Ok so I know this is an old thread but my cruise never did function fully. It did however function good enough for most trips, even pulled a 19.5" fiberglass boat with the truck fully loaded for the weekend with gear for camping for a 1hr road trip up some decent hills. There was twice I had to manually push the throttle down. It wouldn't go past 40% on the scan gauge. Now tonight I put on a new larger vacuum line to the servo and it really seemed to cure it except there is one hill where it get stuck on 30% throttle. The only thing I can think of is the MAP sensor is old and starting to fail? I may throw one in on principle since I ordered a fastman 52mm throttle body that will be here sometime next week when Dan is done with hunting season.

 

Is the cable stretched to the point that the servo simply can't pull it any further? Is it binding?

 

Do you mean TPS instead of MAP? Yes, check the cable adjustment. When you say that you put on a larger vacuum line, do you mean a larger diameter? This may not be a good idea. The larger diameter means that it will take MORE volume (vacuum) to activate. The larger diameter equals more space to fill (or actually to create vacuum in). it may or may not make a difference. I would go back to original size, personally.

 

You said its not pulling hard enough to downshift. Is your tv cable adjusted correctly?

 

I did mean map but the truck runs so good I don't see how that could be bad. The TV cable is adjusted properly, I did double check that. I replaced the vacuum line because I kept finding hairline cracks in it and sleaving over the top with rubber line. Weird thing is it only seems to happen at 55mph in lockup. If the hill is sharp its fine, it will downshift. If it gradually gets steep it can't keep up. If its above 60mph it seems to be fine.

 

Did you check the cruise cable to the throttle body? Nothing hanging up?

 

Seems to move freely. I unhooked it and pulled on it. But I could be missing something. I may have to just put a new cable on, that is literally the last thing in the system I haven't replace. Just to recap I put in a new tps, vacuum line, and servo. All of which improved the cruise function.

 

FWIW, when I bought my '98 it acted strange on cruise, surging speed. TPS solved it. It's a cheap replacment.

 

Did the TPS already. It helped out a bunch but didn't quite do it. I wonder if I cleaned my throttle body if it you help it is kind of stiff or I'll just wait for my 52mm fastman to show up.

 

Have you cured the problem?

I recently drove my 97 1500 with the 5.9 gas engine, when set at 75mph and going up a hill (not loaded or trailer) the rpms fall down and it never down shifts to keep up the speed I set it at. It'll fall all the way down to 60-65 and by that time I'm pissed off and I floor it then it will downshift and get back up to speed. After flooring it and the rpms jumping up to around 2600-3k rpms I can feel the pedal take back over and it goes right back up to cruising speed without a problem them takes a minute to shift back into overdrive and rpms to fall.

I'm going to check for the cable issue but in the meantime.. Any ideas?