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Dodgerench
Dodgerench, ASE Certified Technician
Category: Dodge
Satisfied Customers: 3125
Experience:  30+ years Dodge/Chrysler exp., ASE Master with L1 certification. Driveability/ combustion specialist
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1992 Dodge Dakota: sputter..Im driving it..starts great..champ

Customer Question

why does my 1992 Dodge Dakota Trk. spit & sputter while I'm driving it. It starts great, usually runs for about one mile, then it starts to spit & sputter and will only go about 20-28 miles an hour, it back fires sometimes alot, then after driving about 5 miles, it takes off and runs like a champ again. Got any ideas that will fix this?
Submitted: 4 years ago.
Category: Dodge
Expert:  Dodgerench replied 4 years ago.
HiCustomer welcome to Just Answer!.

It sounds like you may have a weak oxygen sensor... or at least a weak oxygen sensor heater. Erroneous 02 sensor signals produced by a sensor that isn't up to temperature at the time when the fuel system goes closed-loop (when it actively uses 02 signal for mixture control) can act just like this.

Your fuel system is in open-loop control from the time that you start it until it runs long enough and engine block temperature is high enough at which time the PCM switches to closed loop operation for better mixture control. If the 02 sensor is ready and providing an accurate signal, the transition goes unnoticed and everything works fine. A bad signal can drive the fuel system extremely lean, causing heavy loss of power, sags and even backfire through the intake manifold as you roll into the throttle. A bit later, with more heating... everything is OK again as those nasty adaptive values are erased.

You may have a code sitting in PCM memory even without a CHECK ENGINE lamp illumination because Chrysler tended to not turn the light on for oxygen sensor codes in these years. You can have the engine scanned or use the old "flash method" which works pretty well on the 92 models.
Roll the key from off to on three times, leaving the key ON.

Watch the CHECK ENGINE lamp as it does a longer than normal bulb check (close to 5 seconds) and then goes dark.

When the CE light comes back, it will be flashing, so be ready to keep count.

The pauses between flashes tell you what to do, much like Morse Code. Short pauses mean you should continue counting... this digit isn't done yet.

Longer pauses mean the digit is completed and you're moving on to the next one.

All trouble codes are composed of two digits, like 12 or 55, so you will always have an even number of digits once the flash code process is over.

Repeating the process 2-3 times is highly recommended if you're not a flash code veteran... codes such as 12 often become... "3" if the pauses aren't recognized.

Oxygen sensor codes can come up as a 21 or be disguised as a 51 or 52, both of which are mixture-related codes. The code 21 can have several meanings because self diagnostics have improved by the 92 model year but only one 02 sensor flash code had been created. Still, it's good information. Give it a try and let me know what you come up with.

Let me know which engine you have by the way..

Talk in a bit,
Ed
Customer: replied 4 years ago.
I'm trying to replace the oxygen sensor, but can't find where the wire hooks up. Is there a diagram somewhere?
Expert:  Dodgerench replied 4 years ago.
Not really... here's what I could find.

graphic

It appears the wiring pigtail could be pretty long for this application, which means it might connect over the center or even the left side of the transmission. If the parts guy got you the right sensor, the length of the pigtail will be the same and should help in locating and disconnecting the old unit since you can't see much up there. This connector is expected to be square in shape and uses a single thumb tab with no lock mechanism... just lift the tab and pull, it should come right apart.

Ed
Customer: replied 4 years ago.
Well, my husband just said he found it and is finishing hooking it up. We'll let you know how it goes shortly.
p.s. he said he thinks even a mechanic would have some swear words to utter when replacing this gizmo, it is in such a difficult place to replace!
Expert:  Dodgerench replied 4 years ago.
Your husband is a wise man! Swear words are required. =/

Ed
Customer: replied 4 years ago.
Well, however, even with the swearing, it evidently wasn't the oxygen sensor because it is still acting up. When we first start the truck it seems to run great, but shortly it starts to backfire, spit and sputter and when I put the gas pedal to the floor it doesn't do much, then all of a sudden the engine races and if I back off the pedal, it starts to run smooth as a whistle again for a few miles. When these problems started, we thought it was only when it was cold because once it warmed up, we didn't have any problems with it until it sat for a period of time (over night). SO, now, he is perplexed again. We drove quite a bit today to see if there was a pattern to the behavior, but not really. Do you have any more ideas for us?
Expert:  Dodgerench replied 4 years ago.
Aaaaaargh. Yes.

Pushing the pedal to the floor will put the fuel system into open loop mode again, a time when it doesn't look at 02 sensor output and should relieve the symptoms temporarily.

Which engine do you have?
I'm guessing the 6-cylinder 3.9 engine...

Ed
Customer: replied 4 years ago.
He's not absolutely what kind of engine, it is a 6 cylinder and it has fuel injection, 1992. Does that help, or can you tell him how he can tell what engine?
Expert:  Dodgerench replied 4 years ago.
No, we're good. That's the one.

We need to take the distributor cap off to check rotational slop on the distributor shaft.

By that I mean turning the rotor forward and back, measuring the swept area at the rotor tip. If it's more than 1/4", there might be trouble.

It might be necessary to remove the plug wires from the driver's side of the engine to get the cap to clear the distributor top for measurement. Make note of the #1 plug wire position, then pull the wires off. Firing order is 1-6-5-4-3-2 with all odd-numbered cylinders on the left side of the engine, numbered from front to back.

