Ran fine, next day runs like crap (V 6 vortec 4.3)


Asked by Jan 29, 2014 at 08:21 AM about the 1994 GMC Sierra 1500

Question type: Maintenance & Repair

Fuel tank was in the last quarter. Timing mark is jumping all over the place. Only keep it running
if I keep my foot on the peddle. Eyeballed the dist. at #1 position and vib damp mark seems to
be TDC. Pulled the plastic ring on  carb and the two fuel injectors seem to be putting out the
same & equal fuel skirt on both. Dist. is electronic. Computer comes back with all 12's.
Temp.50/60 nite,70/80 day. No sensor on timing mark guide. Dist.wires are correct order.
Seems like timing to me. Runs like timing jumped a tooth or plug wires are crossed. Is there a
fuse that would cause this or a sensor? Computer? Blocked exhaust?  Spark plugs go out that
fast? Electronic Dist. do you TDC from plug wire?  (What is extra line on vib damper.) Water in
fuel (Hard to believe) Thanks Pete

3 Answers


If you feather the gas pedal will it seem to run ok? If so it's probably the idle air control valve either dirty or faulty. Could also be the throttle position sensor.


Symptoms of an Idle air control valve not operating properly are loping idle(high then low), high idle, low idle or going dead at idle. If yours is doing any of these things and you can give it some gas and it will seem to run ok then I would check into either cleaning or replacing the idle air control valve.


Does not make any difference at what rpm you hold it, it till runs the same. Talking to a neighbor and he suggested a head gasket. So far I have replaced plugs, wires, cap and rotor. To me it still sounds like it is missing on at least one cylinder. A timing gun placed on all six wire shows that they are all firing. Also, idle sb about 600 rpm but your right, it is going dead at idle. sure hope neighbor is wrong about head gasket.

1 out of 1 people think this is helpful.

Your Answer

Add photo

Related Questions

Sierra 1500

Looking for a Used Sierra 1500 in your area?

CarGurus has 56,521 nationwide Sierra 1500 listings starting at $2,300.


Search GMC Sierra 1500 Questions

GMC Sierra 1500 Experts

#1 dragonflyoffshore
Reputation 4,390
#2 John Saffrahn
John Saffrahn
Reputation 3,080
#3 Glenn Clingenpeel
Glenn Clingenpeel
Reputation 2,690
View All

Related Models For Sale

Used Ford F-150"
3,253 Great Deals out of 217,198 listings starting at $1,000
Used Dodge Ram 1500"
525 Great Deals out of 13,942 listings starting at $995
Used Toyota Tacoma"
640 Great Deals out of 30,628 listings starting at $2,850
Used Chevrolet Tahoe"
1,147 Great Deals out of 36,615 listings starting at $1,995
Used GMC Yukon"
559 Great Deals out of 14,733 listings starting at $1,500
Used GMC Sierra 2500"
3 Great Deals out of 217 listings starting at $2,895
Used Chevrolet Camaro"
826 Great Deals out of 39,074 listings starting at $2,650

Used Cars For Sale

2017 GMC Sierra 1500 For Sale
19,438 listings starting at $20,851
2016 GMC Sierra 1500 For Sale
85 Great Deals out of 13,353 listings starting at $21,510
2015 GMC Sierra 1500 For Sale
189 Great Deals out of 4,739 listings starting at $15,995
2014 GMC Sierra 1500 For Sale
153 Great Deals out of 4,315 listings starting at $12,500
2013 GMC Sierra 1500 For Sale
91 Great Deals out of 2,663 listings starting at $12,400