My 1999 Dodge Ram 1500 5.2 has been driving really good till this morning. Left the house everything fine and down the road after maybe 15 minutes I notice the idle was little rough but by the time I got to my 4th light. It's was running pretty rough idle with no power taking off and seem like it was trying to die. Gave it some gas and got worse so I floored it to see if maybe something was caught but it did get up but also seemed to be misfiring/back firing in the motor its self but not out the tail pipe.This motor has had new head gaskets, upgrade plume with Hughes. Plugs, cap and wires Full tune up. I am going to go and check inside of the throttle body to make sure that the gaskets hasn't failed but should be fine as well as check oil since I had to run the hell out of it to get it back home so I could take my other truck to work. Again, no engine light to go off of. Any ideas of what to ,look for? Thanks

 

OK, Went out and look down the throttle body and clean as a whistle but notice the back side (inside of the throttle body) is having a real back vacuum leak. I am also smelling gas but nothing leaking as to injectors , lines or rail. I can't remember the part I replaced on the rear of the throttle body but I am thinking it's acting up. I have been hearing this air sucking sound for a week or so but couldn't find it till I removed the air cleaner. It suck the palm of my hand down tight with it acting up. Trying to figure this out.

 

IAC motor is on the back of the throttle body. If it was misfiring, the CEL should have been blinking at you. Might try and see if there are any pending codes.... (need a good scanner for that though.) I might also be tempted to test fuel pressure.

 

Sounds like an issue with the idle air controller, which is bolted to the back of the throttle body. Remove it and clean out the well area in the back of the throttle body.

 

It miss fired when I was flooring the gas to see if maybe some trash may have gotten in there. If you remember I just replaced the fuel pump a little while back and bought the one you recommended. I have a Zurich scanner ( not top dog) but like I said, once again to engine light. I did notice once I got home and it sat. It was little slow to start. Didn't do that this morning when I fought to get it back home.

 

I am curious to the air controller as well. I don't ever remember hearing it suck air like that in the past. I put my hand on the back top part of throttle body and it sucked me hand pretty hard and the idle did change. I mean the suction was very loud. I don't remember where I ought that new one it was replaced with but it was maybe at the max 4 months ago. I know I cleaned it out as well as the rest of the throttle body. I will do a fuel pressure test as Hey said and also as you said and maybe remove it and see if maybe something causing it to act up? I also replaced the fuel injectors with new ones. I just don't understand why I don't even get a check engine light? At least I could get a starting point to work from.

 

It depends on why the engine is screwing up. If it's just a bad sensor reading, the PCM doesn't necessarily know that the sensor is lying....

 

Two things come to my mind...
1) clogged cat, and,
2) new fuel injectors?!? Do you still have the old ones?

 

Yes, I still have the old ones. I did replace the part and the sucking has stopped but I did notice truck is smoking crazy and worst if idled up. Its a gray. I will post picture. I did a video but this new phone wont load to you tube.
I am smelling a lot of gas but haven't found the source at this point. Everything is dry in the motor area and top of tank is dry as a bone. I changed the oil two weeks ago and it's clean no smells. No water in it. Temp on motor is normal is fine. I will have to wait till the weekend to pull the plugs and get a visual and do a compression check on the cylinders. I'm truly at a loss here. Have made so much head way to get it on the road and driving and now this. I don't run it hard and it ran great till the Monday then we are here now. Also I don't have any loss of fuel and no dripping as if something could be loose. The motor sounds fine, no knocking or anything. Thanks guys for the help so far.

 

Gray is usually excessive fuel..... If it was running good before, it's likely just a wonky sensor. Have a look at the two-wire coolant temp sensor. (you should only have one. probably near the thermostat housing.) See if it is loose, or damaged. If you have a scanner that can read live data, see what the PCM thinks engine temp is.