Chevrolet Cruze Forums banner
1 - 19 of 19 Posts

·
Registered
Joined
·
67 Posts
Discussion Starter · #1 · (Edited)
Respectfully request opinions & advice re cranking vacuum test of 1.4L turbo engine

Hello Forum Readers

My project 2011 Cruze LT with 1.4L turbo engine has the following new parts

Camshaft/Valve cover
Intake Manifold (Plan on adding the PCV repair modification and BNR throttle body extension to mount a boost gauge.)
Turbo Charger
Coolant and oil hose/lines for turbo
Serpentine belt and belt tensioner
Thermostat - 217F
"water" coolant outlet tee
Camshaft Position Sensor Solenoid Seals
Spark Plugs
Air Filter without extra foam element for less restricted air flow.
Washed out pre-catalytic converter with Dawn dishsoap
Washed out Intercooler with gasoline
(I should have changed lower or inlet radiator hose when front bumper cover was off.)

engine is lubed with Castrol Edge 5W-30 full synthetic and ACD filter PF22257G

I've flushed out the cooling system with reverse osmosis purified water but have not yet installed Dex-Cool as I'm waiting for the new Lower Radiator Hose (difficult clamp).

While waiting, I put the scanner and vacuum gauge on and ran the engine until it got up to 193F. No codes are being set in the OBD and the CEL is not illuminated. There's about 1.5 hours on the engine since installing the new turbo.

This car's engine starts up with 17" Hg vacuum and as it warms up vacuum drops to 15" Hg. The vacuum gauge indicator needle fluctuates or oscillates a tiny bit. When the rpm is increased from about 700 up to 1000 the vacuum increases from 15" up to about 18". When this happens the MAP reading drops from a fluctuating value of about 5.8-6.2 PSI down to a fluctuating values of about 4.6-5.0 PSI.

Long Term Fuel Trim is about 5%.
Fuel Rail Pressure is steady at 43.5 psi
Upstream O2 sensor voltage varies from .07 up to .8 volts.
DownStream O2 voltage varies from .7-.85 Volts.

I'm thinking there is a bad valve in the cylinder head and that a cranking vacuum test would confirm or deconfirm. By warming the engine up and then shutting it off and attaching the vacuum gauge to the brake boost port on the intake and removing the ignition relay and fuel pump control module fuse to disable starting and fuel, I can then see what the cylinders are pumping out without doing a compression test. If the vacuum fluctuates when cranking, then there is a high probability of a bad valve. If the vacuum holds steady while cranking, then the low vacuum after warming up to temp might be a jumped timing chain. In the later case, I think to remove the camshaft cover and check the timing chain for slack and broken guides. The replacement was done by a Jupiter Chevrolet (Dallas Texas - Don't do business with those guys.) Service Dept tech, so I did not get to check the chain or guides.

Does this diagnostic plan make sense? Will this enable me to diagnose a bad valve or jumped timing chain?

So if there is a bad valve, is there an oil additive compatible with a turbo charger that will render the compression and vacuum acceptable without coking or cooking in the turbo?


Thanks for reading and responding. Nice Day :)
 

·
Registered
Joined
·
3,516 Posts
2 cylinders on top. 2 on bottom. Weakest suction points are top and bottom. That's when the valves open and close.

4 cylinders have always fluctuated. That's the nature of the beast. 8 cylinders would be more constant.

Cranking vacuum will be weak compared to running vacuum.

Running vacuum might tell you variation of weak to strong cylinders. But won't tell you actual compression. Or which cylinder.

Vacuum should be higher at closed throttle then partially open throttle. According to your readings. Sounds like you're hooked before throttle instead of after throttle.

Sounds like..I'm not familiar on port locations to really say for sure on your readings.

Depending on altitude and compression. You should have at least 20 inches vacuum.
 

·
Registered
Joined
·
67 Posts
Discussion Starter · #5 ·
Thank you. Yesterday was the first time I've ever used a vacuum gauge.

//Vacuum should be higher at closed throttle then partially open throttle. // - Yes. That's what the tutorials and instruction videos say. I found it strange that the LUJ/LUV 1.4L turbo engine should behave in such a manner. I forgot to mention in the OP that I had "ported" the new intake manifold by cutting away restrictive to flow material with a trim router and die grinder bit so that the internal ports are approximately 1.75 times larger than the stock part internal intake ports. Perhaps that is the cause of the unusual behavior.

//
According to your readings. Sounds like you're hooked before throttle instead of after throttle.// - I had connected the vacuum gauge hose adapter to the brake booster port on the intake manifold that is located downstream of the throttle body. It's very easy to take off unlike the EGR regulator solenoid connection.

Anyway, I'll have to soon remove the intake to apply the PCV fix modification. Will order next week after paying for new laundry dryer timer.

//
Depending on altitude and compression. You should have at least 20 inches vacuum.// Yes. And that my engine starts up with 17 inches Hg and vacuum falls to 15 inches as it warms up causes my concern. It is likely one or more of the pistons has bad rings. If so, then new long block install is in order.

 

·
Premium Member
Joined
·
8,003 Posts
Maybe I'm missing something, but I'm not seeing anything in the OP to be concerned about. At least not at this point.

A compression check would be a better test.
 

