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Discussion Starter #1
I've been working on my son's 1999 5.2 for the last 2 days. I have swapped in the following new parts: Battery, alternator, camshaft position sensor, iac, tps and all but 2 of the spark plugs.....we can get a socket on 2 of them..... corrosion build up around them?....Anyway.

Over the last 2 days we got the engine to start easy a few times but it stalled when shifting into drive. Other times it shifted into drive ok and we drove it a minute or two but then it stalls. But, most of the time I have to put the accelerator to the floor to start it and then feather the accelerator to keep it running, otherwise it stalled as soon as I take my foot off the accelerator.

I'm at a loss as to what to do. I don't want to blindly swap parts anymore. Does anyone have any checks that might be used to diagnose the problem?

I think I'm just going to go back to some basics and do some compression and leak down checks.....the computer on the fender is the only other thing that is suspect to me at the moment.

I'm hoping someone here has some words of wisdom or can point me to some info that I can use to continue troubleshooting.

Sorry this post is so long.

Thank you for your time.

Bob
 

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Have you tried running it starter fluid to see if it's fuel related?
 

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Discussion Starter #3
I didn't have my hose and gauge with me but I did pop the test port and fuel sprayed out pretty good.

I did try to spray some carb cleaner into the throttle body but it didn't seem to do anything..... maybe that is a data point?

After 2 days working in a parking lot we towed the Durango home. Now I can continue working on it.

I appreciate the response
 

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Discussion Starter #5
Thanks for the response Durango. I did change the the throttle position sensor. I don't think it's timing. At times the engine seemed to run pretty smooth and I actually drove it around the parking lot but it eventually bqould stall and not want to start again.
 

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some things to check/know:
  • the PCM has to relearn the idle settings. You may have to keep feathering the throttle and letting it almost die to speed this process up.
  • dirty IAC passages.
  • the IAC can be damaged if any force at all is applied to the pintle. The gears inside strip. So hopefully that didn't happen to your new IAC.
And, of course, a marginal battery will screw up the IAC learning.
 

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Discussion Starter #7
Is there a way to bench check an IAC?

I have swapped out a lot of parts. I hate to do the shotgun approach. It was a gamble and I lost. Spent a pile of money and nothing changed.

It very well may be that I put in a bad IAC or something.

Now that the car is home I want to try and verify proper function of each of the pieces that I replaced.

I have am oscilloscope....I would really like to watch all these signals going to the the PCM and see what the PCM is outputting.
 

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Is this a new problem or was there a different problem that you were chasing originally that caused you to replace parts?
Since you replaced the cam sensor, did you get the distributor cap on correctly without bending the metal tab on the rotor?
You can also check the coil wire for a bright white/blue spark vs orange. Probably not the culprit, but will help with fuel economy and starting if a weak orange color is seen.
Did you spray water on the intake to clean it off?
 

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I would more likely suspect a vacuum leak or unmetered air.

I don't really suspect an IAC issue here, but you asked:

The IAC is a 4 wire actuator sourced with 5 volts, so my first guess is that it is a stepper motor that rotates an acme screw that moves a pintle valve in an orifice, so testing the motor would involve a stepper motor controller. The pinpoint tests in the manual use the factory DRB to actuate the motor, so I'm guessing that the DRB scan tool has a stepper motor driver built into it.

You would get one of the P0505 series CELs if the PCM detected a problem with the sensor or wiring that involved a short to power or ground. If you have any CELs, you should always post those up front. A $13 OBDII bluetooth adapter and a smartphone running Torque Pro can be exceedingly helpful.

The pinpoint tests essentially have the IAC set to a specific value with the DRB and then you check to see if the idle is at that value. If you can get the vehicle to idle at all, one check is simply to unplug the actuator while idleing and see if there is a change in the idle (Test 393). Another test is to wiggle the wiring while idleing and see if a change occurs (Test 389). The tests should be ideally performed on a warm engine. Stepper motors can also be tested statically using a voltmetter set to Ohms resistance. You're testing for coil shorts when doing this. Two pins would be for one of the coils and the other two would be for the other coil. You never want to test for resistance through the PCM, so always disconnect the actuator for testing from the harness. If testing the wiring to the PCM, disconnect the PCM harness connector from the PCM.

It looks to me like the resistance should be greater than 5 Ohms. For stepper motors in general, each coil should have the same resistance. To figure out which pins are to which coil, just disconnect the actuator and then read the resistance values between the various pins until you get a reading. If the pins are numbered 1-4, combinations to try are: 1-3, 2-4, 1-2, 3-4, 1-4, 2-3.
Report back your findings. If you have an OBDI tool that lets you see data values, then report that back too.
 

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1999 Durango SLT 4x4
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Hi,
Sorry you're having problems with the D.
The reason I tuned in is that I started having the same sort of issue with my 99 D 5.2l.
I, like you, decided to throw some new parts at it. I went with new IAC, TPS and MAP.
My rig only has 104k but, MAN, the throttle body was SUPER dirty! I spent over an hour cleaning it. I used WD-40 to kind of soak it a bit and then it took 2 big cans of Berryman's throttle body cleaner with a pick and brushes to get it shined up.
I'm about to put it all back to see how it goes but I'm skeptical. I have read that the ECM's on these do have issues with the IAC circuit. The good news is that it seems there are plenty of people that know how to repair them.
I don't want to ship my computer but I will if I have to get my "beloved" back on the trails.
I will definitely let you know how it goes with mine and will keep watching this space so please update if you figure it out.
Also, if you use your O'scope on IAC you should see a crisp, square, digital waveform if the signal is good.
Good luck!
 

