91 Suburban Issues - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Jonboy · 03-08-2010, 11:11 AM

The mystery relay is the fuel pump relay. The wire colors are the same as the earlier TPS; I'll be finding out pretty quickly if is is a direct swap. I am putting a 91 engine in a 87 truck. I don't know if there is a seperate ESC module; it may be in the computer. You may also want to check your wiring to the knock sensor also.

JEM · 03-09-2010, 01:21 AM

Quote:

Originally Posted by Jonboy

The mystery relay is the fuel pump relay. The wire colors are the same as the earlier TPS; I'll be finding out pretty quickly if is is a direct swap. I am putting a 91 engine in a 87 truck. I don't know if there is a seperate ESC module; it may be in the computer. You may also want to check your wiring to the knock sensor also.

My '91 TBI 454 does not have a separate ESC module.

jbclassix · 03-09-2010, 12:09 PM

So I looked at a '90 Blazer with a 350/700R-4 and it was in the same location as the '95 Yukon with a 350/NV3500, so maybe it is not separate on 3/4T and 1T models... anyone?

jbclassix · 07-02-2010, 05:18 PM

Update on where I am at and what issues the truck is having now.

SES code 43- turned out that the computer was the wrong one for the truck. Replaced the computer and had no further issues with this code.

I was averaging 10.0mpg and running at 210-220 degrees F- rebuilt TBI unit, installed new o2 sensor, and installed 160deg t-stat. I am now averaging 13.3mpg. With light driving or hwy driving I would run at 160-180 degrees, but city driving or climbing a hill it would climb to 210-215 degrees. I found that the fan clutch was leaking fluid, so I borrowed the '02 fan and new clutch off my 95 Yukon... no change. This concerns me because my Yukon would do the SAME thing and just died about a week ago. I cant loose another engine at this point. Any thoughts?

03-08-2010, 11:11 AM	#1
Jonboy Slots go on anything! Join Date: May 2003 Location: Richardson, TX Posts: 5,957	Re: 91 Suburban Issues The mystery relay is the fuel pump relay. The wire colors are the same as the earlier TPS; I'll be finding out pretty quickly if is is a direct swap. I am putting a 91 engine in a 87 truck. I don't know if there is a seperate ESC module; it may be in the computer. You may also want to check your wiring to the knock sensor also. __________________ 1974 Jimmy- 5.3/4L80e/NP241

03-09-2010, 12:09 PM	#3
jbclassix Junk Yartist Join Date: Jul 2009 Location: Greeley, CO Posts: 2,203	Re: 91 Suburban Issues So I looked at a '90 Blazer with a 350/700R-4 and it was in the same location as the '95 Yukon with a 350/NV3500, so maybe it is not separate on 3/4T and 1T models... anyone?

07-02-2010, 05:18 PM	#4
jbclassix Junk Yartist Join Date: Jul 2009 Location: Greeley, CO Posts: 2,203	Re: 91 Suburban Issues Update on where I am at and what issues the truck is having now. SES code 43- turned out that the computer was the wrong one for the truck. Replaced the computer and had no further issues with this code. I was averaging 10.0mpg and running at 210-220 degrees F- rebuilt TBI unit, installed new o2 sensor, and installed 160deg t-stat. I am now averaging 13.3mpg. With light driving or hwy driving I would run at 160-180 degrees, but city driving or climbing a hill it would climb to 210-215 degrees. I found that the fan clutch was leaking fluid, so I borrowed the '02 fan and new clutch off my 95 Yukon... no change. This concerns me because my Yukon would do the SAME thing and just died about a week ago. I cant loose another engine at this point. Any thoughts?



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