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Re: bad gas mpg and popping
There is a chance that your catalytic converter may be clogged. Sort of like a potato in the tailpipe choking the engine.You can check this by monitoring exhaust flow or disconnecting exhaust prior to converter and see if anything changes. You might take it to a shop that has an exhaust back pressure gauge. With that they can see if there is a variation in pressure before and after the cat. hope this helps.
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Pops, while pushing the gas pedal, and back fires and smells like gas and shakes while pressing the gaspedal, on 91 jeep cherokee l 4.0
spark timing way off. or burned valves.
i dont think a 4L can change cam timing. (gears)
that is gross misfire,
so bad it backfires to the throttle body and air cleaner
in all cases is bad spark timing, or worse burned valves.
bad rotor & cap,?
doing a tune up get rid of that carbon tracked bad cap.
and timing magically works.
ever do a full tune up this decade or in last 60,ooo miles>
Sounds like a bad lifter or a bad lobe on a camshaft. Not real familiar with the brand, sometimes you need to pull off the valve cover if it is a pushrod design and check with fingers on rocker arms while engine runs.
But if this is an overhead cam you would need to pull the camshaft and look at cam lobes. Then look for flattened lifter face. Some overhead cams can have lifter discs to adjust gap between lifter and camshaft. Some of the old VW engines used this system. It worked pretty well, but you needed discs on hand to make precise changes.
Really, really, sorry to suggest that the head gasket may not have oil passages lined up. Always lay the oil gasket over the new gasket to see if each and every hole is punched out and lines up to the old gasket.
Also, each lifter needs to go back to its original spot. The Cam lobes are worn for that lifter and a mismatch can be possible. A mismatch could mean extra play in a badly worn lifter face mated to a badly worn Cam lobe.
If that is what you did then get new or rebuilt lifters. Check out Compcams.com for a detailed description of each engine scheme. Your engine may have a thrust plate for the lifters and it may be incorrectly installed creating noise.
has your check engine light come on and stayed on after changing o2 sensors. I had a bad tempature sensor on my 2006 silverado and i replaced all four 02 sensors they were showing as bad and then i got a code that said catalyst system inefficient bank 1 and i replaced that catalytic converter and cleared my engine code and was able to go through emissions. but you might have to clean your throttle body check your plugs and wires . if you have a distributor check the cap and rotor button. you also have an egr valve that can get cloged up or go bad and a pcv valve it can be a host of things . if your mass air flow sensor is bad it could cause it to run funny . if your tempature sensor is bad it will not tell the engine it is warm and it will run rich and that will eventually cause your plugs to foul and your catalytic converter to get backed up and your o2 sensors to get carbon build up on them . my catalytic converter looked like it was starting to melt out the honey comb inside . hope this helps
As far as I know all hydraulic lifters can go bad, collapes or stick. And yours are definately hydraulic lifters, rollered yes, which will make them more durable, but they can go bad. The machine shop should have down a leak-down test on the lifters. That is the only way to determine if the lifters are good. I would check that you have proper oil pressure, I'm sure you do. I bought a "rebuilt head" for a Saturn DOHC engine, and the machine shop never did a leak down test on the lifters, and I had the samething happening.
here are a couple of different problems that will cause bad fuel mileage. first is air filter, still getting low mpg. then the pcv valve. clean fuel system.the cost of filter about $20 pcv was $12 and the fuel system cleaning and pcv is easy to do. when cleaning the fuel system,clean the injectors the fuel rail and the throttle body be sure that you have them change the oil or that you do it after they work on it. Notice whether the oil smelled like fuel then your engine needs platinum plugs for best spark they can run as much as $8 each.
You should be getting close to 360-390...depending on the type of driving you are doing. Increasing your gas mileage could be as simple as getting a fresh oil and filter job, change your air filter, change your fuel filter...and a biggie believe it or not, make sure you have the proper tire pressure. This will kill your mileage faster than anything else.
City MPG: 16-18 mpg Combination MPG: 18-21 Highway MPG: Approximately 26 mpg