High FT diagnostics with sprays

[MassHoe04]

Appear to be threaded studs for these. Threaded into the top flange. No nut on top. Nut on bottom only.

Still an area to check out. Make sure nothing is loose or has any gaps there.

 

[MassHoe04]

Maybe exhaust flange connections are less likely to happen on these. Not sure...

The two parts on the GM are flat. Probably less likely to form gaps that leak, unless the flange warped.

Where on my other vehicle the cast part of the flange was a tapered cone shape where the collector pipe mated up. It had a two-piece ring that clamped the two sides together. If the pipe and the flange were not mated up straight or the flare on the pipe did not fit the cone shape on the flange perfectly, you get a leak.

Was just something I thought would be easy to rule out and cost nothing to find out.

 

[afpj]

Well, I've been silent on this topic because summer came and the problem went away. Fuel trims back to normal. Then winter came last month and fuel trims went up again. So cold weather makes it look like I have a vacuum leak. I used a nice flammable spray like throttle body cleaner when it was cold (45 is cold here) and sure enough RPM's bumped up if sprayed near the intake manifold gaskets. I've never done a job like this and only because of reading all the great advice on this forum and watching a couple of YouTube videos, I was able to tackle the job. A few minor hiccups like, snapping the white heater hose T (although as you can see in the picture, it wasn't really white anymore. It was tan to brown so it look like it was going to go anytime anyway- God works in mysterious ways). After that though, I got really discouraged and just wanted to button it up so I forgot to put on the RTV dam around the knock sensors, also forgot to put loctite on the intake bolts. It looks like the shop that did it previously did not use loctite and it lasted for a good 100k miles. So I guess I'm okay on that. Fuel trims back to normal even in the cold weather.

Thanks to this awesome forum... happy New Year!