Cruise control lag?

[Skunksmash]

Here's 2 questions. So I don't have to have 2 threads. TBI 5.7L 2WD 700r4.

1. My 87 has some pretty bad cruise control lag. No matter what speed you're at when you set the cruise control, you always lose 5 mph. So for example if I'm doing 65, and I set the cruise, it will actually only engage and cruise at 60mph. This can actually be pretty annoying. Is there perhaps some way, to make it stop doing this? There must be some kind of mod I can do. I don't really want to have to speed up even faster, just to get the desired cruise speed.

2. Sometimes when I'm coming to a stop, the engine dies. Makes me think its some kind of vacuum thing. But the engine always starts right back up, no problem. This is usually at a stop light or something, so its kind of embarrassing.

[Skunksmash]

bump

[chengny]

With the Custom Cruise III, about all you can do (without changing modules) is check the basics of the control systems for the cause:

1. Inspect the vacuum system (hoses and components for vacuum leaks).

2. On the electrical side, check for loose/broken/oxidized terminal connections.

3. Be sure the linkage (between the servo and throttle) has no excessive play and is correctly aligned. Procedure as follows:

1985---87

Servo Unit Adjustment
To adjust servo on V6 and V8 gasoline engines, close throttle, then with ignition and fast idle off, adjust rod assembly length to give .020---.040 (Exc. C, K, R and V models with V6 engine) or .007---.015 (C, K, R and V models with V6 engine) inch clearance between rod and stud.






A couple of basic vacuum system dwgs:





Electrical schematic:






This is GM's diagnostic procedure for Custom Cruise III with high/low set point problems:


Cruise Speed Above or Below Set Speed

1.Perform preliminary checks.

2.Perform electrical and vacuum system checks. If no system malfunction is noted, replace module and recheck system operation.


And this is all they offer regarding adjustment of set point:

Engagement-Cruising Speed Zeroing

There is no provision for engagement-cruising speed zeroing. If cruising speed is too high or low, check vacuum hoses for improper routing, restrictions or leaks and servo linkage for proper adjustment. If cruising speed remains too high or low, replace the electronic controller.

I know that isn't what you wanted to hear, but there is no magic bullet.

[v30crewcab]

I always hit the the cruise button twice and it will engage at the speed I'm running. once and it engages lower. not sure why.
shop I worked at had an 87 that would die at stoplights, a new distributor fixed it.

[Skunksmash]

Thanks for the replies. I'll try hitting the button twice.

If that doesn't work, it sounds like the closest thing to the magic bullet would be replacing the electronic module. After checking everything else of course. I've had the cruise fixed several times. It would stop working, then the truck would go into the shop for something else and I'd tell 'em to go ahead and fix the cruise. So there is no telling I guess.

Anyone happen to know if the electronic controller for the cruise is fairly easily replaceable?