Slight Engine Sluggish

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Sep 13, 2007
Ok, Have a 08 Saturn Outlook with 43k on it.

The problem is when i let the car sit say overnight when i start it for the first time it has i would call a rough idle for 3-5 sec for the engine smooths out. No issues while driving and doesnt do it after the car is warm.
I usually only use shell gas(discount card) so i dont think it is a clogged injector it something.

Now i believe it * MAY be the oil. I have only every used Mobil 1 full syn in the car going back and forth between regular full and EP if it was on sale. Also have only ever used mobil 1 filters. Oil is changed every 6-9k depending on the indicator.

I have really only every noticed this while i have the M1EP in there and not regular M1 so i am wondering if it is something with the EP. I purchased some PP when it was on sale and will switch to that in about 3-5k. Just wondering if anyone else has some thoughts
If the oil you're using is thick for your climate conditions, you may experience the symptoms you describe. What viscosity are you using?
You are using a almost new car with outstanding oil in a climate that the oil is designed to perform in.
I wouldent think it is your gas, as it starts right up.

You may have a bad anti-drain back valve on your oil filter.
However, I dont know how or where it is mounted. If it is on the bottom of the engine, or anywhere facing "up" it a anti drain back valve is kind of a moot point.
If the issue continues you might want to change the filter out and see if that fixes the sound.
What is your typical Oil change interval? How many miles on the car?
M1 is excellent stuff and it might just be a "car noise", I would not lose sleep over it while using a quality synthetic like that.

My Taurus makes noises that I cannot find/diagnose, and my mechanic cannot replicate and or find. I think it is a suspension component, but it only occasionally makes it.

does your Outlook has the 3.6l v6?

My car is doing the exact same thing (caddy CTS 2005 with the 3.6l). Only on cold start (car slept overnight), it starts right away, but sometimes (once every 20 times or little more), it idle rough and make the car shakes a bit.

Dealer cant repeat the problem and never saw it. My oil filter is mounted next to the engine (top) and its a cartridge.
yes it has the 3.6 but my filter is on the bottom of the engine facing the front of the car. I will know more when i change to the PP as i think it has something to do with the M1EP
Maybe your car has the same intermittent problem as mine. Intermittent misfire (P0300) at cold startup (when car slept an entire night).

Is it due to humidity? dont know, is it due bad fuel, dont know! Even dealers dont know. Since then, I bought fuel cleaner and injector cleaner from GM that I put in the gas tank every oil 5000 km. It helps a lot. I think its due to cheap fuel from the stations around here.
Oil is not going to cause those problems. Without looking at some scan tool data and actually seeing the vehicle I can't give you any sure fire advice. But there are some easy and cheap things you can try that can cause your symptoms:

1. Clean the throttle body and IAC passage way. You may have gunk in the IAC passageways that do not allow the pintle to be where it needs to be at start-up. Actually, I don't think you have an IAC, but instead an electronic throttle control that opens the butterfly as neeeded. Dirt will be all around the butterfly and limited idle air and even sticking the plate closed if severe enough. (I didn't pull up the service manuals..getting ready for bed). Easier yet - just spray the cleaner all around in there. In any event - if there is dirt in there you could have a rough engine for a few seconds until the PCM adjusts for it and the engine smooths out.

2. Check your fuel pressure. If no gauge - try turning the key on w/o starting the vehicle and wait 2-5 seconds for the pump to run. Than turn the key off and repeat. Then start the car normally. By doing this you are priming the fuel system and getting max pressure. If this works, keep doing it for awhile. If the problem returns when you STOP doing this,you may have a fuel pump or regulator getting weak. These little devils will cause a rough engine at start up until the pump catches up and then the engine smooths out.

3. Any vacuum leaks? Check all your intake ducts - do this while your cleaning the intake. Be sure everything is seated right and the clamp are tight. A vac leak will cause a rough idle and many times the PCM can compensate for small leaks - which could be why your engine is rough than runs fine.

4. MAF sensor (after the air filter in the ductwork) - is it dirty? Spray some MAF sensor cleaner to clean the wires. Never hurts - and if you are running a K&N filter you'll probably have the filter oil all over the MAF anyway and that needs removing.

