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Throwing Codes and runs Rough

B

bdenglund

NAXJA Forum User
Location
Texas
Hey guys,

The jeep is throwing some codes.
14 & 15
It runs rough intermittently and sometimes has a rough idle. I just changed the 02 sensor and IAC valve and rested the PCM last week. Those did noting to help so any suggestions would be appreciated. Pretty frustrating.

Bdenglund
1991 Laredo
4.0
Aw4
149000 miles
 
Look specifically at where the codes lead you. OBDI certainly isn't perfect, but it is awfully darn good at leading you to the offending circuit.

Code 14: Map voltage too high or too low

Code 15: Vehicle speed sensor signal...no distance sensor signal detected during road load conditions.

Start by replacing your MAP sensor. Then clear codes and see if any return.
 
Ok.. Gonna do that today. Can I get the MAP at any parts store or does the stealership have the only ones that will work??
 
I have had reasonable luck with aftermarket MAP sensors. But I buy all of my aftermarket stuff from Napa. Not real fond of some of the others that carry some cheap-charlie engine management stuff. Napa or dealer.
 
Well I got a new MAP sensor from NAPA installed,and computer reset. The idle seems to be alittle better but there is still a miss whenever you drive down the road. I checked to see if there were any codes after I drove it around a little, and there were none. Kind of thinking the TPS sensor.
 
bdenglund said:
Well I got a new MAP sensor from NAPA installed,and computer reset. The idle seems to be alittle better but there is still a miss whenever you drive down the road. I checked to see if there were any codes after I drove it around a little, and there were none. Kind of thinking the TPS sensor.
Click to expand...

Does it idle high? That's what mine did when my TPS went out.
 
bdenglund said:
Well I got a new MAP sensor from NAPA installed,and computer reset. The idle seems to be alittle better but there is still a miss whenever you drive down the road. I checked to see if there were any codes after I drove it around a little, and there were none. Kind of thinking the TPS sensor.
Click to expand...

Are you absolutely sure that the vacuum line leading to the MAP sensor is pulling good vacuum?

If the map sensor code doesn't return, you did have a map sensor problem and the new sensor resolved it. But you could also have something else going on.

But I can't stress enough that you need to follow the codes. They need to be chased methodically until they are GONE. It is the best strategy. Then if you are left with symptoms after your codes are gone, you should continue with a testing based strategy to find root cause. Don't guess and don't throw parts at it and hope you're right.

A very important question for you. Do you have fresh tuneup hardware? New Champion copper plugs gapped to .035, quality plug wires, distributor cap, rotor, fuel filter?
The importance of fresh tuneup hardware cannot be overstated.
 
Last edited:
Hey fellas,
Thanks for the replys. I did a full tuneup back in February. Champion plugs(.035), wires, dis. cap, fuel filter, air filter, and precision auto injectors. Ill check and see if the jeep is throwing a code again..

bdenglund
 
Well I checked the codes again and there are still none. It still has the slight miss while it is being driven. It is most apparent on the highway and not too noticeable at idle. Any thoughts on what to chase next would be appreciated..

Benglund
 
Alright fellas, I'm at a loss. I just replaced the Coolant Temp Sensor and guess what, still a rough idle. I'm bout to say the heck with it and take it to the shop, unless someone can give me some idea of what to do. Still no codes, the idle is only rough when the engine is cold. If something else comes up I'll let you know..

Bdenglund
 
You can test most if not all the sensors with a volt meter. Just get a chilton, not a Haynes, book and all of the procedures are in there for the most part. 20-30 bucks on a book is hell of alot cheaper then the mechanic will be even if you have to buy a volt meter.
 
Re: Throwing Codes and runs Rough. UPDATE!

Well i finally figured out the problem. When I originally installed the spark plugs I accidentally got a little anti seize on the isolator part of the plug and it was almost all eaten away when I pulled it. So I swaped out the old plugs with new Autolites and it purrs like a kitten now. So I think that changing out the MAP sensor and the plugs have made all the difference in the world.
I also want to say thank you to everyone who took time to respond. I really appreciate it.

Bdenglund
 
Re: Throwing Codes and runs Rough. UPDATE!

bdenglund said:
Well i finally figured out the problem. When I originally installed the spark plugs I accidentally got a little anti seize on the isolator part of the plug and it was almost all eaten away when I pulled it. So I swaped out the old plugs with new Autolites and it purrs like a kitten now. So I think that changing out the MAP sensor and the plugs have made all the difference in the world.

I also want to say thank you to everyone who took time to respond. I really appreciate it.Bdenglund
Click to expand...

Glad you stayed on it and got it resolved. The importance of good tuneup hardware like plugs, etc. can never be overstated.

And thanks for the update. Oftentimes, we never hear back once the issue is fixed!
 
It is irritating when people ask for help and never post their findings. Sort of like; I want you to help me, but i don't want to help anyone else.

Bdenglund
 
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