rough idle, please help

Silvey350 · #1 10-26-2004, 11:54 AM

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.

TIA for the input.

4onFloor · #2 10-26-2004, 02:35 PM

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

skipr · #3 10-27-2004, 01:19 PM

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

Silvey350 · #4 10-27-2004, 04:04 PM

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.

BrakeTorque · #5 10-27-2004, 09:12 PM

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?

AKWE-gt · #6 10-27-2004, 09:31 PM

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

4onFloor · #7 10-28-2004, 01:11 AM

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.

Silvey350 · #8 10-28-2004, 12:00 PM

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.

cdoogles · #9 10-28-2004, 06:13 PM

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?

Fireplug · #10 10-28-2004, 07:39 PM

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.

Silvey350 · #11 10-29-2004, 12:32 PM

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.

Fireplug · #12 10-29-2004, 02:50 PM

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!!!!!!!!

gtmud · #13 11-02-2004, 01:23 PM

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.

skipr · #14 11-02-2004, 05:17 PM

Quote:

Originally Posted by Fireplug

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)

Fireplug · #15 11-02-2004, 09:29 PM

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???

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