I've Got Some Engine Data!

[1987 GMC Jimmy]

I haven't fully figured this out yet, but I took a picture of my screen while everything was hooked up. O2 sensor was cycling up and down. I noticed that it kept flashing error and connected down at the bottom. It said closed loop the whole time from when I started it to when I shut it off, which bothered me. That injector number takes the cake for the absolute worst one. I ran it for more than ten minutes to let it warm up, by the way.

At idle, after running for a few minutes...
Tachometer RPM - 1100
O2 Sensor Voltage - 464.4 (up and down)
INT - 127
BLM - 134
Injector Duty Cycle - 557.12%
TPS Voltage - .74
IAC Steps - 40
MAP kPa - 30
Vacuum - 19 Hg
PROM ID - 9931
Knocks - 4
Coolant Temp - 92*C
Battery Volts - 14.0
AFR - 7.3

 

[Georgeb]

Your tps voltage looks off should be around 4vdc...

 

[1987 GMC Jimmy]

How do I adjust that? And what about that injector duty perentage? It sounds like that's tied into the rich condition.

 

[yevgenievich]

Tps is pretty close to correct. 0.45-0.65 is range for idle. Rpms are too high for idle. Possible throttle not closing all the way, ir vacuum leak. What was the problem with the vehicle?

O2 sensor reading is good, and jumping around 450mv means ecm is constantly adjusting fuel.
INT and BLM just define look up tables in ecm used at the scpecific time.


Edit: Duty cycle likely reading wrong. Program flashing error might be because the definition file does not exactly match the data stream

 

[Georgeb]

DOH! Yeah, .45 on the TPS. What was I thinking?

 

[1987 GMC Jimmy]

It's just running really rich. No code getting set, but it's stinky. I feel like the TBI is weird. The accelerator is kind of hard, and the cruise control servo won't connect without binding the arm.

 

[yevgenievich]

Inspect the tbi unit it self for throttle blade movement. Tps reading a bit high and would try to give more fuel if it thinks you are not at idle. Tps is not adjustable on tbi. Also while running verify the iac steps varies during warm up and equates to change in engine speed. There is also an entry for commanded idle speed, see what it claims. You can also upload your log file together with definition files used.

 

[1987 GMC Jimmy]

I tried the TPS voltage while the truck was off. At idle, it was .86, and at WOT, it was 3.6 at the most. New TPS?

 

[1987 GMC Jimmy]

IAC decreases from like 145 to 40 as it warms up. Idle does decrease to about 850 but then surges back up to 1100.

 

[yevgenievich]

So far tps points to be bad.

 

[1987 GMC Jimmy]

Alright, I guess I'll slap a new one on there and see if that does it.

 

[yevgenievich]

before replacing, visually verify that the throttle closes completely and is not hanging up.

 

[1987 GMC Jimmy]

Throttle closes just fine. I pulled the old TPS, and it was a brand that I've never heard of before (CTS). It was really easy to do after I unbolted the MAP sensor if anyone sees this in the future. I'm gonna put this new one on and see what happens.

 

[1987 GMC Jimmy]

before replacing, visually verify that the throttle closes completely and is not hanging up.

Hey, so I replaced the TPS, and it was the exact same voltage as before (.86). Everything looks free on the inside, and when I pull on the arm, it opens and appears to close all the way. I guess it's not going all the way back, though, since to different sensors are reading the same thing. What should I do?

 

[yevgenievich]

Probe the pins on the connector. One of them should be 5V, other one is gnd. You have mentioned cruise control arm not being able to get installed, do you have a picture of that?