At idle my exhast note seems to pop, rather than a constant tone.Sometimes the engine can almost cut out and can rattle before getting back upto idle speed. It did not do this prior to the work I have done below and grateful for your sound views on here to fix.
My Astra Coupe has recently suffered a chain failure where the plastic guides had broken up. So I removed the head and had all valves, guides and seals replaced as a matter of course. The engineer said that the valves weren't damaged but the seats and valves were worn so just as well replace, skim head and pressure test. When I collected the head he did say that four of the lifters were on their last legs and may need replacing - he put all four against cylinder 1. So got the head back and refitted the head with new head gasket kit and timing chain kit. Whilst I was at it I decided to renew service items so I fitted, plugs, air filter, oil + filter.
Started up fine but the TC & EML light came on. The TC light went out after I turned off and back on again but the EML light remained. Rather than mess about troubleshooting I fitted a EGR cheater, front Lambda sensor and water temp sensor - bingo light gone!
One thing that I will definately need to re-visit is the Balancer Chain - It was a little slack but will re-fit at the end of the month when more funds are available.
The motor drives very nice with great responsiveness throughout the rev range, except when idling...... the engine seems to be struggling to turn over smoothly at idle- almost like its unbalanced or too high compression/low spark. When I look at the bottom pulley it doesnt look to be running dead straight - almost like a very slight unbalance.
So do I just change the balance chain, bottom pulley and/or lifters or is their something else more simple here? dunno..