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Discussion Starter #1
I have a 98 V6 Tacoma, that has a frequent but intermittent stumble at mid RPM and part throttle. No CEL or stored codes, coil packs are original, plugs and wires were replaced in summer of 2018. It did seem one of the plug wires was not firmly staying connected to the coil, and I thought that might be the issue, so I replaced the 2 year old NGK wires with Denso, with no change.

I don't drive it all that much, so I can't see the plugs being worn yet, they are Denso 3194s which have the double electrode like the factory plugs. They have about 10K miles on them.

I would rather not start randomly replacing parts and hoping they solve it. I was thinking possibly TPS, but I would expect it to throw a code if that was the case.

Are there any common issues with first gen Tacomas that can cause this behavior?

Thanks.
 

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It sounds mostly like an air flow issue, so I'd look at the MAF and TPS. Clean the MAF. If you have an OBDII reader that can get live data, check the readings on both sensors. If the TPS is bad, it probably just has one segment that is out. If the contacts are dirty inside, try opening and closing it fully many times to see if that helps.

I've though they are fairly new, it doesn't hurt to check the plugs and wires. If one wire is loose, that will easily cause the engine to stumble. Last is the fuel filter, but this is doubtful since the issue happens at lower RPM ranges.
 

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Discussion Starter #3
I finally got some MAF cleaner, and took it apart this afternoon. I hosed it down, and blew it out with compressed air, and put everything back together and it didn't seem to help.

I do think I might have identified the issue though, I have an OBDII scanner and app on my phone, and played around with the TPS signal. Not sure if this is normal, but from throttle fully closed shows up on the sensor as 11.3% and full throttle as 72.5% at the ECU. Just to be sure, I checked with both the gas pedal, and also by manually opening the throttle body under the hood. This seems odd, but may be normal. Can anyone confirm if this is the right range?

I also drove around the block, trying to keep a constant low throttle, while watching the TPS output in my phone, I tried to hold it stead as I could, showed ~17% most of the time, but noticed the couple times it stuttered/hesitated, the TPS showed less, once 8% and once 2%, which is curious, since like I mentioned, throttle fully closed reads around 11%.

Is the TPS cleanable, or should I just order a new one?

Is this it?


Any other recommended brands?

Thanks.
 

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That appears to be the correct part. Be sure to check if yours is a 3 pin or 4 pin version. The Amazon item and the OEM part look to be the 3 pin style.

No way to clean the TPS. Once the contacts inside wear out, you have to replace. Be sure to follow the calibration steps when you replace it.
 

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I have a 98 V6 Tacoma, that has a frequent but intermittent stumble at mid RPM and part throttle. No CEL or stored codes, coil packs are original, plugs and wires were replaced in summer of 2018. It did seem one of the plug wires was not firmly staying connected to the coil, and I thought that might be the issue, so I replaced the 2 year old NGK wires with Denso, with no change.

I don't drive it all that much, so I can't see the plugs being worn yet, they are Denso 3194s which have the double electrode like the factory plugs. They have about 10K miles on them.

I would rather not start randomly replacing parts and hoping they solve it. I was thinking possibly TPS, but I would expect it to throw a code if that was the case.

Are there any common issues with first gen Tacomas that can cause this behavior?

Thanks.
I had this exact problem concurrently with both my vehicles, 2001 V6 Tacoma & 2001 Honda S2000. After running the fuel tank low and refilling, both cars ran fine. Probably BAD GAS. Especially after a snow thaw or rain.
 

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Discussion Starter #6
That appears to be the correct part. Be sure to check if yours is a 3 pin or 4 pin version. The Amazon item and the OEM part look to be the 3 pin style.
Finally went out and looked at the TPS, haven't been driving much for obvious reasons, so it hasn't been a priority.

I didn't unplug it, but there are three wires going in to the connector, and I was able to snap a photo of it with my phone, and the part number is mostly readable, and it matches the Amazon part. Ordered.

61619


No way to clean the TPS. Once the contacts inside wear out, you have to replace. Be sure to follow the calibration steps when you replace it.
Calibration steps? Those online anywhere?


I had this exact problem concurrently with both my vehicles, 2001 V6 Tacoma & 2001 Honda S2000. After running the fuel tank low and refilling, both cars ran fine. Probably BAD GAS. Especially after a snow thaw or rain.
I don't think it is gas, it has been going on for a while, more than one tank full. That and the funky TPS readings I got while driving make me think the ~22 year old TPS is due to be replaced, even if it turns out not to be the root cause.

I'll post an update when it gets here.

Thanks.
 

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See attached. Basically you just want to confirm the TPS is almost at zero when closed. You shouldn't have to make any adjustments if the TPS is set correctly, but confirm on the new unit when you install.
 

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Discussion Starter #8
A quick follow up, installed the new TPS last weekend, and have driven the truck three times so far with no stumble. Seems to have fixed it.

Thanks for the help.
 
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