Idle Off After Replacing Heads

rfraboni · February 22, 2011

After replacing the heads on my 2004 Avalanche due to leaking Castech heads this past weekend, I have noticed that the idle is rough. The engine after it warms up feels like it wants to stall and catches and the RPMs fluctuate about 100-150 RPMS.

I replaced the plugs and wires when the heads were installed.

I also noticed there was some oil in the intake manifold when it was taken off and let at a slight angle, I think this was being pulled in from the PCV system. I think the PCV valve got clogged by the oil/water mix in the valve covers, it was thick even in the baffles.

I did a cleaning of the TB (while attached) to intake with CRC TB cleaner this evening, and I think it may be running a little smoother, I need to run it more and get the engine fully up to temp.

Any ideas and advice would be greatly appreciated, thank you.

rfraboni · February 22, 2011

I did the Carb cleaner trick around the intake manifold and the truck smoothed out and you could hear the fluid being sucked in.

Any recommendations or tricks for getting the gaskets and intake put pack on the truck safely, because I am thinking I must have damaged the new gaskets trying to orient the intake while putting it on. Threading the EVAP hose under the fuel rail and such.

There appeared to be leaks on both sides in multiple places, so I am guessing another set of gaskets are in order as well.

What is the best way to guage the torque since my torque wrench is not "small enough" and only goes down to 10 ft/lbs and the spec calls for tightening to around 3.7 (44 in/lb) and then to 7.4 (89 in/lb) in sequence.

So any tips and tricks would be appreciated.

txab · February 22, 2011

I'd pick up or borrow the proper torque wrench

rfraboni · February 22, 2011

I took the the intake off again and examined the intake and gaskets, and it appears that I had not cleaned it well when i put the new gaskets on and re-installed in originally. So I cleaned the intake ports and gaskets, as I examined them and did not see any damage.

I re-installed the intake again and torque them to the desired torque in the correct sequence.

It still seems to be idling rough and at first it sounded like the intake was still leaking when sprayed with carb cleaner on the passenger side. When I sprayed after it was warm I could not get the sounds I was getting earlier.

When I rev the engine the SES light flash and then go back to steady.

Should I replace the gaskets again, I have a set of felpro i picked up just incase I saw rips or the like in the other gaskets. The current gaskets werw just installed Sunday and I thought I might have been able to reuse them.

Anything else I should look for the PCV hose is attached and so is the other vacuum hose on the passenger side.

I think it is getting a bit better but still missing.

Thank you

rfraboni · February 23, 2011

Here is where I stand today, still was only getting a p0300.

Yes, I have been assuming it was the intake, I do now own, nor do I know anyone one local with a better scanner than what I can get codes scanned at the parts store.

Listing the changes that were made, over the weekend.

1) removed intake/alternator/exhaust manifolds/ and cylinder heads

2) installed new/rebuilt heads (older style) using fiber head (felpro) head gaskets - torqued down to 22 lbs/ then 90 then 70 degrees in sequence - upper bolts torqued to 22 lbs

3)installed new spark plugs and wires

4)re-installed manifolds to heads with new gm exhaust gaskets

5) re-installed the hoses and alternator

6) re-installed the intake with new GM gaskets (teal colored) - did not torque them down in the correct sequence or to the right lbs since my torque wrench only went down to 10.

Monday (was idling rough) - loosened the intake again and re-torqued to 10lbs in correct sequence. No SES light

Tuesday ran much worse, - major rough idle, SES light on, flashing SES on acceleration - scanned computer at parts store only 2 codes p0300 for both, one was pending.

used carb cleaner and when i sprayed around the intake it would sound like a snaping sound, almost like liquid being pulled through a straw and draing air.

1) Removed the intake completely, noticed I had not cleaned the intake well

2) cleaned the intake, gaskets, and head intake surfaces

3) re-installed gaskets to the intake

4) re-installed intake - setting it straight down on the surfaces

5) torqued all 10 bolts to 44 in/lbs in sequence and then to 89 in/lbs

6) re-connected injectors, MAP, EVAP, coil pack leads, PCV, passenger valve cover hose, knock sensor connector, EVAP hose, fuel line, (everything I had removed)

7) started truck seemed to run smoother, spray carb cleaner around passenger side and was still getting a slight snapping type sound but not nearly as much as before, after a while that even stopped, thought gaskets must have warmed and seated better.

Wednesday, drove to work, didn't notice much of an issue on the way to work 17 miles, no rough idle when at stop lights.

Went to lunch after the truck started to warm it started to idle roughly and and SES light started to flash again during accelerations.

Sorry so long, that is where I am today.

I do have a set of felpro green intake gaskets I could put on, would these be any better? could I have a bad set of intake gaskets from the dealer, and they are just not sealing well?

I am at a loss and any help is appreciated.

rfraboni · February 23, 2011

Dropped it off at the dealer tonight and the mechanic put a tech 2 on and checked it, it is giving a miss on cylinder 5, and a few on cylinder 4. They are going look at it tomorrow and see if they can tell me what they find.

The heads were checked by the machine shop prior to installation and were straight and true I was told, not issue found in the physical inspection, I was having them checked since they had been shipped to me.

They had been rebuilt but not used.

Lets hope for good news.

Rich

gf235 · February 24, 2011

Having similar issue on my suburban, curious what the mechs told you and did it fix the problem?

rfraboni · February 24, 2011

Having similar issue on my suburban, curious what the mechs told you and did it fix the problem?

Got a call from the dealership and they said they have identified the issue and repaired it. The plug in cyl 5 was defective, guess it had a small crack in it.

This is the first bad new spark plug I have experienced. I am going to drive it this evening and see if it is really all better. The mechanic did drive it with the tech 2 and the misfires were supposedly gone and it ran smooth.

Lets hope that this is all it is.

I will update again after I have it back.

Thank you to everyone who has helped and put up with my ramblings and rants.

Rich