I hate cars

I'm not getting my hopes up just yet but it seems promising. I've been fighting this for some time now.

The car surges on hot days and at altitude at low to moderate load and under vtec rpm. Runs fine or at least a lot better when it hits vtec. It has absolutely no power and especially torque when it gets into the surging.

Changed to colder plugs which helped.

Tried a CAI which didn't do much for the surging

Tried 100 octane which really helped but it was still there.

Finally, after a little research, I decided to try the intake air temp sensor. One thing I noticed after pulling it out is the intake manifold gets very hot and transfers heat into the sensor. The sensor was too hot to hold by the threads when I pulled it out and the car had been sitting for a couple hours. I might start leaving the engine cover off to help let heat out.

For testing purposes only, I pulled the sensor out and plugged the hole with a bolt and teflon tape on the threads. Kept the sensor plugged in and wrapped it with heatwrap. Ziptied it as far from heat sources as I could. The test drive was very promising. Surging is completely gone. Torque is back. I'm leaving to Vegas soon so I'll see how it does on the 4 hour trip. Hopefully this is the end of my problems. I'm not getting the hopes up too much because everytime I made a change it seemed to help for a while and then the surging came back but not as bad.

Bearcat94

For the moment assume it is the sensor getting too hot.

I've not seen any other posts on "surging" combined with lost power. That seems to suggest that:

- Your sensor gets hotter than others, or
- The ECU "does something" on your car but not others when your sensor is in a higher temp range, or
- More people have this problem and either don't recognize it or haven't posted about it.

I guess, I am wondering if is a design problem (all sensors get too hot), a part problem, or a car/ECU problem?

Just curious which (if any) you think is the more likely?

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Did a 20 minute drive this morning and it still runs great but temps were only in the high 70s. I'll report back this afternoon.

I've been doing research all morning, trying without much luck to find out what the computer does pre-vtec and during vtec with fueling/timing and also what effect the IAT sensor has on fuel/timing.

All I know for sure is that vtec fueling is on a different map and a cooler IAT adds fuel and timing. That was pretty much expected. If anything, after a couple of light mods, the cold performance is better and hot performance is worse. I suspect it might be leaning out. This is the first speed density car I've ever owned and I'm wanting to go back to a mass air car. This is crazy not being able to add more fuel to the extra airflow. I thought eventually the computer would adjust after looking at 02s but maybe not. Finding info about the ecm on these things is next to impossible.

If worse comes to worse I'm going to take it to a dyno and drive it normal with a wideband up it's ass to see what's going on.

01tl4tl

Air temp = Air density = Fuel Ratio
Dyno was my next thought too

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I forgot to mention that I'm sure the intake manifold transfers heat into the sensor. Hopefully no one flames me but on my other car I've made the readings drop 20 degrees by moving the sensor from the intake manifold to just before the throttlebody. Air temp was obviously unchanged.

If this ends up working, I might lengthen the wires and mount the sensor behind the bumper.

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Got a dyno appt in an hour. Should be interesting.

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Just got back from the dyno. On the way there, I drove around much harder than normal making sure it was hot. Surging was completely gone. The car pulls smooth with much better low end torque. Once I got there I decided to do a couple WOT runs first just for my own curiosity.

Two pulls were within 0.1hp of each other with the best being 209.5 and 182.3lbs of torque. Temp was 95 degrees outside and it's an auto. More on that later.

After the WOT pulls I drove it just like normal and watched the A/F. I let it shift itself and gave it the normal 1/4-1/3 pedal until it hit lockup and 85mph. A/F was fine and no fluctuations. I wanted to screw the temp sensor back into the intake manifold but figured it wouldn't have time to heatsoak. I'll probably take it back some other day for that. After the dyno, driving home, it drove better than ever. I have to wonder how long I've been having a problem with the temp sensor.

Back to the WOT runs, a couple things caught my eye.

At 6,400rpm the A/F went from 13.0 to 11.0 all the way to redline. It's a perfectly straight line from when I hit it at 2,800 to 6,400 and then richened way up and stayed exactly the same to revlimiter. Power didn't drop off at all when it richened up.

I see torque start to jump ~4,800rpm. I guess that's where vtec kicks in?

I thought the revlimiter was at 6,900. Mine hit at 7,100rpm and power peaked at 7,040rpm.

Last but not least, I am happy to say it made at least 175lbs of torque from 2,800 to 5,600. Not as bad as I thought.

Bearcat94

Redline is 6,800 BUT the limiter kicks in at 7,000 (TL-S) according to this R&T Comparo.

Main Article: http://www.roadandtrack.com/article....rticle_id=4459

Data Sheet: http://www.roadandtrack.com/assets/d...d/02073car.pdf

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Interesting how the TL weighs less than the IS.

I let mine bump the revlimiter both times before letting out of it. The stock tach said 6,900 but those usually aren't that accurate. I thought it was interesting that the computer let it get to 7,100rpm.

It's interesting that mine seems to run richer than most of the dynos I've seen. I wonder if that has to do with the air temp sensor.

I just did the SAE correction factor and it brought power up to a whopping 210.33 and 183.03lbs.

Xx06SickspdTlxX

Ive heard that this is common with J series motors, a master honda and acura tech at my work says that hes done everything that he could to eliminate surging on his 3.2 tl and says that he hasnt figured out a solution and has tried everything to his knowlege and that it is common with these motors!

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One last interesting thing. I did the first dyno with the AC on accidentally. I'm pretty sure the compressor kicks off at WOT because there was only a 0.1hp loss.

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Here's an update just in case anyone is interested. I'm back in Vegas. No surging whatsoever. My average mpg was 32 for the 4 hour trip here. I'm going to permanently relocate the sensor to somewhere outside of the engine bay so it's still somewhat useful. I think this is better than just intalling a resistor that tricks the computer since the temp info will still vary by outside temperature.

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One last update. I extended the factory wires and moved the sensor near the cold air inlet behind the front bumper. It's ziptied for now because I only had an hour until I had to leave for Vegas. Discovered I was out of solder and heatshrink after I cut the factory wires so at the latest it will get redone next weekend. When I mount it permanently, it will be mounted in the inlet ducting somewhere outside of the engine bay.

On the 4 hour drive I managed to average 35mpg. I drive a little easier than most with the cruise set at 70mph and no stops. Power just doesn't fade off after the car gets good and hot. One major problem I had before was getting back in the car after a drive and it had heatsoaked. This was when the surging was at it's worst. It's completely gone. The car pulls so much cleaner now. No surging and it feels torquier under partial throttle. Gas mileage hasn't suffered at all.

Costco

Is it running rich? I'm assuming no, since you got such ridiculously amazing mileage figures, at least for a TL. Was your temperature needle higher than usual at all?

You pretty much made a custom cold air intake for your car. Not exactly a CAI, but it functions the same, huh?

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I think it was running lean before. I made a CAI and if anything it got worse. Same with gutting the secondary convertor. Once I moved the sensor out of the engine bay everything was fine. Driving it on the dyno with a wideband showed the A/F to be perfect. At WOT, the A/F was richer than most TLs I've seen. Should give me room to grow if I ever do more mods.

With the sensor out of the engine bay, it only reads air temp and is not affected by underhood temps or heat transfer from the intake manifold. It should be a more accurate reading. I know some CAIs give the option of moving the sensor to the inlet pipe which should be an improvement over the manifold but it's still in the engine bay.