1990 Caddy Deville

[richardf]

My 1990 caddilac deville runs very rough after a few minutes on the road. Heater switch has been on all summer. I turned it off and motor seems to idle fine in driveway. havent put on road yet. Added water and oil. Dont know if 100 degree plus temperatures have been affecting it. Also, it hasnt had a tune up in a year, but, it hasnt been driven over 50,000 miles. Does it just need a tuneup?? thanks

[PAUL T]

I would start with the basics, check the battery terminals for cleanliness & tightness, spark plugs, & plug wires. Why was the heater switch on all summer? Has it been in storage? Run the diagnostic codes and see what comes up. With key on, engine off enter diagnostics by pressing & holding the "off" & "wamer" buttons on the climate control panel. Trouble codes will be displayed on the fuel data center panel. It starts with "8.8.8". First pass will be the history codes "E..." second pass starts when ".E.E" flashes, then current codes will be displayed. When ".7.0" appears it is done. To exit turn key off. Have paper & pencil ready because they only flash for 2 seconds. Report back with your findings. Good Luck.

[richardf]

I would start with the basics, check the battery terminals for cleanliness & tightness, spark plugs, & plug wires. Why was the heater switch on all summer? Has it been in storage? Run the diagnostic codes and see what comes up. With key on, engine off enter diagnostics by pressing & holding the "off" & "wamer" buttons on the climate control panel. Trouble codes will be displayed on the fuel data center panel. It starts with "8.8.8". First pass will be the history codes "E..." second pass starts when ".E.E" flashes, then current codes will be displayed. When ".7.0" appears it is done. To exit turn key off. Have paper & pencil ready because they only flash for 2 seconds. Report back with your findings. Good Luck.

[richardf]

Can you tell me where the fuel filter is for a 1990 Cadillac Deville. Is it under the hood or in the gas tank? thanks

[KHE]

It is toward the rear of the car by the fuel tank - inline with the fuel supply line. There is also a pre-filter on the fuel pump inlet which is in the tank. I wouldn't just change the inline filter at this point - those filters usually last the life of the car, unlike the small filters that were mounted in the carburetors on older cars.

See if there are any trouble codes stored in the diagnostics as recommended in an earlier post.

There is also a ground connection from the engine to the frame near the starter. Make sure that connection is free of corrosion. Also, check the cam sensor plug for corrosion - it is located under the distributor cap.

[PAUL T]

I would start with the basics, check the battery terminals for cleanliness & tightness, spark plugs, & plug wires. Why was the heater switch on all summer? Has it been in storage? Run the diagnostic codes and see what comes up. With key on, engine off enter diagnostics by pressing & holding the "off" & "wamer" buttons on the climate control panel. Trouble codes will be displayed on the fuel data center panel. It starts with "8.8.8". First pass will be the history codes "E..." second pass starts when ".E.E" flashes, then current codes will be displayed. When ".7.0" appears it is done. To exit turn key off. Have paper & pencil ready because they only flash for 2 seconds. Report back with your findings. Good Luck.

Your car has its own built-in OBDI diagnostic code reader. Once you retreive the codes as stated above, post your results and we will help you pinpoint the problem. We can not help you if you do not respond to our questions. There is a wealth of information and a lot of good people that are willing to help here. Talk to us.

[richardf]

None of my dashboard system is working. Air Conditioner included. No displays. That is why I have not posted it. I have tried to have it fixed.

[Cadillac Jim]

The next thing to do is to check the fuses in the main fuse block. It's behind the air cleaner, which is above and behind the headlight on the driver's side. You'll have to take off the air duct to the fuel injection to get to it. It has a plastic cover. Check all the fuses.

There is another fuse block in the trunk, up against the back seat under the felt trunk lining. If you find blown fuses in the front block, you should check these too.

[richardf]

They tried to replace one of my modules to get the dashboard functions and airconditoning working. It didnt work out, so, they want to order three modules for around 1200 to see if that will fix the problems. Would all modules go out at the same time? It is a 1990.

[adallak]

They tried to replace one of my modules to get the dashboard functions and airconditoning working. It didnt work out, so, they want to order three modules for around 1200 to see if that will fix the problems. Would all modules go out at the same time? It is a 1990.

I would not spend $1,200 on a 20 years old car without even knowing if it will solve the problem. I am afraid it is not the last invoice you will get from them.

[PAUL T]

Make sure you do not have the light dimmer turned down. Also, have you had your battery load tested? Are your battery cables clean? Are the battery connections tight? Check the battery ground. A loose battery connection or just a bad battery will cause all kinds of electrical problems. Check the owners manual for fuses associated with what you are having problems with. There are fuses everywhere. If I were you I would find out what modules they are talking about and order them from rockauto.com and save yourself a lot of cash.

[Cadillac Jim]

If all the modules had been blown by, say, a lightning strike, or someone hooking up a n 18 Volt fast charger backwards on a dead battery still hooked into the car's electrical system, the car would not start.

My advice is to never, ever, throw parts at a car to fix it. In particular, your mechanic is throwing expensive parts that rarely (never, in most cases) go bad -- that's why cars have been built that way for the last 20 years.

PAUL T had an excellent idea -- the dimmer turned all the way down. If you can't get the dash lights on with the dimmer switch, and you can't find a fuse, find someone with a code reader and read out the OBD codes. There's a connector under the dashboard on the driver's side for that. Write the codes down and post them here, and maybe we can help a lot more.

[richardf]

If all the modules had been blown by, say, a lightning strike, or someone hooking up a n 18 Volt fast charger backwards on a dead battery still hooked into the car's electrical system, the car would not start.

My advice is to never, ever, throw parts at a car to fix it. In particular, your mechanic is throwing expensive parts that rarely (never, in most cases) go bad -- that's why cars have been built that way for the last 20 years.

PAUL T had an excellent idea -- the dimmer turned all the way down. If you can't get the dash lights on with the dimmer switch, and you can't find a fuse, find someone with a code reader and read out the OBD codes. There's a connector under the dashboard on the driver's side for that. Write the codes down and post them here, and maybe we can help a lot more.

[richardf]

I had my car tuned up and it is running and idling better. The mechanic says the the number 2 and 8 fuel injectors are bad and need replacing. They are not spitting out enough fuel, if any, and that is what is causing the miss in my engine. 536 dollars. Not too bad. Is it safe to drive? It runs ok. Thanks

[Cadillac Jim]

Excuse me? $536 for two clogged injectors??? I would get a second opinion. For openers, get the OBD codes and post them here.

[richardf]

yeah he said they need replacing. Does that sound right to you? I will try some fuel injector cleaner first. I will get the codes also. thanks

[hjb981]

yeah he said they need replacing. Does that sound right to you? I will try some fuel injector cleaner first. I will get the codes also. thanks

Get Techron at a Chevron gas station. They sell it in small bottles. I have heard warnings about using other fuel additives, as expensive fuel system leaks may develop from using them. I don't know if it's true, but better safe than sorry... I have been told the Techron additive is the same stuff Chevron puts in its gas, but probably you end up with it more concentrated if you follow the instructions on the bottle.

FYI: I have seen the modules you are talking about for sale as used from junk yards. I also think that it is a better idea to troubleshoot than throwing parts at it, but maybe you can make some arrangement where you can try changing the modules without having to buy them if that does not fix it. One more thing: are you 100% sure that all the fuses are checked? I would guess that your mechanic did that, but make sure not to miss the MAXI-fuses. Those are resettable, and I think that your car has them. Someone else with better knowledge than I should confirm this.

Those cars are great, and I hope you get that you get it fixed! I used to have an '88. Good Luck!

[richardf]

Not sure about fueses. Are the maxi fuses the ones by the air filter under the hood.

[hjb981]

The maxi fuses are different from the normal fuses that come in different colors and have a little wire in them that melts. But someone else should really take over here, because I don't know what they look like or where to find them (or if your car has them) - I just wanted to make sure that they are not overlooked. It sounds a little like it could be a main fuse to me, but then again if that's the case, it was really sloppy of your mechanic to overlook that and change one of the modules.

[PAUL T]

I had my car tuned up and it is running and idling better. The mechanic says the the number 2 and 8 fuel injectors are bad and need replacing. They are not spitting out enough fuel, if any, and that is what is causing the miss in my engine. 536 dollars. Not too bad. Is it safe to drive? It runs ok. Thanks

Fuel injectors run anywhere from $32 to $118 a piece and they are not that difficult to install. I would put them in yourself and save alot of money. You could try the cleaner first.

Check an owners manual for fuse locations. They could be under the dash, under the hood, or even in the trunk.

[Cadillac Jim]

What I say here applies to the 1997 model year Eldorado/Seville/Deville, and by implication the 1992-2002 Eldorado, the 1992-1997 Seville, and the 1992-1997 Deville. It may apply to other models and years but I don't know about that.

The fuses that most often need service are under a little flap behind the air cleaner on the driver's side. They are all 10 Amp to 30 Amp small automotive fuses and you can get them at an auto parts store. There are two types, the ones with the blade terminals and the ones with the wire terminals, these have the wire terminals.

The main fuse and relay block surrounds the small fuse block. You get to it by raising the plastic cover that the little lid over the small fuses is set into. You will need to remove a 13 mm bolt that also holds a tie for two or three cables that goes into the strut tower. The main fuses are 50 Amp maxifuses, which are large auto fuses with blade terminals. There are a variety of relays, a couple of circuit breakers, and a few other fuses there too. These are the Right and Left Maxifuse Block in the FSM.

The Trunk Compartment fuse bock is accessed by dropping down the trunk liner, held on by four screw-on retainers on the top edge of the trunk opening under the hinges. It's low on the back of the rear seat on the left hand side. It has a variety of 10 Am to 30 Amp auto fuses with blade terminals -- not that this is not the same type as are used under the hood.

[richardf]

I have another question please. How often should I put the Techron (fuel system cleaner) in my gas tank to get some kind of results? thanks

[hjb981]

I have another question please. How often should I put the Techron (fuel system cleaner) in my gas tank to get some kind of results? thanks

Just using it for one tank of gas should make a difference. To get the most out of it, fill it up and go for a long drive, at least 1.5 hours at highway speeds. The car needs to be completely warmed up for that stuff to work well. Some may disagree, and it does not say anything about it on the bottle, but the guy who told me this was a senior mechanic at a Cadillac dealership in California. And cars do clog up in city driving (even though the gas always has some detergents), and they also do clear out again on long highway trips, so it seems reasonable to me that it would work the same with fuel system cleaners.

[richardf]

OK. thanks

[KHE]

The mechanic is likely correct on his diagnosis but a little overpriced. My neighbor has a 1991 Sedan DeVille and had similar symptoms. The injectors used on the 4.5 and 4.9 engine develop shorts in the windings and will not deliver the proper amount of fuel. No amount of injector cleaner will solve the problem - the injector(s) need replacement. You need to use the GM injectors to keep the flow rate the same across all cylinders.

Go to www.gmotors.com and get a quote for two new injectors. You can install them yourself and save a lot of money.