1989 Eldorado Biarritz MPG
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Is that highway mileage? In town? Or a combintaion of both?
When I peddle lightly in town I get an average of 14-15 mpg. On long freeway trips I get around 23-24 mpg.
The first thing of course is to make sure it is tuned well. (plugs, wires, cap/rotor, air filter, clean throttle body, clean EGR valve) Make sure your tires are properly inflated. After that you may want to consider some modifications. Illumina has the best suggestions for that in my opinion like MSD and improved air filter and intake tube, advanced timing.
I have not yet implemented these modifications so I can't give you any idea what you might expect from them.
When I peddle lightly in town I get an average of 14-15 mpg. On long freeway trips I get around 23-24 mpg.
The first thing of course is to make sure it is tuned well. (plugs, wires, cap/rotor, air filter, clean throttle body, clean EGR valve) Make sure your tires are properly inflated. After that you may want to consider some modifications. Illumina has the best suggestions for that in my opinion like MSD and improved air filter and intake tube, advanced timing.
I have not yet implemented these modifications so I can't give you any idea what you might expect from them.
13.8 would be about right if you are making short trips, even if part of the trip is at freeway speeds. Also, if the MPG has been reset fairly recently, the average will appear lower until you get more miles built up for reference.kieblerh said:
You will need a good 50 miles out, and 50 miles back at freeway speed (cruise control on) to get the MPG average bumped up.
You should get a copy of the OEM service manual. I got mine from www.helminc.com for $40.
Changing the plugs is relatively simple and requires only a few tools such as a small ratchet wrench with a few varied length extensions and a spark plug socket. It may be uncomfortable and a little bit painfull to get the plugs out and back in between the engine and firewall but it is not that bad if you are patient and carefull. You can reach the back plugs from the top-driver's side of the engine. That's how I got to mine, I reached under the water heater lines with my slighty above average size hand, wrist and fore-arm. I came out with a few scrapes but not bad. You will also need a tool to measure the plug gap. The proper gap will be listed on the emisions label under your hood.
Replacing the distributor cap and rotor are also simple and require only a combination of screw and nut drivers drivers for tools. Be careful while unplugging the electrical connetions to the coil and be sure that you replace them in the proper locations. Take pictures, draw sketches, whatever you need to remember how they are connected. You will want to take special care to note the position of the spark plug wires on the distributor cap.
I see that you are new to the forum (Welcome!) you need to become familiar with the search tools here as there are a lot of threads that have covered throttle body and EGR valve cleaning procedures in depth.
If you have not done these jobs on any cars before then I would suggest you ask a friend or relative who has experience to help you with them.
PS. I just checked Helm Inc. and our manuals are going for $105 now. Ouch! I must have gotten mine on sale last year. You might try Ebay for one. It is highly recommended here to get the OEM manual over a Haynes or Chilton.
Changing the plugs is relatively simple and requires only a few tools such as a small ratchet wrench with a few varied length extensions and a spark plug socket. It may be uncomfortable and a little bit painfull to get the plugs out and back in between the engine and firewall but it is not that bad if you are patient and carefull. You can reach the back plugs from the top-driver's side of the engine. That's how I got to mine, I reached under the water heater lines with my slighty above average size hand, wrist and fore-arm. I came out with a few scrapes but not bad. You will also need a tool to measure the plug gap. The proper gap will be listed on the emisions label under your hood.
Replacing the distributor cap and rotor are also simple and require only a combination of screw and nut drivers drivers for tools. Be careful while unplugging the electrical connetions to the coil and be sure that you replace them in the proper locations. Take pictures, draw sketches, whatever you need to remember how they are connected. You will want to take special care to note the position of the spark plug wires on the distributor cap.
I see that you are new to the forum (Welcome!) you need to become familiar with the search tools here as there are a lot of threads that have covered throttle body and EGR valve cleaning procedures in depth.
If you have not done these jobs on any cars before then I would suggest you ask a friend or relative who has experience to help you with them.
PS. I just checked Helm Inc. and our manuals are going for $105 now. Ouch! I must have gotten mine on sale last year. You might try Ebay for one. It is highly recommended here to get the OEM manual over a Haynes or Chilton.
Unlike the 1990 and newer engines with multi port injection, the EGR tubes and throttle body should not need cleaning. On these engines, two injectors squirt fuel down the throttle body which ends up self cleaning things.
You might try bumping up the timing a few degrees. Bump it up until you hear a slight ping at low rpm's / heavy throttle. I run mine at 13 degrees advanced and use the cheap gas.
You can also replace the muffler with one that is more free flowing.
Also, check your idle speed. It should be around 550. If it is much faster than that, it is wasting gas and the idle speed controller (ISC) may need to be replaced.
Believe it or not, driving habits can really affect fuel economy. I find that with city driving, getting into the habit of letting off the accelerator and letting the car coast well in advance of stopping at a stop light saves gas. Every time the brakes are applied, all that energy is lost in the form of heat.
Also, avoid warning up the car or prolonged idling. Lots of idling will eat gas mileage up very fast.
I have basically the same car as you (1988 Eldorado 4.5L) and get a consistent 23 city/32 hwy with stock 14" wheels and tires. However, with my cool looking 17" wheels and low profile wide tires, my mileage drops down to 22 city/28 hwy.
You might try bumping up the timing a few degrees. Bump it up until you hear a slight ping at low rpm's / heavy throttle. I run mine at 13 degrees advanced and use the cheap gas.
You can also replace the muffler with one that is more free flowing.
Also, check your idle speed. It should be around 550. If it is much faster than that, it is wasting gas and the idle speed controller (ISC) may need to be replaced.
Believe it or not, driving habits can really affect fuel economy. I find that with city driving, getting into the habit of letting off the accelerator and letting the car coast well in advance of stopping at a stop light saves gas. Every time the brakes are applied, all that energy is lost in the form of heat.
Also, avoid warning up the car or prolonged idling. Lots of idling will eat gas mileage up very fast.
I have basically the same car as you (1988 Eldorado 4.5L) and get a consistent 23 city/32 hwy with stock 14" wheels and tires. However, with my cool looking 17" wheels and low profile wide tires, my mileage drops down to 22 city/28 hwy.
I must respectfully disagree with you on this. While it is true that the EGR tubes remain unclogged in these models the throttle body does still benefit greatly from the cleaning process described on this site. I can attest to that personally. After cleaning mine I noticed a distinct difference and improvement in engine operation.Edahall said:
Idle and acceleration were both noticeably smoother and fuel economy improved slightly.
I recommend the process to anyone who has throttle body injection like mine.
Well, you might be correct on the fact that cleaning the throttle body benefits greatly. I did a search but I'm not sure what cleaning process you're using. Could you provide some links or briefly describe the process? I would like to try it out and it'll be a good test since my engine has 210k miles and the throttle body has never been touched.
I'm not sure if there are posts remaining so here goes;Edahall said:
I removed the air cleaner assembly from the TB, used a can of carburator cleaner, opened the throttle plate and sprayed the cleaner on and around every surface visible, paying close attention to any ports or openings in the walls. I also inspected and sprayed the injectors above for good measure.
Then I took an old tooth brush wet with cleaner and scrubbed anything that looked dirty until every surface and item in there was clean, including the underside of the throttle plates (butterfly plates). Then I gave it a final rinse with the spray.
Put everything back together and disconnect the negative battery cable for at least a minute and that's pretty much it.
I'm betting you will notice a difference when you are done. Let us know.
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