engine OFF, ignition ON, VPWR was 11.8v (which is good)
engine ON, signal wire (red/light blue) was 1v (it should be at least 4.5v)
engine ON the signal return wire (light blue/tan) was 13mv (it should be 0.34-1.96v)
Note that for these tests I backprobed at the sensor itself, rather than at the PCM, which is what I have historically done.
kngamble
I believe you about the O2 sensors. Though I am glad that I have all new ones now considering the age of the carā¦ I had ruled out the MAF a while ago, I canāt remember why, so I tested it tonight and as you can see, the results do not look great. I DO have a brand new MAF assembly, I have not used it because I thought if I could rule out the old one, I could return it. I have cleaned out the MAF sensor several times using special MAF sensor spray (the sensor wire-thingys themselves look good). But Iāll probably end up sticking the new one in there tomorrow after I install the new PCM that I am getting tomorrow. Fortunately, or unfortunately, I live in the triangle area of NC, so Iām quite a ways from your shopā¦ If my problems are not cleared up by Saturday, I will DEFINITELY call you up, thank you very much for the offer! I really appreciate it.
newguynet
Absolutely! But Iāve heard bad things about our dealership and Iām certain I wonāt like the prices. I have not spent all that much, I think, on what Iāve done thus farā¦ Even though Iāve probably replaced some things that were OK, I like the fact that I didnāt have to pay labor for them and I know they will last that much longer.
hellokit
That website is new to me, Iāll check it out for sure and try out that test, tomorrow. I did make a graph a few days ago while I was driving and the car was not shifting properly, it includes TP data: http://badsushi.net/images/livedata_graph_8sep08.gif
Your images have good resolution after left clicking on the image.
Here is a poor resolution picture of a scan tool screen graph of a MAF (Mass Air Flow) sensor: http://www.autotap.com/images/mass_airflow_lrg.gif It might print out at a better resolution.
The voltage values for the MAF, taken from alldata Normal Scan Data Values - Includes Pids, show as 0.6 v to 0.9 v at hot idle; at 30 MPH 1.0 v to 1.5 v; at 55 MPH 1.1 v to 2.0 v.
It gets funner. The Typical Diagnostic Reference Values for air flow measures by the MAF are: 4.0 to 4.3 grams/second air flow at hot idle, and 11 to 13 grams/seconds at 2500 RPM (probably, at 0 mph). EDITED:
Your scan tool graph shows MAF flow in pounds per minuet (lb/min). Set the scan tool from English Units to Metric Units to get it to display in gram/seconds (g/s).
1 lb/min = 7.6 g/s, and vice versa.
ADDED
The air flow rates indicated by your MAF, as shown on the line chart (the chart is REALLY busy!) donāt seem amiss. Unless, the MAFās output is erratic, the MAF seems ok.
Ken,
The O2 sensors have been replaced already. As far as the MAF causing the front O2 heater codes, I would like to know how that can be. Can you give us some feedback from your tech about that?
It sounds like you are really digging in on this thing. I live in Hillsborough and have had a little check engine light experience. Iām a techie and DIY type, but have mostly sworn off this sort of diagnostics. Itās my opinion that the codes are intentionally obscure and that Ford has more info than you do, so they can keep more of the repair business! After about eight resets of the light, some at my mechanic and some at Ray Motors in Hillsborough, I parked the car on the Ray lot, threw them the keys, and told them to call me when the light was fixed and I had an inspection sticker. This was after paying about $150 for a couple of sensors and installation. I knew I was taking a chance and might pay more, but the state was breathing down my neck about the inspection and a $250 fine! Well, in about an hour they called and said come back. The sticker was on and there was no charge. A couple of hoses, I expect on the differential pressure sensor, were switched. I was so glad to get away I forgot to ask any questions!
Unless you are really having fun, I recommend you go this route. Most of the parts are not too expensive and you have changed most of them anyway. BTW, my differential pressure sensor, part of a flow sensing system, had gone bad after being changed for the previous inspection. Iād bet they switched the hoses when it was changed.
The car is a '97 Escort wagon, which I like very much. It cost me $2300 a couple years ago, with 80K miles, and gets 35-37 mi/g! I think itās as good as a Toyota and is much cheaper to work on. I just put a trailer hitch on it and pulled a 1000 lb trailer just fineā¦at some loss of fuel economy, of course, but not bad for 70 mi/hr!
