I have a 1999 Prelude, non-SH. Quite some time ago I got a check engine light. I pulled the code and it indicated a problem with the CKP/TDC sensors. Despite that the car ran fine.

Last week I found the car to be idling roughly; it's RPMs were lower than they should be. Once I got home, with the car sitting in idle the check engine light started flashing. I checked the code again and it returned the same one for those sensors.

So I finally had the sensors replaced. As I approached home the check engine light came on yet again and when coming to a stop the engine was idling roughly. When sitting at home I revved the engine slightly; it hesitated a bit and the revs then dropped back and the car died. I am still able to start the car and drive it around.

The thing to note is that the car is fine when cold; it starts idling roughly when it gets warm. When driven the car seems to run more or less fine; I get the feeling that it isn't quite right, but the problem is really only exhibited when I come to a stop and the car is idling.

I am hoping someone has any idea what might be causing this. Any advice would be appreciated.

 

well when the check engine light starts flashing it means that it has misfire severe enough to damage the catylic converter. the cat can overheat from burning all the gas and can catch the passenger compartment on fire trust me i've seen this happen. this was probably caused by a bad signal from your ckp so i wouldnt really worry about it unless its still flashing. what kind of ckp sensor is it...magnetic pickup, hall effect, magneto resistive? a possible cause of rough idle is a vacuum leak but its not all too likely. my best guess would be that your engine coolant temp sensor is bad becuase it explains why it runs well when its cold but not when its warm. it could be reading almost accurate when cold but continues to read cold when its heated up dumping excessive ammounts of fuel into the engine causing a rough idle. i'm guessing you have a scan tool so go into data stream and check what the ect temp is while it warms up. also check out the short term fuel trim (integrator) and long term (block learn). if it is higher than average look for vacuum leak. yea and also the injector on-time. should be like 2ms or so at idle.

 

Dont listen to that other fool. brolli has no idea what hes talking about. sorry man but you dont. talk about too much information gone bad. anyways, I would suggest checking your timing belt. The ECU gets information from the crank (CKP) and cam sensors. If the ECU sees that they are not lining up at Top Dead Center (TDC) then you may throw a code. My guess is that you have so much slack in your t-belt that your crank and cam are no longer lined up.

Also concerning the rough idle, this CAN be caused by the above, but to make sure check your Idle Air Contgrol as well as your Fast Idle.

I hope this information helps you diagnose your problem.

What were the descriptions of your codes. The more information the better. Does your rough idle happen at startup (cold) or after running for 30 minutes?

 

The only code I've been getting is 8, the code for that sensor CKP/TDC sensor. The problem only comes up after the car has been running about 20 minutes and is warm. When cold it starts and runs fine.

 

ur dizzy is about to crap out on you

 

I just changed the rotor and distributor cap today. The one I replaced was old, but not too bad. In the end it made no difference. I still have the same exact problem. I took a look at the ignition coil for the hell of it and the resistances were fine for that, all within tolerance.

I'm wondering if the computer itself has problems, especially since it keeps giving a code for something thats been replaced. Although, I don't want to spend a few hundred dollars on it just to find out it's something else.

Any ideas?

 

its the sensors inside the dizzy that are going bad, changing the cap and rotor will not remedy this problem

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PrettyLude &raquo;</TD></TR><TR><TD CLASS="quote">its the sensors inside the dizzy that are going bad, changing the cap and rotor will not remedy this problem</TD></TR></TABLE>
what sensors are you referring to? i believe the CKP/TDC sensors in the 4th gen are inside the distributor, but in his case (5th gen) they are behind the crank pulley, and they have already been replaced.

or are you referring to something else?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by brolli &raquo;</TD></TR><TR><TD CLASS="quote">catch the passenger compartment on fire</TD></TR></TABLE>

That's rediculous. Let's all think of the worst possible outcome for his prelude...

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PrettyLude &raquo;</TD></TR><TR><TD CLASS="quote">ur dizzy is about to crap out on you</TD></TR></TABLE>

I would be concerned about this. Like he says, the cap and rotor aren't the whole distributor, there's plenty of other stuff to go wrong. Try a known good distributor if you can. This is the kind of thing that will put you on the side of the road.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MaWeiTao &raquo;</TD></TR><TR><TD CLASS="quote">the resistances were fine for that, all within tolerance.</TD></TR></TABLE>

As nice as those tests are, they don't mean ****. I have had many cars that were towed in because they cut off going down the road and wouldn't crank, and the coil tests perfect. One ignition coil later, they're driving away.

Start with a good distributor if you can get your hands on one. That will let you narrow things down and save some money before you go replacing all kinds of random stuff.

A look at the manual shows the TDC/CKP down by the crank. If you have a code set for that, and it's running rough, I would look into replacing that sensor. If it goes, you better have your walking shoes.


Modified by drdisco69 at 11:14 AM 4/7/2005