Dakota Forumz banner

1 - 20 of 22 Posts

·
Registered
Joined
·
16 Posts
Discussion Starter #1
I'm hoping someone can steer me in the right direction here...

So, I bought this 98 SLT 3.9 with 142,000 miles on it back in April in Atlanta and drove it back home to Wisconsin. Soon after it started developing an occasional surging while accelerating from a stop light, and the exhaust smell is very rich smelling. I've replaced the following;

New Denso O2 sensors (1&2)
TPS - twice
MAP sensor
IAC
Cleaned Throttle Body
New NGK plugs
fixed a broken exhaust stud on the right side exhaust manifold

The previous owner (1st owner) really took care of the truck very well. He gave me a bunch of receipts with all the work he had done and he did a great job of taking care of it. New Catalytic Converter at 120K, Timing chain and distributor were both done around 130K and he's taken care of front suspension work and all new brakes within the last year or so.

I'm really stumped with this one.
I understand these 3.9's have a bit of a rough idle, but the exhaust smell is what I can't stand.
 

·
Registered
Joined
·
16 Posts
Discussion Starter #2
I forgot to mention that the rough idle seems to happen when it has warmed up for a while. Could be a coil issue??
 

·
Registered
Joined
·
16 Posts
Discussion Starter #3
For all of you following this harrowing tale, I'm going to start with a few basic part changes. Coil and Crank Position Sensor. We'll see if that makes a difference. After that, I'll probably park it for the winter and start up again in the spring. With 142K on it, I'll probably pull the intake and change that manifold seal, just to make sure it's not the problem. While I'm in there, I'll verify the timing chain is correct and within limits.
 

·
Registered
Joined
·
16 Posts
Discussion Starter #4
Well after spending the winter looking at the truck tucked away in the garage I'm getting ready to start figuring the problems out. I spent some time learning about Fuel trim and the effect it has on diagnosing problems. When I start the truck, the Short Term FT hovers around -3.5% to about +4.0% and then suddenly it will start missing and run horribly (No CEL) and the FT jumps from -33% to +18% and the truck can't even accelerate.
After shutting it down and restarting, it starts to run OK again and FT is back where it was before. This tells me that I may have an injector problem. With 145K miles on those injectors, they may be ready to be replaced.
I see Bosch injectors with a 4 hole spray pattern, which is supposed to be an upgrade from the single hole Siemens injector in the truck, but I don't know if it's worth the investment.


Not a lot of discussion on here about those injectors..


So, I'll pull and clean the injectors first and see where that leaves me...
 

·
Registered
Joined
·
16 Posts
Discussion Starter #5
Just to record an update for posterity sake, I replaced the coil and it actually seems to have helped slightly. The exhaust isn't as rich smelling as it was prior to this. However it will run just fine and then will randomly start to hesitate and misfire, and while watching the Short Term Fuel Trim, it goes from -3.0% and jumps all the way to -33.0%, which tells me I may have an faulty injector issue. I've been busy with a million other things, and it's not an absolute priority that I get this truck running, so I've been working on it in my spare time. I ordered an injector tester and once that shows up, I'll test each injector. With 145K on the truck it may be worth it to just replace all the injectors, but I'll go through and test them all first.
 

·
Registered
Joined
·
16 Posts
Discussion Starter #6
Another update for those who are reading this..
I tested the injectors Saturday morning and here are the results...

When cold, I get a constant 12.1 OHMS resistance on each one.
I tested the injector pressure drop with an injector tester and everyone was the same. Started at 46.5 PSI and would drop to 31 PSI consistently.
After warm up, the resistance was 12.9 OHMS consistently across all 6 of them.

I'm off work the next few days, so my plan is to change the CPS and pull the injectors and clean them. The truck has developed a horrible rattle in the exhaust which could be the catalytic converter breaking apart, but it was supposedly replaced less than 20,000 miles ago... I'll have to get under the truck and take a good look after work today. This new problem seems to have come up out of nowhere
 

·
Registered
Joined
·
16 Posts
Discussion Starter #7
Well, I got the exhaust system off this morning. The converter catylist material came out like dust when I stood the pipe up on end! Since everything is off, I'm going to install duals on the truck. This afternoon I swapped out the crank position sensor. The one I ordered through Amazon last fall was not correct. The connector was slightly different, so I ran over to O'reilly and picked up the correct one. Got it installed and started the truck. Right now it's crazy loud, with no exhaust, but I wanted to verify the CPS would in fact work.

