Air/fuel meter readings?

[36tudordeluxe]

Have an INNOVATE MTX-L air/fuel meter and am getting what I think are erratic readings varying from 15-24 and then goes to 8.8.8. at idle. Sensor is hooked to header extension that goes into muffler, muffler on other side is not installed. I only have install manual for the the meter and error reading explanations and trouble shooting, none of which explains erratic readings. Any ideas?

[flatjack9]

Isn't there a calibration procedure to go through?

[36tudordeluxe]

Originally Posted by flatjack9

Isn't there a calibration procedure to go through?

yes, that part of the operation works perfectly, things go wrong when the engine is running.

[36tudordeluxe]

Just got off the phone with INNOVATE tech and it's normal for readings to bounce around at idle but my readings eventual go 888 which indicates wiring problem with power source for the meter, suggested I put in a relay for the meter and will do so before proceeding any further.

[Talkwrench]

Let us know how you go with it Bob.. It should be plug and play.. are you on 6 volts still?

[51 MERC-CT]

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If all you are doing is playing around with it while sitting and idling and applying the throttle, all you can expect is somewhat erratic readings.
It's got to be setup under normal driving conditions.
When you get it running you can set the idle values with a combination of idle screws and curb idle screw. For example using pretty much the same setup as yours on a stock engine I am seeing readings of 13.5-14 at idle, around 14 at part throttle acceleration and 14.9 - 16 with occasional spikes to 22+ at part throttle cruise.
The only place that it shows rich is at full throttle 8-12, but I'm not going to worry about that because I very seldom use full throttle.

[40cpe]

Originally Posted by 36tudordeluxe

Just got off the phone with INNOVATE tech and it's normal for readings to bounce around at idle but my readings eventual go 888 which indicates wiring problem with power source for the meter, suggested I put in a relay for the meter and will do so before proceeding any further.

Seems as if I remember you having problems with power to the coil at one time. If you are powering the A/F meter from the same source as your ignition it could be a hint about your ignition switch or source of powerr to it.

[36tudordeluxe]

Put in the relay as suggested and only slightly improved condition before reading "888." Appears the coil problem has been resolved but am getting power source for A/F meter at accessory panel anyway. Based on my observations and what 51Merc states I should expect to see erratic readings when car is sitting at idle but shouldn't see the readings going to "888." Tomorrow will get friend to ride in car and record readings.
Here's what I have now: 850 RPM at idle showing 14hg on vacuum gauge and 11° initial advance; the car starts immediately. Car did go to 220° when I flogged it at 92° OAT and blew out coolant from somewhere unknown at this point but suspect petcock on bottom of radiator but petcock doesn't leak when engine not running. Thanks everyone for the help.

[36tudordeluxe]

Originally Posted by Talkwrench

Let us know how you go with it Bob.. It should be plug and play.. are you on 6 volts still?

No, 12V negative ground.

[George/Maine]

You seem to like shine tools smart tools , adjustable timing light,o2 gauges.
There is not a tool out there that will tell you have a bad cam.
If you try the same thing you best try another idea.
You didn't build that engine and take it back and have it done again.

[oj]

You'll get goofy readings with the insertion device into a short exhaust, like a sidepipe, because of reversion. It'll read lean. I'm told you can add a piece of tubing to the sensor and shove it up into the exhuast pipe as far as possible.
Its best to weld bungs into the pipes up close to the engine and screw the O2 sensor into them, plug the bung when not in use.
I've never seen that '888' reading, I use the LM-2 2 circuit and it took a while before I made sense of it.
I do read out at the far end of the exhaust pipe, it is ok to clamp the device into it because the reversion effect won't translate that far into the exhaust - not that I have seen anyway. Its just when reading relatively short exhausts that you'll get strange readings.

[36tudordeluxe]

Originally Posted by oj

You'll get goofy readings with the insertion device into a short exhaust, like a sidepipe, because of reversion. It'll read lean. I'm told you can add a piece of tubing to the sensor and shove it up into the exhuast pipe as far as possible.
Its best to weld bungs into the pipes up close to the engine and screw the O2 sensor into them, plug the bung when not in use.
I've never seen that '888' reading, I use the LM-2 2 circuit and it took a while before I made sense of it.
I do read out at the far end of the exhaust pipe, it is ok to clamp the device into it because the reversion effect won't translate that far into the exhaust - not that I have seen anyway. Its just when reading relatively short exhausts that you'll get strange readings.

The bung hole for the CO2 sensor is only 3" beyond the end of the header and as you state this is best location but get very erratic readings. Will explore this further when I test drive the car today.

[GreenMonster48]

Originally Posted by George/Maine

You seem to like shine tools smart tools , adjustable timing light,o2 gauges.
There is not a tool out there that will tell you have a bad cam.
If you try the same thing you best try another idea.
You didn't build that engine and take it back and have it done again.

I agree. After reading your threads, take the car to a trusted mechanic. You're hooking up A/F ratio meters and sending away for jet kits before having the car properly diagnosed. You're only going to compound your problems.

[supereal]

Using a vacuum gauge is cheaper and reliable. If any one needs a chart to use with the gauge, I can share a good one. Years ago, we used a combustion checker that was placed at the end of the tailpipe. It used a Wheatstone Bridge to measure the mixture. It really didn't help much. Today's vehicles use one or more O2 sensors to furnish the data to the ECM.

[34PKUP]

Originally Posted by supereal

Using a vacuum gauge is cheaper and reliable. If any one needs a chart to use with the gauge, I can share a good one. Years ago, we used a combustion checker that was placed at the end of the tailpipe. It used a Wheatstone Bridge to measure the mixture. It really didn't help much. Today's vehicles use one or more O2 sensors to furnish the data to the ECM.

And just how does a vacuum gage tell you if the engine is running rich or lean? Isn't an O2 sensor an A/F meter?

[Zeke...PA]

The meter will bounce around, at least mine does, I had set the idle with the vacuum gauge before I had the AFR meter. I was surprised at how much the idle screws changed the readings, at idle went from 11.5 adjusted to 13.8-14.2 at idle. Runs pretty much at 14-14.5 at cruise, the idle circuit also changed the cruise settings, close enough for me, 1/8" over bore, crab dist. Mercury manifold with a 2GC carb, Red's headers. I did a little relieving and port polish also when building engine. My meter is an Innovate MTX-L. Zeke

Changed main jets to #51

[colin1928]

I have the same meter and have had the same problem on mine it was a bad ground wire they are such a thin wire it is hard to get a good connection mine seem to fray at the connection after some time then it does the same as you have
I redo the connection all good for maybe a year

[AnthonyG]

Sensor is hooked to header extension that goes into muffler, muffler on other side is not installed.

Read all the threads and didn't see any mention about the dual exhaust not having a muffler on one side yet. I would think possibly the difference in back pressure from one side to the other could cause errant readings?

[36tudordeluxe]

Will see if I can get a better ground. I too set the idle jets with vacuum gauge got clean plugs at idle but as soon as I drive it runs rough and plugs get real sooty. I wonder about muffler on one side only also.

[JSeery]

Sure it's not a bad power valve or something along those lines?