I've Got Some Engine Data!

[1987 GMC Jimmy]

I will post some pictures whenever I go back to school, and the internet doesn't suck. I was actually able to move the cruise control servo over, and it looks pretty good and doesn't seem to bind up. I've noticed several things since playing with the TBI and all the sensors and stuff. First, the voltage is .86 at idle with the truck off, but if it's on, it'll read .74 at idle. I also noticed some brown gunk in largest front nipple of the TBI body. It's the one that goes to the passenger side valve cover. I won't be able to probe it until at least next weekend, but I'll post a few pictures I took tomorrow. It's not bad rich, but it's not that good. I don't like how the idle starts at 1200 and then it slowly works its way down to about 850 while it's in open loop, but then when it switches to closed loop, the idle starts to go up with 0 change in the amount of IAC steps. Oh, could the brakes have anything to do with the richness and idle bouncing around? I checked the hose connection going into the booster, and it looks fine, but my brakes hiss really loud when depressed, and they're spongy. I know something's wrong with them, but I didn't know if it could affect all this.

 

[yevgenievich]

For testing purposes, cap off the brake vacuum line. Just don't drive around like that. When first srarted ecm will put idle around 1200 and slowly reduce to around 850 as engine worms up and 650 in gear. If you blip the throttle slightly, ecm will command lower idle speed earlier. Jumping back to 1200 might be bexause ecm starts dumping extra fuel in when it goes to closed loop. Check all the vacuum hoses, and how long ago was o2 sensor replaced?

 

[1987 GMC Jimmy]

For testing purposes, cap off the brake vacuum line. Just don't drive around like that. When first srarted ecm will put idle around 1200 and slowly reduce to around 850 as engine worms up and 650 in gear. If you blip the throttle slightly, ecm will command lower idle speed earlier. Jumping back to 1200 might be bexause ecm starts dumping extra fuel in when it goes to closed loop. Check all the vacuum hoses, and how long ago was o2 sensor replaced?

I'll try capping the line when I go back home, and I bought a new digital multimeter to check the voltage on that wire(s). I replaced the oxygen sensor a few weeks ago with a new Delco. Here are the pictures of the TBI you asked for. I'll do whatever it takes to make the richness go away. I wonder if it's a issue with the injector unit itself. Oh, I pushed the servo over with my hand, and it doesn't look to be in a bind after that. I just have to find the clip or get a new one. I know the TBI is dirty I guess I should probably take it off and rebuild it.

 

[yevgenievich]

something is causing the tps to read off. Verify the power going to it and also check during the logs the tps%. Might help if you could record the logs and upload them as well. Generally make sure there is no vacuum leaks and also need to verify the fuel pressure.

 

[1987 GMC Jimmy]

Would those things cause the TPS to read off? I'd think the only thing that could cause the voltage to read high is either the voltage or the TBI is binding up a smidge. I know I need to verify the fuel pressure, too, though.

 

[yevgenievich]

Tps has three wires, one 5v, one ground and one signal. If 5v or gnd are off it can cause the sigal to be wrong. In pictures tbi unit does look ok. It is possibly to make tps adjustable, but should not be needed to if all checks out ok