Start up/idle problem. Please help!

[caseymish]

Ok so I have a 96 RS and about three days ago I got into my car and started it up but the RPM's went up a little over 1 then stayed at one. As soon as I gave it gas to back up the moment I let off the RPMs would almost die or completely die. This is even after warming up for a while. Everytime I put the clutch in the RPMs almost die or do die. But the kicker is that if I drive it for a little while the rpms and everything return to normal? This happens whenever i start the car and driving shortly after starting. I have no idea what it is! Please help!

 

[ZacFields]

I have a 1996 Talon N/T and I am having this same problem I think. Mine is an automatic, though.

After first starting the car, sometimes the idle will fall down to 200 or less and sometimes the car will die. This same thing happens while the engine is cold and I go to stop at a stop sign.

Today I was looking for the ISC because I've heard that could be the problem, but I'm not finding it on my 420a engine. While I was letting the engine warm up (it's really cold here in Iowa in December) I noticed that the engine was idling okay (around 1,000 rpms as the engine was cold) but if I were to rev the engine up to about 3k and then let off the gas suddenly, the RPM's would quickly fall to zero and die.

I could rev the car up to 1.5k or 2k and the engine could recover when I let off the gas, but once I revved it up to 3k and let off, dead.

The car starts right back up afterwards. I haven't been able to find the ISC yet and I can't hardly seem to find any good information to help me find it.

Zac

 

[turboglenn]

I think you both should check for vacum leaks and at least clean and inspect the ISC's when you find them.

 

[ZacFields]

Does anyone know of a good article detailing how to remove your TB? I'd like to do this, but looking at it, it looks to be somewhat complicated.

Zac

 

[123212321]

There are a whole bunch of articles on throttle body cleaning and removing at vfaq.com, under the intake portion of the site.

 

[turbodsm_125]

i am having the same problem with my 1g. i know you have a 420a but try to look for vaccum leaks. i don't know if your car has a maf or a air speed density meter but check that.

 

[ZacFields]

I will check for vacuum leaks. I have a few friends that have been working on DSMs for years that are going to be helping me in the coming weeks.

The good thing about this problem is that the car starts and runs fine, even though sometimes you've got to struggle with it to keep it running right after you start it when the engine is cold. So it might be a couple weeks before I'm able to get back to you guys about this, but I've bookmarked this topic so I will get back on here and let you guys know what did and didn't work. But for indexing purposes, here is what didn't work so far:

-Changed Coolant Temp Sensor (Actually changed both of them. In my 420a, there was one specifically for the guage in the dash, and the other one above it was the "functional" one that communicates with the MAF i guess)

-Changed out the spark plugs

-Changed Air Filter


That is the extent of what I've done so far to remedy this problem. I will update this as I do more things. From the research I've done, this is most likely the ISC motor though. That would explain why this happens when the RPM is dropping from regular acceleration RPM's. The ISC isn't "catching" the RPM's as they fall to the correct idle speed. If the drop in idle speed doesn't kill the engine, then it usually evens out to where it's supposed to be (750-850rpm). It'll drop down to 200, then it'll catch back up to 750-850. Sounds to me like a gunked up ISC motor from the reasearch i've done. It's just sluggish with catching that falling RPM. That would also explain why it gets better once the engine is warmer. Whatever grease/grime that is keeping it from operating correctly warms up and eventually it isn't as much of an issue anymore once the engine is warm.

Again, this is only an issue of "catching" the RPMs when they fall from say 2.5-3k or higher. The car actually idles just fine. No surging that I've noticed. If you get it idling, it will idle all day like it's supposed to.

Sorry for the long post, but I'm having a lot of trouble finding the correct solutions to this problem (EXE: Original poster tends to disappear after the problem is fixed and not take a moment to enlighten everyone as to what worked) so I'd like to fully log this situation for my engine (and the original poster who appears to have the exact same problem) so people that have this problem in the future won't have to waste a lot of money.

Seems like there's always a small fraction of this problem that is different with every situation.

Zac

 

[90gsx16g]

Stuck EGR valve, my friends talon died everytime it warmed up and he stopped at a light. EGR valve was getting stuck when his car warmed up.

