over to one side it'll pull on the hose in a way that opens the crack and lets it suck a gulp of unmetered air. Have you taken it off and looked at it?

yep, the bellows section can hide pretty substantial splits.  if the vehicle has a history of quick-change LOF services where they remove the top of the airbox and bend the ducting to pull the air filter to OMGZORS TEH DIRTZ to the person behind the wheel, that's a common way for it to get damaged.

intake tract checks out.  He's taking it back to his buddy to  see if it jumped a tooth.

AngryCorvair said:

Vigo said:

I know you said no broken hoses but my first suspicion here is a cracked intake tube between the maf and throttle body. At rest it won't leak much but when the engine shakes or torques over to one side it'll pull on the hose in a way that opens the crack and lets it suck a gulp of unmetered air. Have you taken it off and looked at it?

yep, the bellows section can hide pretty substantial splits.  if the vehicle has a history of quick-change LOF services where they remove the top of the airbox and bend the ducting to pull the air filter to OMGZORS TEH DIRTZ to the person behind the wheel, that's a common way for it to get damaged.

a quick and dirty test is to wrap the bellow section in duct tape nice and tight and see if it still acts like it has a leak, some people use this as a permanent fix although not recommended

Well, then i suspect the MAF at this point. I'm not sure exactly what new symptoms these trucks have when you unplug the MAF, but you may want to try unplugging it and seeing if, in spite of the new issues from an unplugged MAF, it doesn't have the original issue. That would be one way to narrow a MAF problem down without graphing its output on a scantool. 

Looping back around...  He took it back to the guy who did the Timing Belt.  3rd hand info is "Mechanic forgot to tighten "something" on the serpentine belt" therefore causing the code."  I think he hosed the tensioner..   ohh well its "fixed" now.