2001 Expy new problem

[k4vbb]

Gonna test the TPS voltages in-situ. It seems I could waste hours with stuck bolts firing the parts cannon at the TPS.

Definitely test the TPS. However, the more information that is presented in this thread, the more I think you have a clog in the catalytic converters.

 

[JamaicaJoe]

Definitely test the TPS. However, the more information that is presented in this thread, the more I think you have a clog in the catalytic converters.

What makes you think that a vehicle that has operated normally in weeks and months past suddenly has a clogged CAT?

 

[EngineerMike]

I have a '99 5.4, it sets for up to 6 months at a time. I add Seafoam to the tank when I leave it and no problems w/fuel setting. I had stumbling like you describe w/no MIL (didn't scan it); changed plugs & boots and it purrs, no stumble. Plugs may have been 2nd round (~167k) so maybe 80k on the plugs at the time. Just a thought.

 

[k4vbb]

What makes you think that a vehicle that has operated normally in weeks and months past suddenly has a clogged CAT?

What makes you think that a catalytic converter will only slowly clog over time?

The last cat I had to replace clogged while I was in the store buying dog food. Drove to the store just fine. Came out, started the truck and it ran like dog-poo. Turns out that the front cat had melted and was shedding material into the rear cat, which plugged up my exhaust. While the truck was running, there was apparently enough heat and exhaust pressure to keep enough of the errant material flowing through the rear cat. However, after sitting for a few minutes, enough of that errant material (a bunch of really fine dust) was able to adhere to the passages inside of the rear cat, and was not able to be blown free by the exhaust pressure.

The fact that it stumbles at higher RPM and under load might be an indicator that the exhaust gases simply can't escape at the rate needed when the exhaust volume increases. Instead of flowing across the front O2 sensors at the rate the computer expects them to, the exhaust gases will linger in the exhaust system, which will in turn signal the computer to lean out the air/fuel mixture. Couple that with the fact that your mode 6 data does not show any misfires, and we have a recipe that might indicate a clogging exhaust system.

I'm not saying that it IS your catalytic converters, but it's something you'll need to check, too. I still think you should check your TPS and various other sensors for functionality. I'd also continue to probe for vacuum leaks. Probably won't know more until you get a better scanner where you can check the long-term fuel trims, and maybe a few other parameters.

I've heard of people removing the front O2 sensors, and then running the engine to see if there is an improvement. However, what we used to do is to hook up a pressure gauge to the O2 ports and take a reading while the engine was running. Should be no more than about 1.5psi at idle, and no more than 3psi at 2000 RPM. Not sure what's available these days, but the older vacuum gauges would typically double as a low-pressure gauge as well. If you're going to go this route, try and extend the hose -- it'll make things much easier.

 

[JamaicaJoe]

What makes you think that a catalytic converter will only slowly clog over time?

The last cat I had to replace clogged while I was in the store buying dog food. Drove to the store just fine. Came out, started the truck and it ran like dog-poo. Turns out that the front cat had melted and was shedding material into the rear cat, which plugged up my exhaust. While the truck was running, there was apparently enough heat and exhaust pressure to keep enough of the errant material flowing through the rear cat. However, after sitting for a few minutes, enough of that errant material (a bunch of really fine dust) was able to adhere to the passages inside of the rear cat, and was not able to be blown free by the exhaust pressure.

The fact that it stumbles at higher RPM and under load might be an indicator that the exhaust gases simply can't escape at the rate needed when the exhaust volume increases. Instead of flowing across the front O2 sensors at the rate the computer expects them to, the exhaust gases will linger in the exhaust system, which will in turn signal the computer to lean out the air/fuel mixture. Couple that with the fact that your mode 6 data does not show any misfires, and we have a recipe that might indicate a clogging exhaust system.

I'm not saying that it IS your catalytic converters, but it's something you'll need to check, too. I still think you should check your TPS and various other sensors for functionality. I'd also continue to probe for vacuum leaks. Probably won't know more until you get a better scanner where you can check the long-term fuel trims, and maybe a few other parameters.

I've heard of people removing the front O2 sensors, and then running the engine to see if there is an improvement. However, what we used to do is to hook up a pressure gauge to the O2 ports and take a reading while the engine was running. Should be no more than about 1.5psi at idle, and no more than 3psi at 2000 RPM. Not sure what's available these days, but the older vacuum gauges would typically double as a low-pressure gauge as well. If you're going to go this route, try and extend the hose -- it'll make things much easier.

