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Discussion Starter #1
The car had 54k original miles. It sat idle in a garage in FLA for a few summers before I bought it. Been driving it since April. After driving about 2000 miles across northern Ontario my mpg actually peaked at 24.9. Naturally, I was delighted, as my Fleetwood (89) only got 17 mpg on a good day. After I had the transmission fluid changed and the fuel injector system cleaned from the front on out, I noticed the mpg dropping steadily. I was driving back in the city but also about 65 miles a day on the freeway. I have since, had throttle service, changed all the plugs, changed fuel and air filters, used Slick-50 oil and gas additives. It is still dropping. Today it hit 18.6.

My next thought is to have the catalytic converter checked. Any more ideas?

Thanks,

Theo
 

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theodorei said:
The car had 54k original miles. It sat idle in a garage in FLA for a few summers before I bought it. Been driving it since April. After driving about 2000 miles across northern Ontario my mpg actually peaked at 24.9. Naturally, I was delighted, as my Fleetwood (89) only got 17 mpg on a good day. After I had the transmission fluid changed and the fuel injector system cleaned from the front on out, I noticed the mpg dropping steadily. I was driving back in the city but also about 65 miles a day on the freeway. I have since, had throttle service, changed all the plugs, changed fuel and air filters, used Slick-50 oil and gas additives. It is still dropping. Today it hit 18.6.

My next thought is to have the catalytic converter checked. Any more ideas?

Thanks,

Theo
Just a thought disconnect the battery for about 20 mins. Reset all of the computers memory and then start driving good luck man
 

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Discussion Starter #4
You know - that's a better idea. Thanks! I'll have them test the converter while they'r at it - I hate to pay for the whole diagnostic thing if it isn't necessary. I'll see if someone can do that for me today.

I also like the idea of re-setting the computer, once we have things squared away.

T
 

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2005 CTS-V, 1994 Infiniti Q45
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Its possible with all of your cleaning efforts you clogged or loged something in the injectors..... You might try running it a litlte more concentrated.....
 

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Discussion Starter #6
HollywoodHicks1 said:
Did you check the O2 Sensor??? I had the same problem on my 90 DeVille and that fixed it.
:coolgleam

Spoke to a couple of young but enthusiastic mechanics. They were reluctant to do the O2 sensor thing because it was expensive and no dashboard lights were indicating a problem. Same with converter. They thought that possibly I had succeeded in actually unclogging the fuel injector system from a previously diminished state - and had restored the car to its original specs. Hmmmmmmmm. They have a point, I suppose. The mpg I'm getting now more closely resembles the GM mpg guidelines for city/freeway driving that were published when the car rolled off the line. Something to keep an eye on. In the meantime, I've doubled up on the fuel additive (STP this time) and I'm driving my first 100 miles on it today.
 

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Discussion Starter #7
elwesso said:
Its possible with all of your cleaning efforts you clogged or loged something in the injectors..... You might try running it a litlte more concentrated.....
:cool:


Added two bottles of fuel additive (STP this time) to 10 gallons of gas. Driving my first 100 miles on it today.
 

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Discussion Starter #9
michiganblkman said:
O2 sensors expensive? they are 25 bucks at AutoZone.
How difficult a job is it, then? These guys were talking $160.00. $110.00 of that is pure labor then? Say $60.00 per hr - less than 2 hours?
 

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theodorei said:
:coolgleam

Spoke to a couple of young but enthusiastic mechanics. They were reluctant to do the O2 sensor thing because it was expensive and no dashboard lights were indicating a problem. Same with converter. They thought that possibly I had succeeded in actually unclogging the fuel injector system from a previously diminished state - and had restored the car to its original specs. Hmmmmmmmm. They have a point, I suppose. The mpg I'm getting now more closely resembles the GM mpg guidelines for city/freeway driving that were published when the car rolled off the line. Something to keep an eye on. In the meantime, I've doubled up on the fuel additive (STP this time) and I'm driving my first 100 miles on it today.
The O2 sensor isn't expensive at all. Like one of the guys on here said, they are about 20 bucks at Autozone. That is where I got mine. You are going to need an oxygen sensor socket. It seems to be a simple job, but if you have no clue what you are doing like I did, then it will be much harder. It didn't even take me an hour to do that though. Maybe about 30 minutes. Those guys were tryna get you for some cash!
 

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When you do it, to make it easier on yourself, drive the car first to get it nice and warm. Pop the hood and let it get just cool enough so that you don't burn yourself. It should be MUCH easier to get out. Also, make sure the new sensor has anti-seize on the threads (its some nasty silvery looking goo) or else that sensor is pretty much never coming out again.
 

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DaveSmed said:
When you do it, to make it easier on yourself, drive the car first to get it nice and warm. Pop the hood and let it get just cool enough so that you don't burn yourself. It should be MUCH easier to get out. Also, make sure the new sensor has anti-seize on the threads (its some nasty silvery looking goo) or else that senser is pretty much never coming out again.
Yeah I agree, cause I burned the hell outta myself a few times!!!
 

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Where is the O2 Sensor Located on the 1990 Deville? I have been all over the engined exhausts front and rear and cant see it?
 
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