87 cherokee chief. engine swap. starts at 4k rpm and doesn't drop off
 

So... it has been almost a year trying to get my 87 cherokee chief manual trans 4.0 to run right. we've replaced the radiator, water pump, tstat, collant tank... still had issues. found out the head was cracked. replaced the head and gasket... then kept having the same issues so the 87 short block was replaced with the 93 cherokee 4.0 straight 6. everything bolts up fine. only difference was the new location of the temp sensor. we go to start it and it turns over and is instantly at 4k rpms and climbing. it doesn't drop down. replaced all vaccum lines in case of a crack we didn't notice thinking it was a vaccum issue. new lines match the diagrams... still does the same thing when you turn it over. instantly high rpm and no decrease. we are now frustrated and stumped beyond belief. the distributor is from the 87. all new plugs and wires... we are at a loss. any ideas?

take your ICA off and clean also clean the hole in the TB. It is beside the TPS on the TB.

could also be your throttle position sensor...this page tells you how to check em...lunghd.com

with IAC removed... same thing happens. no difference. tb hole is clean. now when you start it (and it can only run moments before we shut it down at such a high rpm...) the collant reservoir is filling up like everything is being blown into it and not circulating.

x2

mAjor intake leak somewhere spray down along where intake meets head around throttle body see if anything changes while running ur getting way too much air into combustion chamber man

I had the same thing after a head swap, the intake didnt sit flush against the head and caused a massive vaccum leak. Check out the intake manifold.

X2 YOU MISSED SOMETHING SOMEWHERE :yes:

intake wasn't sitting right. thanks! this brought us from 4000 rpm down to 2100 rpm when starting it though. big difference but we're still running into something. when you give it gas it stays at 2100 idling. any other ideas?

new update. played with the intake again and had to do some tightening. now we are opposite. starting up we are fluctuating between zero and 5 rpms... any ideas?