350 idle problems

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

jgarner87blazer

Junior Member
Joined
May 4, 2011
Posts
3
Reaction score
0
Location
missouri
First Name
John
Truck Year
87
Truck Model
K5
Engine Size
5.7 350
I have a 87 blazer with a 350 tbi motor. Im having surge problems at idle. I have replaced - O2,TPS, MAP, IAC, temp sensor and dont have any vac leaks.
Its runs pretty good after it warms up but the idle is high at that time. Its driving me crazy and Ive spend a lot of money trying to fix it. I need help. I have read everything on the internet and its the same stuff.
 

Swims350

Full Access Member
Joined
Jul 30, 2010
Posts
4,351
Reaction score
811
Location
Logan WV
First Name
Chris
Truck Year
1983
Truck Model
K10
Engine Size
none
check the egr?
 

89Suburban

Supporting Member
Supporting Member
Joined
Dec 7, 2010
Posts
24,450
Reaction score
5,606
Location
Southeast PA
First Name
Paw Paw
Truck Year
2007
Truck Model
Chevrolet Tahoe LT
Engine Size
5.3, 4WD
There are two temp sensors, you replaced the one on the intake manifold, right?
 

jgarner87blazer

Junior Member
Joined
May 4, 2011
Posts
3
Reaction score
0
Location
missouri
First Name
John
Truck Year
87
Truck Model
K5
Engine Size
5.7 350
yes i replaced the right sensor. the one in the intske. my mechsnic says the egr has nothing to do with the idle issue.
 

89Suburban

Supporting Member
Supporting Member
Joined
Dec 7, 2010
Posts
24,450
Reaction score
5,606
Location
Southeast PA
First Name
Paw Paw
Truck Year
2007
Truck Model
Chevrolet Tahoe LT
Engine Size
5.3, 4WD
yes i replaced the right sensor. the one in the intske. my mechsnic says the egr has nothing to do with the idle issue.
I guess if the EGR was sticking opn it would hardly idle, that would be right. Maybe the butterfly isn;t hittin the idle stop, did you try disconnecting the throttle cable and moving the throttle by hand an making sure it is hitting the idle stop?
 

HotRodPC

Administrator
Staff member
Admin
Joined
Aug 29, 2010
Posts
47,008
Reaction score
8,976
Location
OKC, OK
First Name
HotRod
Truck Year
85 K20 LWB
Truck Model
Silverado
Engine Size
454 - Turbo 400 - 3.73
yes i replaced the right sensor. the one in the intske. my mechsnic says the egr has nothing to do with the idle issue.

If you're mechanic tells you, EGR has nothing to do with idle issues, you need a new mechanic.

If an EGR valve gets corroded and dirty with carbon from the exhaust, and it can't close off all the way, then you have an internal vacuum leak. It has everything to do with idle quality.
 

Swims350

Full Access Member
Joined
Jul 30, 2010
Posts
4,351
Reaction score
811
Location
Logan WV
First Name
Chris
Truck Year
1983
Truck Model
K10
Engine Size
none
x a freakin million.

not to mention if you have a mechanic why would you be neededing to ask about it here? Or anywhere, if he's a mechanic he should be able to figure it out, period. if you're doing it yourself or question him, then by all means ask away.

I had a bad idle in my 88 and it was over the egr being bad. I blocked it off and just deal with the light coming on every now and then.

I hear even new ones have issues, I was told to only replace them with a gm, ac delco or delphi brand, NO OTHER!!!!!!!! They'll act up if you do.

A simple vacuum test will tell if it's leaking or not. Plus not asure on your 87 but my 88 has a vac. solenoid for egr.
 
Last edited:

HotRodPC

Administrator
Staff member
Admin
Joined
Aug 29, 2010
Posts
47,008
Reaction score
8,976
Location
OKC, OK
First Name
HotRod
Truck Year
85 K20 LWB
Truck Model
Silverado
Engine Size
454 - Turbo 400 - 3.73
There is 2 reasons to fire the mechanic. #1 he obvioulsy doesn't know what he's talking about, #2, you have GMSB now. FIRE THE MECHANIC !!!
 