If you are willing to come up here, Ken Faucette, on Davis Rd., is a great old school mechanic who has a shop with his two sons. I donāt even ask the price, just leave the car in the lot and everything is done reasonably! The clutch in my '89 F-150 was almost $800, BUT the truck was from Alaska and the whole housing and slave cylinder were rusted solid. It took hours to get the stuff apart and I was delighted I didnāt have to lie under there and do all that banging. Labor was $250, which was reasonableā¦took hours and hours to get done. There is NEVER a charge for looking things over or chasing small problems.
WL
If you are using Internet Explorer or Fire Fox, then you must click on the image after it loads. Both browsers automatically resize graphic files that you view in them if those graphics are larger than the current browser window.
Iāll bet the Maf sensor does the trick. I asked my director of training about the situation this morning and he aggreed. The # for the show is 1-888-660-9535 8-10 sat. Ken Gamble
Quick update, then Iām going under the hood to slowly give every part a dirty look.
The new PCM did not come in today, Autozone doesnāt know why. Itās a special order for, everyone. I went ahead and tried to attach my new MAF (which consists of the sensor itself attached to a big metal piece) BUT the damn thing didnāt fit! The numbers seems to mostly match up, but the metal piece is smaller than what I need, so it cannot be attached to āair cleanerā. Anyways, for some reason, after a couple miles of driving it home after reattaching everything, the car started driving really well. It was shifting when it should, which has not occurred for several days now. No idea why. I tried many speeds. Also, I happened to notice a black rubber hose just dangling in the wheel well of the front-driver tireā¦ Iām going to check that out.
There may not be anything wrong with the old MAF. The low voltages you read may be because of an electrical connector which, by disconnecting and reconnecting, wiped the pins and terminals well enough that the connector conducts electricity better.
Change, and evaluate, only ONE part at a time. Otherwise, you donāt know what caused what change?
I couldnāt think of any tests to do last night. I think the hose hanging in the front-driver side wheel well (before the tire) is a drainage hose for the pan that the battery sits in. Thatās where it seems to attach too, but itās very hard to see in that area. Itās a thin hose, thinner than my vacuum hoses. The car had trouble shifting/staying in gear again this morningā¦ maybe itās because I monkeyed with MAF a little last night, Iāll try hard to check the MAF sensor connections tonight. Since the metal pieces on my old and new MAF sensors are not the same size, I tried to just switch the sensors themselves, but for some reason one of the screws on my old MAF sensor is filled in with plastic! So I canāt remove it! Maybe my soldering iron would melt it off? What the hell is that about?? Curse your Fordā¦
Iām still dealing with drama trying to get a new PCM. I really, really need everything fixed so I can get it inspected and whatnot by Mondayā¦ Maybe the PCM will arrive today, maybe tomorrowā¦
What! Quit when youāve come so far?! Never! You done learned more than what a lot of āmechanicsā know about the engine computer control systems.
Before heading home, set the scan tool to record the MAF voltage and flow rates (in g/s metric units). Be sure that tps %, rpm, vss, and load record, for a dynamic picture.
MIL Illumination and any combination of codes P0135, P0141, and P0155 indicates a fault in the O2 heater circuits. P0135 is for Bank 1 Sensor 1, P0141 is Bank 1 Sensor 2, P0155 is Bank 2 Sensor 1 and P0161 is Bank 2 sensor 2. The codes are normally set due to driver failures in the PCM. Voltage is supplied to the O2 heaters through the Vehicle Power Circuit (VPWR) circuit. It passes thru the heater element and returned to the PCM to be grounded when heater activation is required. To diagnose, inspect connections and harnesses for damage to the suspect sensor(s). If OK, with Key On, check for battery voltage on the VPWR circuit, Red wire, going to the suspect O2 heater(s). If present, check for control side voltage by gaining access to the PCM and backprobe pin 93, Red/White wire, for P0135; pin 94, White/Black wire, for P0155; pin 95, Yellow/Light Blue wire, for P0141 and pin 96, Tan/Yellow wire for P0161. If OK on suspect sensor(s), disconnect the PCM connector and check circuit resistance between VPWR Pin 97, Red wire, and the suspected control circuit pins. Resistance should be between 3 - 30 ohms with readings likely below 10 ohms. If OK, replace the PCM and retest system.
