Engine Surging

[Deep]

Have a 1987 Eddie Bauer with a 302 that is fuel injected. I have replaced the TPS and set it using a multimeter, replaced the IAC and have replaced my external fuel pump. I have new wires, plugs and distributor. Fuel pressure regulator set and checked......but I still have a problem with my bronco wanting to surge and this is an intermittent problem. Starts fine and idle ups okay after the idler stabilizes the engine rpms begin surging and sometimes the engine dies. During driving, if engine begins to surge, I can get it to stop if I accelerate or sometimes if I slow down. Not sure what direction to take next. The bronco has been parked for about 6 months with a full tank of gas....is it possible that the gas is bad? Open to input and suggestions. Last thing, I did check and replace the coil and I run a Jacobs Ignition with a C4 coil.

 

[BroncoJoe19]

Well the way broncos burn gas, you won't have a bad tank of gas for long eh?

Surging is usually IAC, TPS or vacuum leak(s)

Could be MAP.

Why not give it a good going over for vacuum leaks.

AND THEN pull DTCs Diagnostic trouble codes.

BTW... you may want to check the wireing connection to the TPS, and make sure that you have 5 volts there from the PCM.

Checking for vacuum leaks.

Some of the sensors and some of the actuators either read the amount of vacuum, or use vacuum to move controls, therefore it is important to the proper functioning of the engine that your vacuum system is fully intact. Otherwise one may get codes falsely indicating that there is a problem with a controller/actuator, or a sensor when in reality it is caused by a lack of vacuum.

Look at your rubber vacuum hoses (they are about 1/4 - 3/8 inches in diameter, if they are dry rotted or cracked, replace them. IF they slip on/off of their connectors too easily, they may have stretched out a little bit, cut the ends off, and put them back on.

You may listen for a leak. Sometimes using a cut off piece of garden hose is a good aid to listen with. Sometimes a cardboard tube (like from gift wrapping paper) is helpful. Just remember that whenever you stick your head inside a running engine compartment, that you are not wearing any loose clothing or jewelry that can get caught.

Another suggestion is to use a spray can of carb cleaner and spray around the bottom of the intake manifold, and the base of the throttle body assembly. IF there is a leak, you should hear a change in your engine.

Keep a fire extinguisher handy, or use water instead of carb cleaner (it works, but not as well.) Be aware that if you use water and the wires get wet and it runs worse... your wires may be bad, and the water is allowing them to arc instead of jump the gap of the spark plug.

Another suggestion is: to take a propane torch, turn it on (but don't light it) and move it over the vacuum hoses and connections. The engine RPM's will increase if there is a leak and the propane gets sucked in.

Be sure to check the PCV valve, hose and grommet !

 

[BroncoJoe19]

Here you go... How to pull codes in your driveway for free.

http://broncozone.com/forums/index.php?s=&...ost&p=74587

 

[Deep]

Will look over the vacuum system again, I have replaced the MAP Sensor and still no change. Will check for the 5 volts tomorrow and will check the codes, thanks for your suggestions; I will let you know how it turns out.

Well the way broncos burn gas, you won't have a bad tank of gas for long eh?
Surging is usually IAC, TPS or vacuum leak(s)

Could be MAP.

Why not give it a good going over for vacuum leaks.

AND THEN pull DTCs Diagnostic trouble codes.

BTW... you may want to check the wireing connection to the TPS, and make sure that you have 5 volts there from the PCM.

Checking for vacuum leaks.

Some of the sensors and some of the actuators either read the amount of vacuum, or use vacuum to move controls, therefore it is important to the proper functioning of the engine that your vacuum system is fully intact. Otherwise one may get codes falsely indicating that there is a problem with a controller/actuator, or a sensor when in reality it is caused by a lack of vacuum.

Look at your rubber vacuum hoses (they are about 1/4 - 3/8 inches in diameter, if they are dry rotted or cracked, replace them. IF they slip on/off of their connectors too easily, they may have stretched out a little bit, cut the ends off, and put them back on.

You may listen for a leak. Sometimes using a cut off piece of garden hose is a good aid to listen with. Sometimes a cardboard tube (like from gift wrapping paper) is helpful. Just remember that whenever you stick your head inside a running engine compartment, that you are not wearing any loose clothing or jewelry that can get caught.

Another suggestion is to use a spray can of carb cleaner and spray around the bottom of the intake manifold, and the base of the throttle body assembly. IF there is a leak, you should hear a change in your engine.

Keep a fire extinguisher handy, or use water instead of carb cleaner (it works, but not as well.) Be aware that if you use water and the wires get wet and it runs worse... your wires may be bad, and the water is allowing them to arc instead of jump the gap of the spark plug.

Another suggestion is: to take a propane torch, turn it on (but don't light it) and move it over the vacuum hoses and connections. The engine RPM's will increase if there is a leak and the propane gets sucked in.

Be sure to check the PCV valve, hose and grommet !