HOT Start problems

Second Generation Honda Prelude topics

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kytarheel71
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HOT Start problems

Post by kytarheel71 »

Still having trouble with a no start hot start condition. After driving for a short or long distance i sometimes have an awful time getting my 87 si FI car to start. It starts just fine in the mornings. When i go to leave work in the afternoon i have an awful time starting. Once it is running it runs just fine. Every once in a while it has a low idle when i am sitting at a light. Even if i just run to the store a few minutes away it still does the same thing on restart. I have changed the coolant temp sensor, distributer cap, fuel pump and ignition coil with new ones. I pulled the main relay and checked the connections. I even resoldered some of the suspect points. It doesnt look the greatest, has some light corrosion( the green is turning brown in some spots on the circuit board). I will try and post a short video of the starting prblem in a link below.

Another thing i have noticed is when i got to put gas in and i remove the gas cap there is a tremendous amount of built up pressure released. Is this normal. It will vent for a good 5-7 seconds. Could this be a vapor lock of some kind.


Video Link below:
http://www.youtube.com/watch?v=66XV5zkYmo8

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spiffyguido
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Re: HOT Start problems

Post by spiffyguido »

Thanks for the video. That's always helpful.

Any time I have had trouble with hot starts it has always turned out to be related to the coolant temperature sensor. You say you changed this, and just to clarify, you changed the one on the thermostat housing and not the one in the radiator, correct? Are you getting any codes out of your ECU when this happens? Have a check over that coolant temperature sensor wiring just to be sure.

To test the coolant temperature sensor, wait for a time when you are having trouble starting the car. Then pop the hood, unplug the coolant temperature sensor, and try to start again. If the coolant temperature sensor is bad, the car will start right up once it is unplugged. This will make your idle higher than normal, but it won't hurt the car at all to drive around like that. When my coolant temp sensor was bad, my car would often stall at lights because the idle would get so low. Then I wouldn't be able to start it, so before the light went green, I would just jump out of the car, pop the hood, yank the coolant temperature sensor plug off, jump back in, fire up the car and drive off.

Regarding the fuel tank: Every prelude I have owned has released pressure when the cap is opened at the pumps. I assume it's normal.

kytarheel71
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Re: HOT Start problems

Post by kytarheel71 »

Yeah i changed the one on the thermostat. I will try what you suggested about unplugging it and see what happens.

kytarheel71
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Re: HOT Start problems

Post by kytarheel71 »

I tried what you suggested and it did the same thing. What about the distributer? or the main relay just cant be repaired cause it did have some corrosion on it.

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spiffyguido
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Re: HOT Start problems

Post by spiffyguido »

Well, we've ruled out the coolant temp sensor. That's a start.

Distributor maybe. But since you know that your main relay has some corrosion, you may want to start there since others have reported that this can affect hot starts. Any chance you can get another unit from a wrecker to try out?

When it has trouble starting, can you tell if it is trying to choke the engine too much? I.e., can you smell fuel or anything like the engine is flooding? Because you're only having trouble starting hot, we have to make sure that one of the other systems that gives the engine more fuel during cold starts isn't malfunctioning. We've ruled out the coolant temp sensor, but there may be other sensors at play.

kytarheel71
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Re: HOT Start problems

Post by kytarheel71 »

There is sometimes a smell of fuel but not every time. The last two times i drove it , it acted like it was not getting any fuel for a split second withinn the first 1/4 mile, almost just like a blip or something. I just know the startup is getting worse and worse each day after it gets hot. After is starts it just shudders for a second or two till i give it some gas. If you check back on my previous post i replaced the fuel pump. This is actually the second one i have had to put on, the first one lasted only 3 weeks, it just didnt sound good from the very beginning(very loud), got my money back on that one. I am thinking it was just a defective fuel pump from the beginning, at least i hope. The morning starts are OK. I will take a video tomorrow and post it again on how it's acting. The thing is after it gets running it doesnt miss a beat. Plenty of acceleration in every gear, even highway speeds 70mph still gets it.

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spiffyguido
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Re: HOT Start problems

Post by spiffyguido »

When you try to start it, are you giving it any gas at all, or just letting the computer sort everything out? What happens if you put the throttle on the floor when you try and start it? Does that help? Make it worse?

