Hi all,
currently trying to help a friend with a problem on his 3rd Gen 5.7tpi Camaro. Its running a 7730 ECM, comp cams cam but otherwise reletively stock.

Its had a loss of power recently right up to the point that it would no longer run. It spits back through the intake and backfires down the exhaust. It very much sounded like the timing was out.

Now here is where it gets interesting with the esc disconnected and base timing at 6deg the car runs and idles and sounds OK. Also if all SA tables are set at 6deg the car also runs and idles. I've tested this with SA tables 10deg which was OK, and 15deg which caused the previous symptoms to return. All the time this is being checked with a strobe to confirm whats set in the SA is what is happening.

Things we've replaced/tried:

Plug Leads
2x Coil
2x ECU
2x Memcals
2x Stock Bins
2x Reburnt Tunes
Map Sensor
2x Distributor (complete)
Complete Engine Loom
Wiring to the coil
Fuel Pressure checks out ok
Confirmed that the dampener hadn't moved
Confirmed that the Timing chain hadn't moved (keyways etc)


When the engine is running everything on the datalog looks normal and there are no trouble codes. Its just as if the engine for some reason won't take any more than 10deg of advance. Really pulling my hair out with this now.

Any advice greatly appreciated!

 

Sounds like a mechanical issue to me.

Possible the cam isn't installed in time? Have you checked cam timing?

 

Were the rockers adjusted recently?
Sounds like the lifters are tight when collapsed and pump up at revs holding the valves open.

 

Hi there, It is me that is trying to sort this car out for a friend of mine,.

I had the front end off tonight to check, and the cam timing hasn't moved from where I set it about 6 month's ago....

Adrian

 

It had new springs fitted about 2 month's ago, I have also checked them and they are OK,

If I set the timing in the prom at no more than 10* it will idle and rev up fine , if it is any more than 15* it will spit back through the intake and backfire through the exhaust almost if the timing is 180* out...

Many thanks in advance

Adrian