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#1054699 - 12/04/17 06:40 PM Re: Excessive MPG? [Re: ChasUno]  
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Ranger413 Offline
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Southeast, GA
Just picked up a Brain Master II for my Monte. For $40 off of Ebay, any info it can provide will be well worth the cost. Looking forward to giving it a try.




88 MCSS, all stock except for the wheels
#1054700 - 12/04/17 07:55 PM Re: Excessive MPG? [Re: ChasUno]  
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Richie Cat Online content
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Lake Ronkonkoma, N.Y.
Would you like to expand on that?
Copied Brain Master II and came up with "things".


83 SC, 355 w/TPI
#1054731 - 12/08/17 06:15 AM Re: Excessive MPG? [Re: Richie Cat]  
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ChasUno Online content
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ChasUno  Online Content
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Bradenton, FL
Originally Posted by Richie Cat
Would you like to expand on that?
Copied Brain Master II and came up with "things".


Not quite sure what your question is, Richie Cat?

If you mean what is the Brain Master II, it's the dedicated scanner that can read all the CCC ECM sensors in real time, including fault codes. Here's a link to the scanner I bought:

https://www.ebay.com/itm/Alltest-Automotive-Diagnostic-Equipment-BrainMaster-II-Model-3240-/372124509796?_trksid=p2047675.l2557&ssPageName=STRK%3AMEBIDX%3AIT&nma=true&si=mZimOryjpJgVnsr48UoxhMdOe2g%253D&orig_cvip=true&rt=nc

From what I understand, it's the official scanner used by GM dealers when the cars were still being serviced by them. Very limited market for them now, as they only read GM (and some Isuzu) vehicles up to the late 80's, and with many people pulling out all the CCC stuff, there's even less market for them. However, for those of us still running CCC systems, it's an absolute godsend. Since I received mine I have been able to get a much better insight into what my engine is doing, including while the car is running and driving, which I wouldn't have been able to do without it.

I got mind for an absolute bargain price too, so a win/ win for me. If anyone still runs their CCC system, I strongly recommend getting one of these when they come up for sale at a decent price.


1986 Monte Carlo SS

[Linked Image]
#1054732 - 12/08/17 06:47 AM Re: Excessive MPG? [Re: ChasUno]  
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ChasUno Online content
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ChasUno  Online Content
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Bradenton, FL
Further to update on my "tuning" efforts.

Firstly, it appears that my Quadrajet is completely original and unmessed with. All the blanking plugs/ covers were in place, therefore it appears that the carb is untouched since it left the factory in 1986. Unless it was replaced at some point, or rebuilt by someone who replaced the blanking plates/ plugs. As mentioned in a previous post, observing the MC Dwell on the Brainmaster showed the dwell to be on the low side, averaging approx. 23 degrees. I had to remove the IAB blanking plate to get to the adjusting screw, then I attempted to adjust it to increase the dwell. I ensured the engine was up to operating temperature and that the computer was in closed loop, then adjusted the IAB screw. I did get the dwell higher, though it was hard getting it much over 30 degrees (engine running at approx 600 rpm and transmission in drive). Eventually I got it averaging close to 30, though it tended to dip more into the mid to high 20's than low 30's. I have also purchased an analogue dwell meter, so once that's arrived I will try that and see how the readings compare. At the very least, I was able to adjust the MC dwell closer to 30 degrees and it's varying, which shows that the MC solenoid is working and trying to do its job.

One issue I am having is trying to get a stable TPS setting, it seems that the very slightest tweak on the TPS screw causes the reading to jump either way considerably. The Factory Service Manual recommends setting it with the ignition on and the engine not running. However, if I do it this way, then the TPS base setting goes much higher when the engine is started and running. It also appears to go higher when warm after setting it. If I set it with the engine running (600rpm, in Drive), it's also very hard to try and get it set to 0.48v. And when I do get it close to 0.48v, touching the accelerator and releasing it, the reading doesn't go straight back to 0.48v, instead it seems to hover at higher readings (i.e. 0.64v) and slowly drops to somewhere near the base setting. Then if I turn the engine off and keep reading the TPS, it will continue to slowly drop below 0.48v as the engine cools.

Having never worked with a TPS prior to getting my MCSS I am not familiar with how they are supposed to behave. I replaced the TPS sensor a few months back, now I am wondering if perhaps the unit I fitted is faulty, or I didn't fit it quite right? Or is the type of behavior I described above regarded as normal? Or, maybe the throttle shafts are just worn making it hard for the linkages to stay stable?


Last edited by ChasUno; 12/08/17 06:49 AM.

1986 Monte Carlo SS

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#1054735 - 12/08/17 06:57 PM Re: Excessive MPG? [Re: ChasUno]  
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mmc427ss Offline
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mmc427ss  Offline
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As far as dwell goes you are looking for 28-32 varying back and forth at idle. Looking at the threads for the IAB you should see about 7 threads showing in the hole. When you deviate much from that you will need to tweak on the idle mixture screws.

