ZCar Forum banner
Status
Not open for further replies.
1 - 4 of 4 Posts

·
Registered
Joined
·
107,695 Posts
Discussion Starter · #1 ·
Need suggestions about finding problem with fuel/air mix. Where do I begin? Manuel sucks, shop to much money, I can do this! 1. smog fail,to much fuel in exhaust,misfiring, HC and CO way over. 2. did tune up,yes me, didnt make much difference in recheck. Fuel injection He says! Is it too much fuel or not enough air? There is a difference right? What is the diagnosis process at home mind you. HELP!
 

·
Registered
Joined
·
1,770 Posts
RE: 1978 280,fuel/air mix problem

Karen,
First of all you can tune an engine and have it not pass because of engine condition.
You can have the right amount of fuel:air and if your compression is too low you will not burn the fuel and it will show up as high HC and CO. If you have a vacuum leak you have unmetered air getting into the fuel:air and it will show up as too much CO. What to do? Check your vacuum. If it is low, and this will depend on the altitude where you live, (I live at 2500+ over sea level and 17" is a good measure for me) look for vacuum leaks. Start by replacing all of your vacuum hoses and then using a propane torch that isn't lit pass it all around your engine (except by the ignition system components) and listen for a rise in RPM. This signals a leak. Simpler check would be to let the engine idle and remove the dipstick. If it continues to run the same you have a huge leak somewhere. Second thing to do is clean all EFI connections. EFI ECU,s make system response changes based on resistance changes. If the connections are all corroded the resistance is high and the mixture is rich. Last thing you can do is check your mechanical timing. As your engine wears and the timing chain stretches the relationship between the cam and the crank changes. This is your mechanical timing. Your timing gear has a 4 degree and an 8 degree advance position that are there to correct for wear. Actually the manual is pretty good, just hard to read.
 

·
Registered
Joined
·
107,695 Posts
Discussion Starter · #4 ·
<b>RE: 1978 280,fuel/air mix problem</b>

Rob, you are right on all of those points, but I think you forgot to mention a couple of important areas. Although most of us have experienced the connector and sensor problems you mention, don't forget the infamous leaking cold start valve and port injector problems inherent in any older Z. Also the fuel lines have a tendency to leak due to age and rot setting in. So Karen, the bad news is, check everything. And the rest of the bad news is, it will probably consume a lot of time and dollars. Good Luck, though!:)
 
1 - 4 of 4 Posts
Status
Not open for further replies.
Top