Truck Starts Fine and Slowly Fades Out Until It Stalls. Help Please!!

Hello everyone! I am having an issue with my 99 Ram 4x4 5.9 V8 when I start the truck the first time when the engine is cold. It will fire right off and run perfect at idle, after a couple of minutes of idling goes by, it starts to run a little rough and a loud sucking of air starts coming from the throttle body. The idle slowly decreases until the engine is just barely chugging and then it will eventually stall out and die. (The exhaust also starts to smell fumey.) If I give it throttle it will come right out of the chugging and rev up nicely, but as soon as it returns to idle it starts chugging again. If I shut the truck off and start it back up everything is usually fine then. The loud sucking of air starts when the engine begins to lower in rpm and starts chugging. It sounds like the engine is starving for air, and as soon as I open the butterflies on the throttle body it smooths out and runs perfect until the butterflies close back up. Could it be an idle air control valve sticking? Anyone have this happen and know what it could be??

P.S. I have changed the TP sensor a few weeks ago.

Please help! Thanks everyone in advance! I sure appreciate it!!

I'd remove the throttle body clean it and the iac.

this same thing is happening to me!! its so annoying! i cant let my truck run without it chugginf and sometimes dying on me. all the symptoms i described i replaced with parts that i thought would fix it. i replaced my idle air control valve, map sensor(manifold absolute pressure sensor), throttle position sensor. i cleaned the outside of the intake manifold and got inside the hole where the plunger for the iac valve goes tihnking that it might be clogged with carbon buildup in there causing a weird idle. everything iv looked up hasnt really helped. this is the first thing iv seen that is the same thing as me. from what iv found is that it might be an intake manifold gasket leak. im giving up on things it can be cause i think i fix the issue and boom it happens again. have you had any luck? tried things that i havent yet? i need help asap cause i cant take it anymore. and just to clarify for me. my engine turns over perfectly and starts to idle just as it should, but while its idling it will start to get rough and my rpm needle will move around. not a lot but like one notch. and it will make the engine chug and not sound like a fluent pattern, almost like a missfire. and as soon as it starts to chug my intake starts sucking in air like crazy and is so loud and noticable. i felt it not sucking in through the buterfly valves cause there closed but air coming into it through the idling air hole port(like the back of the manifold where air can get in for idling). so logically i figured it was my iac valve. guess its not. i no longer know what to replace after a new intake manifold gasket. please i need some help badly!!! thanks!!

Well to check your intake manifold gasket get some carb cleaner and spray it where the intake mounts to the block. If the idle changes when you hit any spot around it it's because the gasket is blown and sucking in the fluid. Don't spray a ton just a little all around. Also take off the throttle body and look for a pool of oil in the intake. That indicates a blown plenum.

yea that's the next thing I'm thinking. is the gasket located below the butterfly valves or is it lower down. I seriously think that's the cause of this cause you can hear it hissing when I hit the gas and let off you can hear it hiss and slowly fade away. and after I turn it off for a split second it like stumbles before actually shutting off. it would cause a loss of power too right? I really appreciate the help man

< seen this years ago on youtube

http://www.youtube.com/watch?v=mfgmGZ3qR0I

< here was his solution

http://www.youtube.com/watch?v=3JhRi...feature=fvwrel

Hope it helps out.

I seriously wish it was that. unfortunately it's not cause I fixed that part :/ brand new iac valve I installed a few days ago but it still is doing the same thing. runs and starts fine. that's why I'm thinking maybe it is a leak in the intake manifold. cause all the sensors around the intake I replaced. logically thought it would be the idle air control but it would have solved the problem. so the next thing I can try is the intake manifold gasket. I might take it to a repair shop for them to do it and verify if that is the problem or not cause I really don't feel like taking it all apart. any other ideas?

Well if you want to see if its the manifold gasket spray carb cleaner where the intake meets the block all around it. If you hear it stumble then it's sucking it in and you've got a leak.

