Stuttering under load - The Saga of Njordi

[Boerderij_Kabouter]

Idle is still going great... however, I have now started encountering an extreme stutter and loss of power. It is intermittent, but has struck 2 of the last 5 times out for test drives. I am quite sure this problem has nothing to do with any leaking oil seals or anything like that, and I do not think it has anything to do with the throttle body/EGR/IAC.

Checked the diagnostics and I have the following codes active after doing a battery reset:

22 - Water temp sensor signal - open or short in water temp sensor circuit for 500 msec or more
24 - Air intake temp sensor signal - open or short in intake air temp sensor circuit for 500 msec or more
32 - Air flow meter signal - open or short detected continuously for 0.5 sec. or more in air flow meter circuit
41 - Throttle position sensor signal - Open or short detected in throttle position sensor signal for 0.5 sec. or more


So it looks like it is multimeter time. Would love to hear if anyone has a common cause for this combo.

All these issues arise from connections on one half of the center ECU connector. I am going to take a look at that first. Maybe it is just smooshed or melted or somehting.

[Boerderij_Kabouter]

Found a similar problem statement in this thread: https://www.toyotavantech.com/forum/showthread.php?3747-For-the-love-of-all-things-Toyota-please-help! This Previa had the same error codes and the same symptoms.

The issue ended up being a bad spark plug cable. So I am adding that to my list of things to check.

[Boerderij_Kabouter]

I just popped off the outer valve cover to take a peek at the spark plug wires, and found oil in the chamber. In particular, plug 1 appears to be weeping. Does the group think this would be fixed by the valve cover gasket? Or should I also replace the spark plug tube gaskets?

13098

Edit: I have a big order of new gaskets and seals already, so I just called my parts department and added four spark plug tube gaskets (11193-15010) to the order. Dang things are $14 a pop. Woof.

[man_btc]

Have you checked the PCV valve and its hose? I once had problems because a mechanic had put a regular (soft & flexible) hose on it which would collapse and block the airflow under a vacuum.

[Boerderij_Kabouter]

I have not pulled and checked the PCV valve yet. The gasket and hose are in good condition so I have not screwed with it. But you are probably right and I should give that a check.

[John Kaufmann]

Idle is still going great... however, I have now started encountering an extreme stutter and loss of power. It is intermittent, but has struck 2 of the last 5 times out for test drives. I am quite sure this problem has nothing to do with any leaking oil seals or anything like that, and I do not think it has anything to do with the throttle body/EGR/IAC.Agreed.


Checked the diagnostics and I have the following codes active after doing a battery reset:

22 - Water temp sensor signal - open or short in water temp sensor circuit for 500 msec or more
24 - Air intake temp sensor signal - open or short in intake air temp sensor circuit for 500 msec or more
32 - Air flow meter signal - open or short detected continuously for 0.5 sec. or more in air flow meter circuit
41 - Throttle position sensor signal - Open or short detected in throttle position sensor signal for 0.5 sec. or more


So it looks like it is multimeter time. Would love to hear if anyone has a common cause for this combo.

All these issues arise from connections on one half of the center ECU connector. I am going to take a look at that first. Maybe it is just smooshed or melted or somehting.
I think you're close in suspecting an intermittent signal interruption, but I'd look at the TPS connector. The Air Flow Meter -- source of the Air Flow/VS and Air Temp/THA signals -- is delicately balanced through the Throttle Position Sensor, which also influences the Water Temp/THW and Exhaust Gas Temp/THG signals. You can see this on pp.53-54 of the 91 EWD section titled ENGINE CONTROL, which is attached.

It's a beautiful thing when all is well, but it's probably not the most robust way to design that circuitry, and runs up against a practical implementation problem: the TPS wiring is a little too tight for the engine vibration, and over time fraying wires at the TPS connector fail to give a reliable signal to the ECU, which can affect all of those signals (VS, THA, THW, THG) - and of course the TPS signals VC-VTA-IDL, which throw no explicit code but manifest as "an extreme stutter and loss of power."

