MAF readings super high 2.66 lb/m at idle

[mostly_broncos]

4.0 2003 explorer sport trac , tried 3 different known good meters all read 1.3 to 1.5 volts at idle ?

Scanner claims that corresponds to 2.66 lb/m

that voltage is consistent across different sensors that work fine in a 2005 escape.

When its cold it idles for a little while badly then dies with a very rich smell.

Idles much better with the MAF unplugged.

Changed intake port to cylinder head gaskets no help , blocked off PCV hoses to isolate potential vacuum leaks , no help , pulled , EVAP line plugged it no help , pulled brake booster hose and plugged it no help.

Tried every vacuum hose I can find , I don't think its a vacuum leak behind the throttle plate , the MAF sensors all think they are seeing that much airflow but why?

I pulled the PCM harness and have continuity between the C and D also A and F to their respective pins.

Full battery voltage on the hot wire , the ground is fine , the signal return sometimes is a little lower than the other ground say .5 volts not consistently

I checked and cleaned the neg post to radiator support ground , the main cable ground on the starter bolt , the ground near the wiper motor, the ground near the PCM .

This is weird what am I missing? the MAF is legit outputting that high voltage so that appears to rule out the D wire to the PCM .

Does the C wire labeled signal return go elsewhere , other sensors ? Could a short in another sensor feed back to the MAF and change the reading on the C wire and bump up the voltage output on the D wire?

 

[mostly_broncos]

Stepped away from this a little this weekend to reset my brain. I had plugs and wires so I replaced those. The plugs were hideous , all the drivers side seemed original the largest gap was .090 . The little nubs on the center electrode were burned off. The other side weren't as bad which surprised me as they are harder to access .

Fire it up this morning and now on high idle the mass air voltage is 1.7 volts! I shut it down and had an idea to remove the C wire from the mass air plug and try running it. Now I get 1.3 volts at high idle. If I plug that back in it goes back to 1.7 volts.

Without the other ground the mass air outputs zero volts. Without the power wire zero volts

Something is weird about the signal return , but it has continuity to the PCM plug . 7 ohms resistance doesn't seem out of line.

I'm going to unplug the mass air warm it to operating temps with no sensor then plug it back in and see what I have at warmed up idle.

I don't feel like this is a vacuum leak as unmetered air seems like it would present as a low voltage output from the sensor

 

[mostly_broncos]

went to move it today after a week and suddenly seeing torque converter clutch code I've scanned it 20 times this week without seeing that once.

Now it idles good without the MAF plugged in but dies if it warms up . It wasn't doing that before , I fixed some vacuum leaks though so maybe that lowered the idle RPM.

 

[mostly_broncos]

New scanner purchase with live data and I'm playing around with it .Mass air numbers at high Idle are almost 2 lbs declining to 1.5 as the idle drops . The MAF doesn't seem to be dirty and to rule that out I tried different MAFs and they all act the same. At the same time STFT on both banks climbs steadily higher until it stalls around +50%.

If I unplug the MAF it idles better but the STFT on both banks still climbs to about the same area.

If I look at the O2 sensor voltage graphs they cycle from extreme low to extreme high up down up down up down as the Fuel trim goes up. Its a very jagged graph , the S2 sensor graph is much smoother . All the O2 sensors appear to at least be functional . The Fuel Trim starts at zero on both banks then goes up say to 10 then back to 5 then up to 15 then down to 10 . so it steadily goes up and the O2 seems to back it off too much then it goes higher . There are no long term Fuel trim numbers but the battery has been unhooked.

STFT numbers adjust steadily higher , I decide to take my oxy-propane torch and I pull plug from the intake hose where the passenger side PCV line would go , stick my torch tip in and inject propane and the fuel trim numbers drop way down. So I leave the graph running and direct propane in different areas to look for vacuum leaks but so far nothing. .

Is it a vacuum leak ? Propane directed anywhere near the intake doesn't affect fuel trim , only if I put the nozzle in a vacuum port directly, Also as it warms up it runs steadily worse until it won't run at all which if it was an intake gasket I think it would tend to get better at warmer engine temps.

