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Ok, long story short, I just bought my wife a 2005 buick rendezvous, inspected every square inch of this car and found nothing wrong with it, everythign ran great no cil codes or anything. 1 week goes by and the car starts having cil go off, its coolant temp not getting up to operating range, so i replace the thermastat only to find it’s been cut out and left hollow just for the gasket to seal. also found the water pump leaking allt he sudden. Replaced both and 2-3 days later the car has a rough idle on startup occassionaly, generally after its been setting for over an hour but not after its been setting for over like 10-12 hours, sidenote, i also smell gas when this occurs. First i cleaned maf sensor, and noticed varnish in throttle body so i pulled it off and cleaned it also, I’ve checked fuel pressure and holds steady at 50, take fpr vacuum off and it jumps to 57, hit the gas and it goes to about 49 and thats as low as it goes, left it on car for a solid hour after running, it dropped to 47 when i shut it off and stayed at 47 for an hour tell i took gauge off. checked vacuum and i get 17 lbs at idle, it recovers quickly after i floor the gas, jumps to 20 for a brief period after i let go of gas, doesn’t jump or bounce around. i checked pcv valve and it was collapsed just near throttle body so i replaced hose but that had no effect. At this point i realized it doesn’t have an egr valve. went to junk yard today to find out how the electrical was ran and to get everything i needed, at counter the guy told me some engines have optional egr’s, but i’ve never heard that referenced anywhere, isn’t that bad for piston rings and such as well as emmissions and fuel economy to not have that?
tldr; I’ve checked fuel pressure, vacuum, did vacuum exhaust check for plugged cat, pulled plugs for soot as well as spark, everything’s ok. egr is gone and junk yard attendant told me egr’s are optional on vehicles, i call bs. I have a code reader that gives live data, ran for an hour and everything is normal, long term fuel trim at idle is about -5%, other than that everything is beautiful. ALMOST FORGOT, my fuel pressure regulator smells like gas but it doesn’t sputter out, even after 10 minutes off, put seperate handheld vacuum tester unit on it with clear hose and ran for an hour at idle still didn’t get gas to come out. is that normal to smell gas though? i’m so lost and I could swear i’ve checked everything that can be checked, please save me, i feel i’ve bought a cursed vehicle.
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EGR valves aren’t always mandatory in every car. Whether or not it’s got an EGR is going to depend on which engine you’ve got. If it’s got a 3.4, I can’t ever recall seeing one without an EGR valve. If it’s new enough for a 3.6, then it probably doesn’t need an EGR valve. The 3.6 has variable valve timing (VVT) that can close the exhaust valves early enough to leave some exhaust gas in the chamber and do what the EGR used to do. Even without VVT, a camshaft can be profiled to close the exhaust valves early too. If you’re actually missing your EGR valve, you should have a CEL with an EGR code.
That -5% fuel trim isn’t bad at all. How do the fuel trims look while driving? Put some load on it while you’re driving and look at those trims. Do the bank 1 and bank 2 trims look comparably close to each other? I’m not entirely against replacing the fuel pressure regulator, but it’s about a $50 wild ass guess. I’d want to verify there’s no other leaks and see something much worse than 5% on the fuel trims before committing to the shotgun repair. Now that I’m thinking a little, I’d want to try and do a power balance test while the engine is running bad. You might have a misfire problem which would explain the negative fuel trim better than a non leaking regulator would.
Sorry for not giving more information, its the 3.4L. i just went back out and tried to locate the electrical connection that would connect the ecu to the egr and it literally doesn’t exist. the only problem with the power balance test is it takes a long time to get it to reproduce the rough idle, needs to sit for a little while, and when it does do it, its no more than 10 seconds at the longest and it levels out like it never happened. could they have possibly pulled a 3.6l ecu that has itself programmed to no egr or flashed the original to where it wouldn’t throw a code with a missing egr? i’d think it would cause problems changing ecu’s from different engines but as far as that goes i’m clueless. I’ll have to borrow a laptop from some1 before i can run diagnostics while driving, my battery doesn’t last longer than 2 minutes unplugged… thanks for the reply and any future replys!
Should also add its an automatic transmission, 120k miles. no service history marked in owners manual. oil does not smell like gas, performed a vacuum leak for good measure with a cigar, didn’t find anything.
You might want to pull and inspect your spark plugs. The maintenance interval for your plugs is 100K. I wouldn’t be the least bit surprised if the last owner never changed them. Even if they’re not the cause of your problems, it’s never too late to get rid of worn spark plugs.
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