hot start up idle problems

rj95svt

Member
Jan 11, 2007
422
0
16
Hayden, AL
I am having a very frustrating problem with my car. When I crank the car cold it starts and idles perfectly. It does have some minor hesitation but other than that it runs fine however when starting the car warm it's a whole different story. When I start the car after it has been warmed up it initially starts fine but then as the idle is coming down to normal it just tries to stall out. I can give it a little throttle and keep it from going dead but it will not idle consistantly for around 30 seconds to a minute. While it's doing this if I rev the car hard or pull out and hit the throttle it hesitates and sometimes backfires I've also noticed smoke coming from the tailpipes. I can't tell what color the smoke is because I'm sitting in the car trying to keep it running. I have noticed this problem before but it seems to happen more often during warm weather so obviously it's been much worse lately. I iced the intake at the dragstrip this past weekend and let the car sit for about thirty minutes and when I cranked the car it idled perfectly with no hesitation and made better power than normal but that's why I iced the intake in the first place but it seemed to help more than it should have. I only made one pass so I'm not sure if it did or not. I have pulled the codes and the only codes I get are EGR and smog but I have eliminated both these systems so that's normal. I also get a system rich code from both banks. I replaced the O2's a few weeks ago and I'm still getting those codes. Sorry for the long post but I'm trying to give as much information as possible. Any help is greatly appreciated
 
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Sounds like it is running too rich at start if you get a surge for the first 30 sec or so (the time during which the startup tables add fuel).

Had the same problem with Sage2k's car - first we reset the TB and the IAC, the problem was better but still persisted. He has a twEECer, we were able to go into the tune and pull some startup fuel to eliminate the problem.

Cleaned MAF? Idle and IAC good? Fuel pressure a-ok?

Good luck, that's an aggravating issue a lot of people have.
Wes
 
I have cleaned the MAF, IAC, and tried everything I can think of. I would think the same thing as you if my car had any signifigant mods but other than the CAI and O/R X and flowmasters I don't have anything else done to the car. The fuel pressure is 39 with the vacumm off and 32 with the line on at Idle. I wonder if it could have something to do with the ECT sensor?
 
HISSIN50 is the electronic troubleshooting god - hopefully he'll pitch in on the ECT.

In the meantime, you can probably find his troubleshooting tips on the ECT in the search - Try "ECT*" to get past the 3 letter block.

Wes
 
Yes on warm days it did but there was very few warm days during that time of the year so it it didn't happen often. I installed a new IAT and cleaned the MAF really good when I installed the CAI so that should eliminate that as a possibilty. Thanks for the help I'll try the search.
 
I'm still open for suggestions

Did you ever figure this out RJ? I am having the same exact problem, even down to it running rich at warm startup. My situation was a little different since it only started after I put on an IAC restrictor plate and reset my idle (at 900). I did this to get rid of my hanging idle issue, and it did get rid of that but now I have this problem which you also have.

RJ, you might try to set your idle. Check out R.J.'s (different RJ!) instructions on this thread:

http://forums.stangnet.com/showthread.php?t=605187&highlight=Idle+air+delete

Anyone else have any input for us?
 
Did you ever figure this out RJ? I am having the same exact problem, even down to it running rich at warm startup. My situation was a little different since it only started after I put on an IAC restrictor plate and reset my idle (at 900). I did this to get rid of my hanging idle issue, and it did get rid of that but now I have this problem which you also have.

RJ, you might try to set your idle. Check out R.J.'s (different RJ!) instructions on this thread:

http://forums.stangnet.com/showthread.php?t=605187&highlight=Idle+air+delete

Anyone else have any input for us?

I have still yet to figure my problem out. I have replaced the ECT,IAT, and cleaned the entire throttle body including taking off the IAC cleaning it. I also went ahead and reset my TPS. You brought up something intresting though. I haven't reset the idle mechanically on the TB.

I will try to reset the idle on the TB and see if this does any good. Since the car is pretty well stock including the TB I just figured that the settings were right. I shouldn't assume that though so I'll reset it and see if it does any good.:bang:

I'll repost after I do this.
 
I musta' missed this thrad the first time around.

Wes's ECT idea is a good one. The sensor can be out of calibration but not out of absolute spec (ergo no code). Even though you have a new one, I'd check it. Since this is a hot start issue, look for about 0.78 ECT volts with the ECT at 180*F. There could be resistive wiring (which would make the puter see the engine as cold).

Wes's idea about the IAC is also right on. You noted a hesitation when cold. The thing is these EFI cars mask underlying issues so well (on a carbed car, when your choke took a dump, you knew all about it the entire 5 minutes you held the gas down in your driveway, waiting for it to warm up :rlaugh: ). A lack of IAC function can cause cold engine hesitation and obviously stalling once hot.

Also see if your idle bleed screw wandered way off (mark it so you can get it back to where it is now. Then seat it and see how many turns it went in. It should be less than 1.5 turns or so).

I dont recommend such tactics but I have tested a bad IAC by introducing a small vac leak. This should bump the idle up. It allows me to be under the hood and seeing what's going on, running a cylinder balance test (not that you need one - that was part of my example for doing it), etc.



