I have a '95 3.4 that was recently rebuilt. It's begun acting very strange, it doesn't always wanna start, idles rough sometimes, revs rough up the RPM range when in park, backfires when going up the RPM range, RPM's will suddenly drop off when running up to the higher end of the RPM range (this sometime results in it stalling because it will drop below 1k and giving it gas seems to bog it down or something), and fluctuates up and down between 1-2k when in OD at about 50mph.

Has new wires, plugs, coil packs, TPS, fuel pump, fuel filter, also cleaned throttle body and MAFS.

People have said this could be many things, such as the o2 sensor, ICM, MAFS, injectors, and EGR. I'd like to know if anyone here has had this issue and resolved it successfully, or if anyone can help narrow down what the problem is, or if someone could tell me where the best starting point would be to begin throwing money at. Thanks!

 

Is the check engine lamp on? Have you scanned for codes? Have you checked the IAC valve? Have you checked for vacuum/air leaks?

 

The CEL isn't on, took it to auto zone and asked if they could check it even though there was no light on and they said no. Is there another way to check codes? Haven't checked IAC, nobody's recommended that one, where is it located and how would you go about checking it? Briefly looked for vac leaks, didn't see or hear anything wrong in that department. Thanks for the quick help, man, greatly appreciated.

 

IAC or Idle Air Control valve is attached to the throttle body, and controls idle speed.

 

Yeah, checked it out yesterday with my multimeter and it measured in range. Took it off to give it a bit of a cleaning with carb cleaner and since I put it back in, things seem worse than before. It hardly wants to start now and once it gets started it stalls out shortly after.

 

The 95s are OBDI with a OBDII diagnostic connector. Checking codes requres an OBDI scanner, and a OBDII adapter cable. Or, a scanner that works with both OBDI and OBDII.