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2002 Deville, 1990 Deville
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62 Posts
Discussion Starter #1
My 90 DeVille has a few problems and I hope I can get a little help. First let me say I used the car the past week and it's the first I used it since December. With that in mind I figure I need to get a couple of tanks of gas through it to clean it out. I also have been adding fuel treatment.
It has a rough idle and seems like it's going to stall. Also I had it on the highway and it has a vibration around 65 mph. I thought maybe the tires have flat spots from sitting on one spot for so long, but then I noticed the vibration seems bad going up hills and goes away down hills so now I'm thinking its missing slightly up hill. About 20,000 miles ago I changed plugs, wires, cap, and rotor. About 3000 miles ago I changed the EGR valve. I'm thinking the fuel injection system is dirty. Does this car have the single injector? If so It seems like the easiest thing to do is change it and see if it improves. Car has 130,000 miles on it. Any help would be great!!
 

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Blue 1993 Sedan DeVille, 4.9
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202 Posts
Is it 6 or 8 cylinder? I believe it would have more than one injector. I wouldn't put too many fuel injector products in them. Just 93 octane gas from shell or chevron. Should clean it out if it's dirty. Might want to get the injectors tested if it doesn't improve. Double check your fluids. I just bought a '93 Deville from someone and it had obviously been sitting for awhile. Changing the fluids and a tuneup seemed to wake the car up.
 

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2002 Deville, 1990 Deville
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62 Posts
Discussion Starter #3
Thanks ! It's an 8 cylinder. I'm pretty sure it should be the same engine that's in your 93.
 

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70 Deville 77 Fleet 78 Seville 92 Deville 03 Deville
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3,310 Posts
Techron should be the only fuel injection cleaner you should need. Is the SES light on?
 

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Registered
2002 Deville, 1990 Deville
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62 Posts
Discussion Starter #5
The SES light is not on. I didn't use Techron, but I'll give it a try. I just had the car inspected and asked the tech who did it to give it a listen and see what he thinks. He thought one cylinder is not working correctly and recommended a comprssion test. He can't do that for a couple of weeks. Although I put plugs in not that long ago I'm going to try a new set. Not crazy about Autolite, but thats what the local parts person had to I'm going to put in 8 Autolite platinums. Just another thing I noticed.. it seem to run OK when cold and gets bad when it warms up. Any suggestions? I'm getting worried that it might be a valve. That would show up with a compression test. I can do one but it would be difficult at this time and I think if plugs don't work I'll let someone else do that. Any ideas?
 

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Blue 1993 Sedan DeVille, 4.9
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202 Posts
I had a similar problem some months ago on my '91 Deville. I was told that I had an "internal engine" problem. They did a compression test and said one of the valves was bad. I didn't accept that. I got the suggestion to change the fuel injector. I changed the one on the bad valve and it corrected the problem. I ordered a set of bosch fuel injectors from ebay for about $65. Made a world of difference and improved my gas mileage dramatically. I'm going to do the same for my '93 to get better gas mileage. It's worth a try before you spend a lot of money on tearing the engine apart.
 
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