LHS Rough Idle

[Jerryx]

I have a 96 LHS. 69k miles.

Never had any problems of any kind. Then I smelled gas. Poked around and noticed gas leak near the #3 cylinder injector. Found out about the recall, so took it to local Dodge dealer to have fuel rail replaced. They replaced the rail and the o-rings on the injectors. I had them replace all of the belts and timing belt too. Thought it would be wise to replace the timing belt since it had over 65k miles.

I drove it for a few hundred miles and noticed that the idle was rough. Next day it stalls while driving. The codes were for misfire. Took it back to dealer, who told me it must be the wires, since they were the original wires and were disturbed when they replaced the injectors. So I let him replace the wires.

The new wires did not help. It still has a rough idle. I get P0305 and P0300 codes at least once every few days and usually every day. These codes are for #5 misfire and random cylinder misfires.

Before they serviced it, the engine idled fine, now it is still rough, so I thought maybe they put the timing belt on wrong. This morning I took the covers off and looked. At TDC, the marks on the both of the sprockets are right between the dots, dead-on with some pencil marks the techs must have made. I noticed that the bolt on the left side sprocket (near #1) had been replaced. Otherwise, nothing unusual.

Could this be the intake manifold gasket problem?

Any ideas?

Thanks,

Jerry

[theFREAKnasty82]

unfortunately, it is. The 3.5 V6 is notorious for having bad intake gaskets that go bad around the #5 cylinder.

[Jerryx]

Ok, thanks.

I suspect there definitely is a vaccum leak near the back of the engine. I poked around with a stethascope and with the engine at idle I can hear a sucking sound somewhere back there, near cyl #6 or #5. But I can't tell if it's the plenum gasket or the intake manifold gasket where the sound is coming from.

Which gasket usually fails?

Thanks,
Jerry

[theFREAKnasty82]

it's usually the manifold gasket itself that attaches to the cylinder heads. When you get to that, you'll have to replace both plenum and manifold gaskets in the process.

[harveyd]

Thanks for that I will try it too

Originally Posted by Jerryx

I have a 96 LHS. 69k miles.

Never had any problems of any kind. Then I smelled gas. Poked around and noticed gas leak near the #3 cylinder injector. Found out about the recall, so took it to local Dodge dealer to have fuel rail replaced. They replaced the rail and the o-rings on the injectors. I had them replace all of the belts and timing belt too. Thought it would be wise to replace the timing belt since it had over 65k miles.

I drove it for a few hundred miles and noticed that the idle was rough. Next day it stalls while driving. The codes were for misfire. Took it back to dealer, who told me it must be the wires, since they were the original wires and were disturbed when they replaced the injectors. So I let him replace the wires.

The new wires did not help. It still has a rough idle. I get P0305 and P0300 codes at least once every few days and usually every day. These codes are for #5 misfire and random cylinder misfires.

Before they serviced it, the engine idled fine, now it is still rough, so I thought maybe they put the timing belt on wrong. This morning I took the covers off and looked. At TDC, the marks on the both of the sprockets are right between the dots, dead-on with some pencil marks the techs must have made. I noticed that the bolt on the left side sprocket (near #1) had been replaced. Otherwise, nothing unusual.

Could this be the intake manifold gasket problem?

Any ideas?

Thanks,

Jerry

[Jerryx]

Thanks very much.

It was the manifold gasket near cyl #5. I took off the plenum, then the manifold, and you could see where a big chunk of the gasket was missing. I scraped off the old gaskets, cleaned out the residue from the intake ports and the manifold passages, and replaced the gaskets with Felpro brand, started it up, and after about 30 seconds, it was running rock solid. Hasn't run like that in over a year.

The bad news: I have two new problems to deal with.

The drain cock on the radiator has a slow drip. I had a LOT of trouble opening that damn thing, and when it finally gave way, it came out, giving me a face full of glycol. After washing my eyes for 10 minuts, I tapped it back in with a mallet. That drain cock is the worst designed POS I've ever seen. You can barely get to it at all, and when you do, it will barely turn. Whoever designed that damn thing ought to be shot.

Also, I now have a fuel leak. There is a geyser of fuel spraying out of the end of the rail where the return tube comes out. If I move the line just a little, it either sprays out or it almost stops. There is quite a bit of play there. I can't believe the position of the line matters that much.

Any suggestions on these new problems?

Thanks

[Jerryx]

Here's some info for anyone else who's had trouble getting a good seal on the radiator drain after servicing.

The o-ring on the radiator drain plug often gets cracks and the plug sticks. My o-ring had disintegrated when I removed it, so that explains the leak. You also shouldn't turn it more than 1/2 a turn. You turn it 1/4 turn, pull it out a little, then 1/4 turn more. That's all. I turned mine more and cracked it. A new one costs only $5 at the local parts store (but they had to order it). For that price, it's worth it to put a new one in every time you drain the radiator.

Now for the fuel leak...

Thanks everyone for posting info about intake manifold the vacuum leak. This forum is a life-saver.

Jerry