Question about 1991 Cadillac Allante
Intermittent missing, have changed four fuel nozzles but problem still there....run smooth for a short while then begin to miss and can later run smooth again..very perplexing!!!
Takes all to fire a cylinder (Fuel, Spark, Air & Timing) properly. If you have random or multiple misfires, it is likely something that is COMMON to all cylinders - like the air intake/throttle body area - throttle body can get carbon buildup and not open/close properly. Check the fuel pressure to the fuel rail(s), fuel filter clogged? When you turn your key to the "ON" position, do you hear the fuel pump turn on (whine) and then shut off? No whine, means no fuel pump. Check all fuses and fuse relays related to the fuel delivery system. Check the distributor cap/rotor for any signs of carbon tracking/arcing. Do you have good spark from coil? Check wiring for the Campshaft Position Sensor/Crankshaft position Sensor for timing issues. Finally, check compression on all cylinders. Need good compression for combustion to take place. Your old fuel injectors were probably OK. Using a multimeter, check the resitance of a new one versus an old one - probably close in readings.
For a single cylinder - Easiest to check is spark. Pull the plug and look at it. Is it wet and smell like fuel? If so, then swap it with cylinder next to it. If the problem moved, then its the plug. If the misfire is still on Cylinder #2, then swap the plug wire (both ends). If the misfire is still on Cylinder #2, then swap the coil. (see where this is going?) If the plug is dry, then check the fuel injector for operation. Noid light tester or you can get a long screwdriver and stick one end on your ear and the other on the injector - it should make a steady, rhythmic clicking sound if it is functional when car is running. No sound? Replace. Is the plug oily? Check cylinder #2 for compression. No compression or little compression means either head gasket blown or bad/sticking valve (intake or exhaust) = big money to get fixed. Timing on one cylinder is hard to test without correct test tools. Timing is likely not a problem on a single cylinder misfire. Good luck.
Posted on Apr 21, 2014
Testimonial: "There was a lot of information to ponder and I will have to systematic go through all of what was suggested...All injectors had been tested and those that didn't measure up were changed as was distributor cap and rotor and plugs.when injectors were checked using on board computer Number 6 showed no change when isolating that injector..after changing injectors I performed the same test and now number 4 is showing no change...the problem seem to be erratic...I suspect the PCM as I also have brake light on and traction disabled and I haven't any brake issues...Will continue troubleshooting...thanks for your help..."
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Posted on Jan 02, 2017
SOURCE: cadalliac 1991 Fleetwood 4.9 v8
Hows the A/c cooling? F46 is a a/c refrigerent problem.. If its at the right level, it could cause the a/c compressor to rapidly turn on and off, causing a surge feeling.
Posted on Apr 29, 2010
SOURCE: acceleration problems
This firing order diagram would not post in the clarification request for some reason, use this diagram with the information in the clarification request.
Posted on Jun 19, 2010
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