What is the proper operating compression PSI for a 1999 Chevy Suburban c1500 5.7L?

100

Asked by Jan 03, 2014 at 01:20 PM about the 1999 Chevrolet Suburban C1500

Question type: Maintenance & Repair

P0300 misfire - cylinders 2, 4, & 6 - already replaced all plugs/wires, cap/rotor, cleaned
throttle body, replaced crankshaft sensor, & throttle pedal sensor. Want do pressure test
to check for vacuum leaks but don't know the specs & have tirelessly searched the net.

16 Answers

61,085

Generally speaking, 150 psi or higher is good at cranking speed. Have you checked the fuel injectors? They might not be spraying or not spraying correctly. HTH. -Jim

7 out of 7 people think this is helpful.
100

Thanks, I finally found some info as well. I found it to be 9.4:1 KPA which seems to be in about the same range of what your giving. We will check injector's as well.

4 out of 4 people think this is helpful.
61,085

You're welcome. Glad to help. -Jim

2 out of 2 people think this is helpful.
100

There is definitely a differential in the cylinder/spark plug pressure #4 only had 32 PSI. I didn't bother checking all of them since there was more than a 10% difference in the 3 I checked. From what I understand its indicative of needing to replace the head gasket. So that may be my next venture.

3 out of 3 people think this is helpful.
61,085

I'd say so too. Especially if either of the cylinders "next door" ( 2 or 6) test equally low. That means the head gasket is blown between the two cylinders. Also, since the misfire codes are all on the same side(even numbered cylinders) that makes me think head gasket as well. But just to be 100% sure, test all 8. HTH. -Jim

3 out of 3 people think this is helpful.
100

Would there be a different diagnosis or outcome based on the other readings? I didn't think it would make a difference but I am no car specialist...lol I'm just a girl going off Chilton's and some information off the net.

3 out of 3 people think this is helpful.
61,085

Yes, If all 8 cylinders test low it's a jumped timing chain. But with those kinds of readings on all 8 cylinders the truck wouldn't run. If you get a low reading on a single cylinder or even on two cylinders that aren't adjacent to each other it's most likely a valve problem. If a valve is burned or stuck open you'll have a low or zero reading on that cylinder only. But two low readings side by side point to a blown head gasket. -Jim

5 out of 5 people think this is helpful.
10

I had a random misfire on both my chevy trucks with 5.7 engines, both with 200K + miles. Changed plugs, wires, cap, rotor, tps, map sensor, knock sensor, cleaned the maf sensor on my 98 chevy. Nothing helped, The truck even got worse. Replaced the distributor on the 98 and all was solved. So I replaced the distributor on the 97 without changing all the other stuff and it now runs perfectly. Got the distributors off ebay from kjmperformance for $55. The best thing about this part is it has an aluminum base, not plastic like the factory one so I'm hoping it's going to last at least as long at the original.

1 out of 1 people think this is helpful.

1999 chevy tahoe will only run if number 7 spark plug is off.Don't no y

30

I'm having problems as well number 1 cylinder reads 91 pounds of compression and the other 7 range between 45 to 65 and that's while running. Dk if it makes a difference or not whether it's started or not? ??? Any help you can give is greatly appreciated

1 out of 1 people think this is helpful.
61,085

JR08, those can't be good cylinder compression readings. With compression readings that low the engine wouldn't run. Compression tests are done with the engine cranking, throttle wide open, and the ignition system disconnected so the engine won't start. Are those readings in pounds per square inch (PSI)? If so, retest using a different compression test gauge set. Sounds like yours is faulty. The kind where the hose screws into the spark plug hole is best. HTH. -Jim

30

The gauge test we used is in psi and it screws into the plug hole n the test was done with engine running

1 out of 1 people think this is helpful.
61,085

Something isn't right. With compression readings that low the engine wouldn't run. Sounds like the gauge is faulty. HTH. -Jim

30

I'm going to get a new tester soon and will update

1 out of 1 people think this is helpful.
61,085

Ok, good. Yes, please keep us posted. -Jim

10

Also - this engine is famous for the intake manifold gasket leaking and this often causes misfire indications on cylinders. Check to make sure you have not been losing coolant and pressure check your coolant system. If you replace it, make sure you use the FelPro PREMIUM intake manifold gasket - not the standard one.

1 out of 1 people think this is helpful.

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