nikesb1111

So I put a 224 cam in my truck and now I can't get it running. Timing marks are right. It's an 03 silverado with a 5.3. New pushrods and springs. Blackbear tune. It's not throwing any codes other than a p0101. It's very hard to start and when it does start it will only go to about 2800 rpm then slowly die after about 30 seconds. It also sounds like the timing is pretty retarded. Anyone have any ideas?

5speedsilverado

iTrader: (1)

p0101 is a maf problem, gm vehicles dont really like to run without a maf, that is where i would start, maybe look for vaccum leaks too, i believe that is the code mine set when my cap for the booster line fell off.

Mikey 97Z M6

iTrader: (35)

How did you determine #1 piston was at TDC before lining up the timing marks? Its very easy to not be at TDC.

Did you replace pushrods with same length as stock?

Mike

AKlowriderZ71

iTrader: (22)

^^^If the timing marks on the cam gear and the crank gear are lined up, #1 is at TDC. It cannot be any other way.

AKlowriderZ71

iTrader: (22)

For the OP, it sounds like you have a huge vacuum leak somewhere. Something left loose maybe, or not connected at all? What other mods did you do besides the cam? Did you pull the heads or intake for anything?

Mikey 97Z M6

iTrader: (35)

The cam gear could very easily be off a tooth if the crank gear mark was not perfectly lined straight up to begin with and with a slight crank rotation would still line up dot to dot and NOT be at tdc. You are assuming it was at tdc from the beginning. Thats why I asked how he verified tdc to begin with. I like to use a piston stop and degree wheel instead of "eyeballing" the mark.

Mike

nikesb1111

I had the heads off and did all the gaskets and everything. I watched the piston come to the top and the marks were together. I've been trying to find vacuum leaks but haven't ha any luck. I also cleaned the maf. When it is running the maf and map sensor look to be working correctly on the scan tool. I did do pushrods and the length is the same as stock. I checked it with the length checker first and that's what it came out to.

Vortec350ss

iTrader: (20)

Pushrods wouldn't make it run like this. I agree it sounds like a huge vacuum leak. The MAF will throw a code if the truck knows it is running much leaner than it should be for the air the MAF is registering, and the fuel it is throwing at it based on MAF readings. On other words... air is getting in that the MAF isn't reading.

Also, if the cam was that far off you would most likely have crunched a valve against a piston... so we can rule that one out.

Check all the vacuum fittings on the intake, and make sure that the intake itself is seated correctly against the heads.

nikesb1111

Ok so I'm going to pull the intake and take a look at that because I checked all the hoses an stuff already. A bad vacuum leak would make it seem like it's retarded tho?

Mikey 97Z M6

iTrader: (35)

If the pushrods were too long I dont think the valves would close all the way.

Depending on the valve timing events of the cam, it wouldnt necessarily have piston/valve contact. If he was a tooth off it could be severely advanced or retarded. If it was retarded (which he claims it sounds like already) the valve events would happen after the piston was already on its way downward. Ruling out this possibility would be a mistake IMO.

Also, I dont think most tunes even start using the MAF until it goes into closed loop, but its been a long time since I've done any tuning so I could be wrong. But I thought most start up tunes when cold are basically speed density until closed loop condtions are met (ie, coolant gets to certain temp etc.). Again, been a long time with my tuning experiences with EFILive.

Mike