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Username Post: idles perfectly, dies when throttle applied        (Topic#357995)
aero_nautical 
Contributor
Posts: 141

Loc: Arkansas
Reg: 09-12-10
09-09-19 10:51 AM - Post#2775153    

I have a 1993 Suburban K1500 5.7. It ran perfectly until sitting overnight Saturday night.

Beginning yesterday, it idles perfectly but when I add load on the driveline, like to drive away, it stumbles and dies. I can raise the engine in neutral and it does fine but dies under any load in gear.

I replaced the fuel filter, fixed a vacuum leak, but neither fixed the problem. I'm stumped.

Any ideas?



 
rockfangd 
"6th Year" Gold Supporting Member
Posts: 2735
rockfangd
Age: 33
Loc: Utica ny
Reg: 04-13-10
09-09-19 07:04 PM - Post#2775196    
    In response to aero_nautical

Have you checked fuel pressure?
How good does it rev in park? any stumble?
I am kind of leaning toward a TPS or low fuel pressure

Old School GM fan FOREVER


 
aero_nautical 
Contributor
Posts: 141

Loc: Arkansas
Reg: 09-12-10
09-09-19 07:54 PM - Post#2775202    
    In response to rockfangd

can easily rev to 4000 in park, could probably go higher but was afraid to try. When I changed the fuel filter I put a section of hose onto the pipe from the tank and ran it into a clear jug and watched when I turned the key on. It looked like a strong stream in term of pressure so I didn't measure it. I was actually looking for water, sediment, etc.

When it is cranking, before it starts, the tach gives some wild readings like bouncing back and forth from 0 to 6K. I'm wondering about the ignition module inside the distributor since that is where the tach gets its signal.

I was also wondering about the MAP sensor since that is one of the main items that the PCM uses to meter fuel.

I also believe there is a fuel pressure regulator in the throttle body.

I am tending to think it is either an ignition module or the MAP but I don't have an OBD1 scanner. It did knock when I tried to keep it running so it is getting lean from somewhere.



 
CowboyTrukr 
"8th Year" Silver Supporting Member
Posts: 4246
CowboyTrukr
Loc: Salt Lake City
Reg: 06-20-09
09-09-19 09:37 PM - Post#2775208    
    In response to aero_nautical

Don’t guess. Test. Fuel pressure needs to be at least 9, 10 is better.

ICM - parts store should be able to test it. Multiple times to get it hot.
TPS - back probe the leads. Should be ~ 0.45V at idle and about 4.5 at wide open. Do this key on engine off.

I don’t try to spend another man’s money, but when it comes to a TBI engine, a new distributor cures a lot of ails.

Greg

'95 K1500 Z71 EC Short Step 5.7L+0.040/NV3500
'00 Explorer XLT 4.0 V6 Auto
'94 K2500 5.7 NV4500 ECLB - SOLD
‘87 GMC S15 SCLB 4.3 Auto - SOLD

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


 
aero_nautical 
Contributor
Posts: 141

Loc: Arkansas
Reg: 09-12-10
09-10-19 05:47 AM - Post#2775220    
    In response to CowboyTrukr

Greg,

Is there a port to test the fuel pressure or do you have to put an adapter in the line?



 
CowboyTrukr 
"8th Year" Silver Supporting Member
Posts: 4246
CowboyTrukr
Loc: Salt Lake City
Reg: 06-20-09
09-10-19 09:29 AM - Post#2775250    
    In response to aero_nautical

Unfortunately, GM didn’t put one in. You’ll have to insert it in the supply line, either downstream of the filter or in the throttle body. If you elect to do it at the throttle body, you will have to unbolt the fuel line bracket that sits down to the right of the distributor. It’s sitting on one of the transmission bolts.

Greg

'95 K1500 Z71 EC Short Step 5.7L+0.040/NV3500
'00 Explorer XLT 4.0 V6 Auto
'94 K2500 5.7 NV4500 ECLB - SOLD
‘87 GMC S15 SCLB 4.3 Auto - SOLD

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


 
grumpyvette 
Senior Chevytalk Moderator -- Performance Subject Matter Expert --
Posts: 17384
grumpyvette
Age: 71
Loc: FLORIDA USA
Reg: 03-16-01
09-10-19 10:42 AM - Post#2775258    
    In response to CowboyTrukr

https://www.ebay.com/i/332802169903?chn=ps &nor...

http://garage.grumpysperformance.com/index.php?thr...

http://garage.grumpysperformance.com/index.php?thr...

deal in facts, don,t guess or assume anything,
and get a shop manual, pull trouble codes ,
check the fuel pressure, ignition advance and all the sensors



IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!


Edited by grumpyvette on 09-10-19 10:44 AM. Reason for edit: No reason given.

 
aero_nautical 
Contributor
Posts: 141

Loc: Arkansas
Reg: 09-12-10
09-10-19 02:17 PM - Post#2775272    
    In response to grumpyvette

Guys,

I had a lifetime guarantee on my previous distributor with ICM installed. On a chance I replaced it today with a new one (for free) and it runs like a top.

I sincerely thank all you gentlemen for you willingness to help us shade tree mechanics. You are a blessing fellas!



 
rockfangd 
"6th Year" Gold Supporting Member
Posts: 2735
rockfangd
Age: 33
Loc: Utica ny
Reg: 04-13-10
09-10-19 07:37 PM - Post#2775293    
    In response to aero_nautical

Excellent.
I still get surprised at how bad things get under that cap.
That was my next bet.
My truck has done similar but mine is a manual so in that aspect it is pretty different

Old School GM fan FOREVER


 
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