Any ideas anyone? Its too warmed up now it won't stay running but tomorrow I would like some things to try. Because I have an oxy bottle on the torch I guess I could try to add oxygen to the intake and see if the fuel trims go negative. I feel like the O2 sensors are fine though from what I am seeing with propane

 

[mostly_broncos]

I pulled the valve off and blocked the big vacuum line that goes to it and plugged the intake hose where the other hose comes in after the MAF to isolate all that plumbing. Both sides are venting the crankcase to atmosphere , I also pulled the hose from the brake booster and capped it. I pulled the vacuum hose that goes to EVAP and capped that nipple.

I will say that with the PCV stuff out of the picture it seems to run slightly better so there may be a small leak in the hoses , the valve itself also doesn't lock into the back of the valve cover at all so there may be a leak around when it goes into the cover.

I put a vacuum pump on the fuel pressure regulator and it seems like it won't hold vacuum , if I pump it up to 25 inches it drains away in about 10 seconds

 

[mostly_broncos]

It seems like I have vacuum all the time at the EGR valve but no EGR codes have ever been thrown . I am seeing Fuel trim numbers coming down with the hose off the EGR valve, I applied a vacuum pump to the valve and if I pump it up it kills the engine so its not full egr at idle just some. The valve seems to hold vacuum applied by the pump so The EVP is passing vacuum to the valve at idle but I dont get a code, I guess the PCM thinks the EVP is working ok.

 

[mostly_broncos]

It looks like I may have become overly focused on this voltage number , I finally got my fuel pressure tester returned to me and hot idle pressure is only 10 PSI . I'll have to wait until tomorrow to see what cold idle is .

Could be the filter or the pump or strainer clogged up , low voltage to the pump bad ground etc .

I did a tune up and it ran worse , well if its not getting enough fuel then tuning it up will probably want even more fuel , The EGR being opened at idle , the vacuum leaks the , weird wiring issues , MAF strange voltage all obscured the true problem it seems.

Note to self never lend fuel pressure gauge out , if it was in my garage I would have checked that one day one .

 

[mostly_broncos]

Well I dropped the tank and tried the pump with 12 volts and it runs but I noticed some weird black crud in the sock .

I put the pump back in the tank slid the tank back under the explorer and hooked it to the lines then put the old filter on it put a hose on that and put the hose in a giant mason jar and jumped the fuel pump relay with a wire .

The fuel pump sounds fine initially and pumps very strong , then the flow tapers and the pump sound changes . I don't know how long it should take to free pump a gallon of gas into a jar but I gave up before I got 3 quarters full. You can visibly see the stream of fuel drop after 30 seconds or so .


This is hooked up into the old filter with the return to tank hooked up , but with no load it seems like very little should need to go back to the tank. I can try plugging the return line and see if the filter is the issue but I am thinking that possibly the crap in the sock is getting drawn up to the pump inlet and plugging it.

I was using the giant mason jar because I want to see if water or sludge settles out over night to decide if I need all new gas or can safely reuse it.

Maybe I'll set the thing up and make a short video and another without the sock or with the new pump I'll be installing

edited to add with the sock or strainer removed its no better , I also hooked up a battery charger and put 16 volts to it and still no better , it seems like if you leave it alone it works better then drops off again pretty quickly

 

[mostly_broncos]

So with a new pump its up and running , I mocked up the new pump and was able to pump roughly 5 gallons into a can in 5 minutes , at least 10 times the flow of the old pump so I put the tank in and she fired up . It was doing a lot of adjusting but after it got so I could put it in gear without stalling I carefully moved it around the yard.

All the long term fuel trim has been pulled back out and short term both sides are at -8% roughly , if you rev it in park it backfires a bit . The MAF signal is still off, the EGR was seeing vacuum at idle so its plugged , the PCV is still unhooked . I figure I'll start messing with these things tomorrow then try driving a bit and see what happens.

I probably have some hose or harness unplugged I have touched so many things that its a given that everything needs to be rechecked.

The Fuel rail regulator or whatever it is doesn't hold vacuum perfectly the EVP or DTFE is probably wrongly applying the EGR at idle , I don't have any codes for them beyond it noticing that there is no EGR flow .

I have EGR and throttle body gaskets on order and a 174 degree thermostat I may put in . I know the air filter is crap it looks like it got wet and dried out at some point.

I also have a tranny filter to do but I will wait until I am sure that TCC code is either back on or not coming back