car runs rough when it gets up to operating temp

LARRY70GS wrote:

Actually, a vacuum gauge is an excellent diagnostic tool. IMHO, it should be in every mechanics tool box. I use it all the time, but I realize that late model engines with ECM and fuel injection have less use for a vacuum gauge. You can still diagnose valve and ring problems. In any case, a stock 3800 should pull 20" of vacuum fully warm and in Park. Any less than that and you have a leak somewhere, or other problems. My boost gauge is actually partly a vacuum gauge.

Say, Larry,where do you hook the vac gauge up? I hooked it up to the throttle body and to the vac tree atop the S/C and I got zero vac. Am I doing something wrong?

Robo, Dave Jr hooked his up to the line that runs to the fuel pressure regulator and it shows vacuum and boost.

robotennis61 wrote:

LARRY70GS wrote:

Actually, a vacuum gauge is an excellent diagnostic tool. IMHO, it should be in every mechanics tool box. I use it all the time, but I realize that late model engines with ECM and fuel injection have less use for a vacuum gauge. You can still diagnose valve and ring problems. In any case, a stock 3800 should pull 20" of vacuum fully warm and in Park. Any less than that and you have a leak somewhere, or other problems. My boost gauge is actually partly a vacuum gauge.

Say, Larry,where do you hook the vac gauge up? I hooked it up to the throttle body and to the vac tree atop the S/C and I got zero vac. Am I doing something wrong?

I did as Dave did and hooked up a boost gauge to the hard line that goes over the rear valve cover. Shows vacuum and boost. There has to be a spot to check just manifold vacuum.

bigdave wrote:

Robo, Dave Jr hooked his up to the line that runs to the fuel pressure regulator and it shows vacuum and boost.

hey Dave thanks for that! I hooked it up and am getting a steady 18lbs of vac,I think thats how you say it? I suppose if it stays in one place its a good thing!
thanks!

On that scan data log I took the other day, I checked out the O2 data. The two oxygen sensors (reported as O2-A and O2-B) are both reported in the logs.

O2-A has continuously varying voltage (mV), which is a good thing when watching oxygen sensor data in closed loop (from what I read).

O2-B, however - sits at 448.44mV, occasionally going as high as 452.88mV, but never changing between those two readings.

I'm not sure which sensor is which. But from that data I would say one of them is not reporting changes whatsoever.

Check out the graph I made of the data. (Blue = RPM / Red = O2-A / Green = O2-B)

Haha, I think there is only one O2 sensor on the 95's, but I'm not sure.

I guess O2-B is just reporting garbage data, since there is no O2-B...

Rockauto only shows an upstream O2 sensor for the 95's in whcih case yours is performing as it should. Fast response and should be around 850-900 at WOT (which i dont think you did on your run)

Can you read MAF voltage or flow?

Yup. Red = RPM, Blue = Fuel Base pulse, Green = Airflow. No MAF, unfortunately.

This was in park gear, btw. The car is not in motion.

If anyone wants to take a look at the scan with Tunerpro RT, my log is here: http://www.2shared.com/file/7OfX2fnD/riviera_scan1.html

You need these def files: http://www.tunerpro.net/download/bindefs/GM/5B_TPV5.xdf and http://www.tunerpro.net/download/datastreams/GM/5B_V5.adx

My next plans are to try what Abaddon suggested last week and spray brake cleaner around the vac lines and gasket areas.

If it's the LIM and S/C gasket, I think I could probably do that work on my own. Hell, I've done everything else already, pretty much.

I may try and use some thicker oil to boost the compression in Cylinder 4 as well.

I'll probably send out the injectors to Mr. Injector to get sonically cleaned as well.

Don't wanna leave anyone hanging here.

I ended up getting lucky with some financing and got a new truck.

I really liked the Riv, but there were just too many problems to be financially viable for me.

Not sure what was actually wrong with it, but I suspect the LIM was one of many problems on it.

That sux.I know the felling. But ya gotta move on

so you gonna sell it?