Been working on a friends car (190K), it sat for 3 weeks due to a severe oil leak (dealer cross threaded the plug), when I picked up the car I drove it about 2 miles to the car wash to clean the underside. When I stopped the idle was surging 1500-2000 rpms, I asked my friend if it did this before the answer was no. On the way to my house I came off the highway and the car was jerking really bad as it decelerated and continued to do this every time I took my foot off the gas at any speed. I stomped the gas and down shifted (auto) blowing out a large cloud of black smoke, the jerking went away, but I noticed the TCS (comes on and off randomly and I know its not the idle issue) and engine light were on. After fixing the oil plug I started the car and it began surging 1500 to 2000, sometimes it surges 1000-1500 and sometimes 1400-1500 (very fast). Cleaned the IACV and throttle body no change. No change when tapping IACV or pulling the plug, When I pull the MAP plug the idle smooth's out and drops to a steady 700 but almost dies when pedal it pushed. No vacuum leak, TB gasket replaced, radiator fluid was not changed recently (plugged the valve line with wooden dowels so little was lost when I cleaned the valve). I have looked at so many posts and can't narrow it down. There were 2 codes one was stored the other was most likely when I pulled the plug (P1519). Should I try swapping the IACV, any suggestions would be appreciated.

 

OK, since I did not get a reply I replaced the IACV, 5 minutes into letting it warm up (never touching the pedal) the rpm's start jumping 1200 to 2000. I disconnect the IAC now and it does a quick 1400- 1500 rpm bounce, plug it back in to the 500 rpm lope. If I pull the MAP plug now the rpm's smooth out a steady 1200rpm, if I then pull the TPS and it drops to a steady 900. If I pull the TPS first the rpms go up to a steady 2000.
I've looked at thread after thread on this site, u-tube, google, and several others and none of them are close to what this thing is doing, I don't want to throw money that my friend does not have, in replacing parts hoping to get lucky, and this journey started at the dealer so no confidence there, so if any one has a recommendation I would really appreciate it.

 

what was the other code you got ? did you clear the codes ? i am always wary of spraying water on the engine with all of the electrical connectors, it tends to do way more good than bad if not done perfectly

it's possible one of the intake gaskets got wet and it somehow no longer sealing correctly, you might need to pull the intake and replace all the gaskets, which might be a good time to clean the egr ports while you're at it, there are howto's on youtube

the oxygen sensor sits in the exhaust pipe underneath, it's possible it got damaged as it needs to be clean and dry on the outside as it compares oxygen content from the outside to the inside

im actually wondering if there is an air pocket somehow within the iacv that needs to be purged

 

holmesnmanny thanks for the response, the auto parts store only said the one code, and other than pulling the battery I did not clear them. I did not wash off the top of the engine just the bottom of the car using low pressure so it not likely anything up top got wet, and the engine was surging before I went to the car wash. If it was a gasket it should remain consistent when I remove sensors, but it changes considerably. The O2 sensor need to be at full operating temperature before it starts sending information to the computer. As for purging the IACV of air it should do that as the engine runs, I plug the lines with dowels so only a drop or 2 was lost when I pull them. If you look how it ran before I changed the IAVC to after it is a big difference, I will swap back to the old valve and see if it goes back to the way it started, maybe a bad valve from the store.

 

sounds like you got it figured out