My mom has a 2003 Monte Carlo SS. Every 3 to 5 months her car rough idles and the check engine light comes on. She has been told by the chevy dealer that the issue is related to the intake valve. She has had it cleaned several times as well as having had it replaced once. It hasn’t fixed the issue. Also, she needs a quart of oil every 1000 miles. It never leaks out of the car and no one can tell where it goes. GM is paying for the oil as she bought the car new and has had this issue since 2003. Can anyone please help?
I’m probably going to be of little or no help here, but the idle issue is probably being misconstrued. It’s not the intake valve that would cause this and it sounds like what is being referred to is the Idle Air Control valve. This is a common problem with many cars.
Since it’s been cleaned and replaced once, there has to be another issue involved; wiring connector or PCM fault involving the IAC OR it may not be related to the IAC at all. If an EGR valve goes stupid for some reason and hangs open the engine will not idle or will idle roughly.
To at least start with a clean slate, take the car by AutoZone, Checkers, etc. and have them scan it for codes. They will do this free and it only takes a couple of minutes.
Some car makers claim that a quart of oil per 1000 miles is normal but I don’t like that statement at all.
No leaks means it’s burning the oil either past the rings, the valve seals, or both. There is no test for valve seal and a leakdown test MAY reveal a ring problem. Nothing is etched in stone with this test.
Question. She bought it new. Does this mean 4 or 5 miles brand new or a 100 miles give or take new? The latter could point to a dealer demo that saw a rough break-in period.
You might try changing the PCV valve to see if that helps cut the oil loss.
A compression test can reveal bad valve seals. Here is how. If the dry pressure is close to spec. and even from cylinder to cylinder, and the wet pressure is only a little higher, this is a strong indication that rings and valves are in good shape. A leak down test ( if it holds pressure well over time) will confirm the wet dry test. If there are no leaks of oil on the engine or on the ground, then the logical conclusion is that the oil is getting past the valve seals. this may not be fool proof, but close to it. I dont know about the idle problem, but it sounds a little like a cracked vacume hose to me.
I’m not trying to come across as combative, but you’re dead wrong by thinking a compression test has anything to do with valve seals. The valve seals are external to the valve faces and valve seats and are completely insulated away from any cylinder pressures; wet or dry.
The valve seals do not seal in one iota of compression; they’re there simply to minimize oil leakage down the valve guides.
My mom did by the car as a left over. It had about 100 or so miles on it already.
GM has been giving you oil for the past 7 years but they never put a man on the car to figure out why it is using oil? It seems like they admit a problem but since adding oil so frequently is OK with you it is OK with them.
Have they even looked once why it is using so much oil?
Any report on what codes are associated with the check engine light?
I’d like to post the theory that the car suffered a rough break-in period and the oil has been leaking past the rings. Combustion gasses are also leaking past and causing blow-by that is fouling the IAC and PCV. Just now, with 7 years on it, the wear has gotten to the point of excessive blow-by increasing the effect to a noticeable problem every 3 to 5 months. I like Cougar’s idea of replacing the PCV to see if it helps in any way. The other option is a re-ring job.
A 100 miles on it means it was a dealer demo. Many demos are driven by management types at the dealership. However, these cars also get driven at times by salesmen and some of these guys have the metabolism of a hummingbird and a lead foot.
I’ve ridden with a few of them on short hops and I was slouched down in the seat and bracing myself the entire time while wondering if I was going to make it home that evening alive.
It could be that the car got a rough break-in. The part that confounds me, as it does oldschool, is why in the world oil is being paid for with no effort to determine why.
I don’t buy for one minute that GM is paying for the consumption oil being used. Odds are this oil is being covered by the dealer for some odd reason; maybe a reason they don’t want the owner to know. In the interim they’re throwing oil in it while praying the car gets traded off or gets taken out in a collision; effectively ending this problem.
Another more obscure reason for oil consumption could be oil control rings that are gummed up due to irregular oil changes or oil changes that are not performed often enough based on the type of driving.
A quart every 1000 miles is nothing to brag about, but it’s nothing to worry about either…Actually, it’s considered normal…