What did I do wrong? (Spark Plug Change)

[90Brougham]

Okay, today I spent about 4 1/2 hours replacing the spark plugs in my 1990 Cadillac Brougham, that has the Olds 307, I put in AC Delco Conventional spark plugs, and after all that work, I started it up.
I was pleased, for about 10 seconds, then all of the sudden the idle dropped, and kept dropping, until it died. Prior to it dying I revved up the engine, when I noticed the lowering idle, and it back fired through the exhaust. The plugs are gaped to the correct width (.60), I double checked the spark plug wires were on, though number 7, and 2 were the hardest to get to so maybe they are a little loose.  Do any of you know what might be the problem?

Thank You,
Christopher P.Dillon

[beastly beauties]

Hello,   There can be a number of things to obtain the situation you now have. Since you say you've only changed the plugs, I would suspect you solution lies there. Here are some typical mishaps we've all had or done in the past: damage or change in gap when placing in the cylinder head (gap can close up if bumped), wires can be faulty because of age especially prone to failure when disturbed, I've even had faulty or cracked brand new spark plugs, and ignition wires, possible grease or dirt closing gap on plug from trying to blindly place in head when installing, wires not completely connected to plugs. You didn't say how many miles were on the car, and on the suspected above components. Sounds like it should be a simple fix, but its a machine and anything is possible. Hope this helps.  Good Luck,   David Symonds

[90Brougham]

David, It has 109,400 miles. I made sure there were no cracked plugs, I broke the one that was going to be replaced, and I broke a new plug, the socket slipped a little and I did notice until I heard the crunch of the insulator. I have a set of brand new BOSCH plug wires that I was going to put on tomorrow, I will make sure that the are connected. We'll see what happens tomorrow.

Thanks,
Christopher Dillon

[waterzap]

Problem might not be with the plugs. Might be a wire or a vacuum tube that came loose when you did the plugs. Has happened to me many times before.

[90Brougham]

Okay, I just went over them again, I had the firing order wrong, the number one plug was the problem, there is almost no room at all to get to it, but I managed. The wire was was not all the way on, I pushed it until I felt the click. Now it does idle, but sometimes it drops, but it catches itself, and it also very rarely back fires. Due to me having more patience today, than last night after 4 1/2 hours of work, I listened while it was running, and sure enough I could here the hiss of a vacuum leak somewhere on the left side of the engine. Also I noticed it still has some alot of vacuum lines on it from the factory, some of them were from 1989.

Thanks for the help,
Christopher P. Dillon

[Walter Youshock]

I think we've all done that at least once.  Did you also change the wires and. if so, did you put them back in the clips and replace the extra insulation covering on them?  I had a wire burn on the exhaust manifold because I didn't put it back in the clip good enough.  Now would be the time to change the wires (one at a time, if possible) cap and rotor.

[90Brougham]

Due to no one wanting to help me here at home with the wires I am going to take it to a very good mechanic to have the mystery vacuum leak fixed, and the wires replaced. My step dad (who has changed spark plugs and wires countless times), does not want me to fart around with the car any more, I don't know why.

[Walter Youshock]

A vacuum leak can totally mess you up.  Is the engine light coming on?  The wires aren't that bad to change, but it does take time, especially routing them like the factory did.  If you do decide to do it, mark each one with masking tape and plug # and take pictures first.

[90Brougham]

Yep, the check engine light has bee on since around May 20th, I finally got around to checking it about a month ago, the "old school" way, because it is from the OBD1 era, (pre 1996). The check engine light blinked the codes 12, 13, and, 14. Also the cruise control sometimes gives out while I'm driving. I'll cruising around 58 mph, then all of the sudden the car starts to slow down, I can see that the green light is on, showing it is still engaged but the vacuum has failed. Also when the parking break is engaged, and I put the vehicle in gear the parking break disengages itself.

[Walter Youshock]

The parking brake SHOULD release when you put it in gear.  That was a Cadillac feature since 1960.  If it didn't do that, then you would have a massive vacuum leak.

