98 dodge ram 5.9l won't stay running

[Soundguy]

Alright all you automotive guru's I got one for ya.

I hopped in my 98 dodge ram ( 5.9L gasser v8, 4wd, auto, air ) to come home from work tonight.

She's been a 100% straight forward truck. only ever had to change a battery, rear brake cyls, and a starter on her plus things like oil change and filters... oh.. and a TPS and a fuel pump/filter in the tank once.

Got in her, hit the key, she started and stalled out just as fast.. I thought I musta just let off the starter just a hair early and she didn't really start. tried her again... same deal.. as soon as letting off the starter.. she fails.. if keeping key turned.. she almost sounds like running.

I tried giving her throttle when starting and that got her started and running.. engine sounded normal.. no missing or stuttering.. throttle response was normal. i gunned her a few times to get the tach up to 3k to see if it was a fluke, then slowly let off.. she normally idles about 400-600 dead on.. can't remember which.. it's either the line above or below 500... as soon as she hits 500 rpm she dies.. you can start her back up and apply throttle at start and get her over the 500 rpm and keep her running.

I managed to get hom with creative use of 2 foot driving, keeping one on gas, and one on brake, and slipping to Neutral as I approached stops and redlamps.. keeping her at 1000 rpm while we sat, then letting her drop to about 700 to slip back into drive so I didn't hammer the tranny.

got her home doing that with no hiccups.. except the one redlamp I sat at with the punk gangsta kid in his boom boom car thought I wanted to race because i was revving my engine.. he won when the light turned..

In any case.. on the way home I went thru the gears manuall on some stretches so I could get the tach up and listen tot he engine to see if there was any stuttering, misses, hesitation, or loss of power. NADA.. drove like she has since 98.. engine felt good.. gauges all sat where they normally set. she's got a full tank of fuel, and I treated it when I filled her up. she's got like 25 miles on that tank.. it did rain today.. but I have driven her home from the pizza joint, and too work since the rain.. so am partially discounting water.. though I guess it could be a bad/wet batch of fuel?

anyway... I've only had 2 vehicles that have done this.. both fords. one was a 90 crown vic v8 that liked to get dirty throttle bodies. she's stall when you came up to a red light if you didn't keep throttle up.. but she also hesitated bad when the throttle body wanted cleaning.

had a 90 aerostar mini van that one time wouls start / stall but run fine/normal if you started it with throttle. My mechanic at the time said the computer might have forgot how to idle. I thought that was odd but he told me to start it like I was doing, then get out and drive around the neighborhood for 10-15 minutes while the computer re-learned to idle and whatnot. I thought it was hokie.. but.. it worked... did that drive, pulle dback in at home, and let off the gas and it idled fine.. never had the problem again.. traded inthe old van last year on a cash for clunker deal.. van ran good.. body was falling apart though.

now here I am with this dodge... any guesses? I used the foot on the throttle all the way home, to ensure I made it home.. got neighbors with kids 70 feet from that side of the house...so i didn't want to test / play with it tonight gunning the engine or stalling / continously starting it since it's midnight.. will look at it in the am, but would like some ideas to be armed with.

so.. fuel/water? ( no missing )

throttle position sensor? ( ran good at other rpms )

fuel pump ( when it went out last time.. fuel injector lies only had 6-16 psi instead of something like 60.. she would sometimes start and idle.. but mostly not start or run at all untill I dropped the tank and changed the pump.. so don't sound similar )

throttle body? ( no missing or hesitation.. she just dies like key shut off at reaching 500 rpm?? )

that's all I got in my bag of tricks ( no points to check and no generator ) I thought I was gonna have to wake the wife up to come get me in the ford diesel with the trailer in tow and winch the dodge up on there.. REALLY glad I didn't have to go that route...

all advice /ideas appreciated.

ps.. bat meter was good.. lamps were good.. no check engine.. no other indicators ont he dash .. IE.. nothing out of the ordinary.. all gauges were int here 'green' zones once temp came up.. oil pres was good like it always is.. 25-50.. etc.. depending on rpm

soundguy

 

[redneckexplorer]

I don't know about Dodges, but I've had this happen on a couple of Fords.
2000 Explorer and 99 F-150 in both of these cases it was the IAV (idle air valve). On these Fords the throttle body is designed to completely close off,
then the ECM controls idle speed thru the IAV. In my experience, I was able to remove the IAV and clean the carbon with B12 and it worked like a charm.
I suspect the Dodge also has a IAV of some sort, as this is how the computer controls the ide speed thru varying conditions such as AC compressor cycles and neutral or drive sitiuations.

 

[dddenden]

I had a '95 with the same engine as yours and had a similar problem that was almost impossible to find because it was too simple. The coil wire or whatever they call it now - primary ignition maybe??? runs in the far back of the intake and lays right on it. After years of heat the insulation was totally deteriorated and it was shorting out on the manifold. A wealth of test quipment couldn't detect this. Lucked upon it when we installed all new wiring when we were grabbing at straws.

 

[arrow]

SG, do you have a digital odometer that can pop up a key code? I know Dodge used this but cannot recall if they put it in in 98 or 99.

 

[Soundguy]

analog gauges.

so where is the map sensor on this beast?

I put in some gas dry to try to take water out of the equation.. let it set a few hours.. she started up and idled for 25 minutes.. I though.. COOL..fixed.. backed out of the driveway and she stalled did it all the way to work.. had to use the 2-foot drive technique again. It did it less.. like.. half the stop lights I could drive up to normally.. but now and then it would want to stall at idle.. and a quick tap of throttle would 'save it'.. might still be water I guess.. but???

soundguy

 

[racolton]

That almost sounds like a plugged or faulty AIS motor. (Automatic Idle Speed) This controls the amount of air getting into the engine when the throttle plate is closed. I'm not sure if the 5.9 engine has one, though.

Just did a search online and found something similar - and Idle Air Control Valve. (Pictured.) You might try removing it and cleaning it and the passage in the throttle body.

 

[Soundguy]

any idea where i might find that lil booger? I'm no mechanic.. but can turn wrenches on old tractors good...

soundguy

 

[racolton]

I don't know, for sure - the nearest 5.9 liter engine (that I have legal access to) is about 100 miles away. If I recall correctly, there is a large plastic air duct coming from the air filter box that is clamped to the top of the engine. Take that duct off and it will expose the throttle body. The AIC will be mounted to the side of the TB, probably held on by some Torx screws. I think the thing circled in red in the picture is the AIC. (I'm not 100% certain that this picture is even from a Dodge 5.9 L engine...)

 

[Soundguy]

I'll give her a look, thanks.

so.. if it is a bad idle air control thingy.. the way I understand it.. unplugging it should make it idle ( limp mode? )

right?

soundguy

 

[racolton]

Unplug, as in remove the electrical connector? If that part is the problem, then unplugging it would make no difference - it would continue to die when you remove your foot from the pedal. The plunger coming out of the solenoid is spring loaded and relies on electricity to pull it back in to "un-plug" the passageways in the throttle body varying amounts, allowing air into the manifold when the throttle plates are closed.

(Note, this is not a valid way to test if this is the part causing the problem - it could also be the Throttle Position Sensor (TPS), but that requires a scanner tool to test. It's just easier to clean the idle control parts of the TB before digging in deeper.)