stalling 5.7 tbi

**BamBam** · 11-08-2009, 01:19 PM

Ok, guys...I joined this forum just for this problem. Recently bought a used 92 Sub with 5.7 TBI. It's my first GMC ever . It ran ok, but was in need of a tune-up. It would stall while sitting at idle in park or when in gear at a stop sign. It fires right back up very easily. I replaced the plugs, wires, cap, rotor, and air filter. Ran better, but still stalled. Did some research and replaced the Idle Air Control Valve...still stalls. Replaced the TPS next...same prob. Runs great as long as you're on the gas. I can take it down the highway with no problem at all. But if I sit and let it idle for more than about 10 seconds it dies. So I end up double-footing it to keep the rpm's at about 800 so it doesn't stall. Any insight? Thanks in advance!

**unplugged** · 11-08-2009, 05:04 PM

Intake manifold gasket leaks are common. Test for a vacuum leak.

**BamBam** · 11-13-2009, 09:40 PM

The adventure continues! In all, I have replaced the TPS, IAC, MAP sensor, EGR valve, all vacuum lines, fuel filter, plugs, wires, cap, rotor. I took the injectors off and cleaned the assembly, however you can't really clean the injectors, can you? I have yet to test for vacuum leak, but it did run better after I replaced the vacuum lines. Just thought maybe someone had some more insight now that I have replaced more parts.

**Chris Miller** · 11-15-2009, 10:23 PM

It's your intake manifold gasket. My mother had the exact same problem in her '94 suburban. The passenger side gasket was leaking at the #2 intake port.

**justcuz** · 11-17-2009, 10:19 PM

Does it lope or just stall. Put it in park and rev it up, look and see if the EGR valve is opening. This is the problem I am having. The EGR valve is opening with the vehicle in Park or neutral and is almost stalling when you stop and idles very lopey.

I have swapped out the EGR Valve, the EGR solenoid, the MAP sensor, the Temp sensor and adjusted the neutral safety switch. I swapped these out with known good parts from my 93 Suburban. Nothing worked.

It throws a code 32 (EGR) and when I plug the vacuum line or unplug the EGR solenoid it runs fine, minus the EGR function of course.

I looked at a wiring diagram and see that the EGR solenoid shares a curcuit with the O2 sensor. I wonder if the O2 sensor is bad?

**BamBam** · 12-16-2009, 12:03 PM

Ok, in addition to all the work done previously, I have replaced the intake manifold gasket...same problem still. The only other things I can think of are fuel pump (which I was told by previous owner was replaced), and possibly the coil???

**Project Reaper** · 12-16-2009, 12:31 PM

i dont know if you can get this tested but if your running rich as hell because of a bad O2 sensor it will lope and stall at idle. it might even throw, i would check those. if it was just a bad fuel pump then you could just check the fuel PSI lvl and that would tell you right there.

**BamBam** · 12-17-2009, 09:14 PM

Well I found another vacuum solenoid for the egr valve that I overlooked while replacing stuff so I'll replace that as well as the O2 sensor and the coolant temp sensor. That will be all of the solenoids and sensors on that engine. Other than that I have no idea and will probably take it to a GM Garage and let them diagnose it.

**k.daddy1** · 12-18-2009, 07:48 AM

Originally Posted by BamBam

Ok, in addition to all the work done previously, I have replaced the intake manifold gasket...same problem still. The only other things I can think of are fuel pump (which I was told by previous owner was replaced), and possibly the coil???

Replace your fuel pressure regulator. Your not keeping a constant pressure to the fuel system.

**BamBam** · 12-18-2009, 09:26 AM

Ok, I replaced the EGR Vacuum Solenoid and coolant temp sensor. No change. Everyone seems to have a different idea as to what it might be. In all I have changed:

1.) plugs
2.) wires
3.) cap & rotor
4.) fuel filter
5.) EGR valve
6.) EGR solenoid
7.) Idle Air Controller
8.) Throttle Position Sensor
9.) Map Sensor
10.) All vacuum lines
11.) Coolant Temp Sensor
12.) Intake Manifold Gasket

It throws no diagnostic codes other than 12, runs great down the highway, never fails to start on the coldest of days. When it's stone cold, it will idle fine for about 15 minutes till it warms up and then stalls. I'm at my wit's end and it's quickly turning into a money pit.