I have been having some shifting issue a bit more since the weather has been getting warmer. Well since I got the Jimmy last year I had the well-known issue of having it kick you in the *** when shifting from 1st to second gear. But I let that go. Now it IS a 4x4 but my 4x4 is engaging fine.

But for a while it has been giving me trouble, when it's warm on fast starts from dead stop. If I have to stomp on it to take off fast (like to get out into traffic) it will almost die until I let off the gas again and go steady.

Lately when it's warm and I coast at about 45 mph it seems to start getting a hesitation. I thought the take off issue might be a tps or possibly that my spider injector unit was having issues. But a new twist is that I am getting a map sensor code. This just started happening a couple weeks ago. It goes away in the morning (when it's cool) but when it's warm in the afternoon, the take-off issue is there.

I'm wondering if there is a vacuum switch ON the tranny (not the transfer case, the 4x4 is fine) that could be bad. Or as I've read, could it be a locking up torque converter. I've checked things like the tps and the map sensor. All look fine. And there's no vacuum fluid in the reservoir ball. I was thinking of saving up and having the tranny checked out or rebuilt. Am I thinking right? Or could it be a fuel supply issue?

 

I'm thinking that the transaxle control valve that has been discussed lately might be at issue. Especially since my shiftin is normal when first heading out. But it is wonky after driving a while. I notice it if I have to drive across the city (25 miles) to pick up the kids. When it starts to act up it seems to have shiftin problems when coasting at around 45 miles per hour. And then if I have to stop quick (sometimes) It will stall or seem to bog down. I isolated the issue with this. It appears to not want to shift down into 1st gear. And then when it does it seems to lurch quick. But when it stalls it seems to still be stuck in 2nd gear. and when I say it bogs it is similar to when driving a standard and coming to a stop without pushing in the clutch. And then occassionally if I have to make a jackrabbit start, it will bog as though it is still in 2nd gear, until I let off the gas again and then take off.

 

I don't know a whole lot about transmissions yet but I'm kind of thinking the bands might be slipping.

 

No. I've had a vehicle with bands slipping. It's a different kind of action all together. And it's an all time thing. not just when it's hot. And slipping bands won't throw up a code.

If that control switch is bad and sticking, when it comes unstuck it will cause a quick vacuum drop. This in turn will give a bad reading to the map sensor which will throw up a code, which is exactly what mine is doing, even after replacing the map sensor. When I read the thread on here regarding the kick in second and first gear, that was it, as I have had that happening since I bought the truck, but let it go.

 

I would try manually shifting into 1st gear when needed to see what happens but I kinda think this sounds like a fuel issue.
So you have checked to see if are there any codes stored in the computer?

 

No. I've gone all over the fuel issue. And yes I tried the manually shifting into 1st. It keeps it from bogging. It is noticeable that it is having trouble downshifting into 1st gear. But the only code that pops up is the map sensor.

 

Vacuum fluid in the reservoir? Whoa. Never heard that one before. When's the last time you changed your fuel filter? How do you know it's not a fueling issue? What did you do to eliminate this possibility?

 

Everything. It's a long list. Yes new fuel filter last year. I have good pressure. Now I could have spider injector issues. But that is hard to figure out right now. But all the symptoms I have ARE wrapped up in a back trans control valve. Especially since when it's warm it wants to bog down or stall but if I throw it into 1st gear it goes back to normal. As I said, it is acting as if it is stuck in second gear and won't downshift into first. I was having trouble diagnosing this until I read about the control valve and the symtoms fit my situation to a T.


read up on a few of the posts on here about that trany control valve. Tranny fluid in your vacuum lines is a symptom of that.

 

It is possible that the 1-2 shift solenoid is not working properly.

The vacuum system is independent of the transmission itself so there is nothing inside the transmission that could allow fluid into the vacuum system. The item that most commonly goes bad is the transfer case vacuum switch. The failure of the vacuum switch along with a bad transfer case front seal will allow transmission fluid to migrate into the transfer case causing an over full condition and the leaking switch will allow the fluid to be drawn into the vacuum system.

 

Ah, OK. Well I don't have to worry about that anynow. no fluid in the lines and my 4x4 works fine. But that solenoid is something to check on. It's been doing this (to some degree) since I got the truck. So I was figuring having the tranny rebuilt eventually. It's just annoying as hell. It's gotten to the point that when it's hot (and here in Houston, it is) I need to manually shift it into 1st when I stop. More frequently lately.