Was driving awhile abck and the truck wouldnt go voer a certain speed dispite throttle pressure. She coasted and died.

My trucks got a 318 TBI under the hood that starts but runs like **** and wont idle right.

The plugs are showing lean, but they are all firing (to my knowledge).

I did an basic tune up (plugs, wires, cap, rotor, oil, intake) but she still idles like crap.

Replaced the fuel filter and still runs like crap.

Someone suggested the FPR. I found 4-5 in a local yard and am gonna swap them out.

Would a faulty FPR keep the truck from idling correctly?

The FPR is on the rear of the throttle body right? Connected by two hex bolts?

Let me know, going back to the yard tomorow.

Thanks!

 

No one has ANYTHING to contribute?!

 

Does your truck have an EGR valve? If so, try unpugging the vacuum line from the top of it ( It is located at the rear, passenger side of the intake manifold on my 93 magnum 318) If this works then there is a problem in your emissions system.

 

what year is this? You could have a bad fuel pump in the tank. The idle speed is controlled by a motor with a plunger on it right next to the throttle body...these do go bad. What is the idle speed?

 

It's a 1991 D150 TBI 318

The fuel pump is working fine, when it wouldnt start after a month of sitting I cycled it a few times so it was correctly primed and she rolled over. I dont think its the EGR... that wouldnt explain the rough idle... that'd just leach some HP and definatly wouldnt go form runngin smooth to being a POS...

As far as the idle speed, it varys. The idle surges before it dies, but sometimes for periods upto 30 seconds while in PARK she will idle close to normal.

 

FPR very rarely goes bad, I would start by replacing the Idle Speed Control Motor. Cheapest one is at www.rockauto.com under part# SA4T for $55 plus shipping.


If the EGR opens during idle you will get a poor idle and a possible stall.

What is the fuel pressure in PSI? Need to do a complete fuel pressure test to check the pump and fpr operation properly. Cycling the fuel pump on and off to pressurize the system will only cover up a bad pump or check valve in the pump.

What is the idle speed in RPM?


EGR PURPOSE
The Exhaust Gas Recirculation (EGR) valve routes exhaust gases from the exhaust manifold to the intake manifold during specified engine operating conditions.

OPERATION
When the EGR valve is opened (by back pressure modulated manifold vacuum), exhaust gasses are allowed to flow into the intake manifold. The exhaust gas then combines with the air/fuel mixture in the combustion chamber. Since there is less air/fuel mixture to burn in the combustion chamber during EGR operation, the temperature is reduced enough to limit formation of Oxides of nitrogen (NOx) . If too much exhaust gas enters, combustion will not occur. Because of this, very little exhaust gas is allowed to pass through the valve, especially at low engine speeds.


EGR Control System Test

NOTE:
EGR system must pass CONTROL SYSTEM TEST and GAS FLOW TEST to pass FUNCTIONAL TEST .

SYMPTOMS

A faulty EGR system can cause ignition ping, rough idle, engine stalling, sags or hesitation, and/or lack of performance. It is important that this system be free from leaks. Any hoses that are cracked or leaking should be replaced.

VISUAL INSPECTION


Check condition and routing of vacuum hoses. Refer to Vehicle Emission Control Information (VECI) label, (underhood).
Ensure all vacuum hoses and electrical wires are clear of exhaust manifold to prevent deterioration. Due to temperature, vacuum hoses should always be a minimum of three inches from exhaust manifold.
FUNCTIONAL TEST


Start engine and allow to reach normal operating temperature.
Allow engine to run at normal idle speed and set the parking brake.
Allow engine to idle in neutral, then quickly accelerate engine rpm to 2000 rpm.
Watch the stem of the EGR valve to see if there is movement. This movement can be seen by watching the groove on the valve stem.
Repeat the previous step several times to verify movement of the valve. Movement of the stem indicates that the control system is functioning properly, and the EGR gas flow test can now be performed.
If no movement of the valve stem is visible, refer to the DIAGNOSIS test procedure in this section.


EGR Gas Flow Test

NOTE:
EGR system must pass CONTROL SYSTEM TEST and GAS FLOW TEST to pass FUNCTIONAL TEST .

GAS FLOW TEST


Connect suitable tachometer to engine.
Disconnect vacuum hose from EGR valve and connect hand-operated vacuum pump to EGR vacuum port.
Start engine and allow to warm up to normal operating temperature.
Slowly apply vacuum to EGR vacuum port.
Engine rpm should drop as vacuum reaches 3 to 5 inches Hg vacuum, and should continue to drop as more vacuum is applied, engine may even stall. This drop in rpm means that EGR gas is flowing through the system.
Successful completion of this test and the control system test indicates a fully-operational EGR system.
If engine rpm does not drop when vacuum is applied to the EGR vacuum diaphragm, then a defective EGR valve or plugged EGR passage, or tube is indicated. The EGR valve, intake manifold passage, and tube assembly should be inspected and cleaned or replaced as needed. Refer to MAINTENANCE PROCEDURES for cleaning and inspection procedures for the EGR valve and passages.

 

i had my 93 d150 for about two months and then it started to run like crap. It would run ok during acceleration, but when I let off the throttle to slow down at lights, or gave it light throttle to leave a parking spot, it would stall. It would also have a surging idle that centered around 600 rpm. To fix it I just pulled the top vacuum line off of the EGR and plugged it off. It was an instant fix. Note that I live in Canada, and emissions dont matter.