Checking car for vacuum leaks?

[2cool2hear]

What's the best way to check for the vacuum leaks?
We're trying to figure out why the 2000 Saturn SC3 jerks every time when accelerating uphill or putting in reverse after cold start. I think there's a leak in the vacuum because we've already replaced the oxygen sensor, spark plugs, motor mounts, and cleaned out the EGR valve. Air filter is clean. What you think?

I know I could have posted the question on auto forum but I'd like to see what you guys have to say.

Many thanks

 

[6t7gto]

I made a smoke tester following this video.:

I used a mason jar.

david

 

[Stinger]

Smoke test works well. I don't have a smoke machine so I pressure test with my air compressor. I just build a cheap adapter like this: http://www.myturbodiesel.com/images/misc/bleaktester.jpg and then regulate it down and pump about 5psi through it and see what leaks. Some air will leak out the exhaust so you'll need a supply of air, not just a small bike pump or something. You can also spray starting fluid around while it's running and anywhere there is a leak, the engine will speed up.

 

[TheShrine]

I like WD 40 and/or a cheap cigar. Google it....he's your friend!

 

[RandyL]

I know nothing of Saturn,,,,but...

Find your airflow meter, map sensor, or whatever measures the air quantity going in the motor. This could lead you to the problem possibly. Bucking, jerking, especially in reverse often indicates unmeasured air going into the intake. I have found many with cracked intake airtubes on Toyotas ( big 3 inch air tube ).

In reverse, the motor torques in the opposite direction than in forward gears. This can open up a crack in these hoses momentairly..hence the bucking in reverse. Its worth checking..Saturn may use something else, I don't know.

Randy

 

[jimindm]

I would look more at the ignition side. If it is not COP, I would soak it down with a spray bottle of water.

On a non COP, I think it is recommended that the coils and wires are replaced as a set.

 

[Tarheelgarage]

What's the best way to check for the vacuum leaks?
We're trying to figure out why the 2000 Saturn SC3 jerks every time when accelerating uphill or putting in reverse after cold start. I think there's a leak in the vacuum because we've already replaced the oxygen sensor, spark plugs, motor mounts, and cleaned out the EGR valve. Air filter is clean. What you think?

I know I could have posted the question on auto forum but I'd like to see what you guys have to say.

Many thanks

Pardon me, but my crystal ball is not working too great today.....

As far as the jerking/bucking while acclerating uphill. you can rule out a vacuum leak as causing this. I would be looking at secondary ignition.

Now, if you had a decent scan tool with data stream, I would direct your attention to the fuel trims, load pid and maf/map pids to point you to the source of your problem.

 

[Shadowdog500]

I don't have a smoke tester either. I've heard that cigars leave a residue that may not be good. Scotty Kilmer puffs on a cigar and blows into the line to find leaks.

I have used other techniques for finding vacuum leaks. I've plugged off systems and tested with a vacuum pump to locate the bad hose, I've used propane or wd40 and listened for Rpm variations.

I also had a problem like yours that turned out to be an intermittent ground wire to the mass air sensor. The wires were routed under tension and the wire would separate under the insulation whenever the engine would pull on the wire from engine torque. Had to find that one myself after the dealership gave up (after throwing the parts cannon at it at my expense!!).

Chris

 

[GTA Matt]

Its not a vacuum leak. Its a speed density system. Ignition coils are **** in those things btw. You can get a kv tester to see how strong they are, mist them with water to see if they could be externally cracked, etc.