Dakota Durango Forum banner
Cancel
Create thread New Garage Forums

Idle issue

Jump to Latest
1 - 16 of 16 Posts

BlackDurango

· Registered
Joined
·
87 Posts
Discussion starter · #1 · (Edited)
I'm about ready to set this POS on fire! So for the past few months I have been slowly trying to figure out what is causing my idle issue at start up. It's not bad but it sometimes doesn't want to start - having to give it some throttle so it starts up. When it starts, the idle is erratic and low and if I don't give it any gas, it dies. Then it has it's wonderful days when it fires right up with no hesitation. I thought it might have something to do with the temperature on hot or cold days but the problem happens on both climates regardless. When the problem is present and I have issues starting it up, I have to keep my foot on the pedal, keeping a constant rpm and slowly having to let it off so it idles by itself when my foot is finally off the pedal but if I let off too soon, it dies.

In an attempt to correct this problem I have replaced the IAC sensor 3 times already and every time I erase the code for the IAC complaint, it returns shortly after, even after putting a new sensor in. Yesterday I bought a new map sensor and installed the new one to see if it would correct the problem and to no avail, the idle issue is still there. So I returned the new sensor today since it's clearly not the map sensor causing the issue. The CEL does not come on when the ignition is set and it performs a self check so maybe the bulb to it is bad. I'm not aware of any problems if there is any. I randomy hook up a scanner from time to time.

Earler this morning I removed the throttle body in order to clean off all the carbon internally. I remved the IAC valve and cleaned off the plunger and the port inside the TB. I left the whole damn thing squeaky clean and installed a new TB gasket as well.

I hooked everything back up and went to go start it. It ran like crap - missing and everything. I disconnected the negative battery cable for a few minutes and hooked it back up. Still with the idle issue but it now ran smoother than after I made the repair.

At this point I'm Fu***** furious as to why I can't fix this damn problem. I started disconnecting the sensors with the engine running and observed the following:

1. Removing the IAC connector - noticed no change in idle and still with the fluctuating rpm's.

2. Removed the map sensor connector - engine shut off immediately after removing connector.

I will lay down all the facts so no one asks questions that are of the obvious. I damaged the elbow below when I removed the sensor to install the new one. I installed a vacuum line in an attempt to duplicate the elbow but am afraid it will form a kink and restrict the flow to the map sensor. All connectors, pins, and wires appear to be in working condition with no defects noted. I checked the air filter and that is in working condition. Fuel delivery issue maybe? Pump is audible when ignition is set on. And I have replaced the tps once already.

I also took volage reading at the IAC connector and got 13V on two of the four pins. Shouldn't I have reference voltage of 5 on one of those pins?

I've listed just about everything I can think of. Please help!

Thanks!

**New Upddate**

As stated before, when I disconnected the MAP sensor the engine shut off. So, I decided to do it to the remaining two sensors and noticed that the engine would also shut off when disconnecting the tps but not the IAC connector. There is no change in idle or anything when disconnecting the IAC sensor. I also took voltage reasings just now and observed the following:

1. MAP sensor measured @ 5.16 v with ignition on

2. TPS sensor measured @ 5.16 v with ignition on

3. IAC sensor measured @ 13.2 v with ignition on @ two of the pins.

Where do I begin looking for the short? This could also be causing my "no bus" issue from time to time.
 
#2 ·
There's another post somewhere on here explaining the no bus issue, try a search, should find it. Your idle problem may be a low fuel pressure problem. I have a similar problem, but not as severe. I'm pretty sure my pump is on it's way out.
 
Save
Reply Quote Like Like
Discussion starter · #3 · (Edited)
Frosty23_45 said:
There's another post somewhere on here explaining the no bus issue, try a search, should find it. Your idle problem may be a low fuel pressure problem. I have a similar problem, but not as severe. I'm pretty sure my pump is on it's way out.
Click to expand...
Could be... but I hate shotgunnin' parts at it without confirming the actual cause.

Lets just say for the sake of... if it was a low fuel pressure issue, then why does the rpm's stabilize after I let off the throttle as I have mentioned before? After that, the vehicle runs fine - like new. This complaint is only at start up. Low fuel pressure, I think would affect not only start up but driving down the road too. Anybody got the specs what fuel pressure oughta be? Thinking about going to harbor freight and buying the one time use fuel pressure tester just to see.
 
#7 ·
Stupid question but maybe it might help. What condition are your ground cables in? I know when my ground to the block from the battery acted up. I practically had to floor it to start and maintain throttle pressure to the pedal till it decides to stay running.
 