When it is running and hot, does it idle well? Have you ever adjusted the idle? Sometimes what happens to some people is that they set the idle too far one way or the other. When this happens, they don't know there is a problem because one of the peripheral idle control systems compensates for their mistake. For example, a person could close the idle all the way, and the engine would still stay alive when the engine was warm because the idle air control valve would compensate. I just mention it because your car sounds like it is having trouble balancing its fuel/air mix during hot starts. Unless it is an electrical problem, you car is definitely getting either too much fuel and not enough air, or too much air and not enough fuel.

kytarheel71
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Re: HOT Start problems

Post by kytarheel71 »

No i have never adjusted the idle. matter of fact didnt even know i could do that since it is fuel injected, thought the computer did all of that. Most of the time i just blip the gas right after it starts or catches , if i dont it usually stumbles and shudders. Again when i left work today after i stopped at the first red light and when i took off it had a real bad hesitation like it was not getting enough gas.I babied it for about 3 or 4 seconds then it kicked in and was fine the whole way home, it usually only does that one time and then no more. After it runs for a while the idle is good, but when you first go for the first 5 minutes or so when you come to a stop the idle will drop down somtimes to about 500 or lower and act like it will stall, if i put it in neutral while sitting it goes away immediately.
does this sound like an idle issue to you? If so how do you adjust it, i will also look it up in the shop manual. It usually makes more sense if someone who is familiar with explains it in better terms anyway.
Also i just remembered that sometimes when i first start it the idle will fluctuate up and down very erractically, doesent do that very often just every now and then, and that usually goes away as soon as i start driving.

Here is another example of the start issue. Sorry forgot the radio was on.You cant really tell but when it finally started it was very rough idle for a second. Didnt give it any gas at all during the startup.

http://www.youtube.com/watch?v=md1RfclpWjs

Here is one more example with your suggestions, the third try in this video is exactly the problem i was talking about too, its catches and then just quits immediately.

http://www.youtube.com/watch?v=L27v1DNMUeU

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spiffyguido
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Re: HOT Start problems

Post by spiffyguido »

Sorry for taking so long to get back to you. Haven't been around a computer lately.

It could be an idle issue. I don't have the procedure memorized, so check the shop manual. I don't have it with me right now.

Even though the car is fuel injected, there are still some idle settings to adjust, and they are very important. What can happen is that a bad idle can cause the sensors to work too hard to keep the car alive, and this creates some problems. It's a simple thing to check anyway, so have a look at it. The fact that your car will idle as low as 500 or lower sometimes makes me suspicious about the idle. Give it a good check.

kytarheel71
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Re: HOT Start problems

Post by kytarheel71 »

Ok i will give the idle stuff a check, not sure exactly what to do i dont want to make anything worse. I am going to pull the Iacv and see if it needs cleaned. It's so weird though. Today i filled it up with gas and was expecting a hard start but it fired up perfectly, not five minutes before that when i left work it was awful trying to get it started. Very hot outside.

kytarheel71
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Re: HOT Start problems

Post by kytarheel71 »

I cleaned the IACV and still have the same problem. wasnt that dirty that i could see, havent messed with the idle settings yet. What are your thoughts about the TA Sensor. Just noticed that today actually. I hit the jackpot today, found an 86 si on craigslist that was being sold. called the lady and she said $50 for anything that i could get off in a day except for engine,tranny, and rear suspension. We basically gutted the interior, barely used seats, entire upper dash, gauge cluster, dizzy, starter,IACV,steering wheel, complete door panels,mirrors, and many smaller things.

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spiffyguido
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Re: HOT Start problems

Post by spiffyguido »

Great deal on the parts car. Nice work.

As far as the TA (TPS - throttle position sensor) sensor is concerned, I've never known these to cause idle problems. However, it could be to blame for the acceleration problems you have. One car that I drove that had a TPS problem would fall flat on its face above a certain rpm. It could accelerate to that rpm, and then once you hit the rpm in question, the engine would bog back down to idle, and then pick up again. Usually a TPS problem will throw an error code to the ECU (Code 7) when there is a problem.

kytarheel71
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Re: HOT Start problems

Post by kytarheel71 »

I'm thinking we are talking about about a different sensor. there is a senor located on the base of the intake manifold on the front side. It has the same connection as the coolant temp sensor, and is also green. It is listed as the TA sensor, i have seen it also listed as an air charge temp sensor. It has two screws that hold it on the base of the manifold. The only reason i am asking is because i discovered it on the parts car i told u about, i just couldnt removed it because the screw heads were stripped out.

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spiffyguido
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Re: HOT Start problems

Post by spiffyguido »

Oh, I know the sensor you mean. Yes, that's the intake air temp sensor. Honda calls it a TA sensor. I thought you were referring to the TPS because a lot of people call it the 'Throttle Angle' sensor which would abbreviate to TA.

Anyway, regarding the TA sensor, I've never heard of anyone having trouble with it. I'm sure it would throw a code if there was trouble. Do you have reason to believe it might be causing trouble?

kytarheel71
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Re: HOT Start problems

Post by kytarheel71 »

No , I 'm just ready to pull my hair out thats all. today it was cool all day and it was better but not like it should be. Started better cause it was cool i guess. I'm just at a loss because i cant figure this out and it's very frustrating.



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