Sadly, because the wires fray at the connector, it's an extremely difficult repair. The easiest way to fix it is to wire in another TPS connector with a few inches of wire attached, and the easiest way I've found to get that connector is from a junkyard, with the TPS (89452-12040) -- IOW, just cut the harness to give yourself some wire to splice in, and pay for the TPS (which you don't really need, but it never hurts to have a spare). You can also sometimes find the TPS sold that way on eBay.

ToyoDIY says that TPS was used on:

1987-94 Corolla
1990-94 Tercel
1984-95 MR2
1989-93 Celica
1988-91 Camry
1989-91 Lexus ES250
1988-95 4Runner
1990-97 Previa
1992-98 T100

From anything other than a Previa, the wire colors probably will not match, but it's only four wires, so easy to match them up pin-by-pin.

[John Kaufmann]

I just popped off the outer valve cover to take a peek at the spark plug wires, and found oil in the chamber. In particular, plug 1 appears to be weeping. Does the group think this would be fixed by the valve cover gasket? Or should I also replace the spark plug tube gaskets?...
I always replaced the tube seals with the valve cover gasket. In fact, you should find that they are most commonly sold as a set (https://www.rockauto.com/en/catalog/toyota,1992,previa,2.4l+l4,1278143,engine,valve+co ver+gasket,10710).

[Boerderij_Kabouter]

Fantastic stuff!

