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| Comparison Bad MPG; 4 cyl vs. 3 cyl | |
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| Tweet Topic Started: Feb 21 2009, 06:04 PM (1,224 Views) | |
| JRMCCOY_0 | Feb 21 2009, 06:04 PM Post #1 |
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Fresh Fish
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I have a 1990 Chevy Metro (I thought base but I was told it's one of the other two, don't know which). My mechanical knowledge is quite limited because I've only recently started working on Geo's. Dillema: Like I said I have the '90 3-cyl engine but my girlfriend has a 1994 Metro 4-cyl. Same size gas tank but I try to drive about 60 miles in her car and the needle barely moves. I try the same trip in the '90 and I use a little over a quarter tank. I haven't calculated out the exact MPG yet because I keep forgetting to print out the gas reciept and write the miles on it to compare and do the math so, why would I be getting such horrible gas mileage with a 3-cyl vs a 4-cyl? I don't think there's a leak. No puddles under the car when I stop. Other problems that might relate: I think my cadalitic (sp?) converter is bad because I hear a rattling coming from it. The guy I bought it off of "rebuilt" the engine. I'm unsure of how mechanically inclined he was. I recently had to take it into the shop because a bolt came loose on the cam shaft (I believe it was) that caused a key to fall out and threw the whole engine off timing. I got it towed (because it wouldn't even start back up for me) to a mechanic who took it apart and re-timed the engine. I think the carburetor needs to be rebuilt because I'm not sure if it's allowing the proper amount of gas into the firing chambers. Also, I have a significant loss of power (especially going up even small hills.) Spark plugs have been replaced, but I'm unsure if the distributor rotor, distributor cap, or wires need to be replaced. When stopping relatively fast to abrupt and the tank is 1/3 or below, the engine dies. I think it's because the gas sloshes to the front of the tank and the pump doesn't have anything to take. Could also indicate faulty pump though. Shortly after I got the car, I had to replace the fuel filter because it was clogged with this orange goo. I've taken it off again a month later to check it and the fuel was just a little red but no goo. Could it possibly be...: Air/fuel mixture? Carburetor? Spark plugs? Fuel Pump (which I think is good because my father and I took the fuel line off the carburetor to check pressure and attempted to start the car and he said there was really good pressure)? My auto lingo is quite limited so if you could keep it simple I'd appreciate it. I do have a Chilton's manual so if there are parts I don't understand what you're implying, I can look it up. Thanks for your insight. Edited by JRMCCOY_0, Feb 21 2009, 06:20 PM.
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| Johnny Mullet | Feb 21 2009, 06:32 PM Post #2 |
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Fear the Mullet
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The very first test to perform is a compression test on all cylinders. This will tell us how healthy the engine internals are before you start throwing money away on parts. A rattle in the cat means it's melted down. It melted down for a reason, so we need to begin with the compression test please. Post the numbers here for each cylinder. |
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| Woodie | Feb 21 2009, 06:51 PM Post #3 |
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You've got problems, some of which have to do with identification. There's never been a Metro with a carburetor and the first year a four cylinder was ever put into a Metro was 95. If you have all black bumpers, it's an XFI. If the top is painted and the rest is black, it's a base model. If the entire bumper is painted, it's an LSI. The gas gauges might just read differently, that's why you can't tell anything about mileage on less than a full tank, and a full tank is ten gallons. Driving 60 miles takes one to one and a half gallons, simply too much room for error there. That being said, it does sound as if you've got problems. Your rattling cat is probably bad and could be blocking the exhaust. That bolt coming loose and the key getting sheared is fairly common. If the shop got the timing one tooth off when they fixed the key the car would run, but poorly. If it ran fine before that happened, that's probably the case. That orange goo you found in the fuel filter had to go through another filter in the tank to get to that point. There's a cotton "sock" on the fuel pump pickup, they're known to get clogged on the bottom and not on the top causing the car to act differently when the tank gets near empty. Your description of the loss of power would normally have me saying the engine is worn out, get the compression tested and let us know what the numbers are. In this case, the timing being off or the fuel pickup clogged could do the same thing. It's never a bad idea to get a compression test though, that way you know what you're working with. |
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| JRMCCOY_0 | Feb 22 2009, 08:06 AM Post #4 |
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Fresh Fish
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My appologies about the identification. I'm going off mostly what I was told. Since I haven't seen my car since yesterday, I can't remember if the bumper is black or not. It's not generally something I pay much attention to. I'll get those compression numbers and post them as soon as I can. Thanks for the help so far! :-) (Stupid question warning!:) If it's not a carburetor then what is it? It's got a bowl and a valve just under the air filter. Edited by JRMCCOY_0, Feb 22 2009, 08:09 AM.
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| chads4dr | Feb 22 2009, 09:24 AM Post #5 |
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Its called TBI or Throttle Body Injection. It has one fuel injector positioned above the intake flap. It was pretty much a step up from the carburetor. |
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| Bad Bent | Mar 7 2009, 06:03 PM Post #6 |
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Facetious Educated Donkey
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Welcome to the forum, JRMCCOY_0! You say: My mechanical knowledge is quite limited because I've only recently started working on Geo's so, do you like to "wrench?" Because working on a Geo is really rather simple. I just did a cam swap with 8mm-17mm wrenches and sockets, screwdrivers, a timing light and borrowed an inch/lb torque wrench (basics: light, floor jack/stands, thread lock, lith. grease). Geo good. My gas gauge is erratic. The new Catalitic conv. is like $105--$155+. Takes 4 bolts, unscrew and install the O2 sensor and rubber mount. Stainless $125 The guy I got my Geo from had made at least 3 attempts to put new main bearings or whatever to stop the oil leak/low pressure. I got the car with the engine in the back seat, in pieces. One with 50,000 miles off eBay was $525 shipped. Proper retiming means getting to the timing belt by removing the water pump pulley, lower pulley and timing belt cover. There are two timing marks on the upper and lower gears. Like Woodie says. About an hour. Senior Mullet has a great picture posted See Page 2. Unscrew the two Distributor cap bolts and look inside. Check for cracks. Take a little sand paper and gently sand off any build-up on the rotor and posts. I use a cheap eBay "dremel" tool. Blow out any dust. Reassemble with gentle but firm torque. Or just replace and you know it's new. Like chad8329 says it's fuel injected. Yea, I thought "cool" also. I use Lucas gas addative - I'm going to Marvel Mystery Oil after I use up my gallon of Lucas. 4oz/fill up. You'll find Seafoam Treatment is recommended a lot by most of us for occasional injector cleaning. My Geo's model? Not a clue. Edited by Bad Bent, Mar 7 2009, 06:05 PM.
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