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1999 Durango SLT 4x4
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Hi again,
I put my throttle body back on....fired her up and idled for 5 minutes until temperature came up and....
She idles like a new one!
I got lucky that the ECM wasn't acting up.
I also forgot to mention in my previous reply that I also replaced the PCV and grommet. THAT was the most difficult thing to accomplish because the grommet was baked in to the valve cover and was very hard.
I ended up making several slices in it with a utility knife with new blade. That allowed me to remove several pieces of the grommet which then relaxed the grip it had on the PCV valve. I then popped the grommet out with a screwdriver.
The new grommet didn't want to go in so I trimmed a tiny flat in one edge of the tapered lip to get it to go. Then, the PCV valve wouldn't push in so I used my heat gun to soften up the grommet a bit. A little grease on the valve with a hot grommet and she popped right in.
Sheesh! It doesn't need to be THAT tight or THAT hard to do!
Anyway, that's what happened with mine and I hope this helps you in some way.
Good luck.
 

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Discussion Starter #12
Durned Ugly, awesome you got your problem figured out. I'm still working on my problem. I cleaned up my throttle body some more, then I stayed a bottle of sea foam in it. I took off the coil and noticed some cracks in the housing so I changed it. Same issue.

When stone cold it works fine. Throttle response is perfect, idle is perfect, I can rev the engine and everything sound and functions perfect. Once engine gets warm it refuses to run.

I made a DIY smoke machine and looked for vacuum leaks but I found nothing.

I'm really stumped. I'm getting down to the problem being something like a valve that only sticks when warm or the computer.
 

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1999 Durango SLT 4x4
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AngryDango,
Sorry you're still fighting with the D.
I will suggest a test for the ECM that might point you at least in a direction of thought about this.
Since you say it runs great when dead nuts cold, use a heat gun (carefully) to rapidly warm up the computer while the engine is first started. If it seems to do nothing, it may not be the ECM causing the problem. If it quickly starts to run bad as you apply heat, then you've found the location of the issue.
This technique can also be used on other components as you see fit to check heat related failure. This "test" is used every day in shops across the country to find heat related failure.
Even the lowly MAP sensor has a tiny circuit board in it that can crack and expand with heat. I replaced mine....easy and cheap.

If you really want to properly clean the throttle body, you need to remove it.

Not hard at all...just release the three cable ends, remove the three bolts on the cable bracket, uplug the three sensors and remove the four hold down bolts.

Have you checked fuel pressure KEY ON ENGINE OFF (KOEO) and KEY ON ENGINE RUNNING (KOER)?

Fuel pumps fail is various ways and having one seem fine at cold start and then dropping volume as it get warm from operating is definitely inside the realm of possibilities.

The only other heat related things that come to mind are the temperature sensors possibly not reporting properly. But they usually cause hard starts and poor COLD idle when they fail.


I will keep watching to see how you get on and if I have any more "bright" ideas, I will pass them on.
Know that I'm out here cheering for you to slay the dragon.
Good luck.
 

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On my 99D, I was able to drive around everywhere in 100+F degree heat - but only when I had a bag of ice packed next to the PCM. That was pretty solid proof that the PCM needed a refurb.
 

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1999 Durango SLT 4x4
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TowDurango,
Were you able to get the PCM repaired or replaced? It would be interesting to hear what you did to resolve the problem and it may help Angry Dango if he needs to "go there".
 

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Discussion Starter #16
I am out of town this week but this weekend I'll hit the PCM with a heat gun. Hopefully we can get this figured out.

A huge thank you to this site and everyone who responded.
 

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I'm just throwing out thoughts here, but it sounds like once it hits closed loop you're having issues. Can you get a spare temp sensor and just leave the current one in the block and the new one reading ambient air temp? Again no idea if that made sense, but sensors are cheap.
 

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TowDurango,
Were you able to get the PCM repaired or replaced? It would be interesting to hear what you did to resolve the problem and it may help Angry Dango if he needs to "go there".
I bought a refurbished unit from a Florida outfit- Auto Computer Exchange for $199 shipped. I parted out my 99 D, but I still have the PCM available.

A couple of guys locally have asked to borrow my spare PCM for testing. Mine is a no-anti-theft PCM. Most people have anti-theft. It's been a while, but my recollection is that an anti-theft model needs to be factory reset so that the anti-theft code can be read from the BCM module at first start. Once that happens, I don't believe that the PCM is transferrable to another vehicle w/o reprogramming. The first PCM that the rebuilder sent was anti-theft and I either wasn't able to start the truck or it started and died immediately. I had to return it. I believe the guys that borrowed my PCM were able to test with it on their anti-theft vehicles, but that's a hazy recollection. I could probably text them and find out. Interestingly, in both cases, their (transmission-related) issues were with the wiring harness that goes accross the top of the transmission to the valve body.
 

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Tow Durango,
Good point about the PCM programming.
Was your D Federal emissions or California emissions?
That will likely make a difference too.
I might be interested in purchasing it if Cali emissions.
Although, I would defer to AngryDango for first dibs if he needs one:>)
 

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2014 Durango RT, Eibach Coils, 22" Hellcat Reps, K&N Cai, Corsa Exhaust
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Have you checked cylinder compression? If an intake valve is stuck open, it will cause the motor to run like it has a bad vacuum leak. Could be a collapsed or broken valve spring.
 
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