Just try these simple, cheap things. Should be able to do them all for under $10 and an hours time. Good Luck.
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GMBoy, what am I going to do without you?!?!?! hehehe

The throttle body is very clean, I checked it last week. No vacuum leak (I checked it and the dealer checked it also).
I'll try the fuel pressure test that you mentionned and the MAF sensor, I'll be true with you, I never checked it because I'm scared to break it (just because I never touched a MAF sensor).

I'll give it a try! Tks again!
Over the years one of the main causes of rough idles on cold starts (and excessive cold crank times) has been fuel pump check valves. Overnight a leaky valve allows the fuel rail to bleed down.

Easy diag: Cycle the ignition key a few times before cold starting to run the fuel pump before cranking. Might not be the cause, but the diag is free.
well, I tried it this morning, cycle on and off the ignition twice and the car shakes for approx 5-6 secs just like if there was too much gas in the engine and after that, it went away.

I had to tank the car today as usual but I went at a Shell station, put high octane (91) instead of regular (suggested by manufact.) + one full bottle of GM fuel system and injector cleaner. The small shudder on idle is now gone after 100 miles and the car seems to respond a little bit better and there's no sound on small acceleration like pinging or if you could hear the pcv valve shaking.

I'll keep it with premium and one bottle per 5000km just like its written on the GM bottle and see if the problem come back. I'll check tomorrow morning since the car is in my garage and I wont use it tonight.
Originally Posted By: Spykem4e
the car shakes for approx 5-6 secs just like if there was too much gas in the engine and after that, it went away.

I think you just hilighted what the problem is by that statement. I think you have a leaking injector(s). When the car sits, fuel drips down and creates a temporary rich condition at start up because the PCM is unaware of the extra fuel in the mix. Once started and running, things get back to normal and then of course whren you go into closed loop you get the O2 sensor keeping the mixture optimum.

I've got a leaky injector on my 94 Corvette. After is sits a few days, it'll start up rough and you can see it and smell it in the exhaust for the 1st minute of running. I'm gonna replace all the injectors over the winter as it's no issue to me know and the UOA's show no fuel dilution.

To check this, you have to have a fuel pressure gauge and to be even more precise you need a scan tool or other method of pulsing the injectors to see which injector is actually the culprit. But anyhow - if you need more info, just PM me again and I'll send you some details and a tech report.
Ok the priming thing didnt work. I may try a nice tank of 93 v-power next time i fill up and see if that does anything
Oil isn't your problem. You may be haveing a fuel bleed off problem after the car sets for several hours. The fuel rail needs to be pressureized at all times, if it isn't there can be starting problems.
All of GMBoys points are good. It's mechanical.
Originally Posted By: compnurd
Ok the priming thing didnt work. I may try a nice tank of 93 v-power next time i fill up and see if that does anything

93 octaine is no good for your engine either. My alter the computer and cause the engine not to perform well.
i have ran 93 octane in the truck before and it does respond nicely to it, it just does not always justify the cost
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Alright, since I work on the road all day with my car, I have lenty of km's and time for testing it. Yesterday, I let the gas tank at almost empty. I fuel it with Shell-V power 91 octane + AC Delco fuel system cleaner. I let the car sits overnight.

Started the car this morning: it runs great. Give it some throttle, respond very good.
No more small shudder during a stop light.
But I could hear the pinging under very light throttle between 25 km/h and 50 km/h. (approx 20-30mph). The difference this time is that the pinging is not very loud at all. You have to mute the radio to hear it versus without the premium gas that you can hear it with the radio "on" at normal volume.

I disable the air conditioning and the vent and the pinging was gone at same throttle.

I can hear the car pings only since I switched to PP, thats strange. Maybe its just the timing switching from M1 to PP but who knows...

My car calls for 87 octane, does putting 91 will have any bad effects on my engine?

Could it be a timing chain issue that is maybe stretched? Would it be throwing a check engine light? I'm trying to figue out the car since I'm almost living in it.
Originally Posted By: GMBoy

4. MAF sensor (after the air filter in the ductwork) - is it dirty? Spray some MAF sensor cleaner to clean the wires. Never hurts

I never thought about that one. Where is it located? And how do I clean it? I'll do it this week if I can!
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