1988 Chevrolet Silverado Cutting out / flooding possibly

Tiny
OLDDRUM1B
  • MEMBER
  • 1988 CHEVROLET SILVERADO
  • 7.4L
  • V8
  • 2WD
  • AUTOMATIC
  • 60,000 MILES
Truck runs a little rough and then when under power will start cutting out running very rough. Hard to start last time or two. Drove to Neighbors (2 Miles) ran well then once out of their drive way on the way home ran very rough.

Codes No
3rd gen sw off
AC off
Air divert sol div
Air sw sol conv
Batt 13.8
BLM 129
BLM Enabled yes
Clear flood off
Coolant 195
Eng RPM 1150
ESC Counter 25-253
Exhaust O2 Rich-Lean
IAC Position 0
Loop status Closed
MAP 1.37
O2s mv 80-928
O2s crosscut 48-85
P/N switch P/N
Prom ID 5941
TCC Solenpid off
TPS Sensor 0.82
Veh Speed 0
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Wednesday, June 11th, 2014 AT 1:14 PM

17 Replies

Tiny
HMAC300
  • EXPERT
Check fuel pressure with a gauge, autoparts rent it. If tbi should be 9-13 psi. Also check under tbi unit for a blown gasket usually in the rear.
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Wednesday, June 11th, 2014 AT 1:17 PM
Tiny
OLDDRUM1B
  • MEMBER
It will be a day at least to get into town for gauge. Is there a fitting for gauge on gas line?
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Wednesday, June 11th, 2014 AT 1:37 PM
Tiny
HMAC300
  • EXPERT
I doubt it you'll probably have to get an adapter. Of course your could always LOOK it would be a Schrader valve
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Wednesday, June 11th, 2014 AT 1:52 PM
Tiny
OLDDRUM1B
  • MEMBER
Fuel pressure good and TBI gaskets new. Still acting up.
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Wednesday, June 11th, 2014 AT 9:13 PM
Tiny
HMAC300
  • EXPERT
Scan for codes and check vacuum at manifold if 15" or below suspect clogged converter then check compression
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Thursday, June 12th, 2014 AT 5:22 AM
Tiny
HMAC300
  • EXPERT
Also do your basic ignition checkes like adist cap wires plugs etc.
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Thursday, June 12th, 2014 AT 5:22 AM
Tiny
OLDDRUM1B
  • MEMBER
Good Vac and as you can see there are no codes. Its like a sensor going bad with TBI trying to choke out. Plug wires good and cap fairly new, maybe 8 months. What sensor might be intermittent that would cause it to choke out?
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Thursday, June 12th, 2014 AT 8:54 AM
Tiny
HMAC300
  • EXPERT
One other thing I forgot as it's been so long for me to even see one of these earlier model truck is to check the vacuum line going to map sensor. If it's soft replace it as it may be sucking together an d not letting the map work right. Also make sure the wires on top of tbi unit are making good contact as those could cause some of your problem as well. Other than that I'd really have to see this to fix it. Also if you can short the cylinders out and you find one that is missing then pull the valve cover off to see if it's a valve problem or bad cam
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Thursday, June 12th, 2014 AT 10:22 AM
Tiny
TY ANDERSON
  • EXPERT
I would inspect and test the igntion system (spark) first before anything else because it seems to be running just not well so I wouldn't suspect fuel at this time.
Pull spark plug out and make sure they're not worn or black & wet looking. Next check the resistance of each spark plug wire. For every foot of wire should be 1000ohms or 1.0kohms. Wiggle the spark plug wire while testing to check for any breaks in the wire. Next is the distributor cap and rotor. Inspect for any carbon trails where spark is leak or shorting to ground bypassing the spark plug.
These parts are fairly inexpensive to replace on GM products and are considered maintenance items.
It looks like you have a scanner to read the data the vehicle's computer is seeing. Can you provide the short term and long term fuel trims (abbv. LTFT & STFT). If not then the oxygen voltages (both driver side and pass side oxygen sensors if equipped with more than two).
Hope this helps and let me know what you find before you go spend money on tools.
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Thursday, June 12th, 2014 AT 1:53 PM
Tiny
OLDDRUM1B
  • MEMBER
Ty, my friend, thank you for the timely reply. What I have done today ts take the fuel pressure tester back and invest the refund on a set of wires, cap, coil, and rotor. Parts will be here in the next couple of days. Once installed I will get back with you on the progress that has been made.
Charlie
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Thursday, June 12th, 2014 AT 6:16 PM
Tiny
TY ANDERSON
  • EXPERT
Great. Sounds good. Talk to you soon.
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Thursday, June 12th, 2014 AT 8:53 PM
Tiny
OLDDRUM1B
  • MEMBER
Got wires, plugs, coil and cap on. Running better but still seems to act like choke is closed on startup. Once started has fast idle then slows to correct idle speed in around 45 seconds which is much better but startup is still not right.
Charlie
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Sunday, June 22nd, 2014 AT 3:45 PM
Tiny
OLDDRUM1B
  • MEMBER
Ty, did you get my last. Took vehicle out and when its up to speed you put your foot in it it wants to studder step and cough then picks up speed.
Charlie
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Monday, June 30th, 2014 AT 12:01 PM
Tiny
TY ANDERSON
  • EXPERT
Did you get a new rotor for the distributor also?
Have you checked timing?
When you asked for first question you provided some data from some sort of scan tool. Do you have access to the Long and Short term fuel trims (abbreviated LTFT & STFT) on that data list? This will help indicate whether or not there is a disruption in the air fuel mixture assuming the oxygen sensors are reading correctly.
If the timing is correct the next items are probably sensor related.
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Monday, June 30th, 2014 AT 10:45 PM
Tiny
OLDDRUM1B
  • MEMBER
No I do not. Just a cheap scan tool. Sorry I take so long. Was in farming accident and one hand, have to wait on son to come out, again sorry for delays.
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Tuesday, July 1st, 2014 AT 9:27 AM
Tiny
OLDDRUM1B
  • MEMBER
Yes new rotor
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Tuesday, July 1st, 2014 AT 9:30 AM
Tiny
TY ANDERSON
  • EXPERT
When you can explain what is happening on a cold start up or the issue your having on start up?
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Friday, July 4th, 2014 AT 3:07 PM

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