hi all im kinda lost with this one. when i lightly press the throttle (like just open it about 1 or 2 % the engine picks up in rpm (1000 or so) then dips to 250 and keeps surging like this until it either stalls or i let off. it usually only takes a few seconds. this is kinda annoying while backing out of a parking space or trying to creep ahead at a stop sign if i just tap the throttle. its not the IAC. ive replaced that several months ago when it would stall letting off the throttle. i also cleaned the throttle body
and no vacuum leaks that i can tell. the tps is registering the throttle movement when this happens. closed throttle reads .65volts and it will read .68 or so when i crack open the throttle and that's when it starts surging again. also the o2 sensor reads rich when this is happening ( jumps between 800-1000mv. if i give it a slight bit more the rpms pick up (1000-1200) and runs smooth) and o2 bounces between 090-900mv. i let of ant the rpms drop straight to 5 or 600. the tps voltage at WOT is 3.4 volts.
i hope this info helps someone. is it possible its the map sensor? or tps? i hate throwing parts at it. i dont really have the money for it either.

the truck is a 94 ram 1500 4x with the 318. all regular maintainace / tune up parts have been done in the last year.

 

I would still suspect the TPS..... Does the voltage remain stable at small throttle openings if you hold it there?

 

okay so i dont know if this helps anyone or not. i just disabled the egr valve and it fixed it! i just removed the vacuum line and plugged it. now it doesn't surge anymore. it actually seems to have a bit more power taking off, all though i suppose that could be a bit of a placebo effect lol.
so does anyone know what would cause the EGR to do this? by the way the egr is also new. i replaced it when i did the intake plenum gasket and pan.
the next question is doesn't the egr help reduce ping / combustion temp ? if so what could i do to prevent it pinging if i leave the egr disabled? could i use a 180 t-sat vs the factory 195? also would running the autolite 3293's (1 heat range cooler) help? any input would be greatly appreciated!

 

@ heyyou i was think the tps for a while but the voltages seem normal. it registers every movement of the throttle and does so smoothly. maybe the overall voltage is low / high? also i checked the input reference voltage and its 5 volts as i believe it should be.

 

How is the egr valve controlled? Isn't there a solenoid somewhere that the PCM controls to open it??

 

@ heyyou. its electrically controlled by the pcm using a solenoid on the vacuum line. i checked the voltages on the solenoid its 0 at idle. when i open the throttle it briefly reads 13.8 same as batt voltage) then dropps to 0. i dont really want to hold the throttle open too long because im sure my neighbors dont really like listing to it lol

 

Does the voltage change coincide with engine RPM changes? (my guess is "yes"....) Wonder if the EGR valve is bad?

 

im not sure, id have to check but cant tonight. i can see the needle on the egr move as the pcm gives the solenoid power. so i would imaging its working... do you know what conditions are required for the ecm to open the egr? im tempted to leave it disabled, unless it could harm something else?

 

You are correct in your assessment of what it does, but, it's mostly for emissions purposes. Cooler combustion chamber temps also allow a bit more timing advance. Try running with it disabled, see what happens. If you get excessive spark knock, may wanna consider an alternate route. May set a code as well.....

I am not entirely sure what conditions the PCM wants to open the valve..... should be in the service manual though... available here.

 

okay cool. it try driving it for a while a see what happens. thank you for you help if i remember ill post back in a while and let ya know how it works out