So, once I get the Catalytic Converter and exhaust installed, we'll see how it drives...

The only thing I'm not sure about is how a clogged catalytic converter an cause fuel trims to go crazy.


More to come.....
 

·
Registered
Joined
·
16 Posts
Discussion Starter #8
Converter showed up today. I'll have time on Saturday afternoon to install it, but I'm heading down to Atlanta for couple weeks for work, so the project is back on hold for a while....
 

·
Registered
Joined
·
16 Posts
Discussion Starter #9
One more quick update. I ordered my new exhaust for the Dakota. I went with a single after all. I just don't feel it would be worth the extra investment to have duals sticking out the rear of the truck.
So, I bought this Dynomax muffler and pipe through Summit. I got a 50 dollar rebate so the total cost was 112.00 bucks. I'm thrilled...

https://www.summitracing.com/parts/w...e/model/Dakota
 

·
Registered
Joined
·
16 Posts
Discussion Starter #10
Another update;

I installed the exhaust components yesterday and took the truck for a long drive. The truck ran great the whole time. I was monitoring fuel trims and the STFT never went higher than -5.0 or +5.0 and long term fuel trim stayed at or near 0.0% the whole time.

Finally, running like it should. I got out of the truck and the exhaust had NO smell. Absolutely clean.

About an hour later I had to run to the store, so I jump in the truck and head to the store, still monitoring the fuel trim, and all is well. Truck is running great.
30 minutes later, I leave the store, jump in the truck , start it up and it's running like crap. Fuel trim is jumping from -33% all the way up to +14% It did that for a minute or so, and I then shut it off and restarted it. It ran fine the rest of the drive back home....?

I got home and long term FT was at +0.8% and short term trim was cycling between -2.5% and +3.5% again. Exhaust smelled perfect and it idling like a new truck.

Sooooo.... I still have the problem. I'm almost at the end of my rope on this thing. If it weren't intermittent, I might think it was a plenum gasket. But since I can clear the issue by restarting the truck, I really am stumped on this one...

The members on this forum have not had much to say thus far, but any thoughts?
 

·
Registered
Joined
·
16 Posts
Discussion Starter #11
I swapped out the Coolant Sensor yesterday after work, and I think I found part of the problem.. I went to remove the connector from the sensor and the end of the sensor came off with the connector....!

Pretty sure the Coolant Sensor was no good...

I installed the new sensor and went for a long drive. Much better with no crazy fuel trim swings, but I did notice that it would go has high as +9.0% while driving, but then would settle back down near 0.0% or +1.0%. Never went into negative STFT, and Long Term Fuel Trim stayed at or near 0.0%

Feeling much better about this now.
I'm a little concerned about the high-ish positive number, but on the plus side the exhaust smells clean and the truck seems to be running much better.

I just have to figure out why the STFT jumped up to +9.0% occasionally.




Thoughts?
 

·
Registered
Joined
·
13 Posts
n84434, I dont have any help to offer, but am interested in the outcome as my 2005 4.7 surges and "hunts" at idle. Does a OBD scanner give any clues? Good luck in your quest!
John/ ddakota3
 

·
Registered
Joined
·
16 Posts
Discussion Starter #13 (Edited)
Hi John;
Well, I believe I have found the end to my dilemma. I drove the truck to work this morning (76 mile commute each way) and the truck ran great the whole time. My scanner is able to show live data, so I was monitoring the fuel trim data as well as the O2 sensors and everything was well within the range of where it's supposed to be.


To answer your question, Yes, a good OBD scanner with "Live Data Mode" will be a hugely useful tool in diagnosing problems. I'm not that familiar with the 4.7 but I would start with the basics like a clean MAF, clean the IACV (a biggy with surging) vacuum line leaks and O2 sensor condition. If you do have a CEL on, get the codes and see what you're up against.


