I'm trying to fix the rough idle in park on my father in-law's '97 GC with 3.3L. I recently changed the plugs and wires which it badly needed, but that didn't fix the rough idle. The idle is rough when in park, but once it's in drive with the foot on the brake, the idle is smooth.

The van seems underpowered to me, but it also has 246k miles on it. I could be fighting a burned valve or compression issue, but I want to rule out the easy things first.

Tonight I decided to check the air filter and throttle body. The air filter should be replaced and the throttle plate was pretty dirty as was the upper intake. When I did the plugs, I also did a cylinder de-carb with Sea Foam so hopefully the valves and pistons are clean. I got A LOT of smoke out of this.

So tonight I sprayed out the throttle body and noticed drips of the cleaner on the top of the transmission. I looked for the source and noticed it's coming out of the EGR valve! This doesn't seem right. Do I need to replace the EGR valve? I see the EGR valve/transducer is stocked at my local Autozone for $59, which leads me to believe it's a fairly common part, but a search of this forum would not indicate that.

As I'm not a Dodge guy, any other areas I should explore that are common issues on these vans? A couple weekends ago I did the anti-sway bar bushings, which have been needed for quite some time.

-Rod

I highly doubt the motor is tired. Just my opinion of course. That 3.3 is strong, most were anyways. I would say that yes the egr is tired. When the egr is bad it will also affect the a/f ratio and could be leading to your lazy engine.

Yeah, I think the engine's still pretty healthy as well. last night I pulled the front three plugs, disabled the fuel pump, opened the throttle and checked compression. Cylinders 2, 4, and 6 had 150, 146, and 164 psi respectively. I sent a borescope down into cylinder #2, it looked pretty good. A little carbon on the top of the piston, but I could still see the contour of the piston top, so I don't think it's excessive.

I pulled all the vacuum hoses from the manifold and verified they held vacuum. I also replaced the EGR valve/transducer assembly and gasket. With the new EGR system installed and a new air filter, I put a vacuum gauge on the manifold and get a solid 18 in-Hg vacuum with very little fluctuation with the engine idling. If I vent my vacuum gauge, the engine still is able to maintain 10 in-Hg. I wonder if the roughness idling in park is due to a bad engine or transmission mount. I do get some rocking in the engine when I push against the bumper with my knees and the transmission in park.

The exhaust still smells funny and is dark like it's running rich. That would be different from a vacuum leak. The oxygen sensors would also indicate that it's running rich, but the long term fuel trim would imply it doesn't think it's too rich. The fuel rail pressure is 40 psi when primed, and after 4 days sitting with the guage attached, it still holds 20 psi. I don't think an injector is leaking.

Do you know what the fuel pressure should be with the engine running?

-Rod

This is from a helpful website:

"A rough idle or stalling. A large vacuum leak can lean the air/fuel mixture out to such an extent that an engine will not idle at all. An EGR valve that is stuck open at idle can have the same effect as a vacuum leak. So too can a loose positive crankcase ventilation (PCV) hose, a leaky PCV valve or the wrong PCV valve (one that flows too much air for the application). If somebody replaced the PCV valve recently, they may have installed the wrong PCV valve. The rough idle in all of these cases is caused by "lean misfire." The fuel mixture is too lean to ignite reliably so it often misfires and fails to ignite at all. Lean misfire will show up as elevated hydrocarbon (HC) readings in the exhaust, which may be enough to cause a vehicle to fail an emissions test. "

Check this site out,it may help:

http://www.aa1car.com/random-misfire/

Yep, but in this case the indications are a rich mixture: the exhaust is dark, the oxygen sensor stays above 0.45 V much of the time, and the long term fuel trim indicates it's trying to slightly lean out the mixture. Also, the EGR is new, the PCV is OEM and seems to be working (I removed it, it rattled, I cleaned it, and reinstalled) and the manifold vacuum is in the good range according to aa1 and other sites I've visited.

