How do I fix my 90 caddie wierd idling problem?

[vance43211]

I have a 90 caddie. sometime it idles rough. it don't do it all of the time. I use 93 premium gas. I use the bosch premium spark plugs, new pcv valve etc. it been like that since i bought it. my friend 90 caddie has the same issue. I don't like it

[Sergey21]

Originally Posted by vance43211

I have a 90 caddie. sometime it idles rough. it don't do it all of the time. I use 93 premium gas. I use the bosch premium spark plugs, new pcv valve etc. it been like that since i bought it. my friend 90 caddie has the same issue. I don't like it

Bosch = shit for our Caddies (found out the hard way). Get rid of them. You're better off with stock spark plugs or NGK's designed for your vehicle. Bosch works great on imports, not our rides. Did you check your coil, distributor, wires, idle problems are one of 3; fuel problem, ignition problem, air problem. So, start step by step, check fuel pump, your FPR, is your fuel filter clean? Usually, rough idle is caused by a bad spark, causing one of the cylinders to misfire, hence causing your engine to bog, stall, shake, hesitate...etc. Get rid of the crap Bosch spark plugs, check all of your wires, make sure they are wired correctly. Check your distributor and ignition coil, also make sure your CAT is not clogged up. Heavier oil that needed can also cause a rough idle, dirty air filter can also have same effect. Bad pressure from fuel pump can cause a rough idle. A leaky FPR can also cause a rough idle. Any smell of fuel around the car? Any smoke from exhaust? That would be some indication if your car was running too rich or too lean. Lean and rich condition can also be big factors of having a rough idle. If your car gets too much air, it will shake and hesitate on starts, and too rich, is when you burn more fuel that needed, your car will most definitely have a very rough idle, because the fuel that gets into the cylinder does not burn up, and the engine strains to get rid of that fuel and burn it. Like I said, start with one thing, and go step by step. Fill me in on what you check out, I will try to help you out with this problem, and so will others I'm positive, although, Ranger might just tell you to check for a leaky FPR, hence he will most likely think its the culprit of the problem...But yeah man, let me know what you work out. First GET RID OF THE BOSCH!!!! You can also clean out your TB, and your EGR, which can sometimes cause rough idles. Good luck bro.

Just giving you a hard time Ranger. - You know we all appreciate your input brother.

[chubbyranger]

I used Bosch plugs in my 1990 CDV and they were passable (single or +2 only - NO +4s) for the 4.5 motor although you may want to check them for carbon build up and replace with AC Delco if they are looking odd. Other things to check on the 4.5 include the ISC (Idle Speed Control) motor which lives on the intake end of the throttle cable. It reglates the idle to adjust for varying loads and they have a somewhat high problem rate based on postings here. Also check the timing as the 4.5 is a manual adjustment motor. Pull codes:

http://www.cadillacforums.com/forums...s-warning.html (How to pull Codes and got codes or warning lights? Look here!)

Also - see if you can narrow down when it idles "wierd." Check the idle with the Climate Control both off and on. Turn the steering wheel left and right at idle. If the motor bogs down when you turn the wheels or when the air conditioning kicks on that may more strongly indicate an ISC problem.

[vance43211]

thanks for the replies. I just put the bosch plugs in. it had the problem with the ac delco plugs. what is CAT,TB, FPR?

I replace the air filter, pcv valve and all of obvious stuff. I even went to the junkyard and got the 2 pieces that go from the air filter to the input air part in front of the batterry. that part was missing. I have no codes. I fix the 1 that i did have (replacing battery one). detail computer tests show that my intake air was hotter then it should be , that obviosly as happening because it was sucking air straight from the radiator as those 2 pieces was missing.
the pieces is part number 12



I don't think that the fuel filter is an issue. I can usually tell if fuel filter is a issue although maybe they act different on fuel injected cars.

I was thinking about maybe it was the Idle Speed Control motor. on my old 88 caddie, I replace the pcv valve, spark plug when i first bought it and after that the Idle Speed Control motor on that would rev super high. I replace it and then i started 25-30 mpg. that's my problem now. I'm getting 10 mile per gallon and maybe 15 on the freeway. that's not acceptable. I bought this car because my 77 caddie use 12-14 miles per gallon and I was trying to save money. of course I'm not.

I was getting a max of 145 mile per full tank at first. I can get 225 if I mostly freeway drive now since I made these improvement

[Sergey21]

CAT = Catalytic Converter, TB = Throttle Body, FPR = Fuel Pressure Regulator.

Replaced the wires yet?

By the way, you said you use 93 Premium octane...did you just switch to that? I mean have you used like unleaded or premium unleaded before? Switching gas octane sometimes can give your car a hard time.

