RE: runs rough even after tune up

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RE: runs rough even after tune up

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Chevrolet >> Chevy Trucks, Vans & SUV's >> Suburban >> RE: runs rough even after tune up

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RE: runs rough even after tune up - 2/7/2008 4:49:13 PM

aeropatr82

Posts: 14
Joined: 2/2/2008
Status: offline

Check out their website I think they test them as well. I don't think they mess with vortec though.

(in reply to fjdavid)

Post #: 11

RE: runs rough even after tune up - 2/11/2008 1:56:14 PM

fjdavid

Posts: 9
Joined: 1/15/2008
Status: offline

OK, here is a quick review of what I�ve done so far on my 99 Suburban K1500 (130,000 miles) 5.7 liter engine:

Replaced components: cap, rotor, spark plugs, plug wires, idle air control valve, and both O2 sensors after the catalytic converter.
Cleaned: EGR valve, new gasket
Cleaned: Ran Seafoam through the intake and gas tank

Issues:
Still have the rough idle and misfire when accelerating when the engine is cold
Rough idle is not bad when the engine is warm.
Misfire code on Cyl #3, Sometimes #4

Checks:
Fuel pressure is 62 psi when pump is running and engine off.
No vacuum leaks found

I�m not sure what to do next. Suggestions are to replace fuel injectors, fuel pump, EGR valve. Each of these items are looking at $100 - $300 each so I don�t want to just continue to swap out parts that aren�t fixing the problem. Any suggestions?

Thanks,Frank

(in reply to aeropatr82)

Post #: 12

RE: runs rough even after tune up - 2/12/2008 6:27:22 AM

loulblades

Posts: 44
Joined: 12/5/2007
Status: offline

I may have missed it in your posts but did you check compression?

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'08 Impala SS (black on black)
'96 Tahoe LT 4DR/4WD ( http://www.chevroletforum.com/m.asp?m=52358&mpage=16&key=)
'07 Lexus ES350
'66 Mustang Convertible
'03 Impala LS, silver, all options

(in reply to fjdavid)

Post #: 13

RE: runs rough even after tune up - 2/14/2008 3:33:09 PM

fjdavid

Posts: 9
Joined: 1/15/2008
Status: offline

No, I haven't done a compression test. But I'll do one this weekend and post the results. I know that there shouldn't be much of a variance between cylinder to cylinder but about psi what should they be?

Thanks,
Frank

(in reply to loulblades)

Post #: 14

RE: runs rough even after tune up - 2/15/2008 1:52:26 PM

loulblades

Posts: 44
Joined: 12/5/2007
Status: offline

I would say 100psi or better and note that highest to lowest reading is not more than about 20% apart.

_____________________________

'08 Impala SS (black on black)
'96 Tahoe LT 4DR/4WD ( http://www.chevroletforum.com/m.asp?m=52358&mpage=16&key=)
'07 Lexus ES350
'66 Mustang Convertible
'03 Impala LS, silver, all options

(in reply to fjdavid)

Post #: 15

RE: runs rough even after tune up - 2/25/2008 12:13:40 PM

flycast47

Posts: 6
Joined: 2/19/2008
Status: offline

Very similar symptoms with our '99 Suburban have been diagnosed as blocked catalytic converters. Failure codes indicated O2 sensor, EGR and misfire. The shop was able to run a back pressure test to confirm the cat's as the problem. You may also be able to test your vehicle by removing the O2 sensors temporarily and driving the vehicle that way. There will be noise but the open O2 sensor hole will relieve some of the pressure, if that is the problem. The cat's have not been replaced yet and I will post again to confirm the repair.

(in reply to fjdavid)

Post #: 16