Hello this is my 1st post. I just bought a 1988 F150 with the 4.9 EFI. It had 3 bent pushrods and a hydraulic lifter that was bad. "No Problem" Replaced the bent rods and hydraulic lifter. But I took it out and drove it around and on the way back it went from a normal idle to now a fast idle and it won’t idle down. Can someone maybe give me somewhere to start to fix this problem?<o></o>
<o></o>
Thanks<o></o>
Jason <o></o>

 

Could be the idle air control valve sticking open or a vacuum leak. If you had bent push rods it sounds like the engine was over reved. These big six engine are not high RPM engines(rarely take my 84 F250 with I6 over 3k RPM). Hopefully there is no more dammage done to it.

 

i'm thinking vacuum leak. i had a chev cavalier,don't judge me, and the intake gasket cracked and got sucked in, and the computer put it in safe mode. car would idle anywhere from 1500-4000 rpm. took a few days to find the leak cuz i couldn't hear it over the high revs.

 

Found the problem it was the idle control valve. I replaced and it runs good now thank you for all your replies.