'98 K2500 acting goofy

[jfnar]

Here’s the situation. I bought this ’98 K2500 about a year ago. It has a 350 engine and about 150K miles. It seems to be a pretty good truck. One of the things that impressed me when I test drove it was that the transmission was so smooth that you could hardly tell when it shifted if you weren’t looking at the tach. About two months ago, I drove it a couple of miles to my shop and it would jerk pretty good when it shifted. The next day it shifted smoothly again. Okay, jump ahead to last Saturday; my dad and I are heading to the deer woods with a trailer with two 4-wheelers on it and we get about 10 miles down the road and I see the “service engine soon” light come on. The very instant that the light comes on the speed starts dropping off. It was on cruise so I pressed the pedal down and nothing happened. It continued to slow down so I turned around and headed back home. It would only do about 25 mph and pressing the gas pedal down didn’t help, it just seemed to run a little rougher. It was running about 3000 rpm. I turned on the 4-way flashers for safety and I noticed that every time the flashers came on it would lose a little more power and then come back a little when they went off. You could feel it pulsating as the flashers cycled on and off. I turned the flashers off and it smoothed out but still only 25 mph. I tried turning the heater fan on and off and it too would affect the engine speed. Just before we got home it suddenly started running right again. The next couple of days it ran like a new truck. The “service engine” light went off the following day. I took it to town to O’Reilly’s to see if they could hook up to see why the “service engine” light came on and they told me that since it had gone off already their reader wouldn’t tell anything. So I start back home, everything working great, then I noticed that it started shifting hard again. I got onto the highway and after a couple of miles it shifted out of OD into 3rd gear. Engine still running fine doing 55 but it won’t go back into OD. I haven’t driven it since then. I like to work on my older trucks when I can but I’m not up on the later computerized stuff. My gut tells me that there’s something going on in the electronics. I’m swamped at work right now so I’ll have to take it to a garage to have it worked on but I’d like to have some idea what’s wrong before I take it in. It gets pretty expensive to pay someone to swap parts until they accidentally fix it. Thanks for taking the time to read all this. Any suggestions to help point me in the right direction will be much appreciated.

Jeff

[speedygonzales]

With regard to the problem you described, if you have a meter, you should check just a couple of things before you head to the shop. Measure the battery voltage while everything is off. Should be around 12.6 volts. When someone cranks the engine over, the battery should not drop below 11 volts. When the engine is running, the battery should be at 14 volts. If it's less then 14, measure at the alternator terminal also. To me your problem sounds as though your battery is not being charged. If any of those values is not correct, chime in here. It only takes 2 minutes to check those items with someone to help.

Most codes are stored in memory. You're really not going to know what the issue is until it's scanned.

With regards to a shop repairing it, first understand the diagnostic fee. Only agree to that up front. No repairs to be made OR PAID for until you give the approval. Find out what they think it is and why. Ask people if that sounds correct before you approve the work. You want all parts returned after the work is done or NO pay. This doesn't include stuff like hoses belts or gaskets obviously. Be sure the old parts match what is on the repair order.

If you can, try putting the old parts back yourself to see if they repeat the problem. Some are complicated to install so not all can be done this way. At this point, you can see if the old part they gave you is an actual part from your vehicle or a bogus part just to trick you if it doesn't fit. If possible have the service adviser put his initials or some other type of mark like work order number on each part with a sharpy marker to prove it's the part they gave you in case you try to bring it back as bogus later on. In this way, there is no question it was the part they gave you and not some BS you tried to pull on them.

Be very leery of multiple parts replaced. Many MANY times, as you eluded to earlier, one part is changed and it does not correct the problem. Then another part is replaced that does fix the problem. They often can't return or sell the first part since it's been installed so they try to convince you both parts were bad. Not always but more times than I want to count.

Remember that just cause a scanner pulls a code for an item doesn't necessarily mean it's the item. For example, it could be wiring to the item. So watch out for that too.

[Boog]

Pay attention to the battery voltage gauge when this is going on. Low voltage will make the engine go down on power.

[TennesseeZ]

Originally Posted by jfnar

It gets pretty expensive to pay someone to swap parts until they accidentally fix it.

I like the way you put that. My experience with anything newer than @ 93 is limited, and anything I could say would basically be a guess, but I agree that a fully charged battery is going to be essential in tracking your issue down.
I'll also say you've come to the best place on the web to ask for help, the guys who do this all day every day then get on here and try to help DIYers like us are the greatest!

[sfran]

While you are checking the voltage at the battery, take the time to test the grounds. Check the ground from the battery to the chassis and the frame. I just went through a ton of problems with a fuel pump which ended up being a bad ground strap from the motor to the frame and firewall. It took me forever to find, and is probably one of the easiest things to check. I was ready to give up and take it to a shop. It was grounded but couldn't take the load and was so corroded and brittle that it broke into little pieces just from touching it. A good multi meter can perform a continuity test between the components and it should also be able to tell the quality of ground. My truck was starting hard/stalling, under powered, hitching badly on the interstate under slight load in overdrive like the converter was harshly locking and unlocking, then wouldn't run or start at all. I am not saying it is the problem, but take it from me, and many others on here, that a good ground is extremely important for everything to work properly. Also check for corrosion between the double posts on the positive terminal while your checking voltage.

