75, 2.0...fresh rebuild

Ok, finally I got her running, but now she has this surging problem...

At idle, it surges up to about 3500 then falls back, only to surge right back up, and then falls, surges, falls, etc...

Whats causing that surge...

All vacuum lines are new and connected...

2-OH!

Lean at idle, causing it to hunt.

Adjust the knob on top of the ecu. One click at a time till it evens out.

I tried the ECU, all the way clock wise and then all the way counter clock wise... no difference...

2-OH!

Do you have the idle screw all the way in? (its on the TB)

Andyrew:

Yep, all the way in...

I started pinching vacuum hoses and the problem stopped when I found the right one...So, I removed the hose, plugged the vacuum source and all surging stopped...

I was able to adjust the timing, but I am still running 2000 at idle...with the idle screw all the way in...

Any thoughts...

2-OH!

Use brake cleaner and shoot around the intake plenum and all the runners. It will want to die when you find it. Also check the PCV valve and make sure it is clean and not broken. Be VERY careful with the break cleaner. It can and will light off if it hits the exhaust. Aim it directly at the items listed. You have a major leak somewhere. The 2.0 plenums are well known for cracking around the two tubes that pass through them. They crack where they brazed them together, especially if the car was ever involved in a rear end collision that may have knocked the air cleaner off and pushed on the throttle body.

Find the leak.


B

Call me a goofball for asking, but , how did you set the timing? Maybe it's still off? Sorry to say that out loud

Intake leaks or hoses are mis-routed is my bet. Check the timing again while you are at it as it could be way off.

Geoff

Once I stabilized the RPM by correcting the vacuum line routing problem, I was able to set the timing with the RPM at 2000...

Yea, once I get the other leak source located, I will have to re-set the timing...But at least I am getting close to the ballpark with the timing the way it is...Prior to setting it this close, I didn't have enough power to make it up the driveway...

With new vacuum hoses, new intake runner boots and gaskets, I think a mis routed vacuum hose is the most likely culprit...

With new valves and fresh from the motor re-build, could valve clearance be part of the problem...I have a pretty good clatter from back there but on start, cold, I have about 58 to 60 psi oil pressure on a slaved direct pressure gauge...After warm-up, it stabilizes at 25 to 30 psi at 2000 RPM...I feel confident we have good oil flow, everywhere...

2-OH!