Report back and we'll see what we can figure out..


Jim
 

·
Registered
Joined
·
16 Posts
Discussion Starter #14
Just one final update. It's been running great all week and I installed the new muffler which really made the difference.*

I'm sure it was the coolant sensor.

You guys have been a great audience!

peace...
 

·
Registered
Joined
·
5 Posts
Wow! Look at that! Now I own it.

And I dig it a lot. Nice truck and a great vacation to the Great Lakes area to come get it. Joined this forum a couple weeks ago to try to get some read on the intermittent check engine light I've been vexed with and was stunned to find your excellent thread right away. I read it but will go over it much more closely a couple more times to process all the exceptional information you have posted here. Got to admit, my forum threads read a lot more like, "Truck no run. Me not happy. How I up happy truck me?" I too am stumped. As a seeker of trends and exceptions in statistics in my quality positions, I thought this one would be relatively easy to find but I have yet to get anything in the way of cause and effect action. Will have some questions, if you don't mind, after I give the thread another read. Would you mind? All the best! And thanks for selling me a great truck!
 

Attachments

·
Registered
Joined
·
4 Posts
Glad to hear that you have had success. During work on my son's truck, I broke the coolant sensor. It was nice to see that the part is still available, and cheap. His truck had a poor idle as well due to cracked heads, and maybe the coolant sensor.
 

·
Registered
Joined
·
5 Posts
Time to put this thread to sleep

Since I bought this truck last October, I have had a "Check Engine" light glaring at me off and on. The good side of this was that the truck didn't seem to suffer too much from whatever the CEL was unhappy about. It was always the same set of codes: misfire in cyl 1, 3 or multiple. Since I was planning to take it for an extended drive back up north to the tune of 4-5000 miles in July, it was time to take care of a couple other small irritations and say goodbye to the CEL.


Took it to my mechanics with a to do list and kicked back with this months copy of Hemmings Motor News in the lounge for a quiet read. The to do list included fixing the back up light switch, servicing the A/C and advancing the knowledge base as to what's up with the CEL. I had explained to them about the rough idle and lousy gas mileage (18.6 mpg average from a 3.9 had better include a large trailer and a load in the back or something was wrong; it didn't so...uh...something was wrong) as well as the long list of parts that had been thrown at it so far. They said, "No problem. We'll call you when it's ready." They always do.


About 3 hours and 300 pages into the Hemmings, the truck was good to go. I now had a mobile meat locker with back up lights and a satisfying lack of CEL. The latter was chased off by installing a new injector in the #2 cylinder and replacing the fuel pump.


The Dakota is now amazing! It ran and drove before but now it DRIVES! The transformation is astonishing. I have essentially a new truck. So that is the end of this story. Glad I could write it.


Will see you on the road!
 

·
Registered
Joined
·
506 Posts
Seems the troubleshooting and steps you've taken thus far are pretty sound. With a problem this intermittent and which can be corrected by shutting off and restarting makes it that much more difficult. I would be looking for bad wiring or a poor connection to the sensors that the PCM uses to regulate fuel delivery. I'm guessing that when you replaced the cat, you also replaced the O2 sensors, and checked the wiring and connectors there. So the other main sensors are the throttle position sensor (TPS), the manifold absolute pressure sensor (MAP), and the intake air temperature sensor (IAT). I doubt that the sensors themselves are bad, or the problem wouldn't be intermittent and correctable by restarting. But a bad wire or poor connection to the sensor could generate a fluctuating signal, and turning the engine off (removing the vibration) may allow it to 'reset'.

Another possibility is a problem with your 5 volt power circuit. It is generated in the PCM and provides sensor power to the crankshaft position sensor, camshaft position sensor, TPS and MAP sensor. Fluctuating voltage here (or a bad wire) could provide erratic input from all those sensors. The 5 volt power is provided through an orange wire coming from pin 17 of connector 1 on the PCM. (Pins and colors are from a 2000 FSM, but I think it's the same for 1998, especially the orange color as that is pretty standard for Chrysler.) You should see an orange wire going into each of those sensors, and can check the voltage with the connector disconnected and the key on - look for 5 volts.
 