Save
Reply Quote Like Like
Discussion starter · #8 · (Edited)
I don't know, maybe removing the grounds from the frame and cleaning them up would help i guess at this point. Looking straight at the engine, the 2 grounds behind the passenger side of the block, the one behind the drivers side of the block, the two on the passenger side fender by the pcm, the one behind the a/c compressor, the two on the drivers side by the battery, and the 2 on the drivers side in the wheel all looked to be okay. But like I said, removing them and cleaning them up won't hurt.

Can anyone explain why I'm getting 13 v at the IAC connector? That just doesn't seem right. I should get 5 v if I'm not mistaken.

Just a note - I installed a new shorter ground cable from the negvative battery terminal to the a/c compressor. The one that was on there was long and it was chaffing on the engine block. Luckily I caught it in time as it could have caused problems. The insulation of the cable had chaffed off and exposed the strands of the cable. This was when I first got it though.

Anyone have a FSM for this vehicle? Same year and everything.
 
#9 ·
I have a 99 Durango that does the same thing at start up sometimes it will not stay running unless I give it gas. I was told by a dodge tech who worked on a bunch of these motors told me to see if there is oil in the bottom of my intake and there is on mine. He said replace the intake belly pan gasket cuz it is causing a vaccum leak and it mostly is causing my problem. I plan on fixing the gasket in the next few weeks when I get payed.

It might be your problem as well. Also see if u are leaking oil out the back side of the intake.
 
Save
Reply Quote Like Like
#10 ·
^^^ i was going to say 2 things come to mind with my truck.the first being,these trucks need 13.6v to run correctly.i replaced my battery and solved my idleing issue(i'm guessing all my volts at start up were going to the battery) and 2nd,open up your butterfly and look down deep in the intake.if its puddling oil you need an intake plenum gasket.
 
#11 ·
http://www.biodsl.com/durangofsm.htm I don't know if there is much in the way of electrical diagrams/schematics but you might get lucky.

I'd get the fuel pressure checked. If you don't have enough fuel going into the engine it'll mess your A/F ratio and cause a slew of other problems and sensors that don't read correctly. As for the 'no bus' I can't help there...

XRT is bang on, these vehicles can do some crazy things when the battery won't properly hold a charge. When my factory battery went (3 years ago) the vehicle would idle fast then slow, and continue this for half a minute before shutting down. The battery was dead and I think the vehicle was hanging in thanks in part to the alternator trying to charge the non-chargeable battery.

Not that they're not installed properly, but if the screws are loose, even slightly for the IAC/TPS it could cause a difference in voltage. The old 'TPS mod' involved using different screws (can't remember what exactly) to alter the voltage ever so slightly in an attempt to gain better engine response. I doubt any change in voltage on the TB sensors would cause your problem tho.
 
Save
Reply Quote Like Like
Discussion starter · #14 ·
I ordered the FSM for this thing and the IAC motor is controlled by the PCM as an output and not an input. Being that it's a motor, it makes sense that there's 13 volts to it.

There is no oil in the intake. Installed a new gasket when I removed the TB for cleaning.

What I am tempted to do when I have a chance is remove the IAC motor and see if it has any inputs from the PCM. The plunger should move when doing something - can't remember what but I'll have to check what it is. I read somewhere that the PCM may not be sending the output to the IAC motor thus causing idle issues. I have battery powery going to the motor but doesn't mean it's actually outputting how it's supposed to.

All the grounds I find in the engine compartment appear fine.
 
#16 ·
BlackDurango said:
What I am tempted to do when I have a chance is remove the IAC motor and see if it has any inputs from the PCM. The plunger should move when doing something - can't remember what but I'll have to check what it is.
Click to expand...
IAC = Idle Air Control

The plunger moves in an out to regulate the amount of air going into the engine at idle. The PCM controls it to achieve the idle rpm it is programmed to run at.

That's good that you checked to make sure the TPS is getting 5v reference. Next thing I would check is the voltage the TPS is sending back to the PCM. With the key on engine off run it through various throttle positions and make sure it sweeps properly without any dead spots. When I checked mine I unplugged the sensor and used paperclips and jumper leads between the plug and sensor, then hooked my meter leads to ground and the center (IIRC) wire. I assume you have a volt meter since you posted voltage readings in your first post.
 
1 - 16 of 16 Posts
About this Discussion
15 Replies
10 Participants
Last post:
caleprofiveo
Dakota Durango Forum
posts
1.4M
members
58K
Since
2003
A forum community dedicated to all Dodge Dakota and Durango owners and enthusiasts. Come join the discussion about modifications, troubleshooting, towing capacity, maintenance, and more!
Full Forum Listing
Explore Our Forums
Photos & Videos General Automotive Discussion Troubleshooter's Forum 4.7L/4.7L HO/4.7L Gen II Engines Suspensions - Lifted & Lowered