It seems that the Bourdon tube gauge isn't off by much after all. Note the following math: Next question: "What about idle MAP at different altitudes?" MAP sensor is at ~40 kPa which makes sense when I compare with engine load. The MAP sensor (Manifold Absolute Pressure) measures absolute air pressure in the inlet manifold. Want to make a guess here? Some questions might be answered in the datastream, but more than likely we will have to use other testing equipment in order to verify those systems. Moderator: Team. As for the map sensor, if this is not a boosted application (no turbo or supercharger), you only need a one bar MAP sensor. Yes, they are not what you'd expect. I'll record all readings at 1000-ft. intervals. A few weeks ago I was teaching a class and talking about manifold absolute pressure (MAP) sensor diagnostics. This website can also use non-functional cookies, for analytic purposes. According to an OBDII datalog taken from a known good 1998 Chevrolet k1500 5.7 liter, the average of 41 frames taken at a warm idle, in park, and all accessories off, is 35.76 kPA. site design / logo © 2020 Stack Exchange Inc; user contributions licensed under cc by-sa. A properly operating MAP (manifold absolute pressure) sensor is always correct. Koperslagersstraat 37 This ended up being what threw the 33 code. Channel 1 (red) in figure 3 shows the MAP sensor signal. Look at columns two and three; the calculated pressure value and the actual value are pretty close. It might help guide us toward problematic systems that could be the root cause of the original complaint. AN can be very finicky in regards to air temp, humidity, etc. When placing non-functional cookies, traceable data is processed. Why is the rate of return for website investments so high? Creating new Help Center documents for Review queues: Project overview. You can order them direct from: How has the first atomic clock been calibrated?

With a lab scope a Manifold Absolute Pressure (MAP) sensor is measured under the following conditions: key on, cranking, idle, 2000 RPM, 3000 RPM and back to idle with an engine at operating temperature. @All OK, do you have any symptoms, or just trying to figure out what seems to be wierd readings? Are there proposals for preserving ballot secrecy when a candidate scores 100% in a very small polling station? I replaced all my plugs and wires and thought i connected the wire all the way but #1 cylinder wire popped loose from the plug. At both moments the pressure increases shortly and quickly drops after that, For instance it is common for the MAP to have a variance around 1 inHg or 3 kPa when idling in drive vs park. Finally, look at the last two columns. A: When throttle is at ~25%, engine load is at ~55% and engine speed is at ~2000 RPM, I can see the MAP at ~70 kPa. While the Bourdon tube will not show changes in baseline atmospheric pressure, we also know that it uses atmospheric pressure to move the tube. Before starting a measurement, check which safety measures need to be applied.

Does this question even make sense? When you click the "Accept" button you will allow placing non-functional cookies. Let's take a close look at the innards of a vacuum gauge to get a better idea (see the photo at left). It shows right on the chart (top part), idle to be to the right side (high vacuum/low MAP voltage) and left to be WOT (low vacuum/high MAP voltage). Does the vacuum gauge hold steady, flutter, or float up and down? When it comes to engine performance diagnostics, understand that OBDII mode $01 is designed to give us hints toward drivability complaints whether it be perceived by the driver, or in the form of a MIL (Malfunction indicator light) on the dash. Now I'm going to measure MAP pressure (atmospheric pressure) KOEO and idle MAP pressure KOER. Once we can duplicate the problem, at this point, we start asking the datalog or dataset questions. Does the sun's rising/setting angle change every few months? Pin B -- Sensor output The chart below describes the pressure-to-voltage relationship of To run at the same rpm and load, doesn't the MAP have to remain the same? You can view the signals from this measurement by Low MAF and MAP sensor readings, idle shudder.

From your description, you aren't running anything which produces pressure, so can assume your MAP sensor is stock and only covers one bar. So the question in class is, "What should idle MAP be?" Correct functioning of the MAP sensor can be checked by measuring the following signal voltages, Welcome to Motor Vehicle Maintenance & Repair! ~400-500 rpm. I've a rotary with ITBs and have spent a fair amount of time chasing down what we're really seeing with these ITB installs. Hmm. Lower pressure in the Bourdon tube causes air pressure (outside the tube) to curl the tube inward. The vacuum is channeled in to the sealed curved tube. Two single frames of data isn’t really enough to go on if OP provided a datalog (snap throttle and wot)it would help show the bigger picture.

I'll then measure intake manifold vacuum with a Bourdon tube style gauge. rev 2020.11.5.37959, The best answers are voted up and rise to the top, Motor Vehicle Maintenance & Repair Stack Exchange works best with JavaScript enabled, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site, Learn more about Stack Overflow the company, Learn more about hiring developers or posting ads with us.