Oil weight and compression/engine missing

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Jan 26, 2003
So I have this 4 banger 4afe Geo Prizm engine with 139K on it. It seems to miss at constant speed and idles rough. Did 2 AutoRX treatment, some neutra in the gas and crank, changes spark plug wires/rotor/cap, clean throttle body, checked distributor, and igntion coil, changed spark plugs, transmission fluid flush, coolant flush, rebuilt spark plugs, checked battery and cables, cleaned starting injector, cleaned AirMass Sensor. What it does is in the morning or when the car is cold for hours at least 12hrs, it usually never starts on the first try..i can sit there and crank for 15sec...and nothing...but if I crank it once for like 1-2sec and crank the second time it's ok...even then it flutters. That didnt bother me as much, and the problem was gradual till the last couple of months which is constant. The slight miss in the constant speed was cured in the past with new ignition wires (MEGASPARK crappy wires from KRAGEN) but now it's back..it seems like whenever I get a new set after 6months, the missing dissapears or is less dominate. Now its back and I'm a bit tired of it, it also seems to flutter at idle during stop and go traffic. THe car normally uses 5w30 or 10w30, could a thicker oil like 10w40 make things better? Assuming one of the piston has some small compression issue? Could it be the ignitor module..that;s the only thing I dont know how to test but to replace it. Or should I stay away from cheap wires? I haven't heard of anyone having problems with megaspark wires...just that they are cheap and don't last long. Mileage is great if not better than stock after the autorx treatment, went from 26mi/gal to about 29mi/gal. Any suggestions? Thanks
Other things that have been done: Changed Timing belt, drive belts, gas cap inspected, air filter changed.
Yea actually the fuel filter was replaced about a year ago. Did check the coil and it's resistance.
in a honda, cant speak for toyota motor, idle air control valve is one primary culprit of crappy idle. if you have one, take it off and clean it out with carb cleaner or simple green. other typical culprits are vaccum leaks, the worst of which is an intake manifold gasket leak cause its a pain to fix. other potential is egr valve, but i do not think this would affect startup.
Thanks for the input everyone, yea I been a bit hesitant to check the egr valve because it's under the intake manifold..which is quite a pain to get to. I was hoping that a thicker oil may help for some reason or another. Thanks again
You need to check the specs on your temp sensors for the fuel management system. These play a very key role in setting up the A/F ratio for proper engine operation on startup. Neglected by many mechanics and DIYers because it is purely electrical by nature and generally quite reliable. They do eventually fail, and sometimes the process is gradual. The other area to look for is proper fuel pressure with a fuel pressure gauge, during engine operation and whether it holds it on shutdown. Your problem is not lubrication related.
... and next time you swap out the plug wires, change the spark plugs at exactly the same time. You might have carbon tracking, which will spread like a disease if you don't change them both at once.
Or should I stay away from cheap wires? I haven't heard of anyone having problems with megaspark wires...just that they are cheap and don't last long.
Duh! You get what you pay for. It appears 6 months is all you can expect. I am sure the only reason this barnd sells is because it is cheap.
I would begin by replacing ALL the vaccuum lines. even if they look good, especially that one thats underneath all the rest and makes you use that 6-jointed arm to get to. little leaks cause lots of problems...
Well just switched the Plug wires from cheap MEGASPARK kragen wires to Wells from Autozone. Wish they had Bosch in stock but they didnt. The missing is gone, but still got the starting issue.
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