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3K views 18 replies 4 participants last post by  91TexasSeville 
#1 ·
#2 ·
Mahalaleel said:
http://www.cadillacforums.com/forums/showthread.php?t=31714

I have a thread up in the Deville forum, but you guys here seem to know most about the engine, will someone please try to help me?
I have read your prior posts and the many replies.
Let us forget for a moment about the knocking issue and focus on the misfire.

Do this first!

Remove the air cleaner assembly and snorkel. Look down inside the throttle body with the blades fully opened. If there is any, I mean any, carbon build-up on the bottom side of the throttle blades or inside the two tubes sticking up from the bottom of the intake manifold, thoroughly clean these items first. Take care not to scratch the walls of the throttle body or the blades. Use of carb cleaner and a spent toothbrush is normally sufficient for cleaning the throttle body and underside of blades. A coathanger is sufficient to clean the EGR tubes sticking up from the manifold. After the cleaning process, replace the snorkel and aircleaner assembly. Disconnect the battery negative cable for approximately 30 seconds. This will tell the idle speed control to relearn and correct for the cleaning process.

If the cleaning process does not help, repost here!
 
#4 ·
I was going to do this tonight, but I got home too late, so now I'll just ask some questions for when I do do it. How do I get the throttle blades to stay all the way open, safely? And what are the "EGR tubes"... Like I said, I've never done anything but change my own oil, add oil, check tranny fluid, change that, and add coolant and wiper fluid. Stuff anybody can do if they have half a brain.

Also, is there anything I could use in the place of carb cleaner, because I don't have any :drinker:disappoin. That I know of...
 
#8 ·
Well, I cleaned them out as much as I could given the time I had, and drove around. My mileage seemed to improve, but it's too soon to tell. It was also much more responsive... If there IS a way to get the whole carb/throttle body setup off, I could clean it much more thoroughly, and I'm sure it would help a lot.
 
#9 ·
Mahalaleel said:
Well, I cleaned them out as much as I could given the time I had, and drove around. My mileage seemed to improve, but it's too soon to tell. It was also much more responsive... If there IS a way to get the whole carb/throttle body setup off, I could clean it much more thoroughly, and I'm sure it would help a lot.
Yes, the throttle body does come off, but it is really not necessary to remove it. If you insist on removing the throttle body, you will need to replace the gasket between the throttle body and intake. Be sure to disconnect the negative battery cable BEFORE the cleaning. The cleaning can be done with the throttle body still on the car (recommended). After the cleaning process of both the throttle body and EGR tubes (those two little pipes sticking up from the base of the intake), ensure that the throttle blade bottom is clean and does not bind or stick when closed or fully open. Reconnect the negative battery cable. You will be amazed at the improvement! Plan on doing this once a year, more often if it was really dirty to begin with.
 
#11 ·
Mahalaleel said:
....The main problem is that I can't reach into the EGR tubes, so I can't get all the carbon out.............any more ideas?
Do as tulsadeville stated.
tulsadeville said:
......I used a brush from a .410 gun cleaning kit to clean the tubes.
Have been using a gun barell cleaner kit myself for quite a while. Get the one with the different size brushes. Can find them almost anywhere. Comes with an extended handle and the brushes are the perfect size.
 
#13 ·
Mahalaleel said:
How stiff of brush should I use?I don't think anything soft would get it out. I couldn't get some of it out with the hanger, it was so solid.
Wow Man.
Check out the gun barrell cleaners.
Brushes are perfect size.
If the crap is crusty then use the carb cleaner as sugested as well. Spray it in and spray it on the brush. Maybe let it sit for abit and soak. It will dissolve and eventually break down.

Dont think your gonna get much more info than already posted.
Dont know myself personally, but if that dont work then maybe there's something else going on?
No idea what it could be?
But far as it goes it should clean off?
 
#14 ·
Alrighty, so I successfully cleaned the tb's and the egr tubes, and now i'm getting 16 mpg instead of 12 oh joy! But, the knocking/missing still occurs at 50-60 on low throttle. Also, the misfire when rev'ed still occurs. Big WHUMP every little bit.

Any other ideas?
 
#15 ·
Should start with all the plugs instead of just 2. Should also change the wires if they havent been done in a while. A new cap and rotor wouldnt hurt either.

And if some of your injectors are shot like you were told, then that sure isnt going to help.
Could try some injector cleaner.

Know its hard to do, but you should be searching for someone who is reliable and can give you an honest diagnosis. You could have a hand full of different problems; or maybe just one or 2 that are sending bad signals elsewhere that is making it difficult to pinpoint.

Something here might help
http://www.cadillacforums.com/forums/showthread.php?t=30386&highlight=injectors
 
#18 ·
Mahalaleel said:
My mechanic thinks my engine is healthy, but was wondering about my CV joints. Could they be causing the rumbling at 50+?
Rumble could be caused by CV joints or hub bearings, or both. In either case, you need to check the CV joints for the obvious, torn boots, dry, dirty, or worn links. Firmly grasp the tire with your hands at 12 and 6, then at 3 and 9, shake the front wheels when the car is off the ground. There should be no noise or movement. With front wheels off the ground, (if only the front is raised, be sure to block the rear wheels) place the gear selector in neutral, and turn the wheels by hand, left, and right, forward and reverse. Again, there should be no noise.
 
#19 ·
Mahalaleel said:
Hmm, that computer thing sounds like it may be the problem...if it were a bad injector, it would be bad ALL the time, not just at certain times, right?

Think I could get a new ECM, and if it didn't fix it, I could return it?
No, and No. A bad injector if misfiring some or all of the time may not be evident unless you know what to look for. The primary indication is reduced fuel mileage. Over feed is evidenced by black carbon deposits and poor low speed performance, under feed is evidenced by elevated coolant temperatures, and poor performance. Often times electronic parts are not refundable. Check before you buy.

The procedure to visually check all injectors at the same is outlined several times throughout this forum. It would not make sense for me to rewrite it. There is also a diagnostic procedure to check each individual injector by way of the CCDIC, also outilined several times in this forum. Other possible fuel related problems are FPR (Fuel Pressure Regulator) and/or fuel pump. The fuel pump is the least likely of all culprits, but should not be ignored, and tested for correct pressure under normal driving contitions.

A good running older 4.9L Cadillac engine should average 15/16 MPG in city and 22/24 MPG highway driving. These numbers are not cut in stone, but are average for a 13 year old Cadillac with proper maintenance. More is better, less suggest there may be a problem.

A basic tune consists of new plugs, new wires, new cap, new rotor all of the same quality AC Delco. Do not cheap out anywhere here. Do not spring for the dual platinum plugs, buy ONLY what Cadillac specifies in the owner manual. You would be wise to do the basic tune before attempting any other diagnostic. NEVER allow a wire to drape over or lay near an exhaust manifold. This sounds simple, but I have seen this cause big problems more than once and is evidenced by all old problems gone after the tune, but soon to return. As always, disconnect the negative battery cable BEFORE you begin the basic tune.
 
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