I'm getting desperate guys. 3 different forums and no help at all.

I have a 1989 W100, 318. It hesitates and stalls under heavy acceleration. Light acceleration is fine, then I can accelerate as hard as I want to. It will idle and run fine for about 15 minutes and then starts acting up. Pressure test shows 22 pounds with the regulator hose attached and not attached. Pinch the return line and truck dies instantly. Here is what I have done so far...
new fuel filter
new plugs/wires
new pressure regulator
new fuel supply line and return line
new throttle body gasket
throttle body has been cleaned
Please help me out here. I am thinking it is the fuel pump? Putting out too much fuel and flooding the TBI?

 

could be a bad injector... take air cleaner off and run it at idle and once it starts acting up look at the spray they make... should be a fine cone mist if its dribbling out theres your problem... does that have a tp sensor or no?

 

Thanks. I'll check the injector. Yes, it does have a TPS. Possible cause?

 

possible tps sensor,id check the voltage at idle position,if voltage is to high then its getting to much fuel when you snap the throttle,voltage to low then not enough,i had a stumble(backfire) problem with mine,i ended up drilling the holes out larger on the tps so i could adjust the idle voltage down,i went from .69 volts to.59 volts and it made one heck of a difference!!!youll need to do some research and find out what your parameters are for your engines tps..

 

Not getting a code for the TPS but the voltage check was wrong. Reference voltage is supposed to be 5 volts from the PCM and it was. Signal voltage is supposed to be .5 to 1.5 with the throttle closed and it was 5 volts. Didn't change when the throttle was opened.
I did get a code 35-idle control switch open or short. But could not find it in my Haynes manual?
Also got a code 25-idle air control motor circuits. But I can't find anything about that either.

 

you should be able to watch the signal voltage(middle wire,i think) move up without any hesitation as you crack the throttle open,key on engine off,if it doesnt then that might explain a lot,this could cause your IAC to act funny also,as its trying to keep the engine running...

 

If I replace the TPS will that fix the problem with the IAC or is it best to swap the both?

Fuel injector spray looks fine btw.

 

19.09 for a tps from rockauto.com and IAC valve is 19.37
id just replace both or just start with tps if you have limited funds

 

A - buy a FSM - factory service manual. Haines and Chiltons manuals are nearly worthless

B - you should only have 14.5 psi fuel pressure +- .5 psi If you really have 22 you could have issues with the return system or the fuel pressure regulator. There is a complete diagnostic procedure in the FSM.

C - Have you checked and set the timing per specifications?

 

Service manuals available here on CD for 36.29
http://www.autobooksbishko.com/searc...ry=Shop+Manual
Its wear i get all my manuals, and i have several of them.
Here they have it for 26.10 + 5.45 shipping on ebay
http://www.ebay.com/itm/1989-Dodge-Truck-Ramcharger-Service-Shop-Repair-Manual-CD-Engine-Drivetrain-OEM-/360469986230?pt=Motors_Manuals_Literature&vxp=mtr&hash=item53edaf7bb6#ht_1181wt_916
Dave