Fluctuating idle/acts as if starving for fuel..

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

AWick20

Newbie
Joined
May 3, 2016
Messages
8
Reaction score
2
Location
Michigan
Hello all,

New to the forum and I have exhausted all of the knowledge in my small brain so time for second opinions. I have a 1994 Chevy K1500 with the 4.3L TBI Z (123K miles).

I bought the truck for dirt cheap from a friend who did not want to put a new rear end in it, so i gladly took it off his hands and swapped the rearend. Anyways, about a week after this fix, the truck would begin to run rough after about 30 seconds and did not want to move anywhere. You'd press the gas and it would act like there was no fuel/pressure. You could wait about a minute and it would clear up and drive normal.

A few days pass and the truck is stuck acting in this funky manner. It will idle, bog down and then jet back up back and forth until it stalls out. If i sit on the gas at idle, for the most part it will run just fine. When you attempt to drive though the condition will take over and you won't get very far(same problems).

I work at a parts store and figured what the heck I'll replace some of the easy/likely to fail components because the truck is getting to be that age. To date I have replaced:

-EGR Valve
-MAP Sensor
-PCV, Spark Plugs, Wires
-Distributor+cap/rotor(the old one had a lot of vertical shaft play, about 1/8") the rotor button was being cut into by the cap
-Left hand side knock sensor
-Coolant Temp Sensor and Sender
-Fuel pump/tank/filter
-Most vacuum lines
-Throttle Position Sensor
-Idle Air Valve
-Fuel Pressure Regulator

I am sure I'm forgetting something, but that's the jist of it. Luckily, all of those parts only cost me about $300 and I can hope I have eliminated some future problems. I tested the coil and it checked out. I adjusted the timing after the distributor replacement, so I ruled that issue out. Fuel pressure is at a steady 12.5lbs as of today.

I am not sure what else to check or where to go from here. It makes me think that the PCM could be going bad, but wanted others thoughts on what I could test before I throw more parts at the rust bucket(but i still love her). Sorry this post was so long, but I wanted to include all the info I could. Thanks in advance!
 

1995z71

OBS Enthusiast
Joined
Feb 6, 2015
Messages
90
Reaction score
49
Location
Dallas, Tx
Try rebuilding the carb, there is a kit for about $30 bucks and the rebuild is simple. This worked for me when I had a similar issue.
 

AWick20

Newbie
Joined
May 3, 2016
Messages
8
Reaction score
2
Location
Michigan
Try rebuilding the carb, there is a kit for about $30 bucks and the rebuild is simple. This worked for me when I had a similar issue.

I'm guessing by carb you mean throttle body, but is it just a few gaskets to swap or are there actual hard parts in there to be replaced in this rebuild? Just curious.
 

1995z71

OBS Enthusiast
Joined
Feb 6, 2015
Messages
90
Reaction score
49
Location
Dallas, Tx

AWick20

Newbie
Joined
May 3, 2016
Messages
8
Reaction score
2
Location
Michigan

Smitty82

Newbie
Joined
Mar 30, 2016
Messages
41
Reaction score
6
Location
Houston
while your at it. I would replace the intake gaskets. if your not pulling enough vacuum it could cause issues on every thing that surrounds the intake. so replacing all the other intake components will do you no justice. might be your issue if the truck set for a while.
 

AWick20

Newbie
Joined
May 3, 2016
Messages
8
Reaction score
2
Location
Michigan
Well, after sitting around for a few days I got to thinking i should check o2 sensors for the heck of it. I have not seen a truck NOT run from a bad o2 sensor, but you learn something new everyday. I pulled out the sensor and you could hear the internals of the o2 shaking around. As soon as I pulled the sensor it ran better and a new one fixed all of my issues. I plugged the old one back in and the problem returned.

Like I said, I did not think an o2 sensor would actually make a vehicle undriveable. Just posting a reply in case someone else comes across a strange issue such as mine.
 
Top