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Hello I have an 02 explorer with the 4.0L flex engine and recently I replaced the spark plugs and wires, air filter, cleaned out the throttle body and even ran the seafoam spray through the throttle body. Well after doing all of that the vehicle will drop down to 600 rpms when I'm stopped and in gear. After doing the seafoam the idle was still slightly rough but after driving a little more it got back to normal.
When I replaced the plugs and wires I used the autolite AP103 plugs and the autolite wires you get from advance auto. Is it possible that the plug wires could be the cause? Only reason why I changed out the plugs and wires is because the vehicle had around 100,100 miles on it at the time. Should I just go ahead and keep the plugs and go get the motorcraft brand wires? Only thing I haven't done yet is clean the MAF and IAC sensors, wasn't sure if that will help with the idle issue or not.
So after taking some time away trying to figure out the issue I decided to recheck for a vaccum leak. Well I sprayed throttle cleaner around everywhere I thought would be the place I would find a leak, everything seemed okay. Well then I decided to rev the engine and listen, well I heard what sound like air sucking coming from the middle of the engine towards the back. I know I couldn't reach the back of the intake to spray so is it possible that the gasket could be bad? I know its supposed to idle rough when cold, but mine runs fine cold, but after warms up then the rough idle shows.
Sorry, didn't mean to come off as being rude. As for what i've done already...
I went ahead and done the spark plugs and wires. I also removed the maf and iac sensors and cleaned both of them. Also cleaned out place where the IAC mounts on top of the throttle body. I had the place run a smoke test where they went through the gas filler and he also hooked it to the brake booster hose and neither one showed a leak. After that I had him also run that valvoline fuel system cleaner through it and replace the fuel filter.
I don't know why but for some reason I really am thinking that maybe the gaskets for the upper intake might be to blame. Like I stated earlier, it sounds like there's air being sucked in from some where in the middle of the engine, I couldn't get to all of the intake to test though since it seemed like there wasn't a pretty clear shot. I managed to get the three ports along the passenger side and one port in the front behind the ignition coil pack.
The issue with smoke tests are that the system MUST be closed in order to pressurize, some techs are remiss and rely on an obvious leak to puff smoke.. and fail to be diligent on those tough spots..
The system being tested should attain 3-5psi and wait long enough for the smoke to completely fill the void. A bright light is mandatory as some smoke wisps are just that... A wisp!.. Philip