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UIM/LIM Rebuild Pics...In progress....

Personal experience says pull the darn thing

Personal experience says pull the darn thing

Harrry said:
Then an oil change:cool:
Click to expand...

Ok, a few simple items. I cleaned my intake in-place with injector-cleaner at ~145K miles for the first time after getting IMRC 'stuck' codes. Bad idea! I had to replace three of four O2 sensors within 100 miles afterwards.

Pulled UIM/LIM after as I still had IMRC codes popping up. Gaskets were apparently leaking air badly. I say this because I found carbon-tracks crossing the line of the seal in at least five of the runners. I've got the photos if you're interested. New seals with additional RTV-BLUE - BLUE is sensor-safe....

Cleaned everything very carefully. Used a die-grinder to do a simple port-match for about two inches into the UIM (from LIM mount surface). Very nice improvement. No codes any longer.

Repeated the dis-assembly, cleaning, port-matching on a buddies 96 SE with very good results, in less time and without having to change sensors, oil, etc. Would highly recommend this last option!

-JF
 
Port matching...

Port matching...

I'll have to figure out how to post photo's tomorrow- they'd help explain more effectively.

In words, however it went like this...
I knew there would be a problem with carbon build-up when I pulled the throttle-body and it looked about like the opening pic in this thread.

What I didn't expect was that as the carbon came out of the LIM and lower UIM it was patently obvious that cores used in casting the UIM were really poor. Additionally, the low-speed runner was fully 3/16ths smaller (ID) on average than the machined LIM ID. Between these two issues I knew I could get more airflow by cleaning it up.

I used the new gaskets as a template - placing them on the UIM lower-surface and traced the opening with a large framing nail I'd sharpened the end of. This gave me a faint scribe-line about 1/8th of an inch inside the gaskets' port ID.

Using a drywall roto-zip (don't laugh too much!) with the depth-guide in place and 1/4 inch arbor for tootsie-rolls, I ground out the parting line marks and offsets. The arbor was able to reach about 2 inches into the port so I tried to smooth out the short-side radius too. I kept everything as circular as possible and finished the UIM with a few 1 inch flapper wheels.

I finished up by using a 240 grit drum to put a slight chamfer (flaring the top of the UIM bore by ~ 1/16th inch and ~ 1/2 inch down) in the top of the UIM and then bell-mouthed the top corner to avoid tripping the air as it crossed the gasket interface.

Basically, the smallest low-speed runner was just over 3/16ths smaller than the UIM (which is ~1.25" ID) OEM. When I was finished the UIM bores were uniform and just under 1/16th " smaller diameter than the LIM bore. The high-speed runners weren't nearly as bad - but I still smoothed and uniformed them.

The Rotozip is highly suggested - it's large I know, but it can handle 1/4" mandrels easily and will run all day without melting in ones' hand. Also you can't buy a dremel that will spin a 1"x1.25" flapper into the UIM and not stall out. Too much torque required.

I'll try to post some pics this weekend if you're interested.
 
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