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Procedure:
Removed spark plugs, remove ignition relay from position 7 and fuel pump control module fuse from position 67 in fuse box, released pressure in fuel rail, installed quick connect adapter into plug ports, crank engine for 15 seconds.

cylinder 1 - 168 psi

cylinder 2 - 170 psi

cylinder 3 - 170 psi

cylinder 4 168 psi

Plugs were covered with oil. I attributed this to the several pressurizing leak-down tests performed recently. After securing the engine for operation, I wedged the throttle down so it held 2000 rpms and then observed the tail pipe exhaust to not be blowing blue, or black, or white smoke emissions.

I applied a homemade gasket to the inlet tube or throat of the throttle body to seal the intercooler charge tube to throttle body connection. My homemade gasket is a strip of T-REX duct tape applied to a strip of bicycle tire inner tube rubber so that the seam of the tape is 180 degrees opposite that of the inner tube rubber to form a circular collar that would barely slide over the throttle body inlet tube/throat. I sealed the inner tube rubber strip seam with high temp red RTV gasket maker and let it cure overnight. After applying a thin coat of olive oil to the rubber, the intercooler charge tube slipped on easily. I torqued the hose clamp as tight as it could go without breaking. (Throttle body maximum temp measured with laser thermometer was 154F nearest the engine; inlet tube temp was about 130F. I think the bicycle tire inner tube rubber and tape can stand that temp. ) With the throttle body inlet tube gasket seal, the engine showed 18" Hg of vacuum at idle, but long term fuel trim remained above 12%. Next I setup the smoker can and pumped smoke at 3 to 5 psi into the engine. I was not able to see smoke leaking out and used a bright LED flashlight to look underneath the intake manifold. Throttle body and intercooler tube held in the smoke. I took the car out for a test drive and was pleased to find the turbo was providing boost. After the returning from the freeway, inlet manifold vacuum was 17" Hg and LTFT was 8.6%. After running the AC for 10 minutes and then the heat on full for ten minutes, vacuum was about 15" HG and LTFT was up to 13.8%. After engine cooled and upon inspection it was noticed that one of the screws holding the MAF into the inlet air box's outlet tube was missing. I replaced the missing screw and retested vacuum and observed LTFT as showing no improvement. The PCM still detects a vacuum leak even though the engine is tight enough so that it's leak down time from 15 PSI to 5 PSI is now 71 seconds and smoke cannot be observed leaking from the vacuum system.

Car has 67.8 K miles. Parts that have been replaced this year: Camshaft/valve cover, intake manifold, transmission, turbocharger, EVAP purge solenoid, alternator, camshaft actuator position solenoid gaskets/oval-rings, spark-plugs, serpentine belt, belt tensioner idler pulley, thermostat, coolant "water" outlet tee. Next up catalytic converters and brake pads and shoes. Later I'll replace the struts and shocks and install the PCV external check valve kit. I think the cylinder head valve stem seals may need to be replaced. After installing new Cats and brakes and those all important wiper blades, I'll take it to be safety inspected. If it passes then I can pay my car tax and start enjoying my little money pit.
 

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Check the charge pipes; they leak intermittently and only at very low boost or vacuum; something you won't find with a pressure tester.

I would recommend boost leak testing the engine at 20 PSI. I sell a kit that you can also make yourself easily: https://www.cruzetalk.com/forum/34-gen1-1-4l-turbo/236771-cruze-sonic-1-4l-turbo-luv-luj-boost-leak-testing-kits.html

Have you verified that you don't have a leak in the PCV hose coming off the intake manifold and going into the turbo inlet? That tends to crack and leak, causing a vacuum leak.

Valve stem seals don't need to be replaced, nor do you want to do the job, I can guarantee that much. You need two sets of specialty tools for that. I don't recommend it.
 

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Hello, Thank you for you're reply. I cannot add pics as Cruzetalk will not allow my account to post pics or links.
 

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Discussion Starter #5
Thanks. Good tips and advice. :)
 

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2012 1.4 auto

I checked my compression today :

1 - 190psi
2 - 190psi
3 - 190psi
4 - 198psi couple extra cranks?

So these numbers are good. NO boost leak from piston rings or valves.

I keep getting loss of boost though. When accelerating, it just revs to 5-6,000rpm but no PUSH! No boost to move me. Just feels like it's dropping into neutral and revving up.

I do a boost leak test and nothing from valve cover, nothing from charge pipes or intercooler, nothing from throttle body. None of the tubing.

I can hear something though, possible internally in the intake, is that possible?

I just can't pinpoint it. Up to 20psi on boost, let sit. It takes about 90 seconds to drop to 12psi. Then pretty much sits for several minutes to 5psi.

Thoughts? Gas mileage is excellent, just I have no push.

I have read that some have done a factory ECM flash and that has made a difference?
 
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