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Username Post: 1993 suburban 2500 454        (Topic#365812)
Rusde1974 
Newbie
Posts: 7

Reg: 07-15-21
07-15-21 06:01 PM - Post#2823271    

Start it up idles like has a huge cam in it if it idles at all. To get going have to lightly lightly give it gas and maybe it will go. Once going down highway it will smoothen out but if u stop for more than a few seconds the idle will drop and idle like a cam in it again. And if u shut it off it does it all over again. Also going down interstate all of a sudden itfeels like u tapped the brakes and then the service engine soon light will come on and if I pump it slowly 4 or 5 times it will all of a sudden jetk forward and light will go off and it will spit sputter for a cpl seconds then smooth out again. Ive replaced MAF sensor the IAC and the throttle position sensor and fuel filter and even cut off muffler... New plugs and wires also. Any help be much appreciated im ready to see if tnt will fix it lol



Edited by Rusde1974 on 07-15-21 06:04 PM. Reason for edit: No reason given.

 
CowboyTrukr 
"10th Year" Silver Supporting Member
Posts: 4678
CowboyTrukr
Loc: Salt Lake City
Reg: 06-20-09
07-15-21 10:16 PM - Post#2823290    
    In response to Rusde1974

Howdy and welcome!

Have you pulled the trouble codes?

Also, what’s your fuel pressure?



Greg

‘01 Silverado 2500HD 8.1/Allison 1000 Xcab/LB
'00 Explorer XLT 4.0 SOHC V6 Auto
'95 K1500 Z71 EC Short Step 5.7L+0.040/NV3500 SOLD

"The only thing necessary for evil to triumph is for good men to do nothing" Sir Edmund Burke


 
Rusde1974 
Newbie
Posts: 7

Reg: 07-15-21
07-15-21 10:50 PM - Post#2823297    
    In response to CowboyTrukr

I did the jumper wire thing and it just keeps flashing the number 12 and im not sure on the fuel pressure dont have the tool to check it



 
CowboyTrukr 
"10th Year" Silver Supporting Member
Posts: 4678
CowboyTrukr
Loc: Salt Lake City
Reg: 06-20-09
07-16-21 06:40 AM - Post#2823307    
    In response to Rusde1974

Ok. No codes is good and bad.

If you can get to a chain parts store to get the TBI fuel test kit on loan, I’d get a test on the fuel pump.

Just a clarifying question: You replaced the manifold absolute pressure module and not the MAF, right?

Greg

‘01 Silverado 2500HD 8.1/Allison 1000 Xcab/LB
'00 Explorer XLT 4.0 SOHC V6 Auto
'95 K1500 Z71 EC Short Step 5.7L+0.040/NV3500 SOLD

"The only thing necessary for evil to triumph is for good men to do nothing" Sir Edmund Burke


 
Rusde1974 
Newbie
Posts: 7

Reg: 07-15-21
07-16-21 05:51 PM - Post#2823340    
    In response to CowboyTrukr

Yes I replaced the MAP sensor I apologize if I said MAF cuz it apparently doesnt have one of those correct?



 
CowboyTrukr 
"10th Year" Silver Supporting Member
Posts: 4678
CowboyTrukr
Loc: Salt Lake City
Reg: 06-20-09
07-17-21 12:38 PM - Post#2823377    
    In response to Rusde1974

That’s correct. The MAF came with the Vortec L31 engine in 1996.

Greg

‘01 Silverado 2500HD 8.1/Allison 1000 Xcab/LB
'00 Explorer XLT 4.0 SOHC V6 Auto
'95 K1500 Z71 EC Short Step 5.7L+0.040/NV3500 SOLD

"The only thing necessary for evil to triumph is for good men to do nothing" Sir Edmund Burke


 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3956
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
07-17-21 06:13 PM - Post#2823392    
    In response to Rusde1974

  • Rusde1974 Said:
I did the jumper wire thing and it just keeps flashing the number 12 and im not sure on the fuel pressure dont have the tool to check it



It will flash out code 12 three times before it moves on to the next code.

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
Rusde1974 
Newbie
Posts: 7

Reg: 07-15-21
07-19-21 09:39 PM - Post#2823540    
    In response to Chevytech

Yea I know but thats all it flashes is 12 over n over



 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3956
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
07-20-21 04:56 AM - Post#2823552    
    In response to Rusde1974

It sounds like it is running to rich. Test the coolant temp sensor that is used to determine how much fuel to inject.

Specifications are the same for small block and big block engines.

Specifications in this thread:
https://www.chevytalk.org/fusionbb/showtopic.php?t...

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
Rusde1974 
Newbie
Posts: 7

Reg: 07-15-21
07-22-21 07:47 PM - Post#2823730    
    In response to Chevytech

How can u test them? Sorry im an idiot when it comes to that stuff



 
CowboyTrukr 
"10th Year" Silver Supporting Member
Posts: 4678
CowboyTrukr
Loc: Salt Lake City
Reg: 06-20-09
07-22-21 09:49 PM - Post#2823733    
    In response to Rusde1974

Do you have access to a volt meter?

Greg

‘01 Silverado 2500HD 8.1/Allison 1000 Xcab/LB
'00 Explorer XLT 4.0 SOHC V6 Auto
'95 K1500 Z71 EC Short Step 5.7L+0.040/NV3500 SOLD

"The only thing necessary for evil to triumph is for good men to do nothing" Sir Edmund Burke


 
Rusde1974 
Newbie
Posts: 7

Reg: 07-15-21
07-30-21 03:01 PM - Post#2824176    
    In response to CowboyTrukr

Yes but not really proficient in using them? Would a computer make it do what ots doin?



 
udidwht 
Poster
Posts: 50

Reg: 08-08-17
08-04-21 06:24 PM - Post#2824515    
    In response to Rusde1974

Sounds very much like a bad CTS (cooling temp sensor) When they fail they usually fail in the 'full rich' mode -40 degreesF.

Also and I don't say this lightly...

Only replace part/s with...AC Delco part/s. Anything else and it will not meet the calibrated standard that a Delco meets.

1994 Fleetwood Southwind Storm 28ft
P-30 chassis 7.4L 454 TBI 58,306 miles and counting....as of 05/28/19
VIN# 1GBJP37N4R3314754


 
Rusde1974 
Newbie
Posts: 7

Reg: 07-15-21
08-12-21 02:36 PM - Post#2825026    
    In response to udidwht

Changed coolant temp sensor and still does same thing



 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3956
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
08-13-21 05:02 AM - Post#2825065    
    In response to Rusde1974

Another possibility is an IAC (Idle Air Control) issue.

The engine may be “loading up” if the the system has lost control of the idle.

NOTE: The IAC is different for big blocks (your 454).

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
Sabino 
Member
Posts: 167

Reg: 07-16-05
08-13-21 07:49 AM - Post#2825074    
    In response to Rusde1974

I’d check fuel pressure as suggested above

65 Belair 350
68 Camaro 327
93 Suburban 5.7L TBI


 
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