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Hey guys,
Been here before, got some great advice, and I’m back again. Got a 1990 Dodge Grand Caravan with 195k miles on it that’s acting strangely. First off, when it first starts up, it idles fine, but if given any throttle, it revs up to about 1200rpm, then slowly settles to about 600, runs rough for a little while, then rises back to about 800. This will continue for about five minutes, and usually disappears about the time the van is warmed up.
However, recently I’ve been experiencing what I describe as an abnormally sensitive transmission. It downshifts at the slightest sign of a hill, and often seems confused as to which gear it’s supposed to drop into. It’ll shift out of 2nd, mess around in 3rd for a couple seconds, fall back back to 2nd and THEN shift to 3rd. It also likes to randomly shift to 3rd on the highway, gunning the rpms up to about 2800. It’s worrying me because this is a rebuilt transmission and I don’t want to damage the clutch with excessive shifting.
I’m shying away from the idea of a transmission failure. It’s not the shifting that’s at fault, it’s like the computer doesn’t know which gear it wants. The oil level is fine, it’s not burnt or anything. I’m kinda thinking it’s the TPS sensor, but I need some opinions.Thanks guys
EDIT: No CEL, no codes.
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I’m kinda thinking it’s the TPS sensor, but I need some opinions.
I also think it is a sensor input of some form. There are so many to choose from and many of these may not necessarily throw a CEL.
I’d take it down to your local friendly neighborhood shop and have them throw a scan tool on it… see what the computer is seeing. Change a sensor and you’ll be good to go.
Extra Bonus Info:
Here are the top 5 sensors that influence driveability:
- Throttle Position Sensor
- Engine Coolant Temperature Sensor
- MAP or MAF sensor
- Crank Sensor
- Oxygen Sensor
If it’s a 3.3 with a 4 speed trans i would be replacing both the input and output speed sensors as they are not expensive. they had a high failure rate. If you have access to a scan tool that reads transmission data you might see glitches in the speed sensor(s) output.
If it’s a 3.0 lt. with a 3 speed trans i would be checking the downshift linkage for a sticking or binding condition.
Sorry for the late reply guys, been quite busy the last week or so. I was messing with something else in the van, can’t quite remember what, and just happened to notice that the airbox wasn’t completely fastened shut, due to a small plastic deal that was broken on the box. Fastened the box down and have been unable to replicate the problem since. (Pirate air, as ETCG calls it?) If it comes back I’ll drop by again.
Thanks
Alright back again, this time with a legitimate solution. It started happening again, much to my chagrin. My solution came about by accident actually. Was on the highway, it was late, I was tired, and it was shifting all over the place. I wound up getting pissed off at it, and floored it repeatedly. After that, it stopped. Later, I remembered something I had read on a Jeep forum somewhere. It stated that if your TPS is going out, sometimes it can help to ‘recalibrate’ it, so to speak. They suggested doing this by turning the key to the ‘on’ position and slowly depressing and releasing the gas pedal several times. I believe that I ‘recalibrated’ it by flooring it repeatedly on the highway. So, when it started acting up again a couple weeks later, I turned the key to the ‘on’ position, slowly depressed and released the gas pedal, and bam! No uber-sensitive transmission that shifts all over the place at the slightest throttle change. So, my TPS is slowly going out, but this will keep it functional til I have the money to replace 🙂 Hope this is helpful to some extent.
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