rough idle on throttle when sitting

[1-3-2-4]

I have this rough running that only seems to happen more and more as the temp drops but here is the thing.. if you start the car up it will idle normal.. however say you need to leave quickly like a few seconds after you start it runs rough almost like the timing is pulled until you hit 2K OR.... if you sit and wait an extra 30 seconds you can leave and take off as normal.

the stuff below I copied and pasted from USMB but it would of been better if I had the camera in the car but on this past Saturday I exacerbated it by having to leave to follow a friend who's car I worked on.

Well after moving my car out of a friend's driveway and checking out another car I got back into my car and I had to quicky jump in and pull off.

I almost never do this by pulling off right away and never when it does that rough running when you give it gas.

Anyways I went to pull off and I had such a hard time getting over 2,000 rpms and after it did the car "opened up"

I can't think what on earth this is... I'm not sure what temp the oxygen sensor goes back into Open or closed loop but I was thinking of installing a A/F wideband just to see if it's running rich during that time.

It seems like the colder it seems to get the rougher it will run if giving it gas after started but it goes always always after a few seconds.

today would of been a perfect time to have a damn camera mounted in the car...


What I have checked is all the injectors to see if I had a leaking one (checked the ohm reading)

I replaced all sparkplugs and they while needed to be changed they looked good.

The funny thing about all of this is say starting the car back up like coming back from going in the store it's fine.. it's just the sitting for like 1 or 2 hours it will appear.

[Legacy777]

Is this car AT or MT? What year and model?

How old is the coolant temp sensor?

[1-3-2-4]

Car is a 95 and the CTS was replaced 6 weeks ago.. mater of fact I have the old sensor still sitting in the box that the new one came in.

here is a video

http://www.youtube.com/watch?v=Chfwg3vu8eg

[Legacy777]

Is it an auto or manual trans?

The issue I had which was somewhat similar I think was MAF related. It eventually went away, but I never could completely figure what exactly was the problem. If I didn't let the car warm up the rpms would drop and stumble, and then pick back up. The weird thing was that it only did it once I pressed the accelerator. If I didn't touch the accelerator or let the car warm up, it never stumbled

[1-3-2-4]

heh I figured if you looked at the video would of seen it was a manual

And Josh what you describe is pretty much what I'm dealing with it seems to get worst when it's colder.. For your location might not be as bad.. but last year when it reached into the low 40's and lower it was annoying..

If I don't touch the throttle when starting you can hear it's not "smooth" but after a few seconds like 30 or a minute it smooths out and never stumbles when you press the throttle.

I did not get to test my fuel pressure today because of a few things that came up.

i do know that the MAF on this car is a reman because of the red reman sticker on it.. I wonder if pulling the plug to the MAF would give me the same symptoms?

[Legacy777]

I suspected it was a manual, but wanted to get clarification.

I lived in PA for four years so it got cold.

You can try pulling the plug on the MAF. I'm not sure it'd be a good indicator, but you could try it. You should be able to pick up a used MAF on here for relatively cheap. That may be another option.

[1-3-2-4]

From all the searching on USMB I noticed that anyone that did have hesitation that it almost always picked up when it got around 2K I wonder why that is..

And PA is cold enough

[1-3-2-4]

I just came back from pulling the MAF plug.. got all the normal stuff (CEL) so it idled a bit loppy so I decided to drive around the block ha a lady was nice enough to let me go in front of her and I went to give it gas and it did pretty much the same stuff that happens with the sensor plugged in..

Feels like I can make coffee by the time it gets to 2K.. and when it gets to 2K it opens up.

So faulty MAF? I mean it has a red and white sticker that says it's a reman.. only thing is I can't tell if it has a date or something on it..

Also is the temp gauge related to the MAF? I noticed it started to climb a bit when I started to pull off be the engine was hesitating But went down when the rpms started to climb.

[Legacy777]

Replace the MAF with a good working used one. I don't really care for "reman" stuff as half the stuff you get is still broken and crap.

engine temp shouldn't be related to MAF....

[1-3-2-4]

I'm guessing no MAF engine runs richer = higher engine temps?

I just took it out going to clean it but I don't have any high hopes.

date on the reman says 4/4/01

[Legacy777]

more fuel typically runs cooler.

[1-3-2-4]

Took it out and cleaned it but wont know for sure until the morning.

[1-3-2-4]

I guess the site here had issues yesterday right when i was about to post everything kept timing out..

but I wanted to say when the next morning came still same issues..

So I have the IAC here in front of me that I just cleaned.. I was looking in the haynes manual here and one thing I noticed they say run the engine to operating temps and remove the IAC and the shutter should be closed.. well I did not do that but hours later.. I should think the shutter should stay in the same position as when it was at operating temp?

Anyways they make note saying that the shutter should be fully closed.. when I removed mine it has half open as you will see in the picture.. I will test the resistance of the connection.



^After I cleaned it I just moved the shutter to how it was before I cleaned it.

[1-3-2-4]

hhmm well cleaning the IAC did me some good.. stops that stupid funky idle from 0 to 1K then drops to 500 then back to 1K then it idles at 750.

BUT I just checked the fuel pressure today (finally) I got around 31 psi idling and it went up as the throttle opened and pinching the fuel return caused it to shoot up..

BUT here is where I screwed up.. I forgot to check for 5 min to see if the pressure was dropping (it was) it was down to 30 to 20 psi in far less then 5 min that's for sure..

Possible leaky injector? That would explain the rough idle.. possible fuel puddle and trying to burn all at once a few hours later.

Funny is I did a ohm test and it showed good for all 4 of them.

here is youtube video

http://www.youtube.com/watch?v=GC6Y7aOM5yc

[Legacy777]

Yeah it may be a leaky injector. It'd be good to test the fuel pressure again and see how quickly it drops off right after shut off. You can pull the plugs for each cylinder and smell it to see which one may smell of gas.

The IAC valve, you can try putting hot water through the tubes and should see the rotory valve move.

[1-3-2-4]

I did the test again.. 25 psi was the hold pressure when the engine was turned off (haynes says 30) after 5 min the pressure dropped to 14 psi

[Legacy777]

I don't know if that test is conclusive, but I think it's a good indicator that you may be on the right track. What I would suggest is trying to swap out one individual injector at a time and redo the test to see if you have a single injector that is causing the problem.

[1-3-2-4]

also I hear some type of air hissing sound.. hard to tell where but it's between the PS pump and the intake manifold and it only happens (audible) when lightly on throttle.

and when you say swap out do you mean take it out and look for leaks? I don't understand.

[Legacy777]

Remove teh injector, install another one.....assuming you have another one. If not, you may want to get another set.

Are they stock injectors? I've got a set if you need it.

[1-3-2-4]

the injectors are stock