My wifes 03 Grand Caravan with 78K frequently wants to idle about 1300-1400 RPM. If you pull it into gear when it's like this then it surges between 600 and 900 RPM. It also does an occasional lurch while driving down the road at a steady speed. This thing has always seemed very underpowered and seems to have gotten progressively worse. Any ideas whats causing the idle thing? If this van was a horse I'd shoot it!
peter_x
09-08-2008, 04:56 PM
A vacuum leak is often the cause of high idle. Check all the vacuum hoses going into the intake.
Has it had a tune-up (plugs, wires, fuel filter, air filter)?
Jwilli500
09-08-2008, 09:15 PM
Thanks! I'm not sure, I'll hafta check about the plugs, Air filter=yes, fuel filter= no(I beleive its on top of the fuel tank?) Havent heard or noticed a vacuum leak but I will maybe look a bit harder. Again thanks!
A vacuum leak is often the cause of high idle. Check all the vacuum hoses going into the intake.
Has it had a tune-up (plugs, wires, fuel filter, air filter)?
peter_x
09-08-2008, 09:57 PM
Thanks! I'm not sure, I'll hafta check about the plugs, Air filter=yes, fuel filter= no(I beleive its on top of the fuel tank?) Havent heard or noticed a vacuum leak but I will maybe look a bit harder. Again thanks!
No the fuel filter should be somewhere under the body. On the older ones it was on the passenger side, a little behind the passenger door.
Oh and I forgot to mention the coils as part of the tuneup.
TomQuick
09-08-2008, 10:16 PM
I'd start by looking for a vacuum leak. If there has been any work done on / around the engine recently, look in those areas first for a disconnected or broken hose.
Jwilli500
09-08-2008, 10:20 PM
On an '03? My understanding was that the fuel filter was mounted above the fuel tank right next to the sending unit. That'd be great if it's not! I used to do all this kind of stuff on our 95 GC. That 95 would run circles around this 03 turd. On my 95, I pulled the top off the intake to get to the back spark plugs, same deal on this 03? Thanks abunch for taking time! :tup:
No the fuel filter should be somewhere under the body. On the older ones it was on the passenger side, a little behind the passenger door.
Oh and I forgot to mention the coils as part of the tuneup.
Rick99
09-09-2008, 10:41 AM
I wouldn't replace the coil pack as part of a tune up without some reason to believe it was bad. It's expensive, and not a likely cause of these problems. This really does sound like an air leak of some kind-- I can't think what else would cause it. As stated above, it could be a vacuum hose broken or disconnected. It could also be a leak at the intake gasket, though that seems less likely.
You can access the rear plugs by feel without taking anything off-- I've done that, but I always recommend removing the wiper module since it only takes a couple minutes and makes it a lot easier. Especially if you have big hands.
vipergg
09-09-2008, 07:56 PM
I would have the fuel system cleaned along the IAC motor which controls at least the cold idle on these vehicles , if this is sticking this could be the problem . You could also try a couple of tanks of good fuel system cleaner like techron on gumout and see if that helps. When first started when cold most will idle at 1000 or a little above until it warms up.
Jwilli500
09-18-2008, 01:12 PM
Quick update so far. 1) Looked for a vacuum leak and couldnt hear or locate one. 2) Changed the fuel filter. It IS above the fuel tank. It is a PITA! Seems to run a little better. Does the high idle and surging less frequently. Noticed last night when it did the high idle(1400RPM) thing, if I stabbed the throttle briefly it idled down and smooth. The search continues!
Rick99
09-18-2008, 03:43 PM
I can't remember if it was mentioned above, but did you clean the IAC valve? It's pretty easy to do.
Jwilli500
09-19-2008, 02:12 PM
No, I havent yet. can you give me an idea whats involved? Thanks again for responding, I appreciate the info! :tup:
StandOnCliff
09-20-2008, 12:24 PM
Pulling two torx head screws and cleaning the hole out, plus the IAC (Idle Air Control) valve is it. I've included a picture on where it is located. It's also known as AIS (Automatic Idle Speed). It does sound more like a problem with vacuum though. The IAC is to hold it at high idle when it's cold. It also brings the idle up when A/C is engaged and also keeps it from stalling when coming to stops. The brake booster if it was leaking would cause this problem too. Disconnecting the hose going to it and plugging the hose end with a bolt can help determine if it's bad. Intake leaks are hard to find also. Using a hose to your ear and probing with the other end can help locate vacuum leaks.
Jwilli500
09-20-2008, 09:51 PM
I agree that it does sound more like a vacuum leak somehow. With it being intermittent it's hard to catch it and get out under the hood when it's doing it. This is becoming frustrating. Thanks for all you guy's info (and pic!) :tup:
StandOnCliff
09-21-2008, 12:29 PM
I had a little bit different symptoms then yours. Mine would not idle high when it was first started, it didn't come up in idle when I engaged the A/C either. It also was very hard to maintain speed. It seemed to either be losing speed or gaining speed. I also had to drive with two feet when in town. Everytime I had to come to a stop it would stall unless I left my foot on the gas. I changed my AIS or IAC motor and the throttle position sensor and it runs fine now. I failed this test of the AIC.
The AIS motor has basic tests that can be done to it also. Disconnect the electrical connector from the AIC valve and listen carefully for a change in the idle. Connect the AIC valve back up and turn on the A/C and listen for change in idle. When the vehicle is cold the AIC valve should vary the idle as the engine begins to warm up and also when the A/C is turned on. If there are no obvious signs that the AIC valve is working, continue below.
Use a voltmeter and test for voltage to the AIC valve with the ignition key on(engine not running). Backprobe the AIC valve electrical connector and check for power on the purple or purple with a white tracer wire. It should have 12 volts. The yellow wire should have 12 volts also. Both should also remain having power with vehicle running, but voltage will fluctuate. If no power is present at either one you have electrical issues. If all power checks out. Unbolt the AIC motor and leave it connected electrically. Turn the ignition key to ON (engine not running) The pin on the AIC motor should retract(pull in). If it doesn't it's bad. No further testing is possible without a scan tool.
You haven't mentioned if the check engine light is on or not. I'm assuming it isn't. Is it?
Jwilli500
10-03-2008, 03:56 PM
No, The check engine light is not on. I am gonna try to get out there tomorrow and continue troubleshooting with the new info you guys have given me. I did change the fuel filter and that seems to have helped a bit.
StandOnCliff
10-03-2008, 10:40 PM
You may want to do a check on the throttle position sensor also. It shouldn't be bad with 78000 but if you have a voltmeter, it's only time spent. Analog voltmeter's work the best.
The TPS can be checked as follows. Put one lead of the ohmmeter into the center prong of the throttle position sensor and the other probe put into either outer prong. Turn ohmmeter on to read resistance. Move throttle slowly up and down and watch the sweep of the needle on the ohmmeter (digital ohmmeters don't work well). The needle should move fluently with the movement of the throttle. Any spikes or glitches with the needle and it's going bad.
Jwilli500
10-04-2008, 07:43 PM
Quick update: Worked on the van today, I removed the throttle body and man it was carboned up! Pulled the IAC out (Almost couldnt pull it out!) and it was heavily carboned up too. I went ahead and removed the TPS and then cleaned the throttle body. At this point I just decided to replace the the TPS and the IAC with new. So far the thing runs like a watch! We'll see how it does over the next few days. A big thanks goes out to all you guys that have walked me through this! It's been much appreciated!:tup:
