1979 Seville runs lean

[john rutenberg]

My car has a slight rough idle. I have had my injectors rebuilt, replaced the ECM. the distributor, the EES box the CTS and ATS and still the same result. My mechanic put it on the dyno and it runs lean. He thought there was a vacuum leak but we used propane and found no vacuum leaks. We plugged all lines coming out of the intake and throttle body and still the car runs the same. I am thinking that maybe since the car has such low miles and has sat for so many years that maybe one of the valve seats is leaking. I was thinking maybe I would take the heads off and have them rebuilt. It would cost me 125.00 for the heads and an intake gasket set. Has anyone else had a problem such as this before. I know that these cars ran like silk when new. My 79 Eldo with the same engine ran so smooth that you couldnt tell it was running at any time, even with the air on. This is a California Seville and my Eldo is a Federal car so the difference is the AIR system on the Eldo and it doesnt have an 02 sensor. Where the Seville has no AIR system and runs off the 02 senor and the computer. I wouldnt think that would make a difference.

[TJ Hopland]

If you can have all that work done for $125 by some one that knows what they are doing I would do it just to know for sure that there was not a problem.   A compression and or leakdown test will give you a good idea of how the valves are seating.  I spent a lot more than that to have a inline 6 head worked on and I took it off the car myself.

[john rutenberg]

I am doing the work. My mechanic lets me use his bay at the shop. The 79 Seville for California doesnt have smog so all the needs to move out of the way is the ac, power steering pump and alt. Its very simple and while Im in there IM gonna replace the timing gear and chain with an NOS one. Cheap and easy about a 3 day job from strart to finish and r/r the heads.