rough idle, please help

Hey guys, sorry if this has been posted recentley. I didn;t se it anywhere on the board. Anyways I have a problem of my 97 c/k 1500 350 idling in park or at a stop light. It drives fine but as soon as I'm stopped for more than a couple seconds the RPMs drop pretty low, and it starts to vibrate or shake, so I don't know if it's timing or what.:1zhelp: TIA for the input.

try cleaning the IAC valve in the throttle body. cant tell ya exactly where it's located, but most are a 4 wire connector and when you pull it out it will a spring load pintle

Does the SES light come on if you idle too long?

nope skipr, no SES light or anything comes one when I'm stopped or parked and it's idling. I cleaned the IAC valve but no luck. My acceleratior cables are quite loose. Would this have anything to do with it??? I also might go ahead and replace my IAC.

turn up your idler and you will be since its fuel injected get a programmer from a shop or something and turn your idler up becuase it sound like its just something simple like that. Does it run nice while driving?

how's your PCV? if it's plugged than that'll effect the idle.

:iagree:

check all the basics first like the pcv, vacuum lines etc.

btw, you dont want to go adjusting the idle speed screw. there's a proper way of resetting the idle speed in the ecm, turning it will make matters worse.

Yes, it runs nice while driving, But I'll come to a stop light or something and then it doesn't idle very well.
I don't think it's the PCV. I just replaced it 2 weeks ago. Along with my plugs, dist. cap, rotor and wires. Thanks for all your input, btw.

I had a similar problem. Ran fine at high RPM's but at idle it was rough as could be. Replaced everything you did... "PCV. I just replaced it 2 weeks ago. Along with my plugs, dist. cap, rotor and wires" and then traced it back to the coil. Autozone had it for like $20 I think...ran fine ever since. Also, did you check your fuel filter?

I would look at the fuel filter , Replace it.
Also make sure your EGR valve is not trying to open at idle that will give you a rough idle every time.

I'll check the fuel filter, but I changed it about 2 mo. ago. I don't know hoe often you should replace them. Also how whould I check the EGR valve? Thanks.

Well my 97 Sub with the 350 started to Idle rough today. I removed the air cleaner and the IAC cleaned the IAC and the mass airflow sensor and she is back to a smooth as glass idle
ps
NEVER ADJUST ANYTHING ON THE THROTTLE BORE OR YOU WILL MAKE THINGS WORSE IN THE LONG RUN!!!!!!!!

Does your 350 have a TBI system? If remove your TBI, clean out the carbon build up, check your sensors(TPS<AIC) Also, CAREFULLY check your fuel pressure regulator. It mounts on the back of the TBI upper portion. Mine had a broken spring, replaced the entire assembly(dealership item), runs great. Be careful, regulator has allot of tension from the spring . Check out my post regarding a 91 4.3 ltr idle.

Well my 97 Sub with the 350 started to Idle rough today. I removed the air cleaner and the IAC cleaned the IAC and the mass airflow sensor and she is back to a smooth as glass idle
ps
NEVER ADJUST ANYTHING ON THE THROTTLE BORE OR YOU WILL MAKE THINGS WORSE IN THE LONG RUN!!!!!!!!


With a rough idle how can you not get a misfire code on a OBD 2? Mine will lite up a P0305 if I idle too long, but goes out after I drive for 2 driving cycles. This has been going on for a year and a half, and i'm done with it.getting a new truck, and trade it in at 3 years (when warranty expires) My 98 Z71 k1500 has 87,000 and looks great. but is worthless, if the dealer can't fix it after 3 trips to the service dept. I have no need for a 4500 lb paper weight.Second worst $33,000 I ever spent (the first was for college, took my money and my time)

My check engine never comes on because there was no miss fire just a rough idle due to a dirty mass airflow and dirty IAC. .
The idle was between 550 and 700 rpm. now she stays at 650 rpm smooooooth as a babys behind
You do a tune up any time soon??
You clean the maf or iac ??
Clean any egr passages???
Check to see if you ign spark plug wires are any good???

Did a complete tune up (new OEM wires, ac delco platinum plugs, dist. cap/rotor,) I have not cleaned MAF or IAC. thats what caught my attention in your post. My symtoms are the same but the P0305 is very specific to a misfire in #5. I thought it was clogged poppet, there is a TSB out extending warranty to 10 years, 200,000 miles on the injectors.But the dealer refuses to even consider that being a cause.They claim to have tested for that, but they can't seem to remember how they tested or the procedure taken to rule out fuel system.

Let it idle for about 30 min and the turn it off and pull cly 5 plug what does it look like???

Let it idle for about 30 min and the turn it off and pull cly 5 plug what does it look like???


Idle for a half hour? That plug is gonna be a hot MF. I'll try it, thanks

Same prob here, Truck runs real good otherwise, get to stoplight and will idle fine then stumble and stall, sometimes before it stalls will surge to try at keep it alive but will die, idles fine in park or neutral, but I dont like put in neutral or park at light since will die when loaded upin gear, Sucks huh!