89Suburban

Supporting Member
Supporting Member
Joined
Dec 7, 2010
Posts
24,450
Reaction score
5,606
Location
Southeast PA
First Name
Paw Paw
Truck Year
2007
Truck Model
Chevrolet Tahoe LT
Engine Size
5.3, 4WD
:popcorn:
 

Swims350

Full Access Member
Joined
Jul 30, 2010
Posts
4,351
Reaction score
811
Location
Logan WV
First Name
Chris
Truck Year
1983
Truck Model
K10
Engine Size
none
I would agree, I'm sure the guys on here could help you figure out what it is, or tell you what it is. Only thing we can't do is fix it for ya, but if somebody was close enough I bet they might lol.
 

bucket

Super Moderator
Staff member
Super Moderator
Joined
Aug 3, 2010
Posts
28,956
Reaction score
23,466
Location
Usually not in Ohio
First Name
Andy
Truck Year
'77, '78, '79, '84, '88
Truck Model
K5 thru K30
Engine Size
350-454
Agreed, EGR will cause idle issues. Check for slop in the throttle shaft of the TBI unit. If worn, it can cause intermittent vacuum leaks as well as a binding issue that keeps the throttle from fully closing.
 

jgarner87blazer

Junior Member
Joined
May 4, 2011
Posts
3
Reaction score
0
Location
missouri
First Name
John
Truck Year
87
Truck Model
K5
Engine Size
5.7 350
Ive tired everything but the egr. How can i block it off. Should I by-pass egr. How is that done?
 

89Suburban

Supporting Member
Supporting Member
Joined
Dec 7, 2010
Posts
24,450
Reaction score
5,606
Location
Southeast PA
First Name
Paw Paw
Truck Year
2007
Truck Model
Chevrolet Tahoe LT
Engine Size
5.3, 4WD
Ive tired everything but the egr. How can i block it off. Should I by-pass egr. How is that done?
Some guys here have done it, made a plate out of tin or something to stick under it.
 

Swims350

Full Access Member
Joined
Jul 30, 2010
Posts
4,351
Reaction score
811
Location
Logan WV
First Name
Chris
Truck Year
1983
Truck Model
K10
Engine Size
none
they sell them online and at the local auto parts stores, just ask for an egr block off plate, or I can find the part numbers for you. I think one is made by holley, or wieand and is 9007. You'll need a gasket too they don't come with the plate anymore. ebay has them and so does summit. if you have a hand vacuum pump you can test it and if it doesn't hold vac. it's junk.

One quick way is to just unhook it's vac. line and plug that line with a screw or bolt, or remove it from the carb and put a vac. cap on it. That may help some, but if the egr is carbon'd open and not shutting, it needs removed to fully know if it's the problem.
 

89Suburban

Supporting Member
Supporting Member
Joined
Dec 7, 2010
Posts
24,450
Reaction score
5,606
Location
Southeast PA
First Name
Paw Paw
Truck Year
2007
Truck Model
Chevrolet Tahoe LT
Engine Size
5.3, 4WD
they sell them online and at the local auto parts stores, just ask for an egr block off plate, or I can find the part numbers for you. I think one is made by holley, or wieand and is 9007. You'll need a gasket too they don't come with the plate anymore. ebay has them and so does summit. if you have a hand vacuum pump you can test it and if it doesn't hold vac. it's junk.

One quick way is to just unhook it's vac. line and plug that line with a screw or bolt, or remove it from the carb and put a vac. cap on it. That may help some, but if the egr is carbon'd open and not shutting, it needs removed to fully know if it's the problem.
Ok, so a local store should have it, cool. :High 5:
 

Forum statistics

Threads
41,851
Posts
903,515
Members
33,365
Latest member
rossivey
Top