1992 Roadmaster engine troubles.

Hey there everyone, My fathers roadie has been giving him hell recently not wanting to run. He says the car starts and runs, But wont take throttle. And will die at idle after trying to give it throttle. The fuel pressure is 12psi.

He has replaced the Ignition module, Coil, EGR module(NOT VALVE), TPS, O2 sensor, And MAP sensor. And nothing. I was reading around the net and I think it is the FPR.... Anyone have any ideas? Thank's a bunch in advance.

I was reading around the net and I think it is the FPR.I think that the FPR is a good suggestion! Very common the older TBI motor. They are cheap and easy to replace!

He is on his way to pick up one right now.

Don’t get discouraged when you remove the old one and you see nothing wrong with it! They fail without any visible signs of failure! Strange, I know! :screwy:

That's is very good to know! Thanks.

Just got done putting in the new FPR and it did nothing. Anything else? I am thinking about just getting him to get rid of the money pit of a car.

I may be wrong here but is not the 92 RM equipped with a 350 Chevy port injected engine which will not run on 12 psi, pointing to the fuel pump.

It is a TBI 350, Not a TPI. The factory manual we have says 9-13psi and we have a little over 12.

Hmmm. I thought it was 11-13 on a TBI except for the 350s. I guess I was mistaken. I know the 350s had larger Maxi injectors.

Does fuel pressure maintain once the throttle is cracked? Are the injectors spraying a fine cone of atomized fuel, or just streaming/dribbling? It you keep the throttle closed but manually operate the lever on the TPS (pretty easy on a TBI), does the idle increase?

What is the base timing?

In 1992 the Roadmaster got a 5.7-liter V8 engine that developed 180 horsepower & 300 ft lb TQ. It is the same motor as the 350 Chevy Truck motor (LB5) TBI used in the 88-93 models. It has a distributor, not an optispark. Have you change the distributor cap & rotor? How about the fuel filter?

Have good fuel pressure, Put in a whole new dist today. We found it has intermittent spark on 1 and 2. What could it be? We think it has to do with the ESC.

Have you replaced the ingition wires? The ESC would affect all cylinders. BTW, you can have good fuel pressure without adequate flow. Have you changed the filter?

We changed the 2 wires that were intermittent and it didn't change anything, The fuel filter is new aswell. :banghead:

Also, Pressure maintains when you crack the throttle. The injectors are spraying a fine cone till you try and give it throttle then it sputters. And when you unplug the TPS the idle increases.

What is the voltage on the TPS blue wire with ignition switch on? Check the grey wire also.

Ok ignition in the on position, Engine not running the TPS wires read.

Blue 0v
Black 0v
Grey 5.0v

The Blue wire should measure .5-.65v. How did you check this, by probing the wire, or the terminal? I think you have found the problem if you are not getting voltage on the blue wire! Check it again and we will go from there.

We probed the TPS plug. The blue wire did read .0 something, He is going to check it again and give me the right number. Should we check the terminal to?

Just did it again and got.

Blue .021v
Black .018v
Grey 5.0v

I assume this is with the terminal connected to the TPS? If so, the TPS is faulty, or installed wrong!!
Grey wire should be: 5.0v
Blue wire should be: .5-.65v
Black is ground, and of course should be infinite.

BTW, the reason I suggest checking at the wire & terminal is to eliminate the possibility of a bad pin in the terminal. If you have 5.0v on the Grey wire, that means the ECM is sending the correct voltage to the TPS. The TPS varies the voltage back to the ECM on the blue wire based on throttle position. Closed throttle is where you should see .5+v on the blue wire. If you open the throttle, voltage should increase accordingly.