Engine stalling and surging
Thread Starter
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3rd Gear
Joined: May 2020
Posts: 3
Likes: 0
Engine stalling and surging
Engine starts and warms ups then begins to surge. When under load it hesitates and then stalls. When I get it to drive down the road it drives great, until I come to a stop then it will sometimes die. Gas mileage is atrocious.
The timing chain set, ignition coil, all spark plugs & wires, distributor cap & rotor, MAP sensor, TPS, and EGR vacuum regulator have been replaced with new parts.
I have 1 bad TAD/TAB vacuum regulator that I have not been able to find a replacement for at the local JY yet so the hose is golf tee'ed.
I have used the water hose stethoscope to search for vacuum leaks and found none.
Fuel pressure at schrader valve was 35 PSI running, it held at 35 PSI with KOEO for five minutes, when under load it still reads 35 PSI. When it is surging the pressure remains at 35 PSI. The only time it changed was when I tapped the accelerator and it began to bog down to 500 RPM the pressure went up to 37 PSI and stabilized there. So far the pressure looks normal. I was hoping to see it fluctuate during the surging or something so I could finally have a fix for this.
The codes I pulled are below.
KOEO
34 EVP voltage above closed limit
81 Air Management 2 (AM2/TAD) circuit failure
82 Air Management 1 (AM1/TAB) circuit failure
87 Primary fuel pump circuit failure
84 EGR Vacuum Regulator (EVR) circuit failure
KOER
42 System rich - Fuel control
87 XLT Lariat ext.cab short bed 2WD 5.0 EFI AOD 4R235/75R15XL 479kMiles. dual exhaust no cats. new IAC, TPS, MAP, Air tmp sensor, Ign solenoid, plugs, evp regulator, water pump, timing chain set. New fuel pump, fuel filter, and fuel pressure regulator due to running bad gas by PO.
The timing chain set, ignition coil, all spark plugs & wires, distributor cap & rotor, MAP sensor, TPS, and EGR vacuum regulator have been replaced with new parts.
I have 1 bad TAD/TAB vacuum regulator that I have not been able to find a replacement for at the local JY yet so the hose is golf tee'ed.
I have used the water hose stethoscope to search for vacuum leaks and found none.
Fuel pressure at schrader valve was 35 PSI running, it held at 35 PSI with KOEO for five minutes, when under load it still reads 35 PSI. When it is surging the pressure remains at 35 PSI. The only time it changed was when I tapped the accelerator and it began to bog down to 500 RPM the pressure went up to 37 PSI and stabilized there. So far the pressure looks normal. I was hoping to see it fluctuate during the surging or something so I could finally have a fix for this.
The codes I pulled are below.
KOEO
34 EVP voltage above closed limit
81 Air Management 2 (AM2/TAD) circuit failure
82 Air Management 1 (AM1/TAB) circuit failure
87 Primary fuel pump circuit failure
84 EGR Vacuum Regulator (EVR) circuit failure
KOER
42 System rich - Fuel control
87 XLT Lariat ext.cab short bed 2WD 5.0 EFI AOD 4R235/75R15XL 479kMiles. dual exhaust no cats. new IAC, TPS, MAP, Air tmp sensor, Ign solenoid, plugs, evp regulator, water pump, timing chain set. New fuel pump, fuel filter, and fuel pressure regulator due to running bad gas by PO.
Lead Driver
Joined: Feb 2002
Posts: 7,966
Likes: 595
From: Greater Austin, Texas
You mention a PO - did you just recently buy this truck? Has it been this way since you bought it?
The first thing I would look at is the EGR valve to see if it is coming on when it shouldn't be.
The first thing I would look at is the EGR valve to see if it is coming on when it shouldn't be.
Thread Starter
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3rd Gear
Joined: May 2020
Posts: 3
Likes: 0
Then replaced the external fuel pump, regulator, and filter along with the plugs, wires, distributor cap and rotor.
I purchased it from him and it had this problem. I could only get it home by two footing it to keep it above 1000 RPM's.
I took the EGR vacuum hose off while it was surging and there was no change, so I read on another post that you can place a piece of cardboard between the EGR and Intake to test if the EGR was feeding it. There was no change.
Mountain Pass
Joined: Mar 2019
Posts: 183
Likes: 7
From: MO
I thought FPR, but looks like you've already replaced it. If I were you, I'd open the ECU and visually inspect for leaky capacitors. They can cause erratic behavior. Mine did, I replaced it with a $75 Rockauto remanufactured unit and it solved my truck's bucking problem. Worth a look, doesn't cost anything to check it.
Thread Starter
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3rd Gear
Joined: May 2020
Posts: 3
Likes: 0
I removed the ECU to inspect it for damage when I had a bad link in the electrical harness and thought it was the ECU. It did not have any leaking capacitors or corrosion, it looked pretty new inside as well.
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