Buy some seafoam, and clean out your engine. Use half of the bottle in oil, and half in the brake booster line, while the car is on, let the line suck the sea foam in. If you do end up doing that, tell me, I will give you good instructions of the best way to do it.

[vance43211]

Originally Posted by Sergey21

CAT = Catalytic Converter, TB = Throttle Body, FPR = Fuel Pressure Regulator.

Replaced the wires yet?

By the way, you said you use 93 Premium octane...did you just switch to that? I mean have you used like unleaded or premium unleaded before? Switching gas octane sometimes can give your car a hard time.

Buy some seafoam, and clean out your engine. Use half of the bottle in oil, and half in the brake booster line, while the car is on, let the line suck the sea foam in. If you do end up doing that, tell me, I will give you good instructions of the best way to do it.

no. I didn't change them yet. I was thinking of buying a whole new distributor when I do that. my Catalytic Converter is fine. i will now check the Throttle Body and Fuel Pressure Regulator. it sound like the Fuel Pressure Regulator could be an issue. I will find out what that is. I'm going to change my wires now without buy the distributer.

I'll probably need instructions to the seafoam. I usually add 2 quarts of kerosene to a running engine for 5-10 minutes before I change the oil to clean my engines.

I always use 92-93 premeium for my cars. but I don't know what the people before me used. I'm the third owner. I bought it from a guy that bought it from the original owner (all of the paperwork is in the vehicle including the original receipt). he had it six months. he obviously sold it because of the 9-10 mpg issue. other then that the car run great. it has 120,000 miles

I fix the 9-10 mpg issue on my wife old 88 caddie (a lady destroyed it in an accident. we miss it) rather easy. I thought that it would be easy on this car too

[Sergey21]

120xxx miles, change the rotor cap and distributor, if the wires didn't help. And I will most definitely give you precise instructions on doing a seafoam® clean out.

[vance43211]

Originally Posted by Sergey21

120xxx miles, change the rotor cap and distributor, if the wires didn't help. And I will most definitely give you precise instructions on doing a seafoam® clean out.

ok. I see through her receipt that she put a new distributer in at her 60,000 mile tune up. I guess that it's due. how many miles do you need before you should replace a distributer? do they sell seafoam at the regular auto part store?

[cadillac_al]

Hi Vance, I don't see where your mileage is listed. I see Sergey has 120xxx from somewhere. Anyway, I think worn fuel injectors may give you a rough idle. I'm not sure if they would give you the 10 mpg though. MAP sensors are cheap and easy. If you had a Factory service manual, which I don't, you could get into the diagnostic system and be able to check the temp to verify it is getting into closed loop and also check O2 funtions and many other things. The distributer is designed to pretty much last as long as the engine. Even on this forum, there aren't a lot of cases of distributer failure. Sometimes the gear can go bad but a lot of them don't and last the life of the car. These are just a few of my thoughts on it. Did you check the EGR tubes yet?

My Deville is almost at 190,000 miles and is running almost as good as new; it purrs like a kitten. I just checked the oil yesterday, it's been two months since I changed it, it was still full and still golden brown. I was quite impressed myself. It's running Bosch plugs and regular fuel and 15-40 truck oil and it seems to love it. It gets 17.5 mpg around town and country roads which doesn't sound that great to me, but it seems to be about what everyone else gets. When I wear this one out I'm going to look for another 4.9 vehicle. Cheers.

[Sergey21]

Originally Posted by vance43211

ok. I see through her receipt that she put a new distributer in at her 60,000 mile tune up. I guess that it's due. how many miles do you need before you should replace a distributer? do they sell seafoam at the regular auto part store?

You might want to change it, might not. Just check it, see if it has a lot of burnt surface on the inside of the cap. But as far as Seafoam® they sell it at all auto parts stores, even wal-mart. Buy one can of seafoam, then empty half of it, into oil crankcase, then unplug your brake booster line and let it suck the seafoam up, but don't let the engine die, thats at the end. When letting the engine suck the seafoam, when you almost just have a quarter left of the seafoam, let the engine suck the whole thing up, basically try to kill the engine. Once the engine is dead, let it sit for 5 - 10mins. Then turn on the car (it might not start on first try, or act as if engine will die, thats normal) and rev the crap out of it, and watch the smoke come out of your tail pipes, all that smoke is crap build up in all of your line from the brake booster. If you want to do a complete car clean up, buy two cans of seafoam, and empty half a can into your gas tank, that will clean up your gas lines and your injectors. The other half you can add to brake booster line again, if there was a lot of smoke. If you need more help, I'm here man. Will be at work soon.