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Rough Idle - Codes P0151, P0174, P0300

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Scan for codes and make sure you clean throttle body and IAC hole on both sides. Fuel should be 60-66 psi so you are good there. Auto parts scans for free. It could be a broken spider assembly in intake causing this as they early ones had problems like that.
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Sunday, July 28th, 2019 AT 6:05 PM (Merged)
Tiny
DCKY320
  • MEMBER
  • 17 POSTS
Is the spider a difficult thing to replace?
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Sunday, July 28th, 2019 AT 6:05 PM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
The top of the intake has to come off, but it may not be that. They are about $300.00 as well. It could be anything until you get it scanned for codes. Also you cannot block off the throttle because it is getting no reading from MAF so will stall.
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Sunday, July 28th, 2019 AT 6:05 PM (Merged)
Tiny
DCKY320
  • MEMBER
  • 17 POSTS
It did not stall out with the MAF disconnected.
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Sunday, July 28th, 2019 AT 6:05 PM (Merged)
Tiny
ERICPIPKE
  • MEMBER
  • 2 POSTS
  • 1999 CHEVROLET TAHOE
  • V8
  • 4WD
  • AUTOMATIC
  • 118,000 MILES
My 99 tahoe has a rough idle at start up when you drive it for 20 min or so it will go a way its been doing this every winter for the past two years. In the past I put seafoam in and fixed the problem.
I have not put it in this year. What is causing this problem it is running rich leaking out of tail pipe
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Sunday, July 28th, 2019 AT 6:05 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Running rich:

Probable causes include a bad O2 sensor, excessive fuel pressure (bad fuel pressure regulator or plugged return line), leaky fuel injectors, dirty air filter or restricted air inlet, or a defective coolant sensor that prevents the engine management system from going into closed loop mode.
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Sunday, July 28th, 2019 AT 6:05 PM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Of course it wont because when you do that it goes into what is called open loop and sets engine up to run rich. Scan for codes auto parts does for free.
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Sunday, July 28th, 2019 AT 6:05 PM (Merged)
Tiny
ERICPIPKE
  • MEMBER
  • 2 POSTS
How would adding seafoam help any of those things
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Sunday, July 28th, 2019 AT 6:05 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Adding that chemical in there at times can make things worst-troubleshoot the items I've mentioned-
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+2
Sunday, July 28th, 2019 AT 6:05 PM (Merged)
Tiny
LTTLPRNCSSDIDI
  • MEMBER
  • 2 POSTS
  • 1999 CHEVROLET TAHOE
  • V8
  • 4WD
  • AUTOMATIC
  • 115,000 MILES
I was coming off a bridge and when I fully stopped, the truck started lurching violently forward and even a bit of side-to-side. The "check engine" light flashed rapidly on and off before it stalled. I was able to restart it, the "check engine" light steady this time.

Whenever I'm idling at 500 RPMs, the truck starts lurching again; above 1500 RPMs, it's as if there's no problem at all.

Oil pressure is fine, the battery is new, the engine isn't overheating, and there's no smell from under the hood. My computer is telling me the #4 cylinder is in need of maitenance, but a compression test is showing me it's not a broken valve. The spark plugs have been replaced, so I'm wondering what else it might be. Someone recommended it might be a "spider injector" problem. If this is the case, what kind of expense am I looking at to replace it? Is this even a valid diagnosis?
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Sunday, July 28th, 2019 AT 6:05 PM (Merged)
Tiny
MATHIASO
  • MECHANIC
  • 1,209 POSTS


https://www.2carpros.com/forum/automotive_pictures/46384_firing_order_2.jpg



On the ignition coil, switch #3 to # 4 and # 4 to # 3.
tell me where the misfire is now?
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Sunday, July 28th, 2019 AT 6:05 PM (Merged)
Tiny
LTTLPRNCSSDIDI
  • MEMBER
  • 2 POSTS
The misfire is still occuring between cylinders 6 & 2 (ie, the new #3 and the old #4).
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-1
Sunday, July 28th, 2019 AT 6:05 PM (Merged)
Tiny
MATHIASO
  • MECHANIC
  • 1,209 POSTS
What is the original codes for the misfire.
I thought it was #4 only.
Do you have random misfire?
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Sunday, July 28th, 2019 AT 6:05 PM (Merged)
Tiny
SHRNHAULER
  • MEMBER
  • 1 POST
  • 1995 CHEVROLET TAHOE
  • V8
  • 4WD
  • AUTOMATIC
  • 99,689 MILES
I have a 1995 chevy tahoe that sat for about 5 yrs.
I changed the fuel pump, spark plugs, and the fuel filter, but it still runs rough. Starts find but idles rough and studders rreal bad when on the trottle. It has a 5.7 ltr throttle body injected. What else can I do to try to fix the problem.
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Sunday, July 28th, 2019 AT 6:05 PM (Merged)
Tiny
DOCFIXIT
  • MECHANIC
  • 18,828 POSTS
Hook up timing light remove air cleaner so you can shine timing light at fuel spray. Start up spray pattern should be 360 deg and fine spray. Any drips or loss of 360 pattern the injector pentil dirty from old gas deposites. Try some fuel system cleaner it may help. If not replace inj.
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Sunday, July 28th, 2019 AT 6:05 PM (Merged)
Tiny
KELLEYPITTMAN
  • MEMBER
  • 2 POSTS
  • 1999 CHEVROLET TAHOE
  • V8
  • 4WD
  • AUTOMATIC
  • 182,000 MILES
I just bought this Tahoe a week ago, it has done great until now. Now it smokes and the smoke smells like antifreeze and the engine idles rough. Please help with any advice possible.
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Sunday, July 28th, 2019 AT 6:06 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Coolant is leaking into the combustion chamber could mean headgasket, cracked head or block or intake leak-Get it block and pressure tested. Are you overheating?
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Sunday, July 28th, 2019 AT 6:06 PM (Merged)
Tiny
KELLEYPITTMAN
  • MEMBER
  • 2 POSTS
It only over heated once and never did get into the red are on the gauge. It basically just idles rough and smokes.
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Sunday, July 28th, 2019 AT 6:06 PM (Merged)

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