If it isn't the intake gasket it may be a clogged Cat...

Or jumped timing?

Originally Posted by dannewman

Or jumped timing?

Spark timing is all computer controlled, the ignition timing is controlled by the distributor but that would run rough all the time, just ask me how I know that one....

Did you usta' drive a Chevy?

Have you changed the fuel filter lately? Depressurize the system if you do.

no i havent replaced anything related to the fuel. have a few updates but still the same problem. some more options are co2 sensor which seems a little too simple of a fix for me, maybe a clogged cat because i pour out white smoke on start up but thats kinda normal cause its 10 degrees here, when it starts to chug and the idle is going up and down i get a lot of white smoke and it smells funny and leaves a smell i cant determine in the engine bay, and my most logcal asnwer to this problem was my plenum gasket? but after doing more research on if its that or not iv realized that its not sounding like thats the problem. im back to thinking its my intake manifold which im still unsure if its any different from the plenum gasket. all the sensors that seemed to describe my prolem as syptoms havent worked. reaplced iac valve map sensor tps sensor cleaned out the butterfly valves. when i replaced the map sensor i seriously thought that was going to be the answer. such a bummer when it started to sound like it was suffacting.i still think its like a a gasket leak cause my logic is since its cold out, more oxygen molecules can get in through the crack cause its so cold here which is why it seems to have been doing it a lot more and im guessing the increase of air into the engine makes the computer throw in more fuel to compensate for it but then it winds up choking it still it completely stalls out. i seriously am so tired of this problem. ill post a video of it dying soon so you can see exactly what its doing

Have you checked it for codes?

Go to your local auto parts store they should have a code reader that you plug in under your dash...

That will give you a starting point...

Originally Posted by OleTomCat

If it isn't the intake gasket it may be a clogged Cat...

My cat isn't clogged i don't think but it makes noise when it wants to and i have none of these problems these guys are explaining. It could be a possibility for them though.

if its blowing out white smoke that is almost a sure sign of water getting into your cylinders either by a bad head or intake gasket, cracked head or cracked block, there are some other ways its getting in there but those are most like likely, excess gas would be black, oil would be blue. The smell could be anti-freeze that is burning.

no check engine lights or anything. my mechanic friend said the exhaust doesnt look bad. its white but then again its like 15 degrees here everyday so in the beginning it looks white but not like a thick white. plus my truck never over heats or anything, in fact its usually a little below the middle point even after driving for a while. im not gonna rule out the idea of a cracked head or blown head gasket. im praying its not that though. it seems like I'm not as powerful as i should be like going up a steep hill. have to get it into first gear at 3000 rpm just to keep my speed. but no overheating and doesnt look like white smoke cause after like 3 feet from leaving my tailpipe the exhaust just evaporates into normal looking exhaust, not a thick white cloud. i have noticed though when im idling normal and then goes bad and the rpm meter goes up and down sounding like its choking, a ton of exhaust comes out still the same color and antifreeze sprays out the tailpipe. not a lot but like enough to notice a spray pattern on the ground and as soon as i start to movie and it drives normally no more cloud of smoke and no more water from the tailpipe i know it sounds like a bad head gasket but the problem only happens when I'm idling not moving regardless of any gear. this really sucks. thanks

forgot to add. i have an internship at a transmission shop but the owner whos my friend and got me it has this big code reader, not the small handheld kind but you have to hold it with both hands and it checks out like every single sensor in the car, transmission and engine and it costs like 10,000 bucks. do you think if i hooked it up even without displaying any codes it could show me a bad sensor, or tell me if I'm running rich or anything like that

I would try that code reader just incase, it may pick up something. I would do a compression or leak down test on the engine and a pressure test on the radiator while you have the plugs out. The reason you may not be showing coolant out the back at higher rpms is because it may be burning it. Have you checked your cat to see if its not clogged?