2001 Town&Country running really rough

[Barkleymut]

The wifes 2001 Town & Country (3.3L Flex Fuel engine) has been running really rough for a while. It started several months ago and seemed to be only when the AC was on.
Sometimes the engine runs smooth as can be, other times it is hesitating, and almost bucking. Yesterday while stopped at a light it lurched forward and even though I was holding down the brake pretty well it jumped forward about 3 feet.
It almost seemed like a transmission problem but I have ruled that out because it has exibited the symptoms when the trans is in N. I have ruled out an AC problem because it has the problem with the AC off. I replaced the plugs and wires about 20K ago. I just pulled the plugs and they look fine. Just replaced the PCV hoping for an easy fix...no luck there either. The check engine light has not come on at all. After doing some research it looks like it may be a vacuum problem, EGR, IAC, throttle body (kind of cleaned the throttle body yesterday - it was really dirty). Anyone know what else it could be? What should I try next? I'm thinking the IAC.

 

[NHGUY]

Had a surging problem with the 02 Caravan,seemingly it was the EGR valve.I then replaced the TPS as a matter of maintenance.Recently had to replace a newer fuel filter due to the o rings leaking,when I replaced it,engine performance smoothed even more.If you have 100K miles or more,I would replace a few things,for general maintenance sake.

 

[antiqueshell]

Even though the check engine light hasn't come on it may be storing a "pending code" which signals a problem that doesn't happen enough for the ECU to light the lamp. That doesn't mean that it might not be a problem for driveability that you are experiencing. Get a scan tool and check for the pending codes.

 

[Barkleymut]

hmm, never heard of pending codes. Thanks

NH Guy, I replaced the fuel filter (tough job btw) and rechecked the connections a week ago. I have done quite a bit of maintenance on this van over the years, I doubt it is a general maintenance issue.

 

[mechtech2]

If you lurch forward, that means the engine speed is increasing. The idle air motor is first on my list. Clean both the IAC and TB.
These MUST be right to go on, even if they are not the core problem.

 

[Barkleymut]

Well, I finally got a few hours to work on the van. Cleaned the IAC and Throttle body (TB was a real mess). Also pulled the hose that leads down to the EGR. Where the hose comes out of the intake manifold to the EGR was more than 50% blocked with a carbon like gunk.

After I reassembled everything I took her for a ride and the idle ran a little faster than before...maybe 100-150 rpms faster. It seemed to run a little smoother than before as well. Then my wife just took it to the grocery store and said it is running like [censored] again! I'm at a loss. The only thing I can think of at this point is a clogged fuel injector, or maybe a bad fuel pump. How can I test the fuel pressure? I know where the relief valve is but have never tested the pressure before.
Thanks,

 

[Barkleymut]

btw the problem only occurs intermittently. Sometimes it runs great, other times it runs like it has a miss. It seems to run poorly when it is really humid outside.

 

[meep]

the 3.3 is pretty torquey for what it is, and it wouldn't take much to goose it forward.

other items I'd consider:
throttle position sensor
cam/crank sensors
vacuum leaks
egr circuit

IIRC there is a small egr valve (not the main one) up top on the passenger side, near the front? pull the line at idle and see how that impacts behavior. (don't do this in gear...) it really sounds more severe than egr from what you describe.

m

 

[UNC017]

If the EGR valve is sticking open it can cause a really rotten surgey idle. Same for PCV. The fact that it hasn't set a misfire code makes me think its not something tied to a specific cylinder, like a plug, plug wire, or fuel injector. The computer has more trouble setting a code for something that randomly makes all the cylinders misfire, like an EGR valve leaking or a vacuum leak (though that may eventually set an O2 sensor code).

Keep hunting- this one sounds like "the usual suspects" that have plagued engines for 50 years.

BTW- look all around the fuel rail- there should be a capped fitting (the same threaded/tapered fitting format as old R-12 and R-22 air conditioning charge ports) where you can hook a fuel pressure gauge.

 

[Rhymingmechanic]

Originally Posted By: 440Magnum
If the EGR valve is sticking open it can cause a really rotten surgey idle.


I don't know your specific engine, but the EGR valve could be a good candidate for cleaning/inspecting if the passage is partially plugged. I had a low idle on a Saturn that was caused by the EGR sticking open just barely.

