I have a 1997 Saturn with a DOHC 1900 cc motor with 98k on it. all of a sudden the timing chain started to make noise. So I opened it up and replaced the chain and the oil pump. I got it back to gather enough to test it and it was still rattling. so I got a adapter fitting to check the oil pressure. It had 40 psi at hot idle . So I took it back apart and checked to make sure the tensioned was getting oil and the tensioned chain guide was working freely. Then I double checked that all timing marks and every thing ells was as it should be. buttoned it up and it still rattled. Now there is no doubt in my mind that every thing is as it should be in side the timing cover. So my question is there some thing ells that could be causing the chain to rattle. The thing started accelerating slightly when letting of the gas, I lost 4 miles to the gallon and the idle is up to 950 rpm. this started be for the rattle. Would it be possible for the cams to roll over faster than the crank causing slack in the non tensioned side because of some miss setting in the system. Now this is not my first rodeo. I am 71 years old and have been working on these sense I was a kid. but this thing has got me stumped. I guess the next step is to figure out why it is not running right. Also it is only at the 1/4 mark on the temp gage. no codes showing and all checks completed on OBD. Dan

 

98K is quite low mileage for timing chain issues on an S car, but anything's possible.


I would check the following specs to ensure you do not have any out of spec parts in there which might cause you problems:

DOHC Specs for 97

Timing Chain Stretch
Standard: 22.87 to 22.89 in
Service Limit: 23.15 in max


Timing Chain Tensioner
Plunger Extension
Depressed to full extension:
Standard: 0.059 to 0.374 in
Service limit: 0.8626 in


Timing Chain Guide Groove Wear
Standard: 0.0 in
Service Limit: 0.0984 in max
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Have you checked to see if the tensioner oil feed hole is plugged? Didn't quite understand all of your description.


I would definitely measure travel of the tensioner as that is the most likely part to cause rattling in my mind. It would also explain why both the old and brand new timing chains rattle.


You can also use the specs above to ensure the chain you put in is actually in spec.


What brand timing chain did you use?
____


As for accel when removing foot from gas -- is this Auto or Manual?
Either way, sounds like maybe a sticky throttle plate, dirty IAC, small vac leak, unless this is an A/T which would be a larger jump.. Spray around all vacuum lines, intake manifold and throttle body gasket. You know what to do.


Oops, forgot the standard question: Have you ever changed the ECTS (engine coolant temperature sensor)? If not, the original factory resin tipped one has failed or may be failing. The failure results in an overly rich mixture as the temp info is artificially low and thus a non ideal mix.
Additionally, ECTS failure can cause higher idles b c the PCM thinks the engine is at a different, colder temp than it really is.


If you replace the ECTS, source it through a GM dealer, and you might as well replace the connector as well. About $50.


Aftermarket sensors often have different R vs Temp curve and thus calibration is then off


The replacement sensor is redesigned and has a brass tip,

 

You didn't say if you replaced the tensioner or not. If not, then that's what I'd suggest you do. And get it from a GM dealer that sells Saturn parts, not Autozone, Advance, O'Reilly etc. I believe OEM parts are always the best route to go when possible. If you think the cams are rolling too fast (which I can't see happening) then check the keepers on them and make sure none are loose.

 

The chain kit came with everything. It is a PCI brand. now before assembling it I checked the free movement of the tensioner chain guide. I checked the tensioner with air pressure and it worked fine. I assembled it per the Haynes manual. After assemble the was no slop in the chain at any point around the chain and the tensioner was only extended about .080 of a inch. Now that tells me that the parts are to spec. They may not be the best parts around but surely they will last at least a couple of hours. The temp sensor I believe is bad so I will replace it and see what happens . after assembling it two times I just can't believe there is anything wrong with the chain and tensioner. And this just started when the thing started running bad and came about in around 100 miles of driving. I have a bad cold so it may be a couple days before I get to it. I have my fingers crossed. Dan

 

Keep us posted. Now I'm wondering what the hell you're going to find. This could be a learning experience for all of us! Best of luck with it.

 

Are you sure the timing chain cover is not damaged or distorted in shape? You might be hearing the sound of the chain just touching the timing cover.


Since you have the whole kit (assuming cam sprockets too), I would open it up one last time and check the inside of the chain cover and just finish replacing the guides, tensioner, and cam sprockets so "all" timing related parts are new.


I NEVER recommend throwing a handful of parts at a problem (shotgunning parts), but I don't see this as one of those cases since I'm just recommending you complete the timing set rebuild with parts you already purchased.


Also, a measurement of timing chain stretch on the ORIGINAL timing chain may shed some addl light on the problem, as if it is found that the original chain is well within spec, then chain stretch can be ruled out.

 

Well finally got well enough to work on the car. The way the guides are designed There is no way the chain could hit the case. I replaced the thermostat and the temp is back where it is supposed to be and the RPM is now down to 800 still to high but better than 1000. Checked for vacuum leaks but found none. tomorrow I will check the egr valve but not much hope as there are no codes. The thing has no timing marks so not much I can tell there. I wonder if the computer is going bad and retarding or advancing it . This chain noise has to be on the non tensioned side of the chain set up or the tensioner would handle it . Dan

 

So was the original timing chain in spec?


Did you replace the temp sensor or the thermostat? I know you stated thermostat, but since I suggested temp sensor (ECTS), I wanted to be sure which of the two was replaced.


Only asking for confirmation; it's not that I don't believe you.


OK ---again, not challenging your experience:


Have you stethoscoped the noise to the timing chain? I ask because angry lifters lifters and oil flow/distribution issues on these engines can make similar sounds


I know you don't want to, but I would complete the timing rebuild (if nothing else the guides and tensioner) and see what happens.


Also check for oil flow restrictions in the head.


Has the car ever been run extremely low on oil?

 

O.k.
I'm 74 and have to go along with pretty much everything you said so far and have no idea what might be going on from reading the thread. A few years back a friend of mine was running a wrecking yard with a rent to own operation. He was using Saturns simply because in his words. "Keep good oil in them and you can get 400,000 miles out of the engine with little to no maintenance" I know my 94 has 110,000 miles on it an is running trouble free. And yes it has been set aside as a toy to enjoy rather than beat to death. It sounds as if it is some form of a chain tensioner problem and I'd bet a nickel that is where you are going to find a solution.
And yes, waiting to find an answer

 

I've spoken to a few "senior" shadetree mechanics in my family and they definitely agreed that the entire timing set-- tensioner, sprockets, guides and the chain should be replaced as a set. Cam sprocket wear may be part of what you have been questioning regarding the cams seemingly being "off".