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2007 Escalade
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67 Posts
Discussion Starter #1
Hello guys! I am new to this forum. I recently purchased a 1997 STS. I knew nothing about the car when I bought it. It has 175,000 on the odometer. When I bought it, it wouldn't run and I narrowed it down to the fuel pump and replaced it. I have it running now but it is running very rough. The guy I purchased it from said someone told him it was the head gasket. I found out that the reason the cooling system wouldn't hold pressure was it was leaking around the reservior neck where it attaches to the tank. I replaced that and everything looks good. I don't know when the plugs or wires have been changed last. After I got it running, it had a missfire code for cylinders 3 and 4, but you could pull the wires off of 2 and 4 and it didn't make any difference in the way it idled. I really feel that it is something simple to fix. I have searched on here and found many threads about the problem but it seems no one ever comes back and posts the cure to there missfire. I have reset the codes and driven it about 20 miles and the only code now is the generic P0300. I know I will get several responses saying to change the plugs and wires and that it could be a bad coil. It there anyway to narrow it down instead of changing all of those at one time? I checked the intake bolts and all were tight on them. One thing that I did notice is that is sounds like an airpump noise around the intake. It almost sounds like it is sucking and blowing with the stroke of the engine. I have sprayed ether all around the intake but it never made a difference. Can you guys point me in the right direction so I won't have to spend a lot of money replacing several parts when it could be just only one causing the problem? Thanks for your help gentlemen!
 

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1996 Cadillac Seville STS (167k)
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473 Posts
I bought used fuel injectors off ebay. turned out that they were so bad that they were causing the P0300 code. i had brand new Delco wires and plugs so they were not the culprit.
 

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White Diamond '03 DHS (with DTS floor shift)
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86,974 Posts
Check the rubber coupler between the TB and the intake manifold for a crack.

For the misfire, mist the wires in a dark spot at night and look for arcing.
 

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2007 Escalade
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67 Posts
Discussion Starter #4
Will do! The intake leaking noise sounds like it is coming from the passenger side of the intake. I do know that the car sat at the dealership here for a long time. The previous owner's brother works at the dealership and was supposed to get it fixed for him but never did and he finally went and picked it up. Someone had been fooling around under the hood because the engine cover was removed and all the plug wires were labeled with a pen. I am hoping that it is not a head gasket. There is no oil in the water or vice versa and it does not overheat. This car has been sitting for well over a year.
 

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2007 Escalade
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67 Posts
Discussion Starter #5
One thing that I see that I forgot to mention is that the missfire is happening at no matter what RPM it is at. It idles really, and I mean really rough. It doesn't stall or anything. It runs decent at highway speeds but still I feel a miss. The idle is the worst part. The engines looks as though it is about to flip upside down at idle.
 

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1996 Deville (sold), 2000 Mustang GT
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1,300 Posts
A really rough idle could be a sign of bad headgaskets (at least it was for me), that would explain the misfire also. When a car sits for that long most of the gaskets tend to dry up. The bronco I bought hadn't been driven for 6 months, the first couple days I had it, it was leaking every fluid possible, but after driving it for about two weeks, all the leaks stopped because the gaskets weren;t dried out any longer. Since you are hearing noises from the intake manifold I would believe it to be the intake manifold gasket. Also check to make sure the right wires are on the right plugs, I've switched them up before with about the same results you are experiencing.
 

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White Diamond '03 DHS (with DTS floor shift)
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Maybe someone messed with the wires. recheck the firing order.
 

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'93 STS (sold), now looking for a CTS Wagon soon!!
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503 Posts
Cars are fun when the factory bumper to bumper warranty runs out, Huh?

Unless it's a '32 Highboy.......:worship:
 

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2007 Escalade
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67 Posts
Discussion Starter #11
UPDATE

I did the spray bottle in the dark trick last night and oh boy. Sparks everywhere. So today I will be doing a plug and plugwire installation. I will post the results if that cures all my ailments.
 

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'93 STS (sold), now looking for a CTS Wagon soon!!
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503 Posts
Check the rubber coupler between the TB and the intake manifold for a crack.

For the misfire, mist the wires in a dark spot at night and look for arcing.
Mist them with what? ( My GMC truck has a little idle miss ) I'd like to try your trick.
 

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White Diamond '03 DHS (with DTS floor shift)
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Tap water. If they are "leaking" you'll get a light show.
 

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'93 STS (sold), now looking for a CTS Wagon soon!!
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503 Posts
No Sh*t.... I'll try it.... How close do you spray?

Stupid question.... how does that cause this "light show"?
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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I think you just want to mist them enough to lightly wet the wires. The light show will be arcing from wire to wire or wire to ground if they are leaking.
 

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2007 Escalade
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67 Posts
Discussion Starter #17
UPDATE

I replaced the plugs and wires Saturday before I had to leave to go out of town. It seemed to run better but still has a missfire. It doesn't seem as bad but it is still a pretty good one. I am starting to lean more towards an intake leak. I still hear something coming from the passenger side of the intake. As I said before, It sounds like it is in rhythm with a cylinder stroke. I have sprayed ether all over the top side of the intake but the idle has never changed. I have read on here about the intakes cracking. Where do most of the cracks occur on these cars? If it is on the bottom side, I can see where the ether would have no effect. Also, is removing the intake to check it a PITA? Thanks for your help and input guys!
 

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2007 Escalade
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67 Posts
Discussion Starter #18
Just a hunch guys. What should the firing order be as far as the coil pack goes? I just had a thought run through my head that maybe someone could have swapped a couple of the coils around trying to eliminate the missfire and I possibly have wired wrong.
 

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2007 Escalade
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67 Posts
Discussion Starter #19
Scratch that last post guys. I found the answer to my question. Just have to check it when I get a chance.
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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86,974 Posts
If you still suspect an intake leak and have found nothing so far, check the over pressurization valve. It is a spring loaded "trap door" so to speak. It is at the front of the manifold. Be sure it is sealing properly.
 
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