Engine or Tranny problem??

Chris97K1500 · September 28, 2004

My 97 has been acting weird lately. I had the tranny rebuilt about a month ago, 2nd gear went out. Engine doesn't burn oil, runs fine. My problem is that in the morning, the truck stumbles some, sort of like it's running out of gas or it can't make it's mind up if it wants to shift into the next gear. It only does it when it is cold. Once I drive some and it warms up, it stops doing it. When it does it in the morning, it'll only be around 1500rpm's when it happens. Some times it won't shift from 3rd into overdrive. But like I said, once it warms up, no problems. Really has me puzzled, I still have a warranty, but the shop is about 2 hours away from me. Appreciate any help! Chris

budhayes3 · September 28, 2004

Does the engine get into operating temperature OK? Almost sounds like a coolant temp sensor problem or possibly the thermostat is sticking open. Could be alot of things I guess, but this is just my first thought.

budhayes3 · September 28, 2004

Oh yea, when you say stumbles, do you mean hesitate, like the trans is slipping? If that's the case, I'd go back to where the trans was done and have them take a look at it. The trans not shifting into overdrive until warmed up may be a normal condition though. The PCM may not allow it to do so to avoid loading the engine until it reaches a pre-determined temperature.

Chris97K1500 · September 29, 2004

Not hesitating like it's slipping, just stumbling a bit before it changes gear. It has a 180 degree Hypertech t-stat in it. Seems like this has started to happen since it's been getting in the low 50's to upper 40's at night. I'm sort of thinking this t-stat could be messing up the open/closed loop operation of the truck until it warms up completely. Could sort of explain why it goes away once it's warmed up and no problems driving the same road back in the hotter afternoon. I've sent my Wester's PCM back to get reprogrammed for the TransGo shift kit and the 180* t-stat. I may just go buy a $5 stock t-stat and see if the problems go away. Any more ideas? Thanks, Chris

budhayes3 · September 29, 2004

Unless the stat is sticking open, I couldn't really see it messing with closed loop operation...I think that the PCM goes into closed loop around 120-137* or something like that. You could have a defective stat though, and for the 5 bucks and a half hour of your time it could be a consideration.

You've had a couple of good ones lately huh: egr, trans, a couple runnability issues,...we gotta work out the bugs so you can spend more time driving your truck and less time fixin it! Or more time modding it!

Chris97K1500 · September 29, 2004

Yeah, I get something fixed, then something else pops up. Now that it's got over 110K miles, I guess some things are going to go wrong. It did it again this morning after letting it warm up before driving it. So I don't think the t-stat is the problem, it warms up pretty quick and doesn't move once it's up to normal temp. The problem of it not shifting from 3rd to OD is just me having to get used to not having the Wester's PCM . It's in OD, but there's no power, compared to having the Wester's, so it feels like it a slug. I give it some gas, rpm's go up about 400-500rpm's, but I don't speed up, (sort of felt like it was stuck in a gear) unlike with the Wester's. But the initial problem of stumbling going from 1st to 2nd is there, I'm going to call the shop now and see what to do. Probably will take it to them. Thanks , I'll keep you up to date. Chris

And there won't be ANY more mods to THIS truck. My next mod will be a CC GMC D/A 4x4, probably an '06/07 model. 16 more months and I graduate Dental School!

budhayes3 · September 30, 2004

Cool deal Doc, let us know how it all works out...and if I ever get a toothache in KY, I know where to go!

gixxer · September 30, 2004

CHANGE THE FUEL FILTER

Chris97K1500 · September 30, 2004

It was changed, about 500 miles ago, it's not engine related. Called the tranny guy yesterday. Knew exactly what I was describing. Said he'd take care of it as soon as I could get the truck there. That'll have to be early next week. He mentioned in the past when this happened it was either a PCM problem or a sensor gone bad in the tranny. Since it did this with the Wester's PCM and still with the stock PCM, I'd say it's a bad sensor. Thanks, though! Chris