99 Caravan Sport Rough Idle and Stalling

[blase]

Hi folks, new member to the forum but have used the site a lot in the past to help diagnose problems with my van. Today I need serious help because I'm not sure where to even start with this problem. Yesterday driving home my van (3.3L flex fuel) suddenly started running poorly and seemed to have little to no acceleration. Got it home and it started to idle very rough and eventually stalled in driveway. Then it would turn over but not start. This morning it will start (eventually) but it idles very rough from 500 to 1200 rpm and even seems to backfire occasionally. There is also a noticeable "blowing wind" noise coming from the air intake tube leading to the air filter. A couple of times the "wind" noise would stop and the engine would idle fine. However, if I gave it any gas, it would try to stall out. So far there is no SES light or trouble codes with the key method. Pretty good working on van, but all the sensors give me trouble. I don't know if I should start with the EGR valve, cam sensor, crank sensor, tps, or even fuel pump/filter. Any info anyone can give to help me narrow down the problem would be greatly appreciated.

[RIP]

How old are the spark plug wires, plugs and air filter? Was any maintenance done just prior to this starting? Backfiring out the intake indicates a lean condition. Out the exhaust indicates a rich condition. Which is yours? Any experience using a multimeter? First thing I would do is check the coil, spark plug, and cam/crank sensor and TPS connections for anything amis. Look for corrosion or contact damage. You could try disconnecting each spark plug wire one at a time. The one that doesn't change the idle is the one not firing, if any. An easier way to check for spark is to connect a timing light to each wire and look for the one not producing a flash. Next connect a fuel pressure gauge at the fuel rail test port and see what pressure the pump is producing. Better to check it when it's running rough. Look for a steady 49 psi. An Autozone or the like can lend you a gauge. Have them scan for codes. It's free. If all looks good clean the EGR valve and vacuum lines, though I would have doubts it would keep you from starting. Still bad with no code? Change the cam and crank sensors.

I'll never say never but the fuel filter has filtering capacity to spare. It's designed to last the life of the van. Not a likely culprit.

[blase]

Hey RIP, thanks so much for taking the time and your input. To answer your questions and fill you in on today... Spark plugs, wires, and air filter all replaced about 6 months ago. Since then no maintenance done. This morning went over all the sensor connections (unfortunately don't have a multimeter) and all look good. Took apart air intake, cleaned throttle body, and started it up. It startes and idles much smoother, but still not right. Upon start up it still makes a loud "sucking wind" noise from the idle air control motor port, which deminishes as the engine warms up and then the idle will smooth out. The idle air motor seems to be working as the intake will draw more air when you let off the acclerator. Today I was able to drive it up and down the street although it will hesitate when you acclerate from a stop, and it definately lacks accleration. So far still no SES light, although I'm going to take it to Auto Zone anyway to have them check for codes.

[RIP]

Well you're making progress anyway. Just curious. When you inspected the sensor connections did you disconnect them? Maybe reseating the connections helped. Sounds like you may have hit on something in the throttle body area. May be worth taking a second look at both. Once you depress the accelerator the IAC valve is for the most part out of the picture as its purpose at idle is to allow air passage past the closed throttle plate in the throttle body. During warm up with the throttle closed it opens to increase warm up RPM. As the engine warms it closes some. It will open again as you slow to a stop, turn on the A/C, turn the steering or floor the pedal all in an effort to maintain a stable idle and prevent stalling. Your "sucking sounds" screams vacuum leak. If you haven't, take a close look at all the vacuum lines in the area.

[blase]

Well, update for today. This morning I went over all the vacuum lines and visually checked as much as I could. I drove the van and it still lacked acceleration and bogged when you first hit the gas. Took it to the auto parts store and had them hook it to the scanner, but no trouble codes (still no SES light). Stopped on the way home and put in some fresh gas and a bottle of fuel injector cleaner (amateur, but I figured it couldn't hurt at this point). After letting it run for a while in the driveway, the van is running at about 95% of where it was before this all started. It idles fairly smooth, has regained most of it's accleration, and only hesitates slightly when you first hit the gas. I don't know if I was able to correct the problem by something as simple tightening a loose connection or cleaning the throttle body, but for now she is running. I am going to drive it for a couple of days and see what happens, like if the problems returns or if I get a SES light. Otherwise I feel like I would just be guessing by replacing various sensors without a trouble code. I will definately post again if the status changes or if I make any repairs. Thanks again RIP for all your help.

[RIP]

Good news. Hope you made a long term fix.

[blase]

Ok, I wanted to follow up one last time to let everyone know the final outcome. After my last post of checking connections and cleaning out the throttle body, the van only lasted half a day before all the symptoms returned (loss of power, rough idle, and even stalled in the driveway again). Had to break down and take it to the local auto repair shop, where they diagnosed a bad fuel pump. They wanted $680 to replace the pump, which I was not prepared to cover. Did some research and decided to give it a try myself. Got a fuel pump module from Auto Zone for $150 (pump, regulator, and stainer in one) and a fuel pump replacement kit from their "loan-a-tool" service. My dad and I were able to change out the fuel pump in under 2 hours in the driveway this morning. Drove it all over town today and the old girl is running like a champ. The total repair cost me $185 and there is a 1 year warranty on the fuel pump. RIP was definately on the right track with suggesting to test the fuel pressure, as I'm sure that is all the repair shop did. Keeping my fingers crossed.

[RIP]

Great news. Big pat on the back for keeping it DIY and saving all those bucks. Another one for posting the fix.

[plymouthsrock]

So I guess the "sucking sound" was the IAC valve going wide open to compensate for the drop in RPM. Good lesson there, thanks for the post.