Hi,
I was hoping to find someone here who knows something about the toyota
4A-LC engine and feedback carburator system...I've got a 1986 Chevy Nova (Toyota Corolla) and have been attempting to trouble shoot what seems to be a hesitation probelm under high vacuum throughout most of the three years that I've had it. The car runs, but it "chuggles" while coasting in gear, which is increadibly annoying! Lately, it has also started to quit when idleing unless I keep a toe on the accelerator, and the idle hunts up and down at a fairly high but erratic frequency when I'm not keeping some pressure on the gas pedal.
I've checked and/or replaced the following:
- The carb Auxilary Acceleration Pump diaphraghm had a hole in it allowing fuel into the vacuum hoses. I replaced the diaphragm and cleared all of the affected vacuum hoses of fuel.
- I verified that all of the vacuum hoses were routed correctly according to the map on the underside of the hood. All checked OK.
- Followed the emmision control system test procedure in the Haynes manual. All checks OK.
- Replaced the cylinder head with an overhauled one (together with a full set of new gaskets) after finding a burnt valve on the #1 cylinder (I figured I may as well, I had it apart anyway).
- Replaced and rigged the throttle position switch (the car has the California emmisions package) according to pages photocopied from the Toyota manual.
Most recently (within the past two weeks), I've replaced the following (not the first time some of these were replaced, obviously):
- Distributor cap and rotor
- Spark plugs
- PCV valve
- Fuel filter
- Air filter
I've also checked the timing and fiddled with the idle speed repeatedly. Do you think any of this would have solved the problem? Nope! The car still does what it has always done, no matter how many "hard faults" I find. It is almost as if it is mocking me... Could the TVSV be sticking? The problem seems to get worse when as the engine warms up (it isn't overheating). What about the electronics box that controls the various vacuum valves? (Although this seems unlikely, because the problem happens with the throttle closed, and the throttle position switch replaced in item 5 above turns the computer off when the throttle is retarded to idle.)
Any ideas from the experts and /or other Corolla owners out there?
Thanks very much in advance for your help!
Kevin