98' SUB stumbling at mid-RPM's - Off-Road Forums & Discussion Groups
GM Standard IFS Trucks & SUV's All discussion of full sized IFS Trucks, SUV's to include Suburban

Reply
 
LinkBack Thread Tools Display Modes
post #1 of (permalink) Old 02-17-2005, 05:22 PM Thread Starter
 
Join Date: Jan 2005
Posts: 502
Thanks: 0
Thanked 0 Times in 0 Posts
 
98\' SUB stumbling at mid-RPM\'s

Ok here is my dilemma....

My 98' Suburban with 350 has a nagging "stumble" at about 1500-2000 RPM's while accelerating. I have done tons of stuff to this thing in the last 6 or 8 months and it is not better.....here is a list of the new stuff-

Intake gasket
Plugs-wires-cap-rotor
O2 sensor (one by the manifold)
EGR valve
belt-hoses-flush antifreeze
air filter



It is driving me nuts....anyone have any ideas?

Cosmo
Cosmo is offline  
Sponsored Links
Advertisement
 
post #2 of (permalink) Old 02-17-2005, 08:18 PM
SnowKing85
Guest
 
Posts: n/a
Re: 98\' SUB stumbling at mid-RPM\'s

I had the same problem. I would put in a new fuel pump and filter.
post #3 of (permalink) Old 02-18-2005, 11:55 AM
Moderator
 
Shorts's Avatar
 
Join Date: Oct 1999
Location: Texas
Posts: 6,137
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: 98\' SUB stumbling at mid-RPM\'s

Check the fuel filter and pump. Check the timing.
Shorts is offline  
Sponsored Links
Advertisement
 
post #4 of (permalink) Old 02-18-2005, 11:38 PM Thread Starter
 
Join Date: Jan 2005
Posts: 502
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: 98\' SUB stumbling at mid-RPM\'s

Turns out to be a sporadic misfire on cylinder 6.....shop can't get it to duplicate now....just my luck [img]images/graemlins/wall.gif[/img]
Cosmo is offline  
post #5 of (permalink) Old 02-19-2005, 09:54 PM
Journeyman
 
Griasev's Avatar
 
Join Date: May 2004
Location: Midland, MI
Posts: 168
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: 98\' SUB stumbling at mid-RPM\'s

Not trying to 'steal' your post but, I too have the same problem, except that mine's between 800-1500 RPM. I have virtually no excelleration, and dies on me inconsitenly while driving. I've replaced the cap, rotor, plugs, O2 sensor, EGR valve and have re-timed it. Also my Computer spits out codes for lean exhaust, low fuel pump relay voltage, and the EGR valve. Should I be checking the same things as Cosmo? Thanks.
Griasev is offline  
post #6 of (permalink) Old 02-19-2005, 11:13 PM
ron3520
Guest
 
Posts: n/a
Re: 98\' SUB stumbling at mid-RPM\'s

Why not change the #6 injector? It's worth a try. About a $60.00 try.
post #7 of (permalink) Old 02-20-2005, 10:26 AM Thread Starter
 
Join Date: Jan 2005
Posts: 502
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: 98\' SUB stumbling at mid-RPM\'s

Yours does sound like a classic EGR valve problem....maybe all clogged up. How long since you changed it?

Lean exhaust.....hmmmm....I wonder if you have bad carbon build up in your intake. I have a hunch that is part of my problem, except it doesn't jive that I only have an issue with one cylinder (although I may have 2 issues)....I know when I did the intake gasket on mine there was LOADS of carbon buildup and mine is a 98....so it stands to reason that yours is even worse on an older rig.

I am also going to check my throttle position sensor....they will give you goofy acceleration when they go bad. It is basically a sliding scale that varies voltage as your throttle input changes. Sometimes a particular spot on the slide goes bad and you end up with hesitations, etc....prolly not going to be my problem but can't hurt to look.
Cosmo is offline  
post #8 of (permalink) Old 02-20-2005, 12:00 PM
Journeyman
 
Griasev's Avatar
 
Join Date: May 2004
Location: Midland, MI
Posts: 168
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: 98\' SUB stumbling at mid-RPM\'s

Uh, I don't have a #6 injector. They didn't offer MPFI, '87-'95 were the first and las years for TBI.

Well I did the EGR valve about 3 weeks ago. Also About 5 or 6 weeks ago I sprayed some Valvoline TBI cleaner in the intake and that's when it started running like ****. That and I know for sure this motor [yes it is a used '95 out of a G2500, and yes I swapped all of the sensors] always had cheap gas put in it, and nothing good. I usually run Shell Mid-grade. Also just as I encountered this problem my tach will no longer go above or let the motor get above 2500 RPM. Thanks.
Griasev is offline  
post #9 of (permalink) Old 02-20-2005, 12:21 PM Thread Starter
 
Join Date: Jan 2005
Posts: 502
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: 98\' SUB stumbling at mid-RPM\'s

I think he meant my injector....since my #6 cylinder is the one misfiring.

Guess it isn't the EGR then....brand spankin' new....

Sounds like you jarred loose some gunk in there with that cleaner...try a "mexican tuneup"..... [img]images/graemlins/chairfall.gif[/img] maybe it'll cough up what you jarred loose. For info on how to do it....go to the Suzuki/Geo forum and do a search.
Cosmo is offline  
post #10 of (permalink) Old 02-21-2005, 04:18 PM Thread Starter
 
Join Date: Jan 2005
Posts: 502
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: 98\' SUB stumbling at mid-RPM\'s

Yesterday morning I hopped in the old girl and drove her and it was running terrible....while I was out I picked up a throttle position sensor and slapped that on....this morning it seemed to run fine. So....I am keeping my fingers crossed....hopefully that did it....I'll keep you posted.

Might be a good thing to put on your truck. The part is $25 or $30 at the parts store. Doesn't really jive with your symptoms but even if it doesn't cure your problem it prolly wouldn't hurt to replace anyway.
Cosmo is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Off-Road Forums & Discussion Groups forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome