Like a month ago I bought a Deville ’98 (102.000 MI). When I start the car in the morning, or after the car is sitting for 3-4 h, the RPM fluctuates from 950 RPM to 750 RPM until the coolant reaches a temperature of 160-180 F. When it warms up, it seems to be fine, but it wastes too much gas.
I checked the FPR no leaks. Is it possible the FPR to be bad without any leaks? I changed the air filter. Cleaned the TB and after I cleaned the EGR valve, I noticed that MPG is back to normal 17 in the city and I’m not sure how much on the HW (25-27?) The issue with the idle was not gone, so, I changed the spark plugs. It took me about 1 1-1/2 h. It looks more difficult than it is. I did not take anything out. I only unplugged a couple of wires so I can get access to every spark plug. Anyway, I guess the former owner didn’t do the 100.000 maintenance; I changed the original spark plugs. Two of the plugs had a pretty strong gas smell. Now the car sounds like all 8 cylinders work good, but I still have the same issue – RPM fluctuates a bit.
I want to change the fuel filter, should I expect any changes with a new fuel filter? Do I need any special tools?
Thank you

If you remember which 2 plugs were gas fouled, pull those fuel injectors (easy) and look at the tips.....wet? Gum buildup ?? Reman injectors are cheap at RockAuto. Fuel filter is not your problem.

thank you for the quick response!!!!
I'll check. Is it easy to take out the injectors? i remember about one of the plugs, but not the second one. If it's not too difficult I can check them all. Should I try one of the Injectors cleaner products before i change them?

remove the beauty cover, disconnect the vacuum line at the fuel pressure regulator (on the injector rail), disconnect the two fuel rail supply and return quick-connects, disconnect the 8 electrical connectors, remove the 4 retainer nuts. Lift off the entire rail-injector assembly.

so, it's better not to use any injectors cleaner? Just replace them?

OK, Run through a 20 oz. jug of TECHRON with a fill of 93 octane Chevron, Shell or Texaco (top tier fuels; Google) and see if that cleans anything up. If not, start checking injectors.

Can I mess up something else using TECHRON or is 100% safe?
thank you much
you guys are great on this forum

TECHRON is part and parcel of the advertised additional additive in Chevron, Shell, Texaco, and some midwestern chain gasolines. It is recommended by GM and is the subject of "top tier" fuel discussions.

As I posted before, Google "TECHRON" and "top tier".

All the Forum members in the world can't do you any good unless you at least follow advice and form your own opinions. Do your homework........you'll never learn anything unless you study the problem, weigh the options, and apply your results. :banghead:

i will do my homework because i really like this car. I have a Deville 94 (220.000 mi) but i always took it to the shop. I don't want to do this again, shops/dealers are too expensive for a Caddy and many times they "fix" the problems in a way that in 2-3 mo i have to go back.
thanks for all the info!

NOTHING is 100% safe if used wrong. Be sure to follow the instructions.
Can I mess up something else using TECHRON or is 100% safe?
thank you much
you guys are great on this forum

Is this hose suppose to be lose?

Nope.

what is it? it looks like the gasket/seal at the bottom end of the pipe it's warned out. Is there a way I could check if it looses air (vacuum?)

I believe that is the EGR supply line. Notice the heat shield on it? Use a stethoscope to listen for a leak. If it is leaking, it may be the cause of your idle problem.

Thank you Ranger, this would be my next target.