I'm having an issue with my factory cruise control on my 87 GN. The cruise worked perfectly before I did an engine rebuild where I installed a new Comp 206/206 Hyd Roller cam. I also cleaned up the engine bay and removed the cruise control servo etc as part of that effort.
My issue is that the cruise control activates, turns on the cruise light, and as long as I am on steady flat ground does an OK job trying to maintain speed. It is sluggish when corrections need to be made, but I can see the TPS voltage changing so I know the servo is actuating. If I come to a hill with a gradual incline the car doesn't adjust rapidly enough and will begin to slow down. There is also a delay from when I hit the set button to when the cruise control begins to control that wasn't there before. This delay is a few seconds where TPS voltage does not stay at the cruising voltage but drops to 0.44 (closed) and then works it's way up to close to the cruising voltage for that speed.
I went through all of the factory troubleshooting documents and it basically indicates repair action P for when all the electrical tests pass. When I check the resistance between G100 (Main ground to engine block under turbo) and G121 (Cruise control servo ground on DR fender) I get roughly 1.9 ohms which is higher than the troubleshooting guide recommends of 0.1 ohm max. Even when I run a new wire from the battery to the fender where the cruise control module ground fastens I get 1.4 ohms. The next step in this repair action is simply to install a new cruise module and see if it works.
My other question is does the cruise work on other cars with such a mild cam? My maximum vacuum letting off the throttle is 20" and maintains around 10" cruising down the road. This is on par with my factory cam before the rebuild with only a few less inches of vacuum at cruise. My vacuum system is as tight as can be as I can perform test 6 in the factory troubleshooting guide after the car has sat for a week and it will still stroke the cruise servo to WOT.
My issue is that the cruise control activates, turns on the cruise light, and as long as I am on steady flat ground does an OK job trying to maintain speed. It is sluggish when corrections need to be made, but I can see the TPS voltage changing so I know the servo is actuating. If I come to a hill with a gradual incline the car doesn't adjust rapidly enough and will begin to slow down. There is also a delay from when I hit the set button to when the cruise control begins to control that wasn't there before. This delay is a few seconds where TPS voltage does not stay at the cruising voltage but drops to 0.44 (closed) and then works it's way up to close to the cruising voltage for that speed.
I went through all of the factory troubleshooting documents and it basically indicates repair action P for when all the electrical tests pass. When I check the resistance between G100 (Main ground to engine block under turbo) and G121 (Cruise control servo ground on DR fender) I get roughly 1.9 ohms which is higher than the troubleshooting guide recommends of 0.1 ohm max. Even when I run a new wire from the battery to the fender where the cruise control module ground fastens I get 1.4 ohms. The next step in this repair action is simply to install a new cruise module and see if it works.
My other question is does the cruise work on other cars with such a mild cam? My maximum vacuum letting off the throttle is 20" and maintains around 10" cruising down the road. This is on par with my factory cam before the rebuild with only a few less inches of vacuum at cruise. My vacuum system is as tight as can be as I can perform test 6 in the factory troubleshooting guide after the car has sat for a week and it will still stroke the cruise servo to WOT.
