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98 Durango 5.2 run on and stall issues

2122 Views 9 Replies 4 Participants Last post by  GrayChallenger13
Ok, this is a worst nightmare scenario... I am helping friend piece back her Durango after a shade tree mechanic took advantage of her in my book.

There are so many unknowns to this I would just have her sell me the truck for scrap but she's into it too deep now.. Ok enough of the sob story here's what I'm having trouble with.

For some reason she had the engine changed and every since she had it worked on it has a run on pre-ignite issue and mysteriously stalls, we checked the distributor and it appeared tight, we found a smashed harness to the CSPS and repaired that as well as replaced the CSPS with no luck.

You have to crack the throttle to get it to start when warm after it dies. It only dies at then end of an excel or at a stop sign or turn, it is fine at idle.

When you shut it off it pre-ignites until the engine is warmed up. Then that issue goes away. The only code we are getting is an O2 code. We have a ABS light from the brakes we went thought the brakes for her and haven't dealt with the light yet.

Any suggestions or pointers would greatly be appreciated, I hope he put the right engine in and there is not a CPU problem I haven't checked the vin yet to see if he used the right engine.

Thank you!!
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Ok tonight messing with it, I noticed if I shut the key off fast it shuts off with no run on, there is slop in the ignition and I'm wondering if I'm looking in the wrong place under the hood vs in the column, it would explain why there is no code I guess. If I turn the key off lesurily is runs on... Hmmmm, any suggestions?
Welcome to Allpar. Is the radiator fan wired to run all the time the key is on? This can act as a generator after the engine is shut off to produce 'run-on' or 'dieseling'.
Still need more assessment and diagnosis, but it also sounds like it may be running rich.
What is the actual 'P' code? Front or rear O2 and what is it failing for (high/low/stays at center/heater)?
Replace the O2 sensor with an OEM brand (NTK/NGK/Denso, etc). Avoid Bosch.
If you're having detonation, check the timing. Just because the distributor is tight doesn't mean the hack who put it in timed it. I would guess that most of the issues stem from things poorly or not connected. Even reputable mechanics make mistakes, but then again, reputable mechanics make sure everything is working properly before the car leaves the shop.
Why was the engine replaced? Do you know if the engine in there is a new engine or a junkyard pull, and does the mechanic still have the original?
Run-on in fuel injected vehicles is a tricky one. The fuel injectors should not be opening after the engine is shut down. In a carbureted car, even when the ignition is shut off, the carburetor has no idea that it shouldn't be feeding fuel to the engine, and if it sees a vacuum, it will keep doing its job. Hot spots in the cylinders ignite the fuel without the spark plugs firing, causing the engine to keep pulling air and fuel in. With fuel injection, in theory, a closed injector should not let fuel out. However, a leaking seal or injector could be dribbling fuel into the engine until the residual pressure bleeds off. This could also be the source of your apparent rich mixture. What concerns me is that there's something hot enough in the "new" engine to ignite the fuel. Run-on is typically a hallmark of very bad carbon build-up and poor overall engine health. Then again, carbon build-up can also stem from a very rich mixture from something like a leaky injector.
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Timing IS NOT set by moving the distributor on this engine. The crank position sensior controls timing and the dustributor synchronizes the injector pulse to the spark. If the distributor has been moved to attempt to adjust timing (or was transferred from one engine to the other), the fuel synch needs to be reset.
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Ignition timing is determined by the crank position sensor and the PCM. The distributor (cam position sensor) only determines fuel injector timing (sync). The correct position is important, but not too terribly critical and can be set with a good scan tool.
If the hot-wired radiator fan is still spinning after turning the key off, it may keep the 'run' side of the ignition switch powered up breifly, keeping both spark and fuel available for a second or two.
Ah, thanks Valiant. I figured since it's a 318 it must be a setup like the 2.2/2.5, although 1998 is quite late for that.
I guess the question to the OP would be does the truck run normally (like the key was never turned off) or rough (sputtering, coughing worse than it did before the key was off) when it runs on?
Hey everyone, thanks for your replies!

I was aware of the timing and PCM set up, I thought maybe if the guy thought it set the timing he messed with it and it could have left it loose. but never considered the fuel injectors not seating, the engine was a junk yard, and that's all I know, I don't understand why it was changed in the first place all she knows is that it didn't run.. Lol!

My scanner is just a acutron obd2 code reader, I'm looking to update and would like to get a scanner that would allow me more options any suggestions?

I will look at the items you all have suggested and post back. Thanks again!
You could have put a potentially worse engine in the vehicle. If the problem was somewhere else in the vehicle, which I suspect that it may have been given the exceptional reliability of the 5.2/318, you might still have the original problem as well as a potentially-abused engine.

As for the scanner, it depends on what you want to do with it. Snap-On makes some very sophisticated ones that can show graphs and test just about everything on the vehicle, but they are a couple grand at least.
I'm afraid you mite be correct I think they charged her for an engine swap that she very well did not need. I hope not but I think it's the case.

My friend has one of the high end scanner / diagnostics units. He is taking the truck to his shop to see if he can find anything deep rooted as well as adjust the fuel system timing etc. we think the person who changed the engine messed with the distributor, we found some suspect wireing at the CSPS sooooo here we go! I will post what we find.

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