Tucson John68

Hope you guys are not getting bored with my posts?

Well, this morning I tried to start the engine and guess what...it exhibited the same hard starting condition. This is after replacing the entire fuel pump, fuel filter, and fuel pressure regulator. Argh! It does start a little bit easier, but when it does fire up, it still misses on a couple cylinders.

Something I did not write yesterday after replacing the fuel pressure regulator, the HVAC vent position dial is now non-functional and does not move the vent flappers. So air just comes out of the defroster regardless of dial position. The AC light still comes on when rotating it to defrost, so the dial position sensor is working but there is something going on with the flapper servo. Anyway, I looked over the other posts for people who had the same problem. Seems like those things fail when you diconnect and reconnect the battery. Well, I could not fix it by anything mentioned online. I reset the HVAC by removing the fuse for at least one minute. I finally just manually reached under the dash and positioned the flapper to blow out the front vents.

So anyway after not fixing one problem and causing yet another one, I finally gave up and drove it to my mechanic today (Thursday). He will keep it overnight, hook up all the gizmos in the morning, and hopefully it does not start normally. Maybe the HVAC and bad start up in the morning are related? Maybe not, but I still wanted to mention it.

Tucson John68

Just want to keep you guys updated...the problem is not fixed. Here is what I did so far.
1. Replaced fuel pump (Delphi brand) and fuel filter (unknown brand).
2. Replaced fuel pressure regulator (Standard brand).
3. Performed intact manifold gasket replacement (per technical bulletin).
4. Replaced spark plugs (AC Delco)
5. Replaced spark plug wires (AC Delco)
6. Again, replaced fuel pressure regulalator (Standard brand). Second time.
7. Replaced air filter (Fram).

Still, I have a very hard time starting the truck in the morning. Just a reminder, it cranks with a different noise than normal. Kind of like a higher higher pitch. When it does finally try to start, the engine sounds like in the olden days when you have to pump the gas pedal and a few cylinders fire, but not all of them. The engine lopes along with a few cylinders not firing. When I rev it up, it seems like all cylinders start firing. After a few seconds, the enginer idles just fine. I can turn the engine off immediately and it starts without issue. Also, during the day, after it starts just fine, I have no issues starting it. It only has a problem in the morning.

I'm thinking that I got a bad replacement fuel pump. Doesn't the problem seem like a fuel pressure issue. What else will produce and control fuel pressure except the fuel pump, fuel filter, and fuel pressure regulator? I even let the tank go down to one gallon left and then fueled it up with a different brand of gas. No changes, of course. Thoughts?

What about a bad starter? I'm suggesting a starter since when the problem happens, the starter always sounds different. But maybe it isn't the starter since once the engine turns over, wouldn't all cyclinder fire?

kevinkpk

Well, if it is already running even crappy I'd not say it is the starter. A weak starter would cause cranking issues, but I think it is more in depth.
My experience with fuel pressure regulator is the idle is very low. It does sound like fuel starvation except the fact it will rev to 3k rpm, so rule that out (fuel pump). I will think more on it. Can you do a compression check?

kevinkpk

If you can do a compresion check on it, make sure it is cold. It quite possibly be a cracked valve seal (loss of compression when cold, hence the hi noise on crank) and when it heats up the seal could be closing back. i dunno, but i have seen strange things before.

charledl

I had identical problem. Marvel Mystery Oil solved it - 1 qt in crankcase and 1 qt with 1/3 tank of gas.

Tucson John68

Well, it has been more than a year since my first post about my Avalanche's starting problem when cold. The problem has not happened again, though I did not replace anything further (after pretty much changing everything fuel and spark related plus $2500+ in repairs). It is kind of frustrating since there was no smoking gun that said, "THAT'S IT!" The Avalanche now has just over 100,000 miles and starts like it always had...first crank. Whatever it was, or maybe it was a combination of things, I am sorry that this posting is not helpful for anyone who is experiencing the same issues (unless you want to spend more than $2500 in replacing everything).

dcody

I don't normally post but I was having the same problems. I read this blog and was able to fix my truck. I had the same hard starting and I replaced my fuel pump, filter, plugs, and wires. Nothing helped, I replaced my fuel pressure regulator and now its good. It was almost too easy, I replaced it at work in the parking lot with no tools, just a knife to pop out one of the old O-rings.

Offroad1

I am having the issue of a very cold start and occasionally get the code P0300. It will be on for a few days then come back. Upon cold start up, it lopes for a few minutes while I am giving it a little gas to reach 2000 RPMs. Once the oil gets warmed up, it drives and shifts fine with no hesitation. Any thoughts on this?