We're having a problem with our 97 Yukon SLT in regards to the timing. We discovered that the engine coolant was leaking in to the engine oil & as such, it has recently been in to the shop to have it's cylinder head gaskets replaced as well as the distributor rotor & distributor cap. We also had the spark plugs & ignition wire set replaced. Our mechanic is having difficulty adjusting the timing & as such we have been back 2x to have it adjusted. It is firing early & so you feel a hesitation & hear a pinging noise when you give gas. It was doing it again today & so that means we'll have to take it back in a 3rd time.
Is it common for it to be so difficult to get the timing right? Our mechanic has been good to us up until now but it is very frustrating that the problem hasn't been solved & we keep having to go back.