View Full Version : 1997 STS problems

06-07-07, 10:06 AM
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!

06-07-07, 10:36 AM
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.

06-07-07, 11:29 AM
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.

06-07-07, 11:44 AM
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.

06-07-07, 03:11 PM
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.

06-07-07, 03:27 PM
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.

06-07-07, 05:50 PM
Maybe someone messed with the wires. recheck the firing order.

06-07-07, 06:40 PM
I checked the firing order and everything is good to go with that.

06-07-07, 08:23 PM
Cars are fun when the factory bumper to bumper warranty runs out, Huh?

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

06-08-07, 06:35 AM
Yes! Streetrods are fun! Here is my '34 Chevy Standard:


06-09-07, 07:46 AM

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.

06-09-07, 08:00 AM
Stick with A/C Delco parts.

06-09-07, 04:10 PM
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.

06-09-07, 05:03 PM
Tap water. If they are "leaking" you'll get a light show.

06-09-07, 05:58 PM
No Sh*t.... I'll try it.... How close do you spray?

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

06-09-07, 06:28 PM
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.

06-11-07, 09:04 AM

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!

06-11-07, 09:55 AM
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.

06-11-07, 10:12 AM
Scratch that last post guys. I found the answer to my question. Just have to check it when I get a chance.

06-11-07, 01:46 PM
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.

06-11-07, 03:29 PM
Thanks! I will definitely check that this evening. I have another update. I forgot that I put it on a scanner when I first got it and found that cylinders 3 and 4 were the cylinders that were missing. I scanned it again today after the plugs and wires were changed and still 3 and 4 are still missing. They are skipping everytime. A mechanic friend thinks that there may be a problem with one of the valves seating causing the missfire on those two cylinders since they are back to back in the firing order. I am not sure if these cars had this kind of problems or not. Does anyone know what the readings should be on a compression test on one of these engines? Take into account that is has 175,000 miles on it. If I remember right I had #4 cylinder tested and is produced 90lbs.

06-11-07, 10:09 PM
The compression reading should be 10% of each other as I recall.

06-11-07, 11:33 PM
How about the raw numbers? Any ideas on that?

06-12-07, 12:14 AM
How about the raw numbers? Any ideas on that?

I have looked at 610 inch Chevys to 2 liter Mercury V6s...... The cylinders must be consistant.
But if you want to know, it's 140 to 170 psi. Note, there's a 30 lb difference!! But it should be consistant, whatever the psi is.

Mine is a VIN 9 L37 Northstar, 295 HP @ 6,000 rpm, 290 lbs @ 4,400 rpm. The bore & stroke is what's called, "almost square" .... the bore & stroke is almost the same. ( What's bore / stroke?)

The bore is 93mm, diameter of the cylinder walls - stroke is 84mm, the distance of the 'up @ down' of the piston in the cylinder. The engine is considered a "short stroke" engine. Which is why it revs up so high, compared to a regular small block Chevy V8.

06-12-07, 12:34 AM
How about the raw numbers? Any ideas on that?
Delving into the old memory bank (which may have non sufficient funds) I would guess at somewhere around 160 - 180. That said, consistency is more important......... unless they are all at 60.

06-12-07, 06:59 PM
Guys, I did a compression test. Not good news. 7 cylinders tested about 150 and number 3 cylinder is dead at 0. I am leaning towards being a valve problem. The noise that I referred to back in one of my posts is I believe the air getting pushed back through the intake due to a valve not closing. So my next question. Has anyone had any kind of problems like this before? Could it be a stuck lifter or something? The engine is not making any kind of metallic sounds or knocking. I think that the #3 hole is not sealing up and causing the missfire. Any help guys would be appreciated!

06-12-07, 09:22 PM
It is definitely a valve hanging open. Never heard of that before. I am sure once you pull the cam cover for an inspection, it will become obvious what the problem is. Maybe just a broken spring.

06-13-07, 06:19 AM
Can the cam cover be pulled with the engine in the car? I didn't get a chance to look at what was involved in removing it last night.

06-13-07, 07:35 AM
I've owned three N* and each had head gasket failures. Each time it was the No. 3 cylinder. A cracked boot on the PCV valve will cause a hiss. Remove the oil fill cap. If the hiss stops that's it. Is the engine losing coolant. The level should be about three inches from the top of the reservoir.

