still wants to stall

Ok so heres a little background.. I bought my 97 4.6 back in April of this year with 112k miles or so. When I bought it there were some things that needed attention, It ran a with a slight hesitation or a miss but not too bad at all. First thing I did was change the air filter which was horrible, probably the worst I had ever seen. At the same time I cleaned the MAF, and the Throttle body plate. This made it run a little better but I could still hear that it wasn't perfect. Next thing I did was run some seafoam through the brake booster and the gas. I got a decent smoke show but didnt run any different. Next up I changed the fuel filter and that did nothing either.

Fast forward a few months I start getting an idle drop while going to park, usually it recovers but I've had it stall twice. So I did the plugs (2 of which were loose in the back pass side) and the gap ranged from .058-.072 Got them all finished up thinking this had to of been the culprit. Ran with more power for sure but still having the idle drop when going into park. Next step was removing the TB and cleaning out the EGR ports. They were really bad, one was completely blocked and the other was about 1/3 clogged. I cleaned it out really well put in all new gaskets, a new hose for the evap valve since the out side of it was coming off as black dust, a new pcv valve even though mine tested fine I figured I might as well while im in there and I cleaned the IAC again as it had been sticking in the past after being on the highway(corrected that issue a few months ago but cleaned it again anyway).

I checked all of the other vac lines and they seemed to be in good shape. I checked my transmission fluid and it is pretty good in color and at the right level as I have read if the level is off it could cause issues while going into reverse. Im running out of ideas here, the truck hasn't thrown a code yet even after it stalled. My next thoughts in this order would be IAC replacement, o2 sensors, or torque converter. Any insight on this issue would be a great help. And yes after each repair I disconnected the battery so it could re-learn with the new fixes. Thanks in advance for any help you may be able to give.

P.S. the idle drops down to around 400 after I change gears and hit the gas and then remove my foot from the pedal (imagine parallel parking)

A new IAC would be my next move. The idle on my 98 with 4.6 would drop when I came to a stop, then pulse back up, then down and eventually even out. Replacing the IAC fixed that. I guess they can get sticky. I would only replace the two front O2 sensors, the ones closest to the exhaust manifolds. If you have a diagnostic scanner you can watch the voltage on the O2 sensors fluctuate to see if they are ok. Couple of youtube videos out there on it. Another thing that's easy to check is the TPS sensor. Make sure the voltage is just slightly under 1 volt at idle and I think 5v at full throttle.

Thank you for the input, I do have a scanner with live data stream I will check on the o2 sensors today. I will also check the voltage at the TPS. I kind of figured the IAC was my best shot as well but I hate throwing parts at things. The main reason I even mentioned the o2 sensors is because my friends dodge had a similar issue coming to a stop, after a few months it finally put up a code for the o2 sensor.

thewishkah said:

Thank you for the input, I do have a scanner with live data stream I will check on the o2 sensors today. I will also check the voltage at the TPS. I kind of figured the IAC was my best shot as well but I hate throwing parts at things. The main reason I even mentioned the o2 sensors is because my friends dodge had a similar issue coming to a stop, after a few months it finally put up a code for the o2 sensor.

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Yeah, I would check the TPS voltage and o2 sensors with your scanner first since that doesn't cost anything. If they look ok, I would get a new IAC. I got mine from amazon for $52.

http://www.amazon.com/gp/product/B000CGFRT6/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

ok so another bit to add to this: I notice there is oil on both valve covers, where the pcv valve goes in and on the other side where the hose goes in. I know there shouldnt be. lol
Also I filled up today and it would appear my MPG has dropped down to 7.5mpg from around 11.5 after the new properly gaped plugs, cleaned throttle body, and new pcv valve. WTF I was hoping those things would improve mileage by 1-2 mpg not make it worse. Still no codes showing.

More info still. Ran the scan tool and I see the o2 sensors switching but one doesn't seem to switch anywhere near as much. 2 cycle at 0.000-0.750 range one only cycles 0.645-0.750 range not exactly .750 but in and around that area.
Also I'm getting the p1000 code but Ive driven 150 miles in mixed driving over the course of a week since the last time I rest the battery. Could there be an issue with my computer or something else that doesn't let the truck finish the test. Could the previous owner of done something to cause this? I had never hooked the scanner up (best i can remember) on the truck since it hadn't given me a check engine light. o2s12 is the one not fluctuating as much(post cat) not sure if it should be or not.

another update: drove 400 miles now and still says not all test have been completed...

Does your scan tool display readiness? The evap readiness can take a very long time to complete and can hold up an all clear.

To be honest I don't know if it shows it or not. Ill look into that today. I cleaned the hell out of the MAF sensor on Monday afternoon with a can of the MAF cleaner spray and while I was at it I blew out the air filter that was pretty clean with little discoleration and almost no debris. The cleaning of the MAF seems to of helped a little with near stall issue and I notice its not idling as low now around 600-700rpm. Not sure if this is due to cleaning the MAF or just the colder ambient air out side.