Q: Missing and popping under heavy acceleration.

asked by on

I have a 1996 Dodge ram 1500 with a 5.2 318. It is missing or popping when I floor it. I just replaced the engine and tranmission with freshly rebuilt ones from a local shop. The plugs and wires are new. The only thing i can think of is the fuel sync from the distributor is slightly off from taking it out. Any ideas? I can not drive over 80 or even pass someone without it popping and missing. I know the intake plenum gaskets go bad on this year model but it was replaced when I did the engine swap. I'm just lost. No obdII codes are illuminated.

My car has 2000 miles.
My car has an automatic transmission.

Popping back through the intake, along with misfires, is a sign that the engine is running lean (not enough fuel). Here are a few things to check:

  • Check the fuel pressure: There is usually a port on the fuel rail. The pressure should be 45 to 54 psi.

  • If the fuel pressure is low: Replace the fuel pump and filter.

  • If the fuel pressure is high, replace the fuel pressure regulator on top of the fuel tank.

  • If you have access to a scan tool with data, you can verify if it is running lean on a test drive.

  • Look at the readings from the upstream O2 sensors, B1 S1, B2 S1.

  • Look at the readings when at full throttle and the engine is popping.

  • Lean is 0.100 and rich is 0.900. These are rough numbers, it could be anywhere in between. This step is optional, but I like to see verification before I move on.

I wouldn’t worry about the distributor right now. It does not control ignition timing like on older vehicles. It is used as a camshaft position sensor. It would set a code if you were too far off.

There are two sensors that control most of the fuel delivery: TPS (throttle position sensor) and MAP (manifold absolute pressure) sensor. You can test with a multi-meter if you don’t have a scan tool. A lab scope, however, is the best tool for measuring the full range of the sensor, but in this case, WOT (wide open throttle) is the only reading we are interested in.

Both sensors have 3 wires. 5 volts, sensor reading, and ground. The sensor reading wire is in the middle on both. With the key on and engine off, measure the voltage on the middle wire with the sensor connected. This is call back-probing. TPS at idle should be around 0.5 volts, at WOT it should be at least 3.5 volts. Do the same with the MAP. With the engine off, the middle wire should be at least 3.5 volts.

If you still haven’t found the problem, there are some more possibilities. It could be clogged fuel injectors, a wiring issue, or a defective Engine Control Module (ECM). A qualified mechanic from YourMechanic would be happy to assist you with this; a diagnostic inspection of your misfire condition would be a good place to start.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Missing and popping under heavy acceleration.

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Misfires at high speed on a high way

Hello there, a few common faults will cause your 2004 BMW 540i to have a misfire on acceleration. Without knowing what code the engine is storing I can only offer general advice. Likely causes for the car to misfire like...

Q: Engine came back on after getting spark plugs and wires replaced.

Hello. If there are no physical symptoms, it will probably be necessary to rescan the computer and pull the fault codes. A Check Engine Light can literally signal any of hundreds of possible problems. The codes will at least give...

Q: Driver seat loose / moves slightly on acceleration and stopping.

Hi and thanks for contacting YourMechanic. The driver seat has a gear track that the seat rides on and allows the seat to move forwards and backwards. The gears are probably worn and need to be replaced. As for the...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.