Thanks everyone for the suggestions thus far. Today I double-checked the codes: just the 0505 came up, indicating everything's ok. My computer must be a liar.... :-)
Then I checked the TPS (after a 30 mile drive - so it was warmed up). Pin 1 on the connector had 5v. Pins 2 and 3 had about 540 ohms at closed throttle and between 4000 and 4100 at WOT. There didn't seem to be any spikes in resistance as I swept the throttle, so I'm thinking these tests suggest the TPS is OK.
Next I pulled each coil individually while the car idled. With each coil pulled, I observed a VERY significant deterioration of idle smoothness, a notable change in sound and the car shook a bit (especially when I revved it a little). Each coil seemed to make the car shake about the same amount, so I can't say I found any coil that I suspect as being bad. Also, the behavior of the engine when any one coil was disconnected was WAY rougher than my occasional idle interruption, and way rougher than any of the power surging I experience while driving. I'm thinking that if I were actually losing a coil, the harshness I experience while driving would be a lot more severe.
I also tightened the grounds for the KS and the one that appears to ground the injectors and/or coils. There was minimal resistance between these grounds and the "-" battery terminal.
Oh, and I forgot to mention earlier that the spark plugs I've got are only about 1yr or so old - so I wouldn't expect them to be failing yet...
I did notice, however, that one of the wires coming out of the MAF connector showed visible chafing - right down to the stranded copper core (which looked oxidized). Could this compromised insulation be altering the resistive properties of the wire, skewing the MAF readings?? That might be consistent with the fact that my problem never seems to occur until the car has warmed up. Perhaps the computer is running on Open Loop until the car is warm, at which point it begins interrogating the MAF....
thoughts?
Quote:
Originally Posted by AndrewR2442
My vote goes to the 1)spark plugs 2)coils 3)TPS 4)maf. The uneven idle points to coils or spark plugs more often than anything else. You can easily check all of these if you search for the procedures under the 4th gen sticky's.
Check your tps but DO NOT LOOSEN THE BOLTS. That's only b/c I have gone through a headache for about a year now. I unbolted my TPS when i didn't even know what it was. I thought it would be a good idea to clean the inside of that thingy attatched to the intake. Wrong.
I drove on the interstate for about an hour w/it fine. Then on the ride home my car would surge but under 0% throttle. I was set at cruise at 70 and it would jump around. Even when i thought i had it calibrated correctly i would get surges when set cruise on the highway (TPS warmed up). You have to have your tps sensor warm to get an accurate reading in Ohms. Check the sticky's for a good writeup...
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