 

[ZacFields]

Yes but my problem is the exact opposite of that. My Talon is dying really only when the engine is cold. This is what led a friend of mine to suggest I change out the Coolant Temp Sensor because if it's faulty, then it defaults to 180 degrees celcius I believe, which means its basically telling the car's computer that the car is warm even when it's cold. Makes perfect sense because the car needs more gas at idle and such when the car is cold, and it wouldn't be getting that if the coolant temp sensor is saying the car is already warm. But unfortunately, replacing that didn't do any good...except when I replaced the one that's connected to my dash temp guage, it works nicely now instead of only working properly when the car is warm.

Zac

 

[90gsx16g]

Yes but my problem is the exact opposite of that. My Talon is dying really only when the engine is cold. This is what led a friend of mine to suggest I change out the Coolant Temp Sensor because if it's faulty, then it defaults to 180 degrees celcius I believe, which means its basically telling the car's computer that the car is warm even when it's cold. Makes perfect sense because the car needs more gas at idle and such when the car is cold, and it wouldn't be getting that if the coolant temp sensor is saying the car is already warm. But unfortunately, replacing that didn't do any good...except when I replaced the one that's connected to my dash temp guage, it works nicely now instead of only working properly when the car is warm.

Zac

Sorry i mis read what you wrote.

 

[hubz91talontsi]

Its your battery for sure. 100% sure.

 

[hubz91talontsi]

Ill add a little extra. Your alternator does not recharge your battery only holds the charge. Ive had this same problem many of times. Your battery atm is probably around 3V Just enough to run. Charge it up over night and you should be fine. I am 100% sure this is the problem no need to check anything else.

 

[ZacFields]

Well we recently had the battery tested at Autozone and it tested fine. But I've got nothing better to do today and the car's sitting out there begging me to do something to make some progress on this problem, so I'll test this theory out.

Heck, I've got a battery charger and plenty of time. Might as well

*Edit*
Went out there and connected the battery to the charger. The charger wouldn't even charge it because the battery was testing as fully charged.

Either way, one more thing I can cross off the list. When I had the battery tested I also had the alternator tested which was also running great.

 

[ZacFields]

Here's an update:

yesterday when I checked the battery (which turned out to be fully charged) I am told by my girlfriend who is the owner of the car that the car ran just fine today and she didn't have any problems with the idle.

I have heard some people say that disconnecting the negative battery cable and thus restarting the car's computer helped them. But most people said that it only helped temporarily.

So i'm assuming if my girlfriend is correct in saying that the car is running fine now, then the problem must be in my ECU. If the problem were to come back, what are my options with the ECU...hopefully options that don't require the $1,300 part to be replaced

Zac

 

[project1g]

I've had an idle problem.
Here goes... I get in start the car (vroom vroom)
and it sits just fine at 900-1000 but when I put the AC on it drops down to about 500-600RPMs
This morning when I started it up and turned the heater on it only dropped to 700-800RPMs
then turned the AC on to see if maybe it was because the AC hasn't been used in a while
It dropped even further.
Maybe some help?

 

[Locke]

project1g: The AC is either putting too much of a load on the motor (bad bearing) or the ECU doesn't know it is turning on, and thus cannot compensate for the load.

hubz: If it were his battery/alternator, the vehicle would not start up so readily.

Zac: The IAC is likely gummed up. Test it as well.

The IAC is on the bottom/rear of the TB, and cannot be removed with the TB in place. Clean the IAC/s pintle, the air bypass galley, and the TB.

Check resistance between pins 1 and 4 of the IAC, then again between pins 2 and 3. The resistance should be 38-52ohms.

 

[project1g]

project1g: The AC is either putting too much of a load on the motor (bad bearing) or the ECU doesn't know it is turning on, and thus cannot compensate for the load.

Which bearing might this be? And in the event the ECU isn't realizing its turning on what would I have to do to get the ECU to pick up on that?

 

[Locke]

Which bearing might this be? And in the event the ECU isn't realizing its turning on what would I have to do to get the ECU to pick up on that?

The shaft bearings in the AC compressor.

My 1g never had a functioning A/C system, so I have no actual experience with the particulars of their operation. Likely, a signal from a pressure switch, or from the switching circuit for the A/C clutch/pulley.

 

[project1g]

Yummy... Lets hope its the bearings though.

 

[crimsondragon]

Ill add a little extra. Your alternator does not recharge your battery only holds the charge. Ive had this same problem many of times. Your battery atm is probably around 3V Just enough to run. Charge it up over night and you should be fine. I am 100% sure this is the problem no need to check anything else.

What? WTF
Do you mean like an almost dead battery? Cause car batteries do get recharged by our alternators.