I do hope it is not a problem with that CAT's as that would be a very expensive repair on a car that I have put a ton of money into tires (Michelin Defenders) refurbished OEM wheels and lots of suspension (OEM spec) parts.


We today I went out to check the TPS and had a lot of interruptions preventing me from pulling the connector and metering the Ohms and voltages. But what I did instead is looked at my ScanGauge II which has a TPS gauge . With key on, engine off it displays about 18 to 92 from idle to WOT. So I assume this to be % of WOT (my throttle cable must have some slack) . It does so very repeatedly and though this is not so perfect a test as ohming it out or looking at voltage for erratic potentiometer, it does seem to respond and potentiometers tend to clean themselves up when used unless worn. This exercise did esacerbate the misfiring . So I disconnected and shorted the batter leads to clear the ECU memory.

Next I revisited the propane gas-vacuum hose test. As before things looked fine until I got to the fitting on the TB Housing where the Evap hose connects. I have changed the main vacuum line harness, a pricey nylon tubing with rubber fittings affair many years ago when I had an EGR sensor issue. But the EVAP hoses are 24 years old and quite filthy.

The propane did cause a noticeable increase in idle at the bend of that hose. Also repositioning it seems to have minimized the stumble. I don't know if I can cap this fitting for a test (will the engine will call for purge and go lean or will it just remap the short term fuel trim?) , but I will replace it. It is likely this whole run back to the tank is rotted as in past I would smell gasoline at rear with full tank and engine off.

 

[k4vbb]

Purge is typically called for just after startup, and after the charcoal filter is saturated with fumes. I think you should be able to plug this off and test with no issues.

As far as the TPS, I'd definitely get a meter reading on that. 18% open is a lot more than you might think. Between the EVAP hose and the TPS, if these solve your problems then you're golden!

As far as the cats go, I recently replaced the cats in my 5.4L Expedition with some I found on E-Bay. The set comes in a kit, and it cost me 500 bucks. But the kit was easy to install, and did not require a lift or any major disassembly of any other under-vehicle components.

Incidentally, it appears that they can be had for a 4.6L Expedition with 2WD for much less:

Pardon Our Interruption...

 

[JamaicaJoe]

Purge is typically called for just after startup, and after the charcoal filter is saturated with fumes. I think you should be able to plug this off and test with no issues.

As far as the TPS, I'd definitely get a meter reading on that. 18% open is a lot more than you might think. Between the EVAP hose and the TPS, if these solve your problems then you're golden!

As far as the cats go, I recently replaced the cats in my 5.4L Expedition with some I found on E-Bay. The set comes in a kit, and it cost me 500 bucks. But the kit was easy to install, and did not require a lift or any major disassembly of any other under-vehicle components.

Incidentally, it appears that they can be had for a 4.6L Expedition with 2WD for much less:

Pardon Our Interruption...

Thanks; I am going to cobble up a fix for that hose tomorrow while waiting for a replacement. I think I am onto something. I used to have a vacuum gauge somewhere. Need to check my garage, ..

 

[Killer Ride]

I'm inclined to agree with the clogged cats diagnosis, have an exhaust shop check it or get a temp reader and check it that way. These truck are notorious for cats being clogged

 

[k4vbb]

Thanks; I am going to cobble up a fix for that hose tomorrow while waiting for a replacement. I think I am onto something. I used to have a vacuum gauge somewhere. Need to check my garage, ..

Definitely get your vacuum system in order before looking into the cats.

 

[jr1under]

Thanks; I am going to cobble up a fix for that hose tomorrow while waiting for a replacement. I think I am onto something. I used to have a vacuum gauge somewhere. Need to check my garage, ..

Are you still planning to sell it after going through all of this?

 

[JamaicaJoe]

Are you still planning to sell it after going through all of this?

I hate to give it up. I have owned it since 2003 when still in warranty and I have changed oil every 3000 miles (now 97K). Have full maintenance records. It handles and runs great, or will when I sort this out. But it needs paint especially roof and hood. I bought a 2013 so proceeds will go into whatever maintenance the 2013 needs going forward. Probably will put it on Bring a Trailer with a list of good (straight body panels, Florida car, good records) , the bad (small nag list) and the ugly (paint). I have the DORMAN hose for the evap purge valve to throttle body on order. Hopefully that will fix it from leaning out.