Good luck

[jfnar]

Okay, finally got a chance to report back. Battery voltage is 12.44 not running, 10.60 when starter is turning over, 14.30 when engine is running. Ground seemed to be okay. I've driven it a few times since the incident when it lost power and haven't had that problem again but it still kept kicking out of OD and shifting hard. When this would happen, I could stop and shut the engine off for 10 seconds and then restart and everything would work fine again for 5 to 10 minutes and then it would kick back to 3rd again. I was about to buy a new battery when I happened to notice that the positive battery cable was a little loose on the battery. I could turn it back and forth with my hand. Rather than put on the new battery I tightened up the loose connection and drove it again. I only drove it once for about 10 miles but it seems to be working correctly now. I'll get a chance this weekend to drive it more and report back if this was the fix. Thanks again for all the suggestions.

Jeff

[jfnar]

Well, I'm still in limbo. Tightening and cleaning the battery cables seems to have made it run longer before kicking out of OD but it still does it. I took it to a mechanic and he called me and told me there was nothing wrong with it. He said he drove it and it worked perfectly. Of course, he just didn't drive it long enough. I went to his shop and took him for a ride and it took about 4 or 5 miles for it to kick out of OD. I showed him that after it kicks out of OD it will shift hard and that after you stop and shut the key off for a few seconds it will work fine again for another 4 or 5 miles. He's at a loss too. He said that he's going to change the transmission fluid and filter because I have no idea how long it's been since it was changed. He may also change the OD solenoid. After that I'm going to drive it and if it's still doing the same thing I'll look for someone else to work on it.

[jfnar]

I picked up the truck yesterday and it still kicks out of OD. All they did was change the transmission fluid. I now have a new symptom that may be related. It has failed to go into cruise control twice in the last couple of days. It's only done it twice but both times I did the same thing as with the transmission. I stopped and turned the engine off for 10 seconds and then restarted. Both times the cruise control worked after restarting. I called the mechanic and he now thinks it's a speed sensor. I guess I'll give that a try next week.

[speedygonzales]

Did you deal with a transmission shop?

[jfnar]

No, I haven't been to a transmission shop yet. There's not one close by. With my work schedule it's hard to handle these things right. It'll take a little extra planning but I can get my dad to take it somewhere. I'll start scouting for a good transmission shop; hopefully I can find one within an hour's drive.

[speedygonzales]

There are 4 different Aamco places in Memphis. The Aamco here is straight shooters. $39 bucks they tested a vehicle we had. Computer, visual and road test. Then told us it was normal and didn't need anything. Not even a fluid change.

[jfnar]

Speed sensor did not fix it. As soon as I can find some time I'll take it to a transmission shop.

[jrr344]

Mine was shifting in and out of overdrive alot and I couldn't find anything wrong for a long time then finally it gave my a torque converter solenoid code I replaced it and fixed it, did you ever get the trouble code off the computer?

[wayfastwhitey]

Have the gauges cut in and out or jumped the needles, lost light or anything like that? Reason I ask is my previous truck would lose gauge function, cut in and out, feel low on power, jump into third from od, and would feel like it was still in third at stop signs intermittently. It would sometimes shift hard other times it would just not shift at all.

Turn it off, it would clear up for a minute and go back to acting up. I pulled the ignition switch out of the column and drove around with it in my hand twisting and pushing on it until I found a spot where it would stop acting up.

The terminals in the switch had gone bad (purple/white to be specific) and I would tell you I replaced the switch, but I didn't. I didn't want to pay up for a new one so I used auxiliary switches instead.

I had all the switches in the truck go bad within days of each other, and I was really strapped for cash so I did what I had to do. But that's another story.

That ignition switch, while it could be your problem, or it might not be, once it starts acting up will cause ALL kinds of issues, just don't take it apart while its plugged in to the terminal block under the dash if the battery is hooked up. The starter will engage.
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[jfnar]

No problems with the gages. The needle on the gas gage vibrates but it's done that ever since I got it. I finally got the codes from the mechanic. The numbers are P0741 and P1870. I'll do some more research on those when I have time to google.

[wayfastwhitey]

Those are tcc off malfunction and component slippage codes
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[jfnar]

Does that mean I need a new torque converter?

[wayfastwhitey]

Maybe. There's a chance that there's a loose electrical connection under the truck somewhere, or in the truck, maybe the fluid needs attention, doesn't always pay off to jump straight to the worst case.
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[jrr344]

If or when you do change the fluid I would replace the tcc solenoid it could cause all the symptoms you are having and also cause them codes.