Connector (https://www.amazon.com/Ballenger-Motorsports-Connector-Replacement-90980-10711/dp/B087M56CDB?gQT=2&th=1)
Black blue wire (https://www.amazon.com/Automotive-Motorcycle-Purpose-DEFFERENT-AVAILABLE/dp/B01GT39W4G?th=1)
Yellow and red wire (https://www.amazon.com/Automotive-Motorcycle-Purpose-DEFFERENT-AVAILABLE/dp/B01GSXVN80/ref=sr_1_27?crid=P55HY8TEPA6I&dib=eyJ2IjoiMSJ9.PkOGTUq_Ib9Xj372R_yGSHcjkUv9Bxp5N SqUqVeXglCJGCkdvjFZsTEMyb_hHzkHKA6hcoCMjebfo3km4yC jWpHLIuwvgeZM_yhYiEj30QC_xiVtOSbxc16daYON_KPKsQwU3 0OZ_0nTzONZagKFTSrk-LyERSuMSIu2C1y_e_n9uLP18YN8b-sikDKR_Pjk9YPeEy7lLU8KsfmrERoDlo0w3js1A-6wHHh3q_VF1hn91Fcm2wvOLarzIrB1hXuAPxANzjLCtoWORJzh yrUSx78epKJNxq_132Oe1rz6vZW7-bBT9M40WQRoZ4Xbb5NWfPDrnNY3sqQ7BrqWYgM85iAZoz3Nc67 o3Yt2-JFPBt7Je8KTDO-P150REVlPNGdi6QJJiNmMaFrbIZI2dSyPT0nzlOvIgHoxvpiFe F82LDH3EY36Gau3OnaTP7vnRu2A.i6fQ67UHNUb7cdsgb37BIO udJpfbK4BHqUTW-AHEpnM&dib_tag=se&keywords=16+gauge+automotive+wire+yellow+and+red&qid=1737729003&sprefix=16+gauge+automotive+wire+yellow+and+red%2C aps%2C163&sr=8-27)
Blue and yellow wire (https://www.amazon.com/Automotive-Motorcycle-Purpose-DEFFERENT-AVAILABLE/dp/B01GSXRIJ8/ref=sr_1_52?crid=1SGPWBKWMI0UM&dib=eyJ2IjoiMSJ9.PkOGTUq_Ib9Xj372R_yGSIiYTdrVUa9jA ATlElV-wYhdRNFNxGwEB0qCoha1Vmd9H2wUgOSIVoV0plFQ239PQL6YBc pDF9IFA0LNxyHFYXb9TBSHBEGQ0nmx4ZiLe0Xe-YcnLpyxS1g3mn02wV96s5ZowmkSLfkKI5DZYVw6sBz2HkZDMO1 74eYsuITzXp-ZelnnSNhXsKevsFiMZ48n-YHKv28MS6plZqYDw1FRxsiQHEFeY2FnboBuvjg7jiobmeyXVA_ N--wI_n-htKE4mBQnyv-TZge5vfKWUxMuwwX9nWLgcpFaUhG_ekFhDFig87dxpYWfbPiXm ARmeTW04wX-Id0stP34kWau1Jl7f5sKkxyTKcpAUZ2KE06DQBnjmdO1ui1n5l axucBPIFV4bdWwnm5A7FDS_Ii-8liAacdA20k4mnBde5xtYUJpAQ9-.ryzJVC0mgjyjX17Jci_rjk_HyQpl2B8NssNG3Br8Zkk&dib_tag=se&keywords=16%2Bgauge%2Bautomotive%2Bwire%2Byellow%2 Band%2Bblue&qid=1737729058&sprefix=16%2Bgauge%2Bautomotive%2Bwire%2Byellow%2B and%2Bblu%2Caps%2C142&sr=8-52&th=1)
Brown and black wire (https://www.amazon.com/Automotive-Motorcycle-Purpose-DEFFERENT-AVAILABLE/dp/B01GSX0FQG/ref=sr_1_8?crid=14NUF6XJFNA0F&dib=eyJ2IjoiMSJ9.o04lFdFilywAvMLyKvKNt3qL2CWvxayYb a2akCi-li-rXTJnQc6az5SD6ygL0yh7XLT99P6ccEIlrNi1GZewwHypYdLhn 99wusHRf5GYuQTuJSJZTbiy6KnC3UExBQOaPFIM595hpXlkrrY 0kiixmMf9Yh5g3A52DTuEum7qFcR5BTYQle1c3kt97mh2HovYy z5ZWuUlFxXWXaT0OcyjvQPs90_4AKh4uWpkYxgj3Jny7FAvVPO BtfTcr-RdOwIOlQ2OOwEUahXJ5f4SvOlOdUsAuYVQ6AdY9re-BDFzV77hV02qZqTMOtB789zF9kmXjqZAaYWk55hJC_SnDs7-3WEv3sTZ7OfvCezTG4yhp8RbFVrZpbaIcUUCfcTJvTfXRHJDCn r2t-sZsagxtWN0BfCZP19xNtchYD2jcPbpRAHhEh3H7pIMaA0PE0IB MpMB.EVT6xftKjHWoG7w6bhmpi0knCvozHNg7CQDuiKQJDT8&dib_tag=se&keywords=16%2Bgauge%2Bautomotive%2Bwire%2Bbrown%2B and%2Bblack%2B4RCUSTOMS&qid=1737729141&sprefix=16%2Bgauge%2Bautomotive%2Bwire%2Bbrown%2Ba nd%2Bblack%2B4rcustoms%2Caps%2C128&sr=8-8&th=1)

Looks like this is only a hard job if the wires are janky all the way. It is hard to tell from the EWD book where the splice connectors are. I guess it should be easy enough to test continuity of the wires once I have that connector off, but we will see once we get in there. I can't really work on this for a couple weeks but I am pretty hopeful about this fix. THANK YOU @JohnKaufmann

[Boerderij_Kabouter]

I always replaced the tube seals with the valve cover gasket. In fact, you should find that they are most commonly sold as a set (https://www.rockauto.com/en/catalog/toyota,1992,previa,2.4l+l4,1278143,engine,valve+co ver+gasket,10710).

Whoa, that price point is admittedly hard to ignore. The Toyota gasket is $24, the FIPG is like $40, and each plug tube seal is $14. I think I am sticking with the OEM stuff as much as possible though because I intend to restore Njordi and drive it forever. SO the extra $100 is pretty cheap insurance.