Ed
Customer: replied 4 years ago.
Okay. It is dark here right now, so he will check it first thing in the morning at day break. We have to get this thing running and we have both been laid off work for two years, so we are hopeful that he will be able to do this fixing.
He was wondering if you thought it could be a leaking EGR valve?
Expert:  Dodgerench replied 4 years ago.
No, it really doesn't sound like an EGR problem.

My apologies to you... and your suffering husband... my first instinct was the path we're taking now but when you said that the engine ran OK for a mile or so............. and THEN acted up........... it didn't fit the model for a worn distributor drive gear, which was a pretty common thing on the 92-93 3.9 engine Dakota. They typically acted up immediately at startup.

If excessive wear is found (lots of forward-back motion at the rotor), we can still squeeze a little more service out of the worn parts without repair. Just adjustment.

Check it out when you have time and I'll guide you through the steps.

Have a great night,
Ed

Customer: replied 4 years ago.
Thank you. He sure will, first thing in the morning.We appreciate your thoughtfulness and assistance greatly.
Expert:  Dodgerench replied 4 years ago.
Not to worry. We'll get it going again.

Be careful with the Phillips screws on the cap because they can be tight. If they round off, the outside of the screws are 7mm hex which should get it broken loose at least. More swearing is acceptable.

I'm pleased to meet you... um... MsCustomer

Ed
Customer: replied 4 years ago.
You are indeed a breath of fresh air!
Thanks for the tips.
Expert:  Dodgerench replied 4 years ago.
No problem-o. Let me know what you find and we'll press on from there. Have a great night!

Ed
Customer: replied 4 years ago.
It has more than 5/16" in play.
About a year ago when he replaced the rotor & the distributor cap, he found three rotor contacts laying in the top of the distributor.
Expert:  Dodgerench replied 4 years ago.
I've seen that happen!
What you're seeing with distributor shaft movement is a worn distributor drive gear down at the camshaft. It's taken its time in getting there... I kinda expected all these gears to have been replaced by now.

What you can do for now just to get the truck running good again is to turn the distributor about 15 degrees counterclockwise to compensate for the wear. With things the way they are, distributor (cam sensor) timing has become retarded which is magnified on cold engine start because of the extra load on your oil pump due to the extra thick engine oil. It stretches the timing chain and takes all slack out of the timing system, producing a max retard condition that greatly upsets your engine controller (PCM).

Bumping the distributor a bit will get the cam-crank sync back in range, as well as put the distributor rotor tip nearer the cap contact it's supposed to fire to. You may be off so far as to be seeing crossfire to the wrong cylinder at this point.

An exact adjustment can be done later if you elect to replace the worn parts, but for now imagine the distributor as a clock face. You'll be tapping the distributor counterclockwise an amount roughly equivalent to 3 minutes (or seconds... your pref).

It's hard to get at the distributor hold-down bolt (13mm) so if it can't be reached, go to the driver's side of the engine and look down at the distributor housing with a flashlight. Below the bowl there will be a square boss that's handy for placing a drift, large screwdriver or prybar against and then tapping lightly with a hammer (be careful to not pinch wires between drift and housing). Tap until you've moved the distributor enough and do the cold start.

I think you'll say wow.

I have to leave for an appointment but will be back online in about an hour and a half. Let me know how it worked!

Talk shortly,
Ed
Dodgerench, ASE Certified Technician
Category: Dodge
Satisfied Customers: 3125
Experience: 30+ years Dodge/Chrysler exp., ASE Master with L1 certification. Driveability/ combustion specialist
Dodgerench and 7 other Dodge Specialists are ready to help you
Customer: replied 4 years ago.
Thank you! I'm going to print this and run it out to him right now!
Customer: replied 4 years ago.
Is Dodgerench available?
Expert:  Dodgerench replied 4 years ago.
Back now! How'd it go?

Ed
Customer: replied 4 years ago.
You are FABULOUS! My husband used his crows wrench and got down in there. We just got back from giving the truck a ten mile drive and it never once sputtered, spit or backfired! You have no idea what blessing this is to us! Thank you very kindly!

Our son wants to know if you know anything about Volvo's. He has a very nice older Volvo that does almost the very same thing that our truck did.

Thank you again!

I will wait for your response, then I will accept your very helpful suggestions!
Expert:  Dodgerench replied 4 years ago.
Great news! It's not the last thing however... the worn gear is probably going to have to be replaced sooner or later.

If you can find it online, Chrysler technical service bulletin 18-08-03 (Revision A) describes the problem that you're seeing now but really doesn't do a very good job of detailing the repair. The distributor drive gear (53020546) and block bushing (1737725) will need to be replaced at some time or other. The TSB does a pretty good job of describing the actual distributor index procedure but it's not something I'd bother with until the parts get replaced... which might not be needed any time real soon.

No, I don't know anything about Volvos... but it looks like I'm gonna be learning Fiats one of these days. =/

Thanks for your patience, MsCustomer Much appreciated!

Ed
Customer: replied 4 years ago.
Thank you!
Expert:  Dodgerench replied 4 years ago.
You're welcome! Be sure to write back when you decide to finish the job and I'll do what I can to guide you (or the hubby) through the process. I'll keep this thread open for any problems you might have along the way.

Many thanks,
Ed

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