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Author Topic: 88 tbi suburban running rough  (Read 11429 times)

Offline greeneon_01

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88 tbi suburban running rough
« on: June 21, 2011, 09:50:58 pm »
hey guys i apologize if ive asked a question that has already been answered on here. a few weeks ago my suburban started running rough. its tbi setup with 700r4 trans. most of time it starts out running rough but ive noticed sometimes it runs ok then after driving awhile it acts like its got a miss or slightly out of time. it starts and idles fine. its never died or stumbled. just acts like its running rough. ive also noticed it puffs out alot of white smoke when its running rough. ive changed plugs,wires,cap,rotor,iac valve,tps sensor, pcv valve and fuel filter. ive checked the injectors and they seem like they have a decent pattern and spray good. ive sprayed wd40 and checked for leaks on the hoses and intake...none. could it be the vaccuum lines down by the trans? or map sensor or coil? could it be weak fuel pressure? or the pcm? it ran fine before so i dont think its a timing issue. and ive tripled checked my firing order on the plug wires. anybody got any ideas????
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Offline topp

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Re: 88 tbi suburban running rough
« Reply #1 on: June 22, 2011, 12:19:10 pm »
Does it happen when you are giving it throttle?
Does it happen only when the engine is cold or hot?
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'90 Suburban TBI 350

Offline greeneon_01

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Re: 88 tbi suburban running rough
« Reply #2 on: June 22, 2011, 05:50:19 pm »
it does it all the time..right from start up...or itll run fine for awhile...now that i think about it i noticed sometimes it starts running rough after ive layed into the throttle.
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Offline jaredts

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Re: 88 tbi suburban running rough
« Reply #3 on: June 22, 2011, 08:01:28 pm »
Are you losing coolant?  Checked the oil for milky garbage?  Checked the plugs for one that's different?
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Offline VileZambonie

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Re: 88 tbi suburban running rough
« Reply #4 on: June 22, 2011, 08:10:59 pm »
Make sure the EGR isn't open. Unplug the vacuum hose at the EGR valve and manually operate the diaphragm to eliminate that. Any codes?
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Offline greeneon_01

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Re: 88 tbi suburban running rough
« Reply #5 on: June 22, 2011, 10:02:47 pm »
how do you manually operate the egr valve? ive never had any lights come on but ill check the system and see if there are any stored codes.
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Offline greeneon_01

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Re: 88 tbi suburban running rough
« Reply #6 on: June 22, 2011, 10:05:28 pm »
it still has all the smog stuff on it too...could it be that? is it hard to remove all of it since i really dont need it?it still has all the smog stuff on it too...could it be that? is it hard to remove all of it since i really dont need it?
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Offline topp

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Re: 88 tbi suburban running rough
« Reply #7 on: June 23, 2011, 02:25:11 am »
The computer will freak if you just remove all the smog stuff......
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Offline Captkaos

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Re: 88 tbi suburban running rough
« Reply #8 on: June 23, 2011, 12:09:35 pm »
Quote from: greeneon_01 on June 22, 2011, 10:02:47 pm
how do you manually operate the egr valve?

Push up on the diaphram while the truck is running. 
Does the SES light come on when you start it?
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Offline greeneon_01

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Re: 88 tbi suburban running rough
« Reply #9 on: July 06, 2011, 11:40:50 am »
I'm not losing any coolant and the oil looks good and clean. All the plugs are the same. The ses light comes on breifly when I turn the key but goes off after its started.
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Offline topp

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Re: 88 tbi suburban running rough
« Reply #10 on: July 06, 2011, 11:50:07 am »
SES when first turning the key is normal.
Does the Exhaust smell rich?
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Offline greeneon_01

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Re: 88 tbi suburban running rough
« Reply #11 on: July 06, 2011, 05:39:46 pm »
Yes a little...I've noticed it smokes a lot more too...there's oil starting to collect on the tailpipe that never did before. It always smoked a little because of valve seals though so I don't know if that's related or not.
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Offline greeneon_01

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Re: 88 tbi suburban running rough
« Reply #12 on: August 01, 2011, 07:32:19 pm »
ok so i checked the codes and it pulled up a code 13 which i looked up and it said it was an open 02 sensor circuit. Being as everything else on the suburban is original im assuming the o2 sensor was too so i replaced it. but it still runs a little rough but doesnt cut out near as much. Ive noticed now that it runs better when its cold than after its warmed up. Also noticed i now have a hole in the muffler from a big rust hole that mysteriously popped up. (the muffler was in good shape no more than 6 months ago.) Could it be a vaccum leak or could the muffler be clogged up causing overheating in the muffler essentially making the hole...or being clogged causing the 02 sensor to read wrong? temperature seems to be reading ok so i dont think its a temp sensor. I'm not sure what else to do.....
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Offline 87suburban

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Re: 88 tbi suburban running rough
« Reply #13 on: August 02, 2011, 10:19:51 pm »
well pulled the oil pan off the 6.2 an noticed what looks like cracks but the outer bolts for the mains, which now has me somewhat a little discouraged. Anyway, to repair those cracks i'd have to take it to a machine shop to have that done wouldnt i? also, does anyone know of a machine shop around the wheeling/pittsburgh area that has experience in machining an rebuilding the 6.2?
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Offline Dr_Snooz

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Re: 88 tbi suburban running rough
« Reply #14 on: August 03, 2011, 11:49:10 pm »
Having too much oil in the crankcase can cause random puffs of smoke to come out the tailpipe. What do they smell like?
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