I took the van for a short drive last night and it does seem peppier than I remember it being. It is a bit rough from a start, but once it's going about 5mph or so it runs very smooth.

I'm about to suggest he look for something new though. Last night I decided to pressurize the cooling system while fighting the rear brake drums off. The cap seemed nearly loose, so I checked it. It only holds to 4psi. I then pressurized the system to the recommended 16psi and the pressure slowly started to drop. I got the first drum off and noticed a puddle forming under the water pump area. Upon inspection, it would seem the leak is either from the water pump gasket, a frost plug, or something in the difficult to see area blocked by the water pump pulley, oil filter, and what appears to be an oil level switch. The leak I was planning to find was for the rear heater core, which showed signs of leaking a couple weeks ago. After 246k miles, I think it's time to retire this one. In addition to the above issues, it also needs new rotors, rear brake shoes, pads, and at least one new caliper. :(

-Rod

Quick note... when the pipe to the rear heater core blows, it's a spectacular sight in your rear view mirror... it'll make you think you blew a head gasket with coolant spewing onto the exhaust system and boiling off as white steam. Fortunately, a short piece of hose will let you bypass the entire rear heating system.

The fuel rail pressure is 40 psi when primed, and after 4 days sitting with the guage attached, it still holds 20 psi. I don't think an injector is leaking.

Do you know what the fuel pressure should be with the engine running?

-Rod

The good book (Haynes) says 49 psi.

Upstream O2 sensor output should fluctuate much more than the downstream sensor

Thanks for the info!

I think I have my father in-law on board with considering a new vehicle. He likes taking long road trips and will be retiring soon, so I really am not comfortable with him taking such long trips in this vehicle.

-Rod

Thanks for the info!

I think I have my father in-law on board with considering a new vehicle. He likes taking long road trips and will be retiring soon, so I really am not comfortable with him taking such long trips in this vehicle.

-Rod
Shorod a had the same problem it ended being the spark plug wire even though it was new , i ended up taking it to the dealer for a diagno .. they replace number 2 wire :tongue:sovled problem hope this helps Mike

I'll keep that in mind if he decides to keep the van a bit longer. I did put a spark tester in series with the suspect plug wire and it looked good. It didn't indicate erratic or weak spark, but I could have blinked at the same moment the spark dropped out and missed it as well.

-Rod

Rod I have the same van and had planned on replacing the EGR valve to because my check engine light is on and I took it to autozone and had them check it and it was throwing codes for this, anyhow when I went and looked under the hood I noticed several vacuum lines were cracked and I'm missing 2 so rather then jump to replacing the EGR I figured I would fix these lines...my dilemma is I DON"T know where these line go, I've posted this on prob 5 different forums and still no one has been able to help, could you look at your van and the vacuum lines and help me out here? Here are the images of mine


This image is of the EGR solenoid you can see the nipple but I have no line and don't know what happened to it, does anyone know where I can trace this line to or from?

http://i33.photobucket.com/albums/d87/mylove2five/ImportedPhotos00041a.jpg



This image below is showing a broken vacuum line, again I have no idea where this vacuum line connects at:

Top View

http://i33.photobucket.com/albums/d87/mylove2five/ImportedPhotos00039a.jpg

Bottom VIew
http://i33.photobucket.com/albums/d87/mylove2five/ImportedPhotos00040a.jpg

You might check the vacuum diagram under the hood to see where they go. The van I was working on is my father in-laws, so I don't have immediate access to it.

However, if I remember correctly, the vacuum line for the EGR transducer (photo 1 in your post) went through the wire loom (photos 2 and 3) and connected to the vacuum port on the upper intake manifold. From what I can tell of your photos, you only have one broken vacuum line and that's the one that goes from your vacuum port to the EGR transducer. I bypassed the brittle formed hose and just went straight between the two with enough of a service loop that it won't get pulled off or pinched accidently under normal driving.

-Rod