The cruise can disengage when the engine light comes on.  I had that happen on an '82 Brougham on the highway.  Scared the hell out of me.  Turned out to be the O2 sensor.

[Chris Conklin]

I don't mean to embarrass you Christopher, but I have to mention that you are sixteen years old and the owner of a Cadillac! I wish I was as smart as you when I was sixteen and driving an old Plymouth!! You have my absolute admiration and you restore my faith in our youth. I hope to see your posts here for many years to come. You're definitely in the right place for expert advice (especially considering there are probably three miles of vacuum lines in a Cadillac  ).

[90Brougham]

Thanks for clarifying the parking break question, I was told differently be other people, that is a pretty nice feature, just in case someone wasn't paying attention. I gave the O2 sensor a quick look yesterday, while I had the right wheel off, (made it a lot easier to get to the spark plugs), and it looked like it had been in there for awhile. Autozone sells a nice BOSCH O2 senor for around $20. A question though, sometimes when the cruise control gives out I push the accelerator, until I get back to the speed I set it at, and I'm good for another 2-3 miles, would that mean it is still 02 senor related?

Thank you for the compliment Chris, I just wish there was more youth that was like me, but they are getting rarer, it helps I was raised around people that were 20-30-40, even 50 years older than me, so I grew up liking antiques, the good old days, and learning to do things myself, like working on cars. I have a 1961 Corvair, that was my first car, and that definitely helped me to know how to work on a car's electrical, brakes, and engine problems.

Once Again Thanks
Christopher P. Dillon

[Walter Youshock]

You're only 16!!!!  And a Brougham owner?!?!  That's great!  My first Cadillac was a '77 Sedan deVille d'Elegance when I was 18, but I grew up around Cadillacs.

The automatic parking brake feature was so it could be used as a true emergency brake in that it wouldn't lock while the car was running and you could pump the pedal like the regular service brakes.  Also, there's no chance of forgetting to release it before driving away.

If you intend to keep this car and work on it yourself, I strongly advise you to get a copy of the Shop Manual.  If you're looking for an even easier way to get at the engine, the plastic inner fenders can be removed with the front wheels off.  They're held on with torx screws and plastic buttons.  Once loosened, they can be coaxed out of the fenders rather easily and you'll have better access to the sides of the engine.

Not sure the O2 sensor would do exactly what you describe with the cruise.  I remember mine just shut off completely.  Sounds more like a slow leak.  Maybe the vacuum tank?

[90Brougham]

I'm almost 17 now, (September 17th).I'll be looking around for a manual I saw one on eBay, but I don't have a Paypal account, and my stepdad didn't have enough money in his. Is the vacuum tank the one on the front right side of the engine, beside the horns?

Thanks
Christopher P. Dillon

[Walter Youshock]

If memory serves me correctly, I think it's actually under the left front fender where the bumper end is.  It's covered by one of those black plastic splash guards.  I haven't had my '90 for about 7 years so I may have that location wrong.  It's in one of the front fenders for sure.  It's a big plastic pod with hoses sticking out of it.

Too bad I got rid of my '90 shop manual. 

[90Brougham]

I don't know if this will help, but here are two pictures of pods with hoses sticking out of them, the right half of the splash guard is gone.

[curly]

The round tank in the upper photo is the charcoal cannister, used for emissions.
The oval tank in the second photo is the vacuum storage tank for A/C and Cruise.

T Lewis

[90Brougham]

The oval tank has one of the factory vacuum lines, to be more specific 1989. I would guess after 24 years, it is the problem with my cruise control just giving out.

Thanks
Christopher P. Dillon

[Glen]

The parking brake SHOULD release when you put it in gear.  That was a Cadillac feature since 1960. 

Around here I have to explain that to the “mechanic” that is doing my safety check. They try to fail the car for that feature.  They have been taught that the car should not move in drive at 2X idle speed with the parking brake engaged.  When they put the car in drive and the brake pops off they want to fail the car. 

[Dave Shepherd]

Disconnect the vacuum line so it won't release and use the lever to release just for insp. purposes!