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Old 12-25-2005, 03:06 PM   #1
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Default Poor fuel economy

Hi , Im new to the forum and have some questions. Car is an 89 Olds 88 Royale, only getting 20 mpg. 80,000 miles on car, was sitting in a shed for 2 years. The coil pack went out 2 weeks ago when it was below 10 degrees out. Also replaced air filter, O2 sensor(new GM), Coolant Temp Sensor and cleaned the Mass Air Flow sensor. Car runs great other then the fuel economy. I did get a code 64 for the EGR valve 4 weeks ago, unhooked the battery and reset but it reset code 64 again last night. Car was running a little rough when it was first started and then smothed out. Would the EGR valve cause it to get poor mileage? Any other ideas?

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Eric
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Old 12-25-2005, 03:25 PM   #2
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The EGR can have an effect on fuel economy. Does it look like a 'mushroom'? If so, you can clean it. Procedure in Techinfo.

Two other things to check are your catalytic converter (could be clogged) and your Torque Converter slip. What does your trans fluid look like?
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Old 12-25-2005, 04:51 PM   #3
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Yes if you mean by mushroom, as having the black plastic cover and being electronically controlled by the computer. I'll check Techinfo. Trans fluid is red, clean and doesn't smell burnt, I'll change when I change the oil next weekend. Also was thinking the converter could be plugged, but the car seems to pull good, Im more use to the V8 in the Caprice though, so not sure. I guess I could cut the converter out and put in a test pipe to see what happens.

Eric
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Old 12-25-2005, 05:21 PM   #4
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I wouldn't go that far just yet unless your sure the converter is plugged.
Usually you fix whats causing the rich condition and the converter will clean itself out on the first highway hill. PCV valve stuck open?
I remember someone on the board saying there is another condition that causes the egr code to set but can't remember what.
You'll still do well to clean it. Vac leak?
Maybe someone else can remember.
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Old 12-25-2005, 06:25 PM   #5
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I just cleaned the EGR valve, pulled the 3 torx screws and wire brushed the valve seats and lbed them. unplugged the battery to reset the pcm. Was a lot of carbon build up. Im thinking this car was just putted around town,a * the air filter was black and also the MAF sensor was carbon up to. Had a hesitation when first bought. Wheres the PCV at?
Any cheap mods for these cars like intakes or exhaust?

Thanks,
Eric
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Old 12-25-2005, 06:32 PM   #6
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Has anyone mentioned the theromostat?? That definitly can have a toll on highway mileage. Your temp on the dash, (optional cluster) should be reading arounds 80-100 C or 195F for the ECM to be getting the correct readings, and go into closed loop.

89? Hmm, think its the conventional vaccumn. Not sure.

If the converter is plugged, the engine will run like crap. Try revving it up, does it rev quickly? Does it bog a bit? Will it rev right to the redline quickly?

Sometimes some sensors will give abnormally high or low readings, like a MAF sensor, in which it tells the ECM to give the engine more fuel, when its not needed. The only way to tell, is to hook a scanner up to the ECM, and get a datastream while taking the car out for a test drive, which is what we frequently do when a customer comes in with fuel mileage problems.
Good luck!
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Old 12-25-2005, 06:36 PM   #7
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Yes, there are mods, but not much for the LN3.
Search for a rice pipe on ebay -that'* the cheapest/most popular here.
Also, an F-body muffler from Magnaflow will really help.
But before you do the muffler go to www.justmagnaflow.com and get a new high flow 2.5" cat.
The rice pipe and HF cat (along with a fully tuned up engine) will give you a sound that is music to your ears (if you can call it that coming from a V6) and in th e1/4 you go from 17 flat down into the mid 16'*. Not so impressive as the 9C1, but it'll be enough for the average Civic to be put to shame.
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Old 12-25-2005, 07:32 PM   #8
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I forgot to mention I did change the thermostat. Car doesnt have any guages. Could the MAF be bad even though it runs good? You can smell gas when you remove the intake tube. Car does stumble a little when you go from reverse to drive or drive to reverse. Plan on getting a scanner when I get my credit card paid off enough. Just took it for 15 minute ride on the interstate, seems to pull just fine for what it is. What kind of mileage are you getting in the winter? Id be happy to get 25. My mileage is city/highway combined. Ill be selling this or the Caprice in the spring. My Caprice averages 20 mpg city/highway combined even with alot of wide open blasts, 170,000 miles and original O2 sensors.

Thanks,
Eric
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Old 12-25-2005, 11:17 PM   #9
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Quote:
Originally Posted by pontiac6269
I forgot to mention I did change the thermostat. Car doesnt have any guages. Could the MAF be bad even though it runs good? You can smell gas when you remove the intake tube. Car does stumble a little when you go from reverse to drive or drive to reverse. Plan on getting a scanner when I get my credit card paid off enough. Just took it for 15 minute ride on the interstate, seems to pull just fine for what it is. What kind of mileage are you getting in the winter? Id be happy to get 25. My mileage is city/highway combined. Ill be selling this or the Caprice in the spring. My Caprice averages 20 mpg city/highway combined even with alot of wide open blasts, 170,000 miles and original O2 sensors.

Thanks,
Eric
scanner - is as expensive as a paper clip and knowing which terminals to jumper. At least for pulling codes.
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Old 12-25-2005, 11:44 PM   #10
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Whoa! I never meant those el-cheap-o units sold at canadian tire, or walmart, that just tell you what number code is in the ecm. I meant an OTC genisys scanner, costing about 2000-3000 dollars aproximatly. (cheaper if its an older unit) These scanners tell you MAF, TPS, O2, voltages, engine operating conditions, etc. This is a datastream which you, or someone observes while in the driving range. Usually this requires an experienced technician with a scanner to be able to tell you which reading is abnormal.
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