86 SE 2.8 - Misfire on 2 front cylinders (Page 1/5)
willyt AUG 15, 09:28 AM
I have an 86 with a 2.8 that I recently removed the engine and transmission to replace the clutch and fix a few oil leaks. I have everything back together now, and it drives/shifts fine, but I believe I have a constant misfire on two of the front cylinders.

I verified this by pulling the plug wires off of the dist. with the engine running, and the engine sound didn't change.

It looks like I am getting spark to the cylinders - I verified the plug end of the wires are sparking, and I swapped a plug wire and spark plug with one that was firing with no change.

This leads me to believe that it may be a problem with an injector? I did have the injectors off to replace valve cover gaskets, but there definitely isn't an external leak, I double checked that.

I did have a bunch of wiring etc unplugged when I took the engine out - is it possible something could be unplugged? I verified that the injector connections are all plugged in and clean.

Could it be a ground missing?

What is the best way to check if an injector is working? Should I take two off and swap them to see if the misfire moves with the injector? Any ideas or troubleshooting advice would be greatly appreciated.

Thanks!!!
Patrick AUG 15, 04:26 PM

quote
Originally posted by willyt:

I verified this by pulling the plug wires off of the dist. with the engine running...



I hope you didn't do exactly what you posted... as that spark has to go somewhere... and can damage ignition components in the process.

For testing purposes, always ground a disconnected spark plug lead... rather than doing what you posted.


quote
Originally posted by willyt:

What is the best way to check if an injector is working?



I don't know if it's the "best" way, but you can use a mechanics stethoscope with the rod attached and touch/listen to each injector to make sure it's clicking.

[This message has been edited by Patrick (edited 08-15-2022).]

willyt AUG 15, 04:41 PM
Haha I indeed did exactly what I posted. I read that I shouldn't a few minutes after posting the initial message.... oops.

I don't think I initially damaged anything by doing this, because the issue is still localized on two cylinders. However something may now fail prematurely because of damage caused - oh well.

The stethoscope is a good idea Patrick. I need to do some more reading on how to test/fix injectors if that is my issue.

Is there anything else I should be checking into besides spark plugs/wires (spark is definitely good @ dist.) and injectors?

Thanks
Patrick AUG 15, 05:22 PM
If it was three cylinders that appeared to not be firing, I'd suggest checking to make sure that one of the two injector fuses hadn't blown.

[This message has been edited by Patrick (edited 08-15-2022).]

willyt AUG 15, 05:38 PM
It appeared to be only 2, but I did have the same thought. Both fuses were good.
Patrick AUG 15, 05:49 PM

If you haven't got one... get one!

willyt AUG 16, 02:31 PM
Thanks Patrick for your responses. Here is my current plan, if anyone has a better order to narrow this down, feel free to chime in.

1. Listen with stethoscope to see if injectors are clicking.
2. Hook up noid light to check wiring at injectors
3. Double check spark with spark tester
4. Test injectors with 9v to listen for clicking
5. Check injectors with ohm meter
6. Swap 2 injectors and see if misfire moves

If none of these find my issue:
1. Check fuel pressure
2. Check timing
3. Roll the car outside and set it on fire
Patrick AUG 16, 03:56 PM

quote
Originally posted by willyt:

If none of these find my issue:
1. Check fuel pressure
2. Check timing
3. Roll the car outside and set it on fire



Maybe hold off on #3 ... but the first two are so easy that they'd be among the first of my basic tuneup/troubleshooting procedures.
MarkS AUG 16, 10:58 PM
FWIW, my experience with exactly the same problem on my 86 2.8 was the injectors. Messed and messed around with ignition- no joy. The mechanic in town went and disconnected the injectors one by one while running and found the injector with the problem. Here's the thing, I got myself an injector tester and found that the problem injector was the only one NOT leaking under pressure. I replaced all the injectors, problem solved; this was way before I knew injector cleaning was an option.
willyt AUG 17, 10:13 AM

quote
Originally posted by MarkS:

FWIW, my experience with exactly the same problem on my 86 2.8 was the injectors. Messed and messed around with ignition- no joy. The mechanic in town went and disconnected the injectors one by one while running and found the injector with the problem. Here's the thing, I got myself an injector tester and found that the problem injector was the only one NOT leaking under pressure. I replaced all the injectors, problem solved; this was way before I knew injector cleaning was an option.



Thanks for the reply. I agree the injectors seem like the most likely cause of my problem. The weird thing is I had so many things apart, it would make more sense to me if something was just put back together wrong - Swapped wires, missing ground, something unplugged, but I can't seem to find anything like that. I'll do some more work this weekend and see what I can find.

Mark, when you say you got yourself an injector tester, what are you referring to?

Thanks,