·
Registered
Joined
·
5 Posts
Seems the troubleshooting and steps you've taken thus far are pretty sound. With a problem this intermittent and which can be corrected by shutting off and restarting makes it that much more difficult. I would be looking for bad wiring or a poor connection to the sensors that the PCM uses to regulate fuel delivery. I'm guessing that when you replaced the cat, you also replaced the O2 sensors, and checked the wiring and connectors there. So the other main sensors are the throttle position sensor (TPS), the manifold absolute pressure sensor (MAP), and the intake air temperature sensor (IAT). I doubt that the sensors themselves are bad, or the problem wouldn't be intermittent and correctable by restarting. But a bad wire or poor connection to the sensor could generate a fluctuating signal, and turning the engine off (removing the vibration) may allow it to 'reset'.

Another possibility is a problem with your 5 volt power circuit. It is generated in the PCM and provides sensor power to the crankshaft position sensor, camshaft position sensor, TPS and MAP sensor. Fluctuating voltage here (or a bad wire) could provide erratic input from all those sensors. The 5 volt power is provided through an orange wire coming from pin 17 of connector 1 on the PCM. (Pins and colors are from a 2000 FSM, but I think it's the same for 1998, especially the orange color as that is pretty standard for Chrysler.) You should see an orange wire going into each of those sensors, and can check the voltage with the connector disconnected and the key on - look for 5 volts.


You have confused me with the former owner(s). Everything mentioned above had been replaced by one of them prior to my ownership including a new manifold to bumper exhaust and everything connected to it. The gentleman I bought the truck from is an aircraft mechanic for a very large international carrier and has been for many years. He is the author of the bulk of this thread.


Before I bid on the truck, I had a very pleasant conversation with him after reading one of the best, most honest eBay descriptions I had ever seen. It became quickly obvious that no matter what hydro-electro-mechanical challenge he is met with (Female voice from the other room, "Hon, the bathroom faucet is leaking. Would you look at it?"), he approaches the repair with the mentality that the object in question will be taking 350 passengers to Brussels tonight with an assumed high degree of success. To find this thread after buying the truck gave me a bit of a new buyer jolt. I read it very, very carefully many times.


It caused me to sit and give the ramifications of the find a think. After some serious consideration (a single malt Scotch is much preferred over a multimeter for this level of diagnostic) I decided the prime root of the problem was this: my Dakota was built, not by Boeing or Airbus (or even American Standard Plumbing Corporation) but the Chrysler Corporation circa (God help us) 1998. I didn't need 5 volts at pin 17, I needed Pablo.


Pablo is a national treasure. He is the type of mechanic who, if you need your 318 fully rebuilt while it is running and only through the exhaust pipes, he'll think about it for a minute, tell you it will be ready in a couple days and ask how much gas is in the tank. See previous post for Pablo's solution to the rough idle problem. In return, I hand him quantities of dirty, often rumpled pictures of Dead American Statesmen. After that, the vehicle runs perfectly for 10s of thousands of miles.


Granted, this approach doesn't advance the technical content of this excellent forum. Especially since I have no intention of revealing how to get in touch with Pablo. You see, I have this Dodge pickup that needs some work that was built by the Chrysler Corporation circa (God help us) 1983 and I want to be sure he has the time. I am in conference with a group of Dead American Statesmen, even as we speak....!
 

·
Registered
Joined
·
506 Posts
Sorry about that, Q123. When I clicked on the new posts link (the one you posted yesterday), I only went to the bottom of the first page and didn't note the date. I responded to N84434s last post on that page. But I do feel better about my diagnosis - as shown on the first entry of page 2, his problem turned out to be a bad coolant sensor and/or connection. Not one of the sensors I addressed, but one that the PCM does look at when metering fuel.

Glad you got the later issue worked out, and that your Dakota and your older Dodge pickup are giving you as much pleasure as mine gives me!
 
1 - 20 of 22 Posts
Top