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2.4L pt cruiser turbo surging idle

14K views 18 replies 6 participants last post by  Antoniogreens 
#1 ·
Hello I just had to do a head swap for my 2.4L turbocharged pt cruiser. New head with valves and springs, replaced oil pump, water pump, plugs and wires, coil pack and timing belt. Car say sat for a few months because the head got warped due to high temperature cause oil pump went out. Now that I have it running it has a surging idle that I can't figure out. All vacuum lines seem to be fine no cracks or wear. When I take the vacuum line off the brake booster the vacuum just surges instead of a steady sucking. Has anybody ran into this problem or might now of which route I should take now?
 
#2 ·
Welcome to Allpar. I would double-check the crank/cam timing marks. It's easy to be a tooth off. Use a straight-edge across the sprocket bolt centers and a dental mirror to get a head-on view of the cam sprocket timing marks.
The marks must be dead-nuts aligned.
It is good practice to roll the engine crankshaft 2 complete turns after getting the belt on to get it centered and settled-in on the sprockets.
 
#4 ·
Sometimes the spark plug tips tell a story about combustion and mixture. Remove them and keep them in order to which cylinder they came out of. Look for any carbon fouling or other irregularities between cylinders. Are they the recommended Champion or NGK type for the car? The throttle body blade and bore clean?
Even compression in all cylinders?
What year PT?
Have you taken it for a good drive and the problem is only at idle? Any pending (one trip failures) or matured fault codes?
 
#5 ·
I haven't taken it any further than around the corner but the throttle lags until I reach up to 1800rpms, I'm guessing that's when its enough vacuum to operate properly. I replaced the spark plugs with copper champions, replaced wires and coil pack when I did the top end. Throttle body is clean tps sensor and map sensor are fine. But when I disconnect the PCV line from the manifold it seems to run a little better.
 
#8 ·
Cars don't 'get vacuum', they produce it. And the vacuum should be higher at idle than at 1800 RPM.
 
#11 ·
Wow. No belittling was meant. And if I were that sensitive, I might take offense at the 'old guys' remark.

Just trying to steer you in the right direction. As in, turning up the idle would not help fix the underlying problem.

If it was OK before the head work, I would suggest something did not get assembled correctly. Maybe there is a vacuum leak at the intake manifold.
 
#12 ·
I replaced the head because it got warped. And I know you can't adjust the idle it's all controlled by the computer. I'm looking for a little advice before I take the head out to investigate. Maybe a leak between the intake/exhaust inside the head or something that's impairing it to run right ergo not being able to build negative pressure.
 
#13 ·
Just throwing this out there, but before tearing into too much, check the seals at the upper intake manifold where it joins the lower intake. If one of the seals shifted when installing the upper manifold you may have an issue there. That may not be the cause the surging, but worth looking at since it is simple to check.
 
#15 ·
A spray bottle of water around the seams might cause a 'reaction' or change in speed if there is a vacuum leak. A vacuum leak will usually cause a fast idle, like unplugging a hose on a running engine.
 
#17 ·
It is easy to get the exhaust one tooth off on these engines. They will look lined up! Count the number of teeth between the marks on the intake and exhaust cams using the belt. It should be an even number, if not the intake and exhaust cams are not in sync. It will not set a DTC because the cam sensor is on the intake cam. Nothing monitors the exhaust cam. It will cause the symptoms you are having.
 
#18 ·
Could the Idle Air Control valve be screwed up? Make sure the connector is firmly in place. I had a surging idle recently and replaced the IAC valve and it solved the issue.
 
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