My girlfriend noticed her 98 Chevy metro was not running well. We ran a diagnosis tool and it was giving 02 sensor codes. The car would start but wasnt running well and would stall after running for a while and hitting the gas would sometimes stall the car, and other times would rev the engine as expected. We replaced both 02 sensors and nothing changed. We started checking the intake the car would run just fine and pep back up if we sprayed carb cleaner into the intake. Leading us to believe it wasnt getting fuel and needed a new fuel pump. To big a job for me to do in the driveway so we took it to the shop. After doing some of their own testing they noticed I’d you sprayed the carb cleaner anywhere near the intake the engine would come back to life. They believed that the vacuum was leaking somewhere and that was the cause of the troubles. They replaced the intake gasket, and fuel injector gasket. No change. Any thoughts or ideas about what the problem could be would be greatly appreciated, thanks!
One way to locate a vacuum leak while the engine is running is to run a propane torch or hose (not lit) along all the hoses and other possible sources of vacuum leaks. The increased fuel will momentarily bump the RPMs. If their hunch was a VL, something like this would have been a good thing to do before replacing parts.
You may still have a vacuum leak somewhere.
at 20 years old any of those hoses could be deteriorated to the point of crumbling in your hands.
@shanonia has the right way to check these with an unlit torch.
Pass it close to each vacuum hose from one end of the hose to the other.
Yosemite
I have a couple Geo Metros as well. The good news is that this is a SUPER SIMPLE car to work on and the engine bay offers easy access. Your description sounds like as classic of a vacuum leak as you can get.
This is a 20 year old car and the rubber lines are likely cracked. For a few dollars you can just replace them all which is what I would do. Pull off a couple of different sizes and have them matched at a parts store. Buy 3 feet of each and it will cost less than $10 total. Cut sections of line to the length of the pieces you have removed and replace them. Systematically remove one piece of line at a time and cut new pieces according to the length of of the old line. I always do it this way because there is no confusing where the lines go. There is also a vacuum line routing diagram as well as some ignition system/timing parameters on the underside of the hood unless the sticker has been removed.
The sticker will look something like the one pictured here. http://geometroforum.com/topic/8004968/1/
I also suggest signing up for the GeoMetroForum.com as that is the main resource for these little cars. It is free as well.
In addition to the hoses, there may be vacuum switching valves and “jets” the hoses plug into. A crack or leak in any of those is also possible.
Yes, some of the nipples may be plastic so make sure they aren’t cracked either. Something else to consider is the EGR valve. These are known for plugging up on these cars and needing to be cleaned. Another issue is that the diaphragm can crack and allow for a vacuum leak. Check the brake booster and lines as well.
I had a friend with a 1970 SS 396 with really rotten vacuum lines. He had to idle for about five minutes in the cold before he could drive the car. Swap the hoses out and he could move right away. Best $3 job ever.
The vacuum lines on a Geo Metro are cheap and easy just like the rest of the car. Sometimes the simplest of problems can cause horrible running conditions.
I was changing the oil in my riding mower once. I thought I had the oil and filter but didn’t realize that I didn’t have the filter until all the old oil was drained out. I really wanted to mow the lawn and live a ways out of town so didn’t want to have to drive in to get a new oil filter. I started to see if an oil filter from one of my cars would fit the mower. Yeah, the mower uses Geo Metro oil filters! That sounds funny but a 1985 Ford 302 V8 filter will also fit the Geo Metro as well as the riding mower.
These are great little cars!
There’s probably a good description somewhere on the net how to check the entire vacuum system of a car systematically. If so, I don’t know where it is. The propane idea above is good, but before I did that I’d visually check all the vacuum hoses and test all the vacuum operated devices (like the brake power booster and egr valve) that they hold vacuum to 20 inches using a hand held vacuum pump gadget. Mighty Vac I think is one brand name. Not overly expensive.
If you feel lucky you could just replace the PCV valve. And cross your fingers. If that fails, it can cause this symptom. Be sure also to check any rubber boot that goes between the air cleaner and throttle body for cracks.
The vacuum lines on these cars are super simple. The EGR is not super cheap and usually doesn’t fail although it can. It usually plugs up. I would just replace the vacuum lines since it is so cheap and easy and see where it goes from there.
The geometroforum.com page is ideal for this. You will be able to find all the technical details of anything related to the car. Yes, the PCV system is also simple. The hose/boot between the valve cover and PCV unusually doesn’t crack but the valve can plug up and need to be cleaned. It won’t cause the behavior you describe though.
The good news is that the car in question is EXTREMELY simple to work on and 20 year old vacuum lines commonly fail on them. The routing should be on the underside of the hood or on the firewall. If not, replace the lines one at a time so you don’t confuse them. There aren’t that many. Odds are this is a cheap and easy issue to repair.
True, if it fails plugged up and closed. But if it fails stuck open, could be related.