car idles at 3000rpm and slight tap after rebuild

[kinney90]

ok so heres the deal i just got done rebuilding a stock 420a and the only thing i replaced was the timing belt and piston rings. in the beginning i got the four basics, spark, fuel, air and compression but the car wouldnt start.n so after checking the ECT and a hole bunch of other sensors i tried starting the motor with the cam position sensor unplugged and i got it going but it idle at about 3000rpm and there was (what seemed to be) a valve tap so i plugged the CPS back in but still no change in rpm...... but now i can start the car with the CPS plugged in but still the high idle and and valve tap. and im 99.99999999999% sure my timing is correct please help!!

 

[jcarmichael]

my first guess would be an intake leak? possibly Idle air control vallve or ISC however the isc usually causes idle surge. is the throttlle cable on properly?

 

[Potenze]

if you just did a rebuild, and this is the first start, then there is going to be some valve noise. the high idle does sound like either an exhaust leak or the throttle cable needs to be adjusted.

check out terry's idle surge guide.

And just let it run for a little bit, the tap will go away.

 

[kinney90]

yea i figured it was just no oil in the top end yet but i heard it and the thought of timing popped into head and got scared and shut it off and thanks that website helps alot im going to start knocking things off that list tomorrow ill let you guys know whats up

 

[josh1095]

check throttle plate, IM leaks, vac lines left off etc,etc, your problem lies there. good luck to you
oh and you did the right thing. dont let it idle at 3k on a fresh rebuild, not good. just find the intake leak and your idle will be perfect. the lifter tap will go away in 5 minutes, no worries

 

[kinney90]

ok iv found the vacuum leak there is a three pronged vacuum connector on the back side of the IM and if your standing at the bumper looking towards the back of the car, what lines goes to the far left prong. for the life of me i cant find any lose hoses in the engine bay unless is there another line that goes to it that maybe sits on top of that air box under the IM? and btw the chiltons manual for the car doesn't illustrate it as well

 

[Potenze]

Two of those three on the back are EGR related. Here is some vacuum diagrams from Autozone, Hope it helps.

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[josh1095]

hes got a 420a, not sure if the diagram is applicable.