·
Registered
Joined
·
67 Posts
Discussion Starter · #8 ·
Thank you. I forgot to mention in the list, the new alternator, water pump and power window regulator installed by the dealer under the extended warranty. Geez, the Cruze, like the Malibu is a POS. No wonder the local Pick-N-Pull is full of GM junk.
 

·
Registered
Joined
·
67 Posts
Discussion Starter · #9 ·
Thank You. :)
 

·
Registered
Joined
·
67 Posts
Discussion Starter · #10 ·

·
Registered
Joined
·
67 Posts
Discussion Starter · #12 ·
I anticipate having time to work on my vehicles this next weekend, and the weather is forecast as fair, so I'll be out there. I'll run the vacuum test again after I complete coolant and radiator hose replacement. I'm thinking the valve guides are a bit loose or that the throttle body isn't opening sufficiently (GM TBs are known to have problems.) upon revving up the rpm and/or that the second catalytic converter is partially clogged.

Perhaps my hope to save this car from it's rightful fate as salvage parts will be fulfilled. Nevertheless, I'll never buy another GM vehicle and will always advise others to shun GM like a plague.
 

·
Registered
Joined
·
3,516 Posts
I anticipate having time to work on my vehicles this next weekend, and the weather is forecast as fair, so I'll be out there. I'll run the vacuum test again after I complete coolant and radiator hose replacement. I'm thinking the valve guides are a bit loose or that the throttle body isn't opening sufficiently (GM TBs are known to have problems.) upon revving up the rpm and/or that the second catalytic converter is partially clogged.

Perhaps my hope to save this car from it's rightful fate as salvage parts will be fulfilled. Nevertheless, I'll never buy another GM vehicle and will always advise others to shun GM like a plague.
You won't succeed.

I was born and will die gm.

I'll never own Ford. They most redicously built cheap car.
 

·
Registered
Joined
·
67 Posts
Discussion Starter · #14 · (Edited)
Hello. Thanks for the reply. Yeah me too. My last Ford was a 97 Ranger, and it was okay until the block cracked with about 90K miles on it. I took good care of that little truck too; it was a bit disappointing. My current new car is a Hyundai with 20 year 200K PT, 5 year or 100K bumper to bumper & 7 year body rust warranties. But I'll never buy another GM. They dislike their customers so much that they purposefully design their product to fail. If one must have a GM vehicle, lease the **** thing and let the service techs deal with the problems.

I've nostalgia for old Mopar cars. Loved my 67 Fury with the 383 V8, nice freeway cruiser. Mine was a white sedan like this one.

http://carphotos.cardomain.com/ride_images/4/297/4081/38242040001_large.jpg

My father was proud of his 63 Chrysler New Yorker similar to this one.

https://classiccars.com/listings/vi...-new-yorker-for-sale-in-arlington-texas-76001

My Uncle loved his 1960 Fury. I recall riding about in it when I was six year old and holding my toy airplane out the window to see its propeller spin.

http://www.2040-cars.com/_content/cars/images/78/369978/005.jpg

Gosh, I've not thought about this one in many years. My earliest memory of riding in a car involved my father's 1949 Dodge maybe in 1960 or 61. It was a dark olive green four door sedan as I recall the family riding over western Appalachian hill country roads in east Tennessee.

https://c2.staticflickr.com/8/7013/6455959521_0e6a79bb0e_z.jpg
 

·
Registered
Joined
·
67 Posts
Discussion Starter · #16 ·
Yes, very sad. Oh well, I've plenty of pics to feed my MOPAR fix and some salvage yards still have some vintage tin.
 

·
Registered
Joined
·
67 Posts
Discussion Starter · #17 ·
Good advice. Gotta get me a compression tester kit. Groovy.
 

·
Registered
Joined
·
354 Posts
@OP
What is the problem your diagnosing?
Negative symptoms other then idle vacuum.

Your scan values are all in range of a healthy engine.
Pretty poor intake vacuum @ 15 in/hg idle vacuum instead of 20

What are the piston tops looking like? Shiny black, dull black, golden brown, white. All consist with eachother?

My guess is a bad ring landing. Compression test will bring clarity. With everything you replaced, im surprised that the issue hasn't subsided...
 

·
Registered
Joined
·
67 Posts
Discussion Starter · #19 ·
Collected more data last weekend while Cruze was parked in driveway.

After warm up to 219F
RPM 780-790
Vacuum 17" Hg
MAP 5.9-6.1 psi
Load 18.8%
LTFT 11.7
Cooling Fan on

Idle with Heat on Max with fan at #4
RPM 770-790
Vacuum 15" Hg
MAP 6.5-7.0 psi
Load 21.2-22%
LTFT 11.7-12.5
Cooling Fan off when ECT fell to 198F

Idle with AC on Full with fan on #4
RPM 770-790
Vacuum 10" Hg
MAP 9.1-9.6 psi
Load32.9-34.5%
LTFT 5.5-6.3
Cooling Fan on when ECT greater than 198F


AC on Full with fan on #4 with RPM @ 2000
RPM ~2000
Vacuum 14" Hg
MAP 7.1-7.3 psi
Load 18.0-18.8%
LTFT 2.3
Cooling Fan on when ECT greater than 198F

Heat on Max with fan at #4 with about 2000 RPM
RPM ~2000
Vacuum 20"-21 Hg
MAP 4.2-4.4 psi
Load ?
LTFT 3.1-3.9
Cooling Fan off when ECT fell to 198F
 
1 - 19 of 19 Posts
Top