[John Kaufmann]

...

Connector (https://www.amazon.com/Ballenger-Motorsports-Connector-Replacement-90980-10711/dp/B087M56CDB?gQT=2&th=1)
Black blue wire (https://www.amazon.com/Automotive-Motorcycle-Purpose-DEFFERENT-AVAILABLE/dp/B01GT39W4G?th=1)
Yellow and red wire (https://www.amazon.com/Automotive-Motorcycle-Purpose-DEFFERENT-AVAILABLE/dp/B01GSXVN80/ref=sr_1_27?crid=P55HY8TEPA6I&dib=eyJ2IjoiMSJ9.PkOGTUq_Ib9Xj372R_yGSHcjkUv9Bxp5N SqUqVeXglCJGCkdvjFZsTEMyb_hHzkHKA6hcoCMjebfo3km4yC jWpHLIuwvgeZM_yhYiEj30QC_xiVtOSbxc16daYON_KPKsQwU3 0OZ_0nTzONZagKFTSrk-LyERSuMSIu2C1y_e_n9uLP18YN8b-sikDKR_Pjk9YPeEy7lLU8KsfmrERoDlo0w3js1A-6wHHh3q_VF1hn91Fcm2wvOLarzIrB1hXuAPxANzjLCtoWORJzh yrUSx78epKJNxq_132Oe1rz6vZW7-bBT9M40WQRoZ4Xbb5NWfPDrnNY3sqQ7BrqWYgM85iAZoz3Nc67 o3Yt2-JFPBt7Je8KTDO-P150REVlPNGdi6QJJiNmMaFrbIZI2dSyPT0nzlOvIgHoxvpiFe F82LDH3EY36Gau3OnaTP7vnRu2A.i6fQ67UHNUb7cdsgb37BIO udJpfbK4BHqUTW-AHEpnM&dib_tag=se&keywords=16+gauge+automotive+wire+yellow+and+red&qid=1737729003&sprefix=16+gauge+automotive+wire+yellow+and+red%2C aps%2C163&sr=8-27)
Blue and yellow wire (https://www.amazon.com/Automotive-Motorcycle-Purpose-DEFFERENT-AVAILABLE/dp/B01GSXRIJ8/ref=sr_1_52?crid=1SGPWBKWMI0UM&dib=eyJ2IjoiMSJ9.PkOGTUq_Ib9Xj372R_yGSIiYTdrVUa9jA ATlElV-wYhdRNFNxGwEB0qCoha1Vmd9H2wUgOSIVoV0plFQ239PQL6YBc pDF9IFA0LNxyHFYXb9TBSHBEGQ0nmx4ZiLe0Xe-YcnLpyxS1g3mn02wV96s5ZowmkSLfkKI5DZYVw6sBz2HkZDMO1 74eYsuITzXp-ZelnnSNhXsKevsFiMZ48n-YHKv28MS6plZqYDw1FRxsiQHEFeY2FnboBuvjg7jiobmeyXVA_ N--wI_n-htKE4mBQnyv-TZge5vfKWUxMuwwX9nWLgcpFaUhG_ekFhDFig87dxpYWfbPiXm ARmeTW04wX-Id0stP34kWau1Jl7f5sKkxyTKcpAUZ2KE06DQBnjmdO1ui1n5l axucBPIFV4bdWwnm5A7FDS_Ii-8liAacdA20k4mnBde5xtYUJpAQ9-.ryzJVC0mgjyjX17Jci_rjk_HyQpl2B8NssNG3Br8Zkk&dib_tag=se&keywords=16%2Bgauge%2Bautomotive%2Bwire%2Byellow%2 Band%2Bblue&qid=1737729058&sprefix=16%2Bgauge%2Bautomotive%2Bwire%2Byellow%2B and%2Bblu%2Caps%2C142&sr=8-52&th=1)
Brown and black wire (https://www.amazon.com/Automotive-Motorcycle-Purpose-DEFFERENT-AVAILABLE/dp/B01GSX0FQG/ref=sr_1_8?crid=14NUF6XJFNA0F&dib=eyJ2IjoiMSJ9.o04lFdFilywAvMLyKvKNt3qL2CWvxayYb a2akCi-li-rXTJnQc6az5SD6ygL0yh7XLT99P6ccEIlrNi1GZewwHypYdLhn 99wusHRf5GYuQTuJSJZTbiy6KnC3UExBQOaPFIM595hpXlkrrY 0kiixmMf9Yh5g3A52DTuEum7qFcR5BTYQle1c3kt97mh2HovYy z5ZWuUlFxXWXaT0OcyjvQPs90_4AKh4uWpkYxgj3Jny7FAvVPO BtfTcr-RdOwIOlQ2OOwEUahXJ5f4SvOlOdUsAuYVQ6AdY9re-BDFzV77hV02qZqTMOtB789zF9kmXjqZAaYWk55hJC_SnDs7-3WEv3sTZ7OfvCezTG4yhp8RbFVrZpbaIcUUCfcTJvTfXRHJDCn r2t-sZsagxtWN0BfCZP19xNtchYD2jcPbpRAHhEh3H7pIMaA0PE0IB MpMB.EVT6xftKjHWoG7w6bhmpi0knCvozHNg7CQDuiKQJDT8&dib_tag=se&keywords=16%2Bgauge%2Bautomotive%2Bwire%2Bbrown%2B and%2Bblack%2B4RCUSTOMS&qid=1737729141&sprefix=16%2Bgauge%2Bautomotive%2Bwire%2Bbrown%2Ba nd%2Bblack%2B4rcustoms%2Caps%2C128&sr=8-8&th=1)


