I have a 98 360 w/55k. When the engine is cold it is experiencing a really rough idle that goes away when the engine warms up, it acts like it wants to stall. I haven't cleaned the T Body or replaced any sensors. Could it be carbon build up? To avoid knocking I am running 93 octane, have the entire life of the motor. Would a sensor cause that?

any ideas would be appreciated.

 

Well, I think you might have nailed your problem in your statement. A 360 (5.9L) engine only requires the use of 87 octance gas. In fact, there are many reasons why you shouldn't run such a high octane in a 360.

A higher octane fuel is normally required in higher compression ratio or high performance engines. This is because they run at higher combustion chamber temperatures. These higher temperatures could auto-ignite the fuel/air mixture. This means that instead of a stable flame front burning throughout the cylinder, the gas combusts erradically. This is the cause of "spark knock." So, in order to prevent this, higher octane gas has a higher flash point temperature. Unless your engine is knocking/pinging on 87 octane, you do not need anything higher.

The reason for the driveability problem is that since the gasoline has a higher resistance to ignite, when the engine is totally cold the mixture will not burn completely. Thus it's power will be reduced and will have a rough idle.

I would try using 87 octane in the truck, even the service manual says it only requires 87. This should take care of your problem

Good Luck

 

Thanks for the info. I am always getting grief from using high octane gas to mask the knocking/pinging problem associated with these motors. I have tried both 87 and 89 and get knocking under acceleration. The PCM was replaced and the same thing happened.

When I run the 93, I don't get the knocking and have great power when accelerating.

I think it's another mopar scam that they don't recall these Dodge Lambs and rewire the spark plug wires, which are also a cause of the knocking/pinging.

So, I guess I am screwing up the motor by running the higher octane to mask the knocking/pinging.

I called Dodge on the topic once and since the manual says 87 or higher (I got one of the first 98's out there, with a owner's manual that was half assed 97 and 98).

I always thought I was doing the engine a favor by running the higher octane as I do in my Charger and Linoln.

 

It sounds like someone must have done some major damage to your engine, or at least major modification. I have never heard of a 360 engine pinging on 89 octane if it was experienced on 87 octane. Knock/Ping is usually caused by higher cylinder temps, higher combustion ratio, or too much advance/retard on the engine timing.

Are you running a heavy trailer a lot in a mountainous area?

You are not screwing up the engine by running 93 octane, you just can't expect cold idle and driveability quality by using it.

Good luck

 

My truck is 100% stock. It has pinged/knocked whatever you want to call it from day one. I heard that it was either due to a PCM problem or spark plug wiring needed redone. It never was a heavy ping/knock just effin annoying for a new engine and vehicle that costs 24k. I don't think I am suffering from the plenum gasket thing, as I don't burn oil as per the TSB on the thing.

Dodge builds crap and they know it these days. From what I have seen on this board, most of the folks have swapped out all the original crapola just to have a good running engine. So much for a Magnum, more like a wuss.

Mopar hasn't built a good engine and transmission since the early 70's. I've dogged my 73 Charger, and to this day, has not given me the problems that the 98 360 cid does along with its feable transmission. I have had the car since 79 it has a 400 cid 120k miles and original tranny.


I baby my Ram and have had ongoing problems from the start due to the fact the damned thing was put together in Mexico. So much for Latino quality.

Never again will I buy Dodge.

 

Being employed as an engineer for DaimlerChrysler, I definitely have to disagree with you. Dodge/Chrysler/Jeep has made huge strides in the past couple years with quality. More vehicles are being selected for Quality awards, and continue to improve.

As far as not building a good engine, I believe the Hemi is your answer. Wards Auto has rated the Hemi engine as one of the Top ten world engines 2 times out of the last two years.

As far as quality in the mexico plant, the mexican workers take extreme pride that they are able to build dodge trucks. They have one of the best quality records, the problem with your truck is the engine, which is not built in the mexico assembly plant.

Obviously, to each his own, I am not looking to start a fight. I have never had a problem with my Ram, and I hope you can eventually resolve your problems.

 

Too bad they didn't take pride when putting my truck together. Go check out the reviews on www.carreview.com.

I am definitely not alone.

I am not trying to argue either, the build is really shabby.

I do not and will not believe that mexicans build quality. Otherwise, they'd have economy of their own.

Where are their "big 3" automakers?

My previous list says it all.

Most Dodge dealerships agree.

 

Sell it.
Why put more money into it? So you can keep it around to complain about it?

 

Exactly. Like I said before, sell it if you hate it so much and use the time you spend complaining doing something more productive. And if you didn't want a Mexican built truck, why did you buy one in the first place? They build Rams at the Warren, MI plant too.

 

I own a Mexican built Ram 1500 truck and its the best vehicle that I've ever owned. I brought it new in 2000 and the only major thing that I've had to replace on it was the air conditioning condensor. I've got no problems buying a truck that was made in Mexico.