The GRAPH is pretty; but, is it ART?
From looking at the graph, everything seems (to me) to be behaving normally. It IS too much (data) going on, for too long (time), with too many VARIABLES (speed changes, load changes, stuff) to be able to compare the sensor values to desired values.
We need to shorten the sensor recording time (to seconds), and have fewer variables, to get a clearer view of the sensorsā outputs.
For a graph of the tps (throttle position sensor) the engine doesnāt have to be running, and the recording time could be for about 30(?) seconds.
For a graph of the MAF (Mass AIR Flow) sensor, make a recording with the engine off. Then, in PARK, start recording at idle and slowly increase engine speed to 2500 rpm; and, slowly decrease. Then, chock the wheels, and hold the brakes, and put the transmission into DRIVE. Make a graph, of the MAF, at 700 rpm and increase to 2500 rpm (while holding the BRAKE). [If one had the rollers, one could do this with a manual transmissioned car]. A roadtest recording, done in snapshots of a few seconds, could be helpful, also.
We want to cut out as many of the variables as possible; such as: changes in vehicle speed, changes in load (uphill, downhill, coasting, winds, drafting, being pushed, braking). If the recording time is shortened to seconds, a recording can be done with fewer variablesā¦such as coasting down to a lower speed, onlyā¦during acceleration, onlyā¦etc.
Is that cloudy enough?
Will your scan tool show MAF voltage values at hot idle, 30 mph, and 55 mph? If not, backprobe MAF signal wire, use long test leads, and observe multimeter while better half drives at those speeds. Pizza pie.
Yes, itās art, I call that piece āEternal Frustration.ā It will be up on Ebay shortly.
ā
Doh, I only graphed what you asked for in your second to last post. I guess I took you too literally.
Obviously (?) the graph I made was during actual driving. If you compare RMP to VSS you will see that all is definitely not well. For most of the graphsā time, the car was not shifting properly. That is why you see really high RPMs when Iām only doing 30 or 50mph. It wasnāt because I was going up any steep hills or anything. Towards the last quarter of the graph, the car finally gets into the correct gear. I believe that each X tick mark represents one second.
Maybe Iāll get my new PCM today? I bleepin betterā¦ After I do, or if I do not, I will do all the tests you suggest, the way you suggest, and graph them they way you want.
No, I donāt think the scan tool records MAF voltage. However, the first post on this page is a post by me when I recorded MAF voltages by backprobing:
From your graph O2 Sensors Onlyhttp://badsushi.net/images/livedata_graph_8sep08.gif , the rear oxygen sensors are reading high, from 0.55 to 0.75 volts. What is the significance of that? And, what are the units, at the bottom of the graph, from 1 to 60? Time divisions in tenths of seconds, or?
Re-read previous page. I made changes, and added stuff (words).
Yes, I know those results on the MAF voltages; but, I donāt think you could do the āSelf Testā with your scan tool (not YOU, the SCAN TOOL). Itās, probably, the factory model where you can command a āSelf Testā of the MAF.
I think that if you can get a good backprobe performed, on level ground, at hot idle, and at 30 mph and 55 mph cruise speeds, that the voltage readings could be useful information, and could be compared to the āVoltage To Mass Air Flow Conversion Tablesā. This āTableā, from alldata, shows where a certain MAF signal voltage will correspond to a certain air flow (in g/s units).
EDDITED ADDED
I was afraid that you hadnāt made good contact with your needle backprobes, and that that may have yielded the low voltage figures on the MAF.
The light blue/red wire (not, red/blue) is the āSensor Inputā to the PCM. The tan/blue wire is the āSensor Returnā. The red wire is Vehicle PoWeR.
The red wire should be 12 volts. The Sensor Input should be 4.5 volts, constantly. That is the voltage supply (after the voltage is dropped by the resistor in the MAF) to the sensing wire in the MAF. The Sensor Return is the voltage which corresponds to air flow.
If the Sensor Input is really low, and you canāt clean the contacts, or something inside the MAF, and bring the voltage to 4.5 volts, the MAF is bad.
Does your repair manual show the desired resistance, in the MAF, between pins red and light blue/red? If those ohms are high; then, voltage will be low. This (ohms check) would be a double-check against validity of the the voltage check.
If you check around, maybe on the Web, you may find Repair Kits for your MAF. If so, that would be much cheaper than a complete MAF.
