I am seeing very poor fuel mileage. About 6 m/gal. I have removed the cat. converts. There is not engine light. Replace the ignition (plugs, wires, cap, rotor) & replaced the air filter with a cold air kit. Changed the fuel pump & filter. The down side to the truck is that it has 190,000 miles on it but it does not burn any oil.
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Re: Poor fuel mileage
What kind of exhaust do you got, the converter actually may help get better mileage. scan egr for errors in emmisions, get the timing checked mabe running rich, check pcv valves,test knock sensor, 02 sensor( scan might not pick up) lemme know how it goes
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So what is the question? It would appear that you have a catalytic converter issue going on. Replacement is the proper thing to do; removal is illegal in most jurisdictions. Besides, unless you want a constant Check Engine light lit, along with the possibility of very poor fuel economy, replacing the cat is the best option. Without it, the O2 sensors will not operate correctly and the PCM will default to a preset fuel usage that will decrease your fuel mileage by 20 to 35 percent.
Check the timing chain. Some times the chain will shift with worn teeth and get out of synch. This will cause the engine to lose power and back fire. Sometimes with a flame through the carb. I did that one once. Easy fix if it is the problem.
Cauases or fault codes are not cut and dry, but here are the possible causes of codes P0316 and P0306 which are related codes.
P0316 - Engine Misfire Detected on Startup
- Engine Light ON (or Service Engine Soon Warning Light) - Engine fails to start - Engine runs rough
- Crankshaft Position (CKP) sensor harness is open or shorted - Crankshaft Position (CKP) sensor circuit poor electrical connection - Faulty Crankshaft Position (CKP) - Ignition System - Fuel Injectors - Running out of fuel - Fuel Quality - Faulty Engine Control Module (ECM)
P0306 - Cylinder 6 Misfire Detected
- Engine Light ON (or Service Engine Soon Warning Light) - Lack/loss of power - Hard start - Engine hesitation
- Faulty spark plug 6 - Faulty ignition coil 6 - Ignition coil 6 harness is open or shorted - Ignition coil 6 poor electrical connection - Clogged or faulty fuel injector 6 - Injector 6 harness is open or shorted - Injector 6 poor electrical connection - Improper spark plug 6 - Insufficient cylinder 6 compression - Incorrect fuel pressure - Intake air leak
Symptoms are rough running, stalling, poor gas mileage, and especially a strong smell of rotten eggs (sulfuric acid). The main cause is old age, but poor/cheap/contaminated fuel can also be a contributing factor.
If you connect a vacuum gauge to the intake you should see a gradual drop in vacuum while running if the cat is obstructed. sometimes you can hear a hissing noise from inside the cat as the exhaust tries to get through it as well. Worn injectors, (they don't have to be leaking) a sensor or two that are out of range but not far enough to trigger a code and poor fuel quality (mandated alcohol in fuel) will also cause a drop in mileage. Rings and cylinder walls may have some wear as well... small things, when combined with others, will contribute to mileage problems. As a car gets older, there usually no single "magic bullet" that will fix that completely though. Other than the poor mileage, does it run well?
Sounds like you might have an oxygen sensor problem. Your catalytic converter(s) maybe defective or dirty. That in turn can dirty up the oxygen sensor. A defective oxygen sensor will send faulty info to the computer, interpreting the fumes as cold (even when the engine warms up). That causes the computer to adjust the fuel mixture to very rich, giving you poor gas mileage and the fuel smell. Hope it helps.
There is one before each catalytic converter (usually up right near the exhaust manifolds), and one after each cat (or if you have a Y-pipe exhaust that brings the two sides together to one pipe and one converter, then there's one after that single converter). Why do you want to change them? Have you gotten failure codes or are you having poor gas mileage? Or have they just been in there a long time? They're usually good for about 60k miles, although of course they can fail early. Usually the symptoms are poor fuel economy, running rich (seen by black smoke out the tailpipes and some rough idling, as well as blackened spark plugs), or fault codes dealing with system-lean or system-rich descriptions. Those symptoms are indicative of bad primary O2 sensors (the ones closest to the engine). If your secondary sensor(s) are failing (the post-cat sensor or sensors) you'll trip a check-engine light warning you of poor catalytic converter efficiency.