I have a 2004 Dodge Caravan with a 3.3L v6. The car surges when you try to go a constant speed. It's very small but my wife says it has been worse. I have a code reader called Mentor. It said that the EGR position sensor was high, so I would assume that it was open because since the light came on she has been getting crappy gas mileage. but the mentor does not show a misfire code, but the engine also does not have individual coil packs, it has one. I replaced all spark plugs and wires,and everything still acts the same. A new coil is around $90, could it be the coil missing or chatter in the torque converter?

Your surge can be caused by the EGR system. Recommend you fix that first. Could be an EGR system vacuum leak: http://www.obd-codes.com/trouble_codes/generic/p0402-exhaust-gas-recirculation-flow-egr-excessive-detected.php

First off the EGR is not a position sensor. Is your code showing the thottle position sensor as high, or are you getting an EGR code, or perhaps both?

Many codes can be thrown because of a malfunction up stream of the part that the code indicates. let us know the exact code or codes you're getting.

Ron

I know what the EGR valve is but the Mentor is saying that the EGR position sensor is high, I didn't write down the code number. It said:

-EGR position sensor performance/rationality
-EGR position sensor high

The van has 48,000 miles, I don't know what could be wrong at that many miles besides standard maintenance. I read in another faq that someone had this similar problem and he said that he unplugged his egr valve and his vehicle ran fine. I'm not sure what that caused or what it didn't cause but he left it unplugged. but how would an egr valve make a vehicle surge at constant speed. All it does is recirculate exhaust gas to be reburned in the motor. the check engine light was on for over a week and then went off for one day and then came back on. When the light went off the van ran fine, but when it came back on, it still ran fine. I haven't driven it enough yet to see if it will do it again.

Well it could be the egr going south but not bad enough to throw a code yet . I just spent $200 to get my egr replaced at 56000 miles but it had thrown a p0404 code (egr) but the symptoms were similiar to yours . this isn't the first case I heard about the egr's and I wonder if they were running crappy egr's in the 04 model year because the other one i read about was a 04 too .

but how would an egr valve make a vehicle surge at constant speed. All it does is recirculate exhaust gas to be reburned in the motor.

As you said, the EGR system sends exhaust air back to the engine. This effects the fuel air mixture. If the EGR valve is oscillating possibly due an internal or external vacuum leak the fuel air mixture, determined by the engine electrical system, will compensate to maintain the ideal mixture of 14.7 parts of air to 1 part fuel. This makes the engine surge as it tries to keep up with the EGR malfunction.

There are many things that can cause a surge. My starting point would be the EGR system since you have an indicated failure there.

thanks for the help you guys. The van hasn't had the problem again since I worked on it. but I think it will soon come back. I'll unplug the egr valve and see if it stops, if it does then I will investigate the egr system. Does the van have a screw-off valve stem type cap that you can take off to test the evap system? Would the evap system leaking make it do that. I'll check all vacuum hoses and look over it again when it starts doing it again.