i've got a 3.1 with a 700r4 tranny. the damn thing has been pissing me off lately....when cold it runs fine, but once it gets hot, and i drive it in stop and go driving, the idle becomes more and more choppy when i'm not moving. at worst, the idle will fluctuate up and down somewhat rapidly, and will hit maybe 400 or less rpm. if it sits long enough at idle, it will just crap out.
today was the worst of my experiences with it. i had to go up a steep hill from a stop sign and i was doing fine until i got midway up the hill. the car sputtered, and i had to give it gas just to keep it running...it gave a few small pops (maybe backfires?), and on the next stop sign it died on me. it didnt want to start back up, so i had to push it to the sidewalk (argh, embarassing) to get it out of the way of a bunch of people. just to let you know, it wouldnt crank right after it stalled on me. i had to wait for like five minutes...start it, and get it up to about 2500 rpm so it would settle down. then, it wanted to die a couple of times while accelerating on level streets (i quickly popped it into neutral and gave it some gas to keep it running), and it would do the same if i went up an incline.
this all took place in close to 80* weather, and the cars temp was at 220.
I greatly appreciate the fact that you took the time to look over this, and i was wondering if u guys could give me ideas to what the problem is...

thank you

 

Wow, something definitely isn't right. O2 sensor bad? That would cause a bad idle. Not sure if it would be THAT bad though. Mass air maybe? I don't really know. Just trying to get the ball rolling on this topic.

 

my cars got a rough idle too, do u think the o2 will help it, it doesnt do it till it runs for a few min, car never gets over 120 degrees, i run the fan all the time..also i get about 11 miles to the gallon, its a 2.8 v6

 

it could be injectors, or egr, or problems with your fuel vapor system. From what you've described, it would probably be injectors or egr. However, do a tune up while you're diagnosing this stuff. Might as well, it's cheap.

For injectors, check the injector resistance first, and then run an injector balance test.

There are about 10-15 things that could be wrong, for warm idle problems.

 

220 is that normal for a v6? if you have not had problems with this in the past and have not recently worked on your ride i would check everything from the above mentioned to the obvious like fuel filter,evap canister does it have a catalytic converter? just trying to help

 

thanks for the quick replies, guys.

i was scratching my head as to what the problem was... i will look into the injector resistance and getting an injector balance test (courtesy of 91Z28-350) when i get some time to, otherwise i'm up for the annoying task of torque braking the car every time the rpms start fluctuating, and avoiding stop and go traffic by all means possible.

 

and to answer hank's question...220 is normal for me in city driving... but i'm usually 3/4 of the way between 100 and 220 on the freeway (when air is being picked up constantly from underneath)

also to hank...what is the evap canister? is it that thing that is right next to the intake canister, blocking the hole that gives it cold air? and yes, its got a catalytic converter

 

Yes, that's it. It's got alot of tubes running to it. I can't say exactly where it's located on a 3.1, but for my 350, it's on the driver side, near the headlights.

I'd bet the problem is most likely the injectors. I had that problem just recently, and 4 of my injectors crapped out on me...also causing me to run rich. For me, just checking the resistance was enough. 4 of the injectors had resistances in the low single digits.

Just make sure the obvious things are OK, like vacuum tubes and/or vacuum leaks, as well.

 

Sounds exactly like what my car was doing (except that I never had problems restarting it after it died). Generally, when I had problems like that with my car (the '88 Camaro in the sig), it was a signal to me that I needed to preform a basic tune-up:

* new wires
* new plugs
* new distributor cap
* new rotor
* rebuild distributor
* make sure the base timing is set correctly
* clean the throttle body
* the idle air control valve pintle and surrounding areas
* change the oil

As long as your problem is not due to something major, the above should help things out a lot.

As far as the idle quality goes... As long as I have had my car (got it with ~115,000 miles), the tach has always been "jumpy". And, a lot like yours, it would tend to start to dip really low sometimes, even so much that it would die. I found that, even with the basic tune up stuff, I could never get the tach (and engine speed) to sit still and get the engine to idle smoothly for more than a second or two. I was starting to get to the point where I thought that these V6s simply couldn't idle very smoothly (this is my first car).

So, anyway, what I ultimately ended up doing (as a sort of "last-ditch" effort) was to change the timing chain. I actually spent all this last weekend doing it, and I just now got back in from test-driving it for the first time with the new chain. I'll just say that that's the first time that I've ever seen my tach needle sit still with the car running. The idle is *much* smoother, and it the idle speed doesn't try to dip down like it used to. Plus, the car just generally feels stronger (about as much as these engines can).

Anyway, just something to think about--especially if you have a high-miles engine. You can do a search on the V6 boards--my bet is that you'll pull up nothing but praise from people who have done the swap. In fact, if you *really* want to stick to the books, you should change the chain every 30,000 miles or so. In my case, this chain had about 125,000 miles on it--and with more than an inch of slack, it showed.

But, you're probably making a good start by working with the injectors--they can really affect idle quality, too.