 

[jr1under]

But it needs paint especially roof and hood.

Yeah, I had mine repainted in 2022 by a budget chain store and it was still $2k. I imagine that number is way higher for a quality shop.

 

[JamaicaJoe]

Yeah, I had mine repainted in 2022 by a budget chain store and it was still $2k. I imagine that number is way higher for a quality shop.

It seems that in my area people are buying new cars and crashing them soon after, so we have a plethora of "production shops" that would rather not deal with repainting an entire car , taking it down to bare metal, and R&I all the attendant parts. They are making a fast buck totaling new cars from what I see in the parking lot and on street. I was hoping to find a shop close to home (it is a traffic problem) . So I got discouraged and spent my paintshop money on a newer car. I did get one quote that was reasonable (but not very detailed) and probably should have dropped it there and not worried.

 

[JamaicaJoe]

Still working this problem. I replaced the filthy suspicious vacuum hose from manifold to the Purge Valve. Reset the ECU I think, but still having problem. Checked with propane and the leak is gone. I looked the crusty hose over and could not see a definite crack, but happy to get that out of there. Things to check. 1) There seems to be another large vacuum line leaving back of manifold and perhaps I did not get propane to waft down far enough this time or winds have changed. 2) Need to check the purge valve itself to see if it is leaking when it should be shut. I will test/plug the hose for good measure. I am going to get FORSCAN and try to sort this myself.

 

[JamaicaJoe]

Got my FORSCAN going today. First checked out my 2013 and apart from my ABS problem in that vehicle, the engine appears fine.

So I went to look at my 2001 with the drive-ability problem and discovered a DTC that the purge valve circuit was opened or shorted. It was still stuttering away like before I changed the suspected leaky vacuum hose.

I took a lot of data looking at the Mode 6 misfires, virtually zero. Then went under the hood and found the control connector for the purge valve had slipped off! I guess I had not pushed it on fully. Now with that DTC code gone away, and suddenly it drives pretty close to perfectly. The LT and ST fuel trim look pretty normal LT is <1 to 3% , though on Bank 2 the waveform is a bit triangular vs the Bank 1 is more square wave. But it runs well. I did get a new DTC P0500 code for VSS vehicle speed sensor circuit. I think what is going on is that the battery is shot and even though I ran a marine battery in parallel during my initial testing, this battery is going to dog me. I will be replacing in now that it seems the FORSCAN is flagging it.

EDIT: The LTFT in my 2013 is basically a steady line where the 2001 seems to jump all over. Is that because it needs to learn an average state and then revert to STFT as priority?

 

[jr1under]

EDIT: The LTFT in my 2013 is basically a steady line where the 2001 seems to jump all over. Is that because it needs to learn an average state and then revert to STFT as priority?

Yes, I think that's correct. From my experience and the OBD SysOp manual, I know that LTFT requires several driving cycles before it settles.

 

[JamaicaJoe]

Yes, I think that's correct. From my experience and the OBD SysOp manual, I know that LTFT requires several driving cycles before it settles.

I am happy I don't have to tow it in for a repair. I will drive it this weekend and get it settled in and burn off some of the old fuel and replenish.

 

[jr1under]

I will drive it this weekend and get it settled in and burn off some of the old fuel and replenish.

So, is it running the way you want now?

 

[JamaicaJoe]

It seems to run fine with the purge hose changed and the ECU KAM keep alive memory, erased. I have a known battery problem , starts fine, but has a low voltage after cranking, indicated on FORSCAN . I suspect that low voltage is corrupting the KAM , on fuel trim, and I am also battling the AC which after adding about 8 oz of Freon is not cooling. Cycling the clutch frequently, and while engaged pressure drops below 20 then back up to 55 PSI on low side after disengaged. Not cooling. The rear AC is not blowing cold either yet the expansion valve is cold. I just now cobbled up a vacuum gauge and tomorrow, I will be checking manifold and vacuum reservoir in case another vacuum leak is affecting the blend doors.

 

[JamaicaJoe]

Back working on this beast.