Looks like this is only a hard job if the wires are janky all the way. ...

Nice find on the connector pigtail. That is the key, because (as you will find) that is where the wires break. Since the pigtail wires are all black, and long enough to ease the strain on the harness, I would not even bother with more wire: Just cut your existing harness wires as close as possible to the TPS connector, and splice in the new pigtail, with heatshrink -- then tape them together in a strain-relief bundle.

[Boerderij_Kabouter]

Well, unfortunate find this morning. I dug in to find that the previous owner must have been chasing the same gremlin... the TPS connector has already been replaced with a new one and the wires extended. I tested everything for continuity back to the ECU pins and all four wires are giving solid connection even when going crazy stretching and moving the wires around. They used high quality marine butt connectors, so the previous owners work appears to be high quality. Very sad to find this is not my problem.

I am looking at how to test the TPS sensor itself now in the Factory Service Manual. Maybe the sensor itself is faulty.

[Boerderij_Kabouter]

Continued fiddling revealed that the spark plug tubes for cylinders 1 and 2 were both very loose. Simple stupid stuff is always the stuff that gets you! Hoping that this stupid mistake is the issue. I might replace the spark wires with Toyota OEM ones.

EDIT: I have been test driving the van all day, letting it get hot, putting it in differnt situations, cold starting, running highway, start stop, and it is running perfectly. Idles at 700, no stuttering or weird power loss issues at all. Darned spark plugs weren't plugged in!!!! :doh:

Anyway, this issue appears to be sorted. On to fixing my soggy bottom!

[Boerderij_Kabouter]

And another update. I was hoping that the spark plug wires would be fine for a bit after getting them all plugged in. But I was just going to replace the valve cover gaskets yesterday, and when taking off the spark wires, two of the spark wires broke. And I also found that one of the spark plugs was not torqued in place. Woof. Cheap parts are just so rarely worth the money.

New spark plugs wires on order and I have to wait for them to show up.

Sheesh.

[Previologist]

Continued fiddling revealed that the spark plug tubes for cylinders 1 and 2 were both very loose. Simple stupid stuff is always the stuff that gets you! Hoping that this stupid mistake is the issue. I might replace the spark wires with Toyota OEM ones. !

I wouldn't use anything else.