you have another vacuum leak somewhere
Bit of a long read, but I can't make sense of the problem.
Some monts ago I bought a mk1 Jetta coupe from a guy down in Oregon. Bone stock with 126K on the 1.7l. Fixed up a few minor issues and started daily driving it. Around the 4th of July driving one day the fuse box began to get hot and melt a bit, turned out to be my fuel pump fuse not making complete contact and arcing. This car has melted a few fuses when I drove it up from OR, many of the fuses were the wrong amperage, there was a 30amp fuse jamed in the fuel pump slot.
After pulling the old fuse box, checking all the relays and installing a brand new fuse box I attempted to start the car and it devloped a large vaccum leak, I discovered a few of the injectors were loose and the seals were bad. Replaced all seals and cups. Went to start it and, nothing. It will start and run at high RPM's then either die or struggle really hard and it has a popping coming from the airbox.
That's where I am at now, stumped and frustrated. I don't want to tow it to a shop pay $100 and have them stare at it and tell me nothing. Hoping someone here could lend a hand.
a propane hobby torch can also work, and doesn't leave flammable liquid on things for a few seconds.
Another hypothesis: When you get a used CIS car...particularity a mk1 where someone has had their hands under the hood, they will often adjust things like the idle and air/fuel ratio to compensate for undiagnosed issues. You may very well have fixed the issues, and the state of tune is now off.
For vac leaks, the manifold itself can develop a leak at times, the Idle air stabilizer is prone to failure, the idle screw o-ring can go bad, boots should be fully removed for inspection, and while you have them off, check the airflow metering plate for sticking.
If all this fails, you might need to do a fuel pressure test.
Here is the procedure for adjusting your air fuel ratio correctly
Remove all injectors from cylinder head.
Remove the fuel pump relay and install a jumper wire with an in-line switch,Turn the switch ON.
Hold injectors in suitable container and lift sensor plate several times.
Move jumper wire switch to Off position.
Using 3 mm allen wrench, turn CO adjustment screw counterclockwise 1 to 2 turns.
Move jumper wire switch to on position.
Turn CO adjustment screw clockwise until injectors just begin to spray.
Turn CO adjustment screw 1/2 turn counterclockwise.
Move jumper wire switch to off position and install injectors.
Start engine and run until it reaches operating temperature.
The procedure for the fuel pressue test
Ensure that fuel delivery rate is within specifications and that fuel filter is not clogged.
Ensure that electrical connectors are securely connected.
Install pressure gauge with lever in closed position.
Start engine and run at idle.
Pressure should be 4.7 - 5.4 bar (68-78 psi).
If system pressure is not within specifications, check fuel distributor pressure relief valve for damage or contamination. Note; The system pressure is adjustable by adding or removing shims from the relief valve.
If pressure is still not within specifications, replace fuel distributor.
Adjust idle speed and CO to specifications.
Last edited by jiffyjetta; 08-22-2012 at 10:56 AM.
Thank you Jiffyjetta. Loki, believe it or not it still has the plug over the fuel adjustment on the air box, I don't think this one was messed with much, but I wll go through the tests and see what I can find.
Well after letting the car sit for a while. Finally took it to a local shop, the found the warm up regulator had gone bad. So hopefully that is the last domino in this line of stuff breaking.