06-13-07, 07:58 AM
It doesn't seem to be losing coolant. It isn't overheating with temps being 103 here and with the AC on. I am thinking it is a valve because to me it would seem that it would have some sort of compression if the gasket was blown, but the gauge doesn't even move on that cylinder. It is almost like the gasket isn't even there or there is a hole in the block. And the noise I hear is not like an vacuum leak, it is almost like an airpump noise. You can hear it in the intake and it seems to be in rythm with a piston stroke. When I pulled the plug on that cylinder, it looked brand new like it had never been run yet. I think the missfire on the #4 cylinder is caused by sucking the air being drawn in from the #3 cylinder since the are back to back in firing order. I hope that it isn't a head gasket and I get lucky and it be something that is relatively simple and cheap to repair. I will keep my fingers crossed.

06-13-07, 09:55 AM
I seriously doubt that it is a head gasket. You'd still have SOME compression. Hell, I think if you put the engine together with NO head gaskets you'd still have SOME compression. If you can hear the noise in the intake manifold, I would suspect an intake valve hung open, thus compression is entering the intake on the compression stroke. Cam covers should be able to be removed with the engine in the car.

06-13-07, 10:07 AM
Those are my thoughts exactly. I just hope it won't be an expensive fix.

06-13-07, 02:20 PM
When I pulled the plug on that cylinder, it looked brand new like it had never been run yet.

That's exactly the way plugs look when they've been burning coolant.

07-10-07, 11:05 PM
Just an update guys and looking for suggestions. I pulled the rear valve cover up as far as I could (couldn't seem to get it off with engine in the car). No loose parts rattling around in the head. I talked to a guy today that knew a little about the car but I don't really know how much I would rely on it. He said that the head gaskets have been replaced. It started skipping on #3 cylinder and the guy didn't want to fix it. He feels like it is a valve train issue as I do. All cylinders have good compression, but number 3 has nothing. The needle on the gauge won't move. With engine running, you can hear the air being pushed back into the intake. The car sat for a long time before I bought it and I am wondering if maybe a valve is stuck open or something. Do these engines have lifters or does the valve/spring ride directly on the cam lobes? I see the silver caps under the cam lobes and they are all moving up and down but I can't tell what is going on under them. If I pull the intake shouldn't I be able to see the intake valves? Any suggestions guys? I am ready to get this thing running correctly. I am thinking of using some kind of cleaner like seafoam in the intake and crankcase to see if it may "unstick" the valve if that is the problem. Thank for all your help so far guys!!

07-11-07, 09:39 AM
The needle on the gauge won't move. With engine running, you can hear the air being pushed back into the intake.
The intake valve is stuck open for some reason. You need to get the cam cover off and have a look.

07-11-07, 10:01 AM
I can't seem to get the rear cam cover off with the engine in the car. I can lift it up enough to look at it. I am assuming that the cam lobes ride directly on top of the valves/springs and that there are silver caps on top of the valves/springs in between the cam lobes. When I spin the engine over and look, the silver caps on top of the valves are moving up and down with the cams as expected but I have no idea what is going on under those caps. That is why I was wondering if I pulled the intake if I could see the intake valves in the head and see if they are sealing properly.

07-11-07, 10:33 AM
Never done this before. Hope this helps. It's not the FSM, but it looks like you have to follow the pictures. I assume the right side is the rear. Good luck, here are the steps and pics (from AllData I think). Let us know how it goes.

1)Disconnect both battery cables, then remove tower to tower brace.
2)Disconnect DIS wiring connectors and mounting bolts, then remove DIS and right bank spark plug wires.
3)Disconnect PCV valve, then remove purge canister solenoid from rear of cover.
4)Remove wiring harness from cover, then the cam cover mounting screws.
5)Support front of engine cradle and remove front cradle mounting screws.
6)Remove right and left torque struts.
7)Lower engine cradle to provide clearance at rear of engine compartment.
8)Remove cam cover.
9)Reverse procedure to install.

07-11-07, 11:18 AM
Thanks! I was hoping I wouldn't have to drop the engine any, but if I have to, I have to.

07-11-07, 02:35 PM
I think you've done an exellent job troubleshooting and isolating problems. I'm learning a lot. Please keep us posted. thanks,


07-11-07, 07:53 PM
I pulled the intake today and one of the intake valves is hanging open on #3. I can't really tell 100% if it is bent or not, but it looks to be like it is unfortunately. I can push down on top of the valve/spring and it looks like it is possibly moving around. I was hoping to not have to pull the engine but it appears like I am going to have to. Anyone else have any ideas as to why the valve won't close other than being bent? How in the hell would the valve have got bent rather than floating one of them?

07-11-07, 08:02 PM
something we like to call FOD in the world of turbine engines :)

check your intake for signs of metal shavings/parts, rocks, acorns, mice, squirrels etc (especially if it was sitting for a long time...)