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Username Post: 89 GMC TBI 350        (Topic#185983)
e3forever 
Newbie
Posts: 3

Age: 40
Loc: Oklahoma City
Reg: 03-30-08
03-30-08 03:04 PM - Post#1399976    

1989 GMC TBI 5.7L With new short block. It used to have a propane system on the old engine, I removed it when I installed the new one. Now it starts great but runs poorly. At idle it lopes and sometimes backfires though the throttlebody if the MAP sensor is unpluged it idles fine but runs really rice, while driving it has a extreme lack of power and falls on its face or surges bad. I have replaced the TPS, IAC, tried many used MAP sensors, and ESC modules. I got codes 33, 34,& 43.Someone PLEASE Help!



 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3923
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
03-30-08 03:42 PM - Post#1400002    
    In response to e3forever

I see it’s your first post. Welcome to the message board.


There is a wire that must be unplugged when you set the timing. If this is not done the timing will be wrong. Did you unplug the set timing connector when you set the timing?

Do you need instructions for the set timing wire?

If you did have the set timing wire unplugged and did not clear the trouble code there should be a code 42 also.

Check and see if vacuum is getting to the MAP sensor.

Make sure all the ground wires are connected that bolt down with the studs on the front of the intake. These are the ECM and ECM sensor grounds.


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.


 
nickmac 
Frequent Contributor
Posts: 1113
nickmac
Loc: Tennessee
Reg: 02-13-07
03-30-08 05:12 PM - Post#1400087    
    In response to Chevytech

Do you have the knock sensor hooked up. That is the code 43. It should be just in front of the starter on the block above the oil pan. There should be one wire going to it, I believe dark blue, but not sure on color.

Dan
'04 Chevy K1500 Silverado 5.3 4x4
'08 Ford Mustang GT 4.6


 
e3forever 
Newbie
Posts: 3

Age: 40
Loc: Oklahoma City
Reg: 03-30-08
04-01-08 02:56 PM - Post#1401746    
    In response to Chevytech

Yes, I had the wire for setting the timing unpluged while setting the timing and the MAP sensor is getting vacuum. There is also a loud hissing sound coming from the throttle body, is this normal? I know quite a bit about engines and I've never heard this before.



 
e3forever 
Newbie
Posts: 3

Age: 40
Loc: Oklahoma City
Reg: 03-30-08
04-01-08 02:58 PM - Post#1401748    
    In response to e3forever

My knock sensor wire is plugged up but I don't know if is working properly, is there any way to tell?



 
Randy_W 
None
Posts: 27804

Reg: 01-06-02
04-01-08 04:33 PM - Post#1401823    
    In response to e3forever

Hook up a timing light or anything that will give you a timing/dwell reading. Tap the engine with a hammer near the sensor, if the timing retards, it's working.

Randy

DON'T mess with Old Men, we didn't get old by being, STUPID!!!

"The veneer of civilization is very thin!" (Arlo)


 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3923
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
04-01-08 07:05 PM - Post#1401993    
    In response to e3forever

Did you have to swap the front pulley/harmonic balancer?

Did you use the old timing Tab/timing chain cover?


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.


 
someotherguy 
Senior Moderator
Posts: 29386
someotherguy
Loc: Texas
Reg: 08-01-03
04-02-08 03:40 AM - Post#1402130    
    In response to Randy_W

  • Randy_W Said:
Hook up a timing light or anything that will give you a timing/dwell reading. Tap the engine with a hammer near the sensor, if the timing retards, it's working.


* With the transmission (if automatic) in gear, and engine warmed up to the point it's gone into closed loop operation.

So in other words, get a helper you can really trust to put it in gear and hold the brake firmly while you rap on the passenger side exhaust manifold with the hammer.

If it's not in gear, the ECM ignores the knock sensor signal.

Richard

06 Silverado ISS / 06 Silverado SS / 06 300C SRT8


 
Randy_W 
None
Posts: 27804

Reg: 01-06-02
04-02-08 03:43 AM - Post#1402133    
    In response to someotherguy

Richard is correct, I forgot that part!

Randy

DON'T mess with Old Men, we didn't get old by being, STUPID!!!

"The veneer of civilization is very thin!" (Arlo)


 
freddiefribbs 
Forum Newbie
Posts: 1

Reg: 10-23-12
10-23-12 05:06 PM - Post#2282477    
    In response to nickmac

what was wrong with this truck i would really like to know



 
tardisguy 
Contributor
Posts: 181
tardisguy
Age: 36
Loc: San Antonio, TX
Reg: 09-15-10
10-23-12 08:01 PM - Post#2282525    
    In response to freddiefribbs

kinda sound like what my truck was doing. the fuel pressure was low so the IAC was staying open making the sucking sound at the throttle body and making the truck surge and fall on its face. There is a rubber hose between the fuel pump outlet and the fuel outlet in the fuel tank. if that hose gets old and brittle from time and fuel soak it will split so most of the fuel the pump is moving will just shoot back into the tank through the split hose. the truck will start fine but under a load the engine starves for fuel.

Andrew
91 Chevy C1500 ext cab, TBI 350, NV4500, 2in suspension lift. (DD)
2012 Mitsu Outlander Sport (DD#2)



 
Bill K.b 
Senior Member
Posts: 4517

Loc: upstate NY
Reg: 10-24-05
10-24-12 04:12 AM - Post#2282579    
    In response to tardisguy

Hiss could be a vaccuum leak, too.

Those who can, do. Those who can't, criticize it on the internet.

Driving 2002 Express 2500
2002 Express 2500 extended
1988 G20 conversion
1993 GMC 3500 dually

Plus cars for swap and sale
& yes, I once tried a frame swap on a 51 Chevy.


 
patgizz 
Member #76
Posts: 8594
patgizz
Loc: Cleveland, OH
Reg: 01-30-00
10-24-12 05:28 AM - Post#2282608    
    In response to Bill K.b

holy zombie thread batman.



 
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