The TPS voltage may vary but you are only interested in shooting for that .48 volts when the engine is at normal temp and idling. Yes throttle shaft slop, weak carb return springs may cause erratic voltage. But varying voltage a tenth or less shouldn't be a problem.
Bob

#1054817 - 6 hours ago Re: Excessive MPG? [Re: ChasUno]  
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ChasUno Online content
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Bradenton, FL
Thanks as always Bob, for your input and sharing of experience and wisdom. Hopefully I will get closer to getting my MCSS running akin to a Swiss Watch. Maybe!

Anyhow, another fuel up and another update. I didn't do so well with the last tank of gas, though I suspect there's a number of reasons for that. Down to 11.7mpg, though not as bad as the lowest I got. Here's the latest Fuelly result:

[Linked Image]

A number of reasons for the drop in mpg compared with the last tank - firstly, I was doing a lot of tuning with the car idling in drive, so that likely used extra fuel. Also, I was still trying to get the mixture control solenoid to dwell around 30 degrees and it seemed to be dropping more down in the low to mid twenties at idle. As a result it spend a lot of the last tank running rich. Also, one time I forgot to plug the electric choke connector back in so on one short drive the idle revs were sky high and it was choked like crazy. Oops!

As also mentioned above, I was having a nightmare trying to get the TPS to give a stable reading at idle. Furthermore, I think I discovered another issue with regards to the TCC lock up system. I had noticed that it didn't seem to want to go into lock up as easily as it did, and when it did it would come in and out of it at random if I was below 55mph. At the same time this became apparent, I also noticed that when engaging cruise control the car would surge back and forth, many times and at random, even though the speed had been set. I thought that maybe the cruise control system had a fault in it somewhere, and started reading the Factory Service Manuals to get an idea of where to start looking. Looking at how the system worked, it takes most of its signals from the VSS to tell the vacuum solenoids to accelerate or decelerate. I thought that it was using the TPS data, but from what I can tell, it doesn't. Now, something else had been noticeable recently, and that was that the speedometer needle was getting a lot more jumpy and erratic. Of course, the VSS also takes its data from the speedo cable, so to confirm, I plugged in the Brainmaster and checked the VSS readings. When traveling at a constant speed, i.e. 35mph, the VSS reading could fluctuate by as much as 10 mph (it would spike more up than it would down). It would do the same at higher speeds too. Therefore, unless I'm mistaken, the erratic VSS signal is causing the Cruise Control to be unstable as it is trying to match an at times wildly fluctuating speed. It also means that at low TCC lock up speeds, the TCC controller is seeing a sudden change in speed and drops out of lock up. Thus my mpg will be suffering at speeds below 55mph because the TCC doesn't stay enganged constantly as it should. At least, that's my theory. If I'm correct, then I need to get my speedometer cable oiled so that it stops jumping all over the place, which will also stabilise the cruise control and TCC lock up.

Back to trying to set the Idle Air Bleed for the mixture control dwell. As I had mentioned earlier, I had been using the Brainmaster to set the MC Dwell, with common advice being to use an analogue dwell meter. A little bit of hunting on Ebay and I had another new toy to play with:

[Linked Image]

It's a surprisingly large meter, though luckily it's in very good condition and in a nice case. Today I tried it out to make sure it worked, and also to have another go at adjusting the MC Dwell. I connected the meter to the green MC Dwell connector on the carb, set it to 6 cylinder dwell scale, had the engine up to operating temperature and in closed loop while idling in drive at approx. 600rpm. I also had the Brainmaster connected simultaneously showing the MC Dwell reading digitally. As per previous attempts, turning the IAB screw didn't seem to get the reading much above 30 degrees,nor did it seem to cause the reading to change much. In a fit of frustration I turned the screw I think a whole turn, and lo and behold, now I was getting readings well above 30 degrees! I also had the analogue meter needle fluctuating between approx. 26 and 35 degrees. Video below shows the meter in action:

https://youtu.be/ySbESl4iOQI

Is this the sort of behavior expected of the MC Dwell when being read by an analogue meter?

Interestingly, the Brainmaster scanner readings weren't that far off the analogue meter, and in fact matched it quite well. I guess that I am very used to observing digital devices so it wasn't that hard for me to work out the highs/ lows/ average of the digital read out. I certainly agree that the analogue dwell is a lot easier to comprehend needing just a glance at the needle rather than taking note of the numbers.

And here's a picture of the IAB screw showing approx. 7 threads above it. Hopefully not too far off?

[Linked Image]

I took the car out tonight and continued reading the MC dwell via the Brainmaster. It now seemed to be on the high side of 30 degrees, so I tweaked the IAB screw by abouyt 1/4 of a turn, and now it's reading around 30 - 36 degrees at idle in drive. I will tweak it a little more on each drive until the number more settles around 30 average, and I will double check it with the analogue meter once I feel it's getting close.

Hopefully I'm on the right track and will get my '86 running better than she has in years. Oh, and if anyone could confirm that an erratic VSS reading will cause unstable cruise control operation and also affect the TCC lockup that would be very helpful. I can then add oiling/ replacing the speeometer cable to my list.

Onwards and upwards hopefully!


1986 Monte Carlo SS

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