Engine stuttering at Idle

**mike171562** · 03-24-2010, 12:26 PM

I washed my engine bay 3 days ago and now my engine is stuttering at idle. I used plastic bags to block off, the PCM, Fusebox, and electrical connectors first, just used a regular garden hose on a cold engine, when i finished, i started the car and let it reach operating temp and turned it off. The car runs fine until it warms up as soon as it starts reaching operating temps, it starts to randomly stutter so I'm thinking maybe my o2 sensors? Before this it was running fine, Spark Plugs, wires, and fuel filter were changed last week before this happened. anybody got any ideas? this is really pissing me off there are no engine codes or lights

**seth_12** · 03-24-2010, 01:41 PM

I doubt its the water. I wash my engine all the time and never use any bags, check your fuel pressure. It should say 55psi to 60psi. Any problems cranking it up?

**mike171562** · 03-24-2010, 01:45 PM

No, it cranks fine and runs smooth until the temp guage starts to rise. It was running fine before i got it wet, how do you check your fuel pressure?

**seth_12** · 03-24-2010, 01:48 PM

So when the car starts running hotter, it runs like crap?

**mike171562** · 03-24-2010, 01:51 PM

it never gets hot, just normal operating temp around 180-190, when the temp guage starts to rise is when it start happening, when i first start it up, it idles smooth, i just changed my plugs and wires so i dont think its a misfire, dont really want to pull them all off again unless i have to, i still got the cuts on my hands from doing that, i tried unplugging the maf for a few minutes , but it didnt change anything.

**Cutlass** · 03-24-2010, 05:52 PM

Usually in a situation like this where you wet down the engine and it misses, its ignition system related. The plugs wires usually. You say they are new...so that shouldn't be an issue. Things should eventually dry out.

**seth_12** · 03-24-2010, 05:56 PM

Take your spark plug wires off and your plugs and see if any water got to them. The easiest way to change plugs on a Ls1 is to take the ignition coils off first, that will give a little bit more space and saves you from getting your hands cut all up.

**mike171562** · 03-25-2010, 06:00 AM

I noticed my throttle position sensor wires were exposed at the plug and touching each other, i taped them off, but its still doing it, also noticed this morning, my a/c vents are blowing on the floor and not out the main vents, this means a vacuum leak correct? could this be the cause of my issue?

**jiveass** · 03-25-2010, 06:15 AM

coolant temperature sensor could also be a culprit.

**stew215** · 03-25-2010, 06:16 AM

A vacuum leak will definitely make the car surge. I am not sure if that would be related to the vent not working.. Hopefully some one will have an answer for you.

**mike171562** · 03-25-2010, 06:53 AM

Originally Posted by needls1again

coolant temperature sensor could also be a culprit.

i replaced the temp sensor on the engine block by spark plug number 1, it broke when i was doing the plugs, driving home in traffic yesterday, i noticed it starts when i stop the car and let the idle fall below 600 rpms or so, if i keep it under a light load and just coast at 900+ rpms it runs ok, its like its idling too low , when i stop it idles around 600 and thats when it starts stuttering, its got to be a closed loop issue, it idles fine for the first few minutes after i start it.

**seth_12** · 03-25-2010, 06:30 PM

Hmmm....i would say drive up here, and my buddy could look at it. He is a badass mechanic and would have that issue fixed in no time, but it would be a 3 hour drive.

**iamsam38** · 03-25-2010, 09:46 PM

I swapped a LS1 into my 71 Chevy Truck and I am having the same problem. I took the engine to the car wash before installing it and hosed it off too. I have the same exact problem. What was the fix? Did you ever get it resolved?

**mike171562** · 03-26-2010, 05:37 AM

not fixed yet, im still living with it and dont have the money to start throwing parts at it. i drove around with an ODB II reader and recorded a bunch of data, but its nothing useful

**seth_12** · 03-26-2010, 10:35 AM

Check your fuel pressure...when my fuel pump was acting up it would drive normal in the high RPM's, but when i come to a stop in the low RPM's it would stutter and wanting to turn off.

**mike171562** · 03-26-2010, 11:05 AM

would that explain why it only happens after the car warms up? any way to check it without buying a pressure guage, I'm broke at the moment

**seth_12** · 03-26-2010, 10:35 PM

no you have to have the gauge...most mechanics check that for free. It wont even take a min to hook up the gauge and check the pressure.

**02fbody35th** · 03-27-2010, 02:29 PM

you can rent a pressure gauge from auto zone. you just have to put up the cash and they give it back to you when you return the tool

**mike171562** · 03-28-2010, 04:49 PM

Ok, i unplugged both my front o2 sensors and drove around and the problem seems to have disappeared. The bucking at idle stopped and seems to drive smoother. Guess this means my o2's are bad? Is it ok to drive around with them unplugged for a few days until I can get replacements?

**02fbody35th** · 03-28-2010, 05:03 PM

i dont know for sure but i dont imagine that being to healthy for your engine. the front 02 sensors read the exhaust to make adjustments to your air fuel ratio at the bare minimum it will deffinatly kill yor gas milage, i dont know man if it was your rears i would say yeah no big deal, they just monitor that the cat is working correctly. maybee somone else can chime in hear and let us know if its ok or not. but if it was me i wouldnt