chev engine start up rattle/noise

Messages
907
Location
Canada
Bought my son a 1994 Oldmobile Cutlass Supreme past Febuary, 100K miles or 160k kms, auto, 3.1 v6. Car has been doing great in the 8000 miles he put on it todate. At start up the engine has a rattle and shake, once temp guage just starts to move at idle this rattle dissappears and engine smooths out. I am guessing/hoping this rattle is only a steel time chain? thanks, Cyprs
 
Messages
855
Location
Arizona
there could be several things causing this, plus it could be a combination of things also. Check the exhaust for puff of light blue smoke at startup You will want to uoa oil to check for an intake leak, or have cooling system pressure checked Check the maf sensor to see if it has any crude built up on it If money is not an issue and your mechanically inclined you may want to remove the injectors and have someone clean them on the ASNU machine As far as the temp change, what happens is when the ECM gets all the proper signals it will change to a open loop, all this means is the oxygen sensor is taking over fuel control instead of it running on a pre-programmed ECM function (closed loop). One of the critera for this to happen is the engine coolant tempature must be above a certain temp, not sure what it is on your specific application but it typically ranges from 90 - 120 on various applications. I wouldn't worry about the timing chain, failures of those on newer cars are rare.
 
Messages
2,287
Location
Middle of Iowa
My bet would be piston slap. My wife had a 1994 Grand Prix with the same thing. No matter what oil I ran, I sweat it would sound like a diesel for the first couple of min. until it warmed up.
 

Cyprs

Thread starter
Messages
907
Location
Canada
It is a Fram Wear Guard for filter, did same with the AC filter too C65. I bought 4 Valvoline High mileage oil filters, box claim they filter much more, too much restriction on them with extra filtration? Thanks MC, will check a few of those things out, thanks for the detailed and informative trouble shoot options. DH, possibly if it is piston slap, how serious is this, I have heard some people run their engine a long time with some slap? Oil OCI's todate on this 3.1. On getting the car at 100k miles I put in 0-30 XD3 HDEO group 4 POA, tbn 12, 100C visc of 12, found nearly 3/4 litre oil consumption (no leaks) in 3k miles oci, engine loudest at startup with this syn 0-30. Second OCI with one litre conv 10-30 SL oil thrown in with 3 litres Esso XD3 0-30 hdeo syn oil there was 1/2 litre consumption in 3k miles. Now at 2K miles with a blend of (2) 15-40 conv XD3 HDEO liters and (2) litres 0-30 syn XD3 syn oil, very little oil consumption, bit quieter engine at startup now with this blend, but start up noise is there. The oil does not get excessive dark, engine was maintained good from what brother of previously deceased owner told me. This brother owned car briefly and told me engine did not consume oil in his OCI periods. Considering what is happen with my OCI oil consumption results, does this shed light on the engine noise? And should I consider straight 0-40 XD3 syn this winter when it can get down to -40F (0-40 still has -60F flow rate and 15.7 visc at 100C) (0-30 12 visc at 100C and still -60F flow rate) or a blend of 0-30/0-40 XD3 syn? Do chev engines like a heavy oil like my Nissan QR25DE which also has a steel time chain needing good heavy lubricatiing oil? lot of questions, sorry bout that guys, should have give OCI background on first post. thanks much, Cyprs
 
Messages
119
Location
Atlanta, GA
I have owned numerous higher mileage cars. Many of them made some start up noise that disappeared when the engine warmed. Most likely nothing to worry about...just take it easy until it warms.
 
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