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Discussion Starter #1
Hi, everyone,
I'm a new member. I have a '94 Frontier. I have a rough idle problem, right now. On start up, the truck idles pretty rough, and will even stall. As soon as the truck is warm, everything is fine. Does anyone have any clues for me?

Thanks
 

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Welcome.

Based on the limited amount of info you gave, there could be a million different reasons, but the first thing that came to mind given the age (and therefore likely mileage) of your truck was the plugs? When was the last time they were changed?

We are going to need a lot more info to try to diagnose the problem. Are you supercharged? 4 banger or V6? Any mods to the engine/fuel system? Do you seem to have full power once the truck is warm? Where are you from (ie how cold is it there in the mornings right now)? Is it just the first start of the day? What happens if you start the truck, get it warm and then shut it off and try to start it again? Have you changed anything on the truck recently? Lots of questions, but all good info to have for a diagnosis.

I should add that compared to some of the guys (or even some of the gals) on here, I'm not a gear head, so I'm probably not the one that will be able to completely answer your question, but I can at least help get the ball rolling.
 

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Discussion Starter #3
Welcome.

Based on the limited amount of info you gave, there could be a million different reasons, but the first thing that came to mind given the age (and therefore likely mileage) of your truck was the plugs? When was the last time they were changed?

We are going to need a lot more info to try to diagnose the problem. Are you supercharged? 4 banger or V6? Any mods to the engine/fuel system? Do you seem to have full power once the truck is warm? Where are you from (ie how cold is it there in the mornings right now)? Is it just the first start of the day? What happens if you start the truck, get it warm and then shut it off and try to start it again? Have you changed anything on the truck recently? Lots of questions, but all good info to have for a diagnosis.

I should add that compared to some of the guys (or even some of the gals) on here, I'm not a gear head, so I'm probably not the one that will be able to completely answer your question, but I can at least help get the ball rolling.

Hi,
Sorry for the limited previous info. My '94 Frontier is the XE-V6. 132,000 miles. I'm in Houston, right now, so the outside temps are warm, even in the morning. There are no modifications to the engine or fuel system. I'm pretty sure I have full power, once the truck is warmed up. If I shut off the truck, and start it back up while it's still warm, the problem is not there. The problem returns when the truck is fully cooled off again. I have made no changes to the truck. The truck is not supercharged. So, the problem happens just when the motor is not at operating temperature.

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Well, my first thought is still the plugs if they've never been changed (plus this is cheap and relatively easy to do), but I've got a couple other thoughts as well. I'm sure one of the more mechanically inclined guys will jump in here sometime today and give you some more ideas, but here are a few possibilities off the top of my head.

1. Sparks, as previously mentioned. Easy to fix, goto AutoZone and buy new ones then spend a couple hours changing them.
2. If it is really only a recent problem, you could have gotten some bad gas that isn't burning right in the engine. Fill up with 91 or 93 octane and pour some octane booster in the tank.
3. Your cats could be going bad, meaning that until they heat up they aren't letting enough flow through. I think only a mechanic will be able to check this for you.
4. Could be some kind of an intake or fuel/air mix issue, but I'm not sure why this would improve as the engine warmed up.


Another question: The check engine light isn't on? Seems strange that the truck could get to a stall point and not throw any kind of code.
 

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Discussion Starter #5
1. Sparks, as previously mentioned. Easy to fix, goto AutoZone and buy new ones then spend a couple hours changing them.
2. If it is really only a recent problem, you could have gotten some bad gas that isn't burning right in the engine. Fill up with 91 or 93 octane and pour some octane booster in the tank.


Another question: The check engine light isn't on? Seems strange that the truck could get to a stall point and not throw any kind of code.[/QUOTE]

Hi, again,
Thanks for your help. The spark plugs were changed, recently. The rough idle (when cold) is not a recent problem. There is no check engine light on.

Thanks
 

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This sounds very similar to the rough idle I had on my Pathfinder. Cleaning the mass air flow sensor, and a complete seafoam treatment fixed it right up. Seafoam and MAF cleaner should run you less than $20 at the local parts store, and should only take a few minutes of your time. I was quite supprised at the amount of buildup on the sensor wires for the MAF, you would think that they would be clean because the MAF is downstream of the air filter, but they had a "fuzz" of fine particles all over them. Just my $0.02, I'm no mechanic.
 

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Definitely clean the MAF sensor, that was going to be my first suggestion but I see hydrotech "got the drop on me" so to speak.
 

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The MAF is a good point as that would change the mixture.

The Seafoam is also possible, but I've heard it can be harmful to vehicles with very high mileage, so do some research on that before you do it. Might be better off taking it to Jiffy Lube and having them do their injector system cleaner instead. It will be 2-3x more expensive there, but at least they would have to cover it if damaged the engine or exhaust system.
 

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My guess would be to check the O2 sensors, I am not sure on that model, but most have a heater wire, that heats the sensor to make it give a proper reading. If it runs fine after it's warm, check to make sure you have some voltage on the heater wire. I hope this helps. Just a guess, but still could be your problem. Especially with 100K+ on it, they may need to changed anyway.
 

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Same problem

Hi there. I just thought I would add that I am having the same problem. I have a '98 Frontier, 2.4 L 4 cylinder with ~152k miles. My SES light came on awhile back and I had the code checked and it came back with the Manifold Absolute Pressure (MAP) sensor or solenoid...I think the code was P1015. The engine still ran fine. About a month ago I changed the fuel filter and it immediately started a similar rough idle only when cold. Once I get to temp. it runs normally. I just had the code checked again and I got back fuel injector code. So, now I am thinking I may have some debris in an injector or something like that. I am planning a seafoam treatment to try to clean the injectors and I will report back. I am guessing that your rough idle comes from an injector or exhaust gas issue -- that could include O2 sensors, the MAP sensor, the MAF sensor, etc. Good luck and if you figure it out please let me know.
 
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