 

[Barkleymut]

Ok, Just cleaned the EGR really well. Replace the TPS, took her for a test drive. Still runs like [censored]. Now I'm thinking it may be a fuel injector that is a little clogged. I've run a LOT of Techron concentrate through the van over the past few months. The van ALWAYS stutters pretty bad when I'm going up one hill near my home. Again it cannot be a trans. problem since it runs rough while I'm in Neutral. I'm at a loss. Any ideas are apprciated.

 

[meep]

arcing internal to coil pack?

spark plug wires?

either will KILL hill climbs or general acceleration.

these use a pretty stout high volt ignition, AND it's wasted spark system.

mine had a great deal of acceleration B****hing and it turned out to be arcing wires.

 

[Barkleymut]

the plug wires are only a year old so i doubt its that. if it were the coils then i would think it would not be intermittant, but im not sure

 

[KB2008X]

As I was reading this thread the first thought I had was the ignition system. You said you’d pulled the plugs and they looked OK, and replaced the plug wires, but that doesn’t mean that the ignition system is functioning correctly, all the time.

It’s too bad that you can’t see what is actually happening under the hood during one of these malfunction events. However, you may be able to induce such an event and observe what happens, by brake-torqueing the engine. It will also serve as a decent test of the secondary side of the ignition system.

It’s best to do this at night away from any light sources, and in an open area with plenty of room in front of the vehicle. Have your driver start the engine and with their foot on the brake, and the front tires pointing straight ahead, put the van in drive. You need to stand off to the side so you don’t get run over, but can still watch the spark plug wires and coil. Have the driver rev the engine slowly to about 1500 – 2000 rpms. You’re looking for spark arcing out of the plug wires to ground or to another plug wire, or for spark arcing out of the coil to ground, or between the towers or to a plug wire. Don’t brake-torque it for too long, five seconds is plenty. Leave the engine running with the transmission in Park. After about a minute repeat the whole process again. If, after a few cycles, you don’t see any spark arcing, try spraying the wires and coil with a fine mist of water. Use just water, nothing else, and only a fine mist.

You can cycle through the brake-torqueing process several times before you need to leave the engine off for an hour or so to cool the engine and trans.

It may take a few hours to catch the problem like this. This is not a definitive test for the ignition system. Failing to see spark arcing does not mean the ignition system is OK.

If you can catch the engine acting up while you’re driving it, with a competent assistant in the van with you, it would be the ideal time to do this test.

Be aware that you may find a bad motor mount this way and the engine may literally try to jump out of the engine bay. Make sure the driver is ready to turn off the ignition at all times. You may also find that the front brakes are not holding as well as they should. Again, make sure the driver is ready to turn off the ignition at all times and has the front tires straight, and do not stand in front of the van.

Keith

 

[Barkleymut]

Thanks Keith. The cel just came on for the first time ever on the van along with some serious knocking. Took it to advance and the code was for 2nd cul misfire. I pulled the plug and it looks ok. The wire on visual inspection looks fin, but it is a spare original wire that I had to replace one of the replacement wires with when I pulled the boot off the replacement one. I will do your test tonight and report back. Thx

 

[Barkleymut]

The wires and coil appear to be fine, I checked last night and there was no arcing

 

[SteveSRT8]

You may be unable to see the problem. Test the wires with an ohm meter. You also may have a bad coil. Can you swap them out?

If the problem moves with the coil, there it is.

And the lurch forward happens a lot when an engine nearly dies as vacuum assist dies with it, then when it catches again the brakes are hardly applied at all.

Misfire codes are serious, and they virtually guarantee a real problem.

 

[Barkleymut]

I'm about to use a sledgehammer to fix my "problems". I pulled all the fuel injectors and now I cant get one of the connectors to snap back in correctly. I'm also trying to replace the coil but I cannot get the connector to come apart.
When I took off the plenium cover to access the injectors the passageways for the air to go into the cylinders were extremely dirty.

Any other ideas ya'll have?

It is running kind of rough at idle and will run extrememly rough at moderate acceleration.

Other things I think it could be (feel free to tell me any that it cannot be)

camshaft position sensor
crankshaft position sensor
02 sensor
vacuum leak - I disconnected the EGR while the engine was running and it was moving a lot of air (don't know if that means anything

 

[Kestas]

Can you fabricate a metal pate to block EGR flow for diagnostics? This may help bracket the problem.

 

[Barkleymut]

Yes I can block the egr, how will this help? is it ok to run the car with the egr blocked for a long time?