If either of you can view PIDs, that would be pretty cool to see what it does during hot-start-up.

Also, are we real sure about the verbage with the O2 codes? It can be confusing.

If you ever drive the car, does it try to stall during a rolling idle too (there should be a dashpot function occuring, to keep your rollling idle around 1000-1400 RPM)?

Random thoughts.
Good luck.
 
I messed with it some last night and I'm starting to get a little frustrated. It acts like the IAC wasn't working at all when messing with it last night. I unplugged the IAC and the car acted no different than it did before.

Here recently the car started dieing at idle with the A/C on (cold or hot). When the A/C compressor kicks on the idle rpm drops till either it dies or gets very close. This is a new problem that has just started. I believe the IAC has went bad now. Additionally I never had a problem with the car dying when I came to a stop but I let my dad drive it two nights ago and he said it died every time he stopped at a redlight. I haven't driven it since then just messed with it idling in the yard.

The car has always had a hesitation after start up. Cold or hot it has never mattered. After about 30 seconds to a minute the car doesn't hesitate at all.

The very first thing I suspected being wrong was the ECT and IAT sensors. I checked the resistance with both the old and new sensors and both were identicle furthermore changing them made absolutly no difference whatsoever in the way the car ran. I was hoping to buy a tweecer this weekend and if I did I was going to do a datalog so I could see exactly what the computer was seeing from all the sensors but the plan on buying the tweecer may have fell through (the guy who had it put it up for sell on ebay so I'm not sure if I'll get it or not now).

I am sure about the O2 sensor codes. I realize that there is a rich adaptive limit codes which actually means that the car is lean but the description associated with the codes said bank 1 rich and bank 2 rich. It's also unmistakeable the black smoke and raw fuel that pours out the exhaust sometimes especially during hot start up.

I have been haveing some problems haven't I:bang:
The funny thing is it always ran great after a minute or so of running until now and as long as the A/c is off it idles fairly well now atleast for short periods of time.
I am prbably going to buy a IAC this afternoon to see if this helps some of my problems.
 
Someone please correct me if I am wrong, but isn't the car supposed to not do anything when you disconnect the IAC during an idle? I think the IAC only goes into effect when you are driving. I know that to mechanically set your idle you have to disconnect the IAC and when I do it I notice no difference in the way it runs too. Maybe my IAC is bad too? :shrug:
 
Someone please correct me if I am wrong, but isn't the car supposed to not do anything when you disconnect the IAC during an idle? I think the IAC only goes into effect when you are driving. I know that to mechanically set your idle you have to disconnect the IAC and when I do it I notice no difference in the way it runs too. Maybe my IAC is bad too? :shrug:

The car should die or come very close to it with the IAC unplugged and everything setup properly.

The IAC does help out during cranking, idle and transitions to and from idle.

Wes
 
I am talking about the IAC isn't compensating for the A/C compressor kicking or any kind of load on the engine. The IAC is supposed to compensate for the loads and keep the engine at a steady idle.

It also dies after you rev the engine with or without the AC on with the IAC connected or not.
 
From your sig info, I just don't see much to make me think your pcm is hosed by
the addition of mods.

I'd put a new IAC (ISC for Tweecer folk :)) in there

If you got all mechanical options setup like Ford intends .............

You pull the IAC plug and it should stumble or die

If it don't ...
the tb blade stop screw is holding the blade too far off the tb wall :D

Grady
 
From your sig info, I just don't see much to make me think your pcm is hosed by
the addition of mods.

I'd put a new IAC (ISC for Tweecer folk :)) in there

If you got all mechanical options setup like Ford intends .............

You pull the IAC plug and it should stumble or die

If it don't ...
the tb blade stop screw is holding the blade too far off the tb wall :D

Grady

How come you are supposed to mechanically set the idle with the IAC unplugged if it is supposed to stumble or die? :shrug:
 
There are a couple of idle adjustment methods. I do it different than most folks in that I set it so when the engine is hot and unloaded, I have no IAC function (it will go from 1-6% DC actually, but for all intents and purposes, it's off). I do this so I dont have to rely on the sucker most of the time. Folks have also been able to use the bleed screw (as I recall, Grady can't stand that thing. I know I cant) and not have to touch the throttle stop.

Most folks do have an IAC DC while idling.

I like the IAC replacement or re-cleaning idea. This would explain the lack of idle compensation for loads, stalling at lights, etc.

Good luck.
 
There are a couple of idle adjustment methods. I do it different than most folks in that I set it so when the engine is hot and unloaded, I have no IAC function (it will go from 1-6% DC actually, but for all intents and purposes, it's off). I do this so I dont have to rely on the sucker most of the time. Folks have also been able to use the bleed screw (as I recall, Grady can't stand that thing. I know I cant) and not have to touch the throttle stop.

Most folks do have an IAC DC while idling.

I like the IAC replacement or re-cleaning idea. This would explain the lack of idle compensation for loads, stalling at lights, etc.

Good luck.

Just want to clear things up a bit...what do you mean by "DC?"

:stupid: