And sometimes it starts right away like a brand new car, this started to happen more often after I installed a stereo in my car, the car drives perfect after it starts. My mech checked the fuel pressure and it's @44psi and no leaks, the plugs and wires were changed the past winter(AC Delco plugs and NAPA's best wire) but I didn't use any silicone coating on the contact nor gap the plugs(mech told me the plugs are pre-gapped). I question my own work as one of the plugs went bad after about 30miles but the car was checked by a professional and at that point everything else is fine. Did my bass rattled something loose?

Have you checked your taste in music lately? Could be the kinds of tunes you're running in it. "STOP,,,in the name of ,,," or "You picked a fine time to leave me,,," or "Knock 3 times on the ceiling ,,," will put you at the sid of the road in no time.

Yes they are pre-gapped but it is good protocol to always give the gap a quick check. The pre-gapped plugs have, 99.9 percent of the time been correct. Then there was the time the gap was to be 35 and it was 20. Hm? That would have proved a small problem.

I must ask, what could/did you do that killed a plug in 30 miles?

I would double check and make sure the wires are good and tight in those plug holes. I doubt if a loose one would stop the car from starting. Even when I had a bad misfiring of plug cables, the car started first time. Does the 98 still have a CPS (crank position sensor)? That little puppy causes more hard starting than people realize. Over on the Jag forum there was a guy whose car would not start. I suggested he check the integrity of the CPS. Yep, a new CPS and he was on the way. He mentioned that the car hasn't run so well in a while.

Does the 98 still have the bank of 4 coils or are is it direct ignition on each plug? I would guess that carbon tracking on a bad coil cause a start problem. If you have the 4 coils, you can check the primary and secondary ohms. Still a good ohm reading that isn't a 100 percent solid test. The coils can react different between cold and hot. If the coils have mileage on them, if it were me, for 20 a piece......I would change them. If for nothing else, peace of mind.

For what it is worth my 2 cents. The Deville is still a new baby to me but this I know…..recently I had a misfire problem. I checked and at night you could see the arcing. BTW if you’ve never used that trick, what you do is start the car in the dark (no hood lights allowed) look at the engine for any arcing between plug cables, coils, etc. Anyhow, I changed the coils, plug cables, plugs and a new air filter. Dealer cost would have been over $1,000, my labor cost was $0.00 (I come cheap) and parts were $295. The car purrs fine. Sooooo learning to spot / find problems is a way to save a lot of $$$$. Car forums are great for saving you money. IF anything, if you do finally need a pro to look at the car you can tell them what you did or didn’t do to diagnose the condition.

And sometimes it starts right away like a brand new car, this started to happen more often after I installed a stereo in my car, the car drives perfect after it starts. My mech checked the fuel pressure and it's @44psi and no leaks, the plugs and wires were changed the past winter(AC Delco plugs and NAPA's best wire) but I didn't use any silicone coating on the contact nor gap the plugs(mech told me the plugs are pre-gapped). I question my own work as one of the plugs went bad after about 30miles but the car was checked by a professional and at that point everything else is fine. Did my bass rattled something loose?

It tends to get worse when my car warms up but it starts fine when it's cold. As for the plug I think there was a factory defect because my mech told me it wasn't making any spark, I don't understand how can a spark plug go wrong after just 30 miles but who knows, maybe that whole batch was bad.

I had to start twice today after a short trip.

It tends to get worse when my car warms up but it starts fine when it's cold.
I had to start twice today after a short trip.
Check the FPR.

My mech told me the FPR is fine, no leaks and making 44psi which is normal.

Sometimes a leak may not be evident but still be bad.
http://www.cadillacforums.com/forums/showthread.php?t=51523&highlight=FPR

Bump...

My mech followed the direction for checking the vaccum for the FPR and it does hold a vacuum(I saw the pressure guage), so he's saying my FPR is fine. The car started fine for three days at the shop and as soon as I got it back it started doing it again. wtf???

Okay today started the car and it ran like it's misfiring, car finally threw me a code but the misfire went away when the engine warmed up...this time my mech told me it may be a dirty/leaking fuel injector. Plugs and wires were changed last year and it doesn't misfire under load.

Sweet I guess I can start using my credit card:crying:

Your symptoms are indicitave of a rich fuel condition (hard start when warm) which would lead one to the FPR or injector(s). Sounds like you have the FPR covered as well as ignition and fuel pump. Injectors would be the next logical thing.

You check for bad FPR by pulling the vacumn line then looking for fuel leaking out of the FPR - while at idle. Not by checking if there is vacumn at the hose.

If there is any fuel coming out of the vacumn connector, replace the FPR.

Okay this problem is really comfusing me...I had my mech do the powertune injector cleaning for the injectors, car starts fine after that. HOWEVER, whenever my mech has the car it never starts hard for him hot or cold, but when I get it back it does; the only difference is that I have my stereo on and he didn't. Also he said my car threw more codes, PO606 and P106, one of them is computer'related.

I have an aftermarket stereo installed and I ran all the wires myself, I kept the factory radio(to avoid the sleep mode problem) but has a CD player, a 1000 watt subwoofer amp and a 100 watt 4 channel amp. My car seems to start hard whenever my stereo is on but it's fine when it stays off; if radio is on whenever I drive it will start hard within a day(depending on how high I turn the volume), if radio stays off the car will run fine after about a day or 2. Can it be that my stereo is somehow interfering with my car? But how??? The whole system was in another vehicle and that car ran just fine...

Remember this is a perfectly working car until I installed my stereo, and the car is fine when the stereo is off. WTF!?!??:bonkers:

Remember this is a perfectly working car until I installed my stereo, and the car is fine when the stereo is off. WTF!?!??:bonkers:

Then you have a very bad stereo install did you install it yourself?

was what the process in whcih you installed it any routing to the underhood area?

did you use an adapter kit for the wires or you just used the wires that were there and tested with a multimeter?

It could be but not likely that maybe the amp is sucking so much power it caused other car functions to have not have sufficient power and they malfunction.

Do you have a high amperage alternator or a couple caps? Which you DO need.

last but not least try to have the radio on but turn the amp off and see if that helps I'm leaning towards the power factor let us know how big you amp is.

My stereo is installed correctly but I didn't use a wiring kit, I kept the factory radio to avoid the sleep mode problem and ran a seperate power wire from the battery for my new CD player. Car sits at about 12.4v with the engine off and varies from 14.5v to 13.3v with the engine on and other things running. My stereo is composed of...

Clarion DXZ745MP(not hooked up to any speakers)
MTX Thunder Pro504, runs 4 speakers and probably pulls ~20 amps(but the amp CAN pull close to 50 amps)
Crossfire CFA1000D, runs 2 12" subs wired to 1 ohm, by manual the amp may pull more than 120 amps itself.

I remember the night before the check engine light came on I was beating the system pretty hard, so the more power I use my car starts harder afterwards. Any idea as to what can be done to solve this?