99 Suburban Idle Problem

Myles · 03-17-2005, 11:31 AM

I have a 99 Suburban with a 454 that has a rough idle problem. It is worse sometimes than others. It runs fine above idle. The following items have been
replaced: fuel injectors, pressure regulator, plugs, wires, cap, rotor, intake gasket, oxygen sensors and the throttle position sensor. Does anyone have any ideas? I have been to 2 different dealers and have had no luck.
Thanks

Skyjockey · 08-02-2005, 05:16 PM

Run a compression check. I have a 454 in my motorhome and it had the same problem. Seemed like it ran great at rpm's above an idle and it turned out it had a bad exhaust valve in the number 2 hole. Valve guide was worn bad enough that it seemed to settle out above idle, but idled rough and was worse in the winter.

Ford4x4Chik27 · 08-03-2005, 10:52 AM

How bout the fuel filter and pump?

72'CaminoKid · 08-05-2005, 10:24 PM

Hey, i have the smae car, excpet a 350, my dad has a 96 silverado, and we've recently been having similar problems, and we also replaced a lot of the same things you did, with no success...... today we cracked the case, it turned out to be that the cat convert. was clogged and no good. the way to test that, dependent on your capabailities, equipment, and exhaust setup, would be, if possible cut off the exhaust right before the cat's (like a few inches), and make sure there is a reasonable gap between the pipe comming out of the manifold and the rest of the exhaust (so that the majority of the exhaust isnt still goin through the cat). i'm assuming you have true duals back to the muffler, or even all the way out if you dont have stock exhaust, so you'll have to do this twice. after completing this, run your truck for a few minutes, driving it around, and see if the problem gets better ( obviously it will be VERY loud) if that solves the problem, just get your cat's replaced. you may want to weld back or clamp your pipes back together until you have the cat's replaced. also note, when cutting the pipes, dont use a torch or plasma cutter, (throws too much spark and molten metal to be near all that oil and gas) use a cutting wheel. if you cant do this, just completely unbolt the exhaust from both side of the block, make sure to pull out the donought gaskets, and try the same test...... this would be my best guess at the problem. since you say it mainly does it at idle, it could aslo be the ignition coils...... let me know if either of these solutions help, if ya need more detail, let me

03-17-2005, 11:31 AM	#1
Myles Junior Member Join Date: Mar 2005 Posts: 1	99 Suburban Idle Problem I have a 99 Suburban with a 454 that has a rough idle problem. It is worse sometimes than others. It runs fine above idle. The following items have been replaced: fuel injectors, pressure regulator, plugs, wires, cap, rotor, intake gasket, oxygen sensors and the throttle position sensor. Does anyone have any ideas? I have been to 2 different dealers and have had no luck. Thanks

08-03-2005, 10:52 AM	#3
Ford4x4Chik27 Senior Member Join Date: Sep 2004 Location: Sac-Town, Cali Posts: 1,585	How bout the fuel filter and pump? __________________ '93 Isuzu Amigo, Toyota Axles/Tcase/Drivelines, 35" MTR's '01 Pathfinder, making a huge effort to keep it stock, since it's my DD

08-05-2005, 10:24 PM	#4
72'CaminoKid Senior Member Join Date: Jun 2005 Posts: 2,268	99 suburabn problem, possible solution Hey, i have the smae car, excpet a 350, my dad has a 96 silverado, and we've recently been having similar problems, and we also replaced a lot of the same things you did, with no success...... today we cracked the case, it turned out to be that the cat convert. was clogged and no good. the way to test that, dependent on your capabailities, equipment, and exhaust setup, would be, if possible cut off the exhaust right before the cat's (like a few inches), and make sure there is a reasonable gap between the pipe comming out of the manifold and the rest of the exhaust (so that the majority of the exhaust isnt still goin through the cat). i'm assuming you have true duals back to the muffler, or even all the way out if you dont have stock exhaust, so you'll have to do this twice. after completing this, run your truck for a few minutes, driving it around, and see if the problem gets better ( obviously it will be VERY loud) if that solves the problem, just get your cat's replaced. you may want to weld back or clamp your pipes back together until you have the cat's replaced. also note, when cutting the pipes, dont use a torch or plasma cutter, (throws too much spark and molten metal to be near all that oil and gas) use a cutting wheel. if you cant do this, just completely unbolt the exhaust from both side of the block, make sure to pull out the donought gaskets, and try the same test...... this would be my best guess at the problem. since you say it mainly does it at idle, it could aslo be the ignition coils...... let me know if either of these solutions help, if ya need more detail, let me

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
problem with the Door open light	BTAY	Ford Truck Forum	4	03-30-2006 10:27 AM
Diesel problem	jgn	Dodge Truck Forum	2	06-01-2005 05:22 PM
fueling problem	Bob k	Ford Truck Forum	1	04-14-2005 04:02 AM
Biggest tires on a stock 93 Suburban	93 Burbon	Chevy Truck Forum	2	03-20-2005 09:35 AM
Problem starting	Keith23	Chevy Truck Forum	3	03-10-2005 09:43 PM

08-02-2005, 05:16 PM	#2
Skyjockey Junior Member Join Date: Aug 2005 Location: Farmersville, Texas Posts: 2	Run a compression check. I have a 454 in my motorhome and it had the same problem. Seemed like it ran great at rpm's above an idle and it turned out it had a bad exhaust valve in the number 2 hole. Valve guide was worn bad enough that it seemed to settle out above idle, but idled rough and was worse in the winter.