Engine 87 Running Real Rough

R82148V

Member
May 26, 2020
75
22
18
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Hey Everyone,

Been doing a ton of research and getting completely confused.
It has what I think is a rough idle, stumble when stabbing the throttle and sluggish acceleration as in low power.
It starts up just fine after 1 second. No visible smoke from the exhaust. At idle, the engine rocks. The exhaust note sounds lower in tone than normal. No leaks.
You can see the engine shake and feel it in the car. I don't think its missing. The rough engine sounds uniform, but definitely not smooth.
All this is at COLD START UP. When slightly stabbing the gas, there is a stumble. When stabbing the gas harder, there is almost a quick cut out. When revving it up, it just feels heavy, like low power. No throttle response.

I haven't done KOER codes yet. I did get KOEO code 82 & 84.
I have no idea where to begin to troubleshoot.

I have replaced:
Plugs
wires
cap/rotor
IAC
All vac hoses and lines
Cleaned everything and tested what I could

Would perhaps EGR or bad injector make this happen?

Thank you!!
 
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Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
37,328
13,166
224
Massachusetts
You should really try and perform the KOER codes along with the cylinder balance test at the end of the code reading. It will be very helpful to you and us in terms of trying to diagnose the issue


 

R82148V

Member
May 26, 2020
75
22
18
.....
You should really try and perform the KOER codes along with the cylinder balance test at the end of the code reading. It will be very helpful to you and us in terms of trying to diagnose the issue


Sounds good and you're definitely right.. I'm using this for code retrieval. I'll get back you asap.

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Thanks again!
 
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Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
37,328
13,166
224
Massachusetts
That should do the trick. At the end of the code reading sequence for the engine running codes, blip the throttle and that will initiate the cylinder balance test. It should blink the cylinders number (or a 9 if all good) if there is an issue
 

R82148V

Member
May 26, 2020
75
22
18
.....
UPDATE!!

Wanted to let everyone know that I was able to figure everything out. I hope this will help someone someday.

I wanted to perform the cylinder balance test that 5L5 was stating, but since it was running soooo rough. I didn't want to keep it running. The engine ran like it was going to rip off the mounts and I just installed new ones! Instead of doing a balance test, I did a sound check with each injector using the screwdriver method. As It's running and using a long screwdriver, wooden dowel or even a shop vac hose, you put one end of the tool against the injector and the other end against your ear. You should here the pulsing clicks IF the injector is firing. Of course this test will not tell you if one is clogged or dirty. Anyway, I checked all (8) and could only hear (4) working!! Cyl 2,3,4 & 8 were working and the rest were not. Hence the heavy duty rough idle and bad throttle response.

Instead of taking the upper intake off to test everything, I just tested through the Black 10-pin (Salt and Pepper) connector. These connector separate the engine bay harness and EEC harness. Top of the 10 pin connector runs to ECC and the bottom half runs to the components. I disconnected the Black 10 pin connector and checked all EEC ground injector wiring from top part of the connector to each EEC pin using a DMM. They ohm out at 2 so I knew the wires were good on that half. I used the bottom half of the black connector to test each injector ohm to see if they were open circuit meaning dead which the DMM would be infinity or OL. I probed Pin #1 and each injector Pin. They all read 16 ohms, which told me the coils in the injectors were fine and also the wiring (hot and ground) going to the injectors were fine.
My last test I wanted to jump each injector to the BATT to see if they opened. I used the bottom portion of the black connector again for this test using the DMM probe wires and alligator clips. I clipped both probes to the BATT, and probed pin #1 with the positive probe and the negative probe to each injector pin. Only Cyl 2,3,4 & 8 made a clicking sound and the rest didn't.
Diagram of the Salt & Pepper 10-pin connectors and EEC PINS below.

With all this testing, I was pretty much certain (4) injectors were stuck closed. Stuck closed because I checked fuel Pressure KOEO and it was steady at 38lbs.
I picked up (8) reconditioned injectors from SouthBay Fuel Injectors. Model# FOTE-D5B. These came with a 4 hole tip.
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What I had in there were E6TE-A2B that come with a single pintle hole tip.
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I decided to change all (8) just for the fact of age with this being an '87.

Got everything installed, wired up, double checked everything. Go to start it and it started right up! It idled high for about 6 seconds and calmed right down to a very very nice super smooth idle! I bet you I can place a marble on top of the intake and it wouldn't move. The big test was yet to come.. How it felt giving it gas just in neutral.. Would it stumble? Hesitate? Misfire? Feel Sluggish or even stall?

NOPE!!! It performed amazingly! Just barley giving it any gas and you can feel the power behind it! It accelerated smooth, instantly and came right back down to a clean smooth idle immediately. No hang ups. It actually caught me off guard. It accelerated so quick, smooth and powerful, this is going to sound funny but it was kind of frightening. Which is a good thing ;) .. pfff haha

I've owned this car since '94 and there always was a power/acceleration issue. It seemed to get worse over the years and internet was scares back then. Nothing like it is today and the information you can find especially on STANGNET!!


Anyway, The car / engine only has 72k original miles on it and it seriously feels like a brand new engine.!!
I didn't state this before, this beast sat covered for the past 12 years. Been working on it a little each day for the past 2 years, taking my time to do it right.
Engine bay is coming along nicely!! I took everything off, cleaned, painted, inspected and rebuild all that I could. The only things I replaced were the Radiator to a 2 Core, the reservoir, fan, EVS, Fuel tank and ignition components. Replaced every hose, vac line, gasket while learning every detail using STANGNET!

She doesn't look too bad for almost 35 years old! hahah

I'll be doing a complete restore.

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