Ok, noticed something strange on wife's 100% stock 200k mile 00 accord 4cyl. While using my scanner and reading live data the other day I noticed while driving and sitting the iat temps were what I thought way high. It was 15-20* f outside and while driving the iat temps on scanner were showing 80-90* f

So I pulled iat sensor, it was covered in carbon. So bought a new oem honda one thinking this was reading wrong because of the carbon. I installed it and checked again while driving, it was warmer today 50* f outside and now when I read iat on scanner it saying 100+*f.

Are these engines supposed to read that high iat since the sensor is so far in on the intake manifold so close to head??

I have never messed with these cars much, all other n/a cars I have scanned the iat sensor are close to the air filter and when driving the temps norm read real close to ambient air temp.

 

Yes they do run a bit warmer were they are located closer to the head. They also suffer from heat soak a lot of the time. However, I'm pretty sure that those calculations are taken into account when the ECU processes the data.

There have been members, myself included, that have tested moving the IAT on the other side of the throttle body with no good results on a stock ECU. Only way to move it and have good results would be if you can modify the ECUs processing calculations. A stand alone engine management system or chipped ECU and tuning software woudl be required.

Out of everything I tried with the stock ECU and IAT sensor. Leaving it in the manifold and accepting the higher temps was the best option. besides that, stock Honda's get better MPG with a warm intake and fuel charge.... that's the way the ECU is tuned.

 

Do those temps I'm getting seem like they are in the ballpark of what they norm are?

 

I'm trying to track down an issue with the car. It has a no start condition from time to time. It cranks but won't start. It does this norm a few tries, then it starts and runs perfect. It seems to be temperature dependent around the 20-35*f outside temps when it does this. And only if the car has been ran and shut off for a couple hours. If it sits less or more time it always fires up.

I have changed a few things on the car, plugs, wires, complete dist, main relay, iat sensor, fuel pump. All with absolutely no change in situation. It seems like it's not getting spark, but it never does this no start when I drive it, if it does, by the time I get to check for spark it fires up...

When I saw the iat temps so high, I thought I found the issue. Nope, back to drawing board.

 

Using your scan tool, what do your engine coolant temps look like when these issues happen? Don't go by the gauge, go by the scan tool ECU ECT sensor readings, these cars use two separate sensors for the ECU and the gauge. Might be able to see if it is within a certain temp range that this issue happens.

I have never personally had an issue like this that wasn't main relay, ignitor, ignition coil, ignition switch or temp sensor related.

 

the intake manifold gets hot with engine temp the reading is correct . u can get an infrared thermometer to verify

when the car doesnt start you need to immediately check for spark and fuel

 

Thanks ghostaccord, finally someone with some knowledge on here. My scan tool is a obd2 wifi adapter that I can look at live data and pull codes on an app from my phone. I have no idea how accurate it is. There is only one coolant temp reading on this scanner, which I assume is the one the computer is reading, not the Guage one. According to it, it reads fine, nothing weird. Warms up and seems to mimic the Guage on the cluster.

I had originally suspect that coolant temp sensor, but after scanning it seems fine.

The hardest part about this issue, is that it is not something that happens often. 99% of time it's when wife driving it, when it does it to me I get out spark checker and try to test, as soon as I give it enough time to hook up tester and crank it over to see if spark, the sob fires right up.

I gave up and started throwing parts at it, just to try to fix it. Next up I was planning on changing that coolant temp sensor. It's the one under the dist correct ?

If you have any other ideas, I would greatly appreciate them.

 

I have never checked fuel pressure yet , I can not find the correct adaptor for the fuel line.

I did replace fuel pump/strainer.

It only does this no start thing only if it sits for a couple hours. If it sits all night, fires up every time. Super cold, or warm outside. I would think if it was fuel pressure bleeding off it would tend to do that if it sits all night, so I really don't think an injector is bleeding off psi. When it doesn't start,and finally get it to fire up it runs perfect, no missing , nothing

 

Harbor Freight has a $20 fuel pressure kit with the correct fitting.

ect sensor should read 2000-2500ohms when completely cold and 180-250ohms when the car is completely warmed up.

I've seen a lot of threads with this issue under 32 degrees and some have determined it to be the cold conditions affecting the ignitor. There is a supposed "fix" lying around these threads somewhere. I've seen it within the last 3 weeks.

However, if it's happening on a warm startup I would think it would possibly be the ect. You could smell the vacuum hose for the fpr after a few minutes of shut off and if it smells like fuel the fpr vacuum hose could be bad and it could be leaking fuel into the intake manifold which could explain the "carbon" on the iat. It could actually be fuel buildup as a result of this. The fuel would flood the engine which would prevent it from starting after a hot shut down. Also the very next time it does this you could turn the ignition to on, then hold the pedal down for a full five seconds to put it into clear flood mode then immediately start it. The clear flood mode would tell the injectors not to fire so it would only use the fuel that is possibly leaking into the intake manifold.

 

How do your IATs look when you have this condition? Next time it does this check the IAT during the no stat condition. With the ignition on engine not running scan the IAT. Sounds like it could be IAT heat soak related. If it only does it after it has been sitting for a certain time period.... just throwing that out there!

 

Thanks for your help!

I haven't checked the fpr , I will. Is that a somewhat common with these cars ?

When it fails to start and it decides to fire up, it doesn't miss or anything. Which kinda leads me to believe it's not flooded. But I will check that.

As far as iat temps,I don't know. Haven't been lucky enough to get it to not start when I had scanner.