Bad tach?

[mnewman]

Starting to run down some more issues on my '86 BII. Not having a CEL has it's ups and downs. No light makes it easy to ignore an unhappy system.

Current codes are

18 - SPOUT
32 - EGR pressure
89 - Ignore. Swapped to 5spd from auto.

For the most part this thing runs great. Sometimes when it's cold it stumbles a little bit when I give it light throttle but not always. Again when; cold sometimes it idles down pretty quick and acts normal. Sometimes it likes to hold high idle until it builds heat. Again not all the time. Only issue I've noticed when warm is after decelerating in gear it will buck and stumble when I apply throttle but clears up and goes like normal. Hot idle is pretty steady. Other issue (related?) is the tach sometimes will read very high. The issues don't seem to be in time with each other so I assumed the tach itself was going bad. Is there any chance the code 18 and weird stumble could be caused by the tach going bad or would the tach reading off be a symptom of a bad pickup in the distributor?

I went through the testing procedures I found online for the code 32 and the sensor seems to be open on the feedback side so I'll get one ordered tonight.

 

[rusty ol ranger]

Starting to run down some more issues on my '86 BII. Not having a CEL has it's ups and downs. No light makes it easy to ignore an unhappy system.

Current codes are

18 - SPOUT
32 - EGR pressure
89 - Ignore. Swapped to 5spd from auto.

For the most part this thing runs great. Sometimes when it's cold it stumbles a little bit when I give it light throttle but not always. Again when; cold sometimes it idles down pretty quick and acts normal. Sometimes it likes to hold high idle until it builds heat. Again not all the time. Only issue I've noticed when warm is after decelerating in gear it will buck and stumble when I apply throttle but clears up and goes like normal. Hot idle is pretty steady. Other issue (related?) is the tach sometimes will read very high. The issues don't seem to be in time with each other so I assumed the tach itself was going bad. Is there any chance the code 18 and weird stumble could be caused by the tach going bad or would the tach reading off be a symptom of a bad pickup in the distributor?

I went through the testing procedures I found online for the code 32 and the sensor seems to be open on the feedback side so I'll get one ordered tonight.

18 has something to do with the TACH signal IIRC.

My 87 has thrown an 18 for years and i dont notice anything. So i just ignore it

But there is a resistor in the wireing harness (cant remember where) that goes bad that usually causes the 18 code.

Check the plug at the coil too. It could be a distributor issue or even a bad ECM but id start with the resistor

 

[mnewman]

Thanks. I didn't really think the tach was related but I've run into this on much older Fords (non-EFI) so I figured I'd ask the experts. The diagram looked like it wasn't wired in series.

I was reading about the resistor and I did find a copy of a test procedure so I will look at that. I didn't look at the coil connector but I will now.

I've put a lot of miles on this as-is but it sure would be nice to get rid of the stumble after deceleration.

 

[rusty ol ranger]

Thanks. I didn't really think the tach was related but I've run into this on much older Fords (non-EFI) so I figured I'd ask the experts. The diagram looked like it wasn't wired in series.

I was reading about the resistor and I did find a copy of a test procedure so I will look at that. I didn't look at the coil connector but I will now.

I've put a lot of miles on this as-is but it sure would be nice to get rid of the stumble after deceleration.

If you figure it out let me know. My 87 does that too. I gave up on it.