diagnosing the 6.9L want advice

[learner]

Hi ALL!!- I've bought a 87 w/ 6.9 IDI. This truck is going to teach me a LOT! It has a serious miss, slightly worse when warmed up. no apparent water in the oil (I changed it IMMEDIATELY) and vice versa. no coolant blowing out of the system. I'm thinking maybe it's a head gasket - maybe stretched bolts, I've read that this is a common problemI want to run a compression test, but can't find an adapter for my gauge. Can anyone tell me where I can find one?
On another subject- I need to find a REALLY GOOD service/ repair manual ( OR SET thereof) to study, but neither parts stores or manual writers seem to have anything comprehensive. ANY suggestions, anyone?

 

[towcat]

welcome to the site. before you get carried away, tell us more about the miss. are you popping out the intake or exhaust? have you felt the injector lines to see if an injector is hanging open and is allowing compression gasses to backflow through the injector. does the miss change as you rev it up or is it consistent? before you assume the worst, let's check the somewhat simple stuff first

 

[learner]

Thanks, Towcat!! Will do these 2 tests 1st thing.Note:no back-breathing or popping in the intake. "Chuffing" in exhaust. No sweet smells of coolant in the exhaust, either.

 

[79jasper]

I very highly doubt you have a head gasket problem.
My money would be on injectors.

Sent from my SAMSUNG-SM-G935A using Tapatalk

 

[icanfixall]

Welcome to the forum. Right off my first guess is an injector is not firing correctly. If an injector hangs open you can't build pressure to pop open the injector so it will have a miss. Also that injector hard line will feel very hot because hot exhaust gas backs up in the line. that can melt the plastic return line cap on the top of the injector is worst case issues. That injector can also be staying closed from dirt stuck in the valve body on the injector. Its called the pintle and nozzle area. The very best manual money can buy is the Navistar CGES 435 service shop manual. Any Navistar can sell this to you. Just tell them the year you want. Mine is the CGES 435-1 for the 1991 year. All the 6.9 and 7.3 engines share the same internals so any Navistar shop manual will tell you the same information.
Who did you purchase this truck from in Nevada?

 

[MTKirk]

Hi ALL!!- I've bought a 87 w/ 6.9 IDI. This truck is going to teach me a LOT! It has a serious miss, slightly worse when warmed up. no apparent water in the oil (I changed it IMMEDIATELY) and vice versa. no coolant blowing out of the system. I'm thinking maybe it's a head gasket - maybe stretched bolts, I've read that this is a common problemI want to run a compression test, but can't find an adapter for my gauge. Can anyone tell me where I can find one?
On another subject- I need to find a REALLY GOOD service/ repair manual ( OR SET thereof) to study, but neither parts stores or manual writers seem to have anything comprehensive. ANY suggestions, anyone?

Buy a factory service manual. There is one for the chassis, and a separate one for engines. I got both used on e-bay for $115, WORTH EVERY PENNEY!

 

[learner]

Hi MTkirk! Thanks for the reply. While on the hunt, I contacted the local IHC shop & parts dept. Charlie in parts told me that thete were 3 distinctly different production groups of engines in '87 as a result of being a mid-year change, and IHC actually wrote 3 different manuals for JUST the 6.9l that year, covering each group by serial#'s. If the engine manual you have mention any of this, AND my
serial # - 6.9D U2 U398921* - is includud somewhere therein , PLEASE let me know the exact title and Ford's
part#s for these books. I'll be able to find my own set. THANKS AGAIN!

 

[Leroy]

i have one .. really good ?? you decide ..

but i guarantee it's also worth every penny .. FREE

link#5

http://fordfab.com/weblinks.html

 

[Koch13351]

My truck had a "miss" when I got it. It turned out to be a loose rocker arm. The bolt had backed out enough to where it was no longer opening the intake valve. Pop your valve covers off and give it a look

 

[learner]

Thanks for the offer Leroy. I really appreciate it. My mailing address is po box 1066 Virginia City, NV, 89440

 

[Leroy]

[sending] signed sealed delivered - it's yours [^link]

. \ some assembly required

 

[Leroy]

i agree .. you're miss is likely a bad injector or injectors ..

crack open the injector lines one at a time and listen / look for changes in how it's running and smoke ..

i had one that was poping off low pressure and then dribbling after the pop .. it had a miss and slight ignition knock .. slight white smoke ..

it was number #1 right in the front .. i could hear it when i lostened it at the line ..

put it on the pop tester at the injection shop to look at the bar pressure and pop patern and it was weak ..

 

[learner]

Thanks EVERYONE for your replies!! I Have an interesting ? for the gang--- do any of your trucks have a OEM odometer that's only has 5 digits + 1/10 mi. ?( just pure curiosity) I'm wondering if the seller hid the REAL nilage by swapping it, not being concerned about legalities. I find it VERY unlikely that FORD would do that in DIESEL.
Personally, I'm not the LEAST worried as I bought the truck because it was only $1300 and was everything I want in a work rig. ( and MORE!) I PLAN ON getting EXTEMELY gooky.

 

[learner]

WOW! THAT was Q-wick! If it isn't what I need, I'll send it back or onward into the ether. Karma, you
know. I owe ya one! Thanks again!

 

[superds]

My 88 only has five digit plus tenths. Right now reads it has 34500 miles. Could be 135k or 235k or 335k, etc. Who knows!