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Low idle when cold

 
Old 03-08-2010, 12:58 PM
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Cosmo Kramer
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Default Low idle when cold

My car on Saturday just started idling very low on cold startup, to the point that it barely runs unless I put my foot on the pedal. It doesn't surge or bounce around, just low.

I was thinking of checking the resistance of the Temp 2 sensor at the EZF and LH plugs when it is cold, any other ideas?

I hope it isn't the ISV, I don't feel like doing the Tawny Kitaen pose on top of my engine LOL!
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Old 03-08-2010, 01:10 PM
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Has the ISV / ICV ever been replaced on the car? I fired my '87 up this past weekend and the ISV was stuck open causing it to idle at about 1200 RPM for about 30 seconds. It was cold the night before and the car had been sitting for a couple of weeks.
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Old 03-08-2010, 01:54 PM
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Isv was working fine and tested over the winter. Was working normal until two days ago started it up and no cold idle.
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Old 03-08-2010, 02:03 PM
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the flyin' scotsman
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Ted............you may want to send John speake a note on this.

The ISV can be activated/checked through the diagnostic port on the newer cars so perhaps there's a possibility of checking through the LH or EZK connectors. Did you try the WD40 trick?
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Old 03-08-2010, 02:24 PM
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Cosmo Kramer
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I think the ISV is OK, unless it died completely overnight. I don't think it is stuck as I ensured it was free and lubed when I refreshed the intake.

Could be something not signaling it to open. Idle is perfect when warm.
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Old 03-08-2010, 02:32 PM
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Mike Frye
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Ted,

Probably a dumb question, but does it sound low (or does it miss) or does it sound OK but just shows lower than normal on the dash tach?

I don't think I've heard anyone have a low idle unless it was combined with a surge.

High idle=unmetered air
surging idle=could be almost anything including ISV
low idle=???

Most of the inputs on these cars raise the idle for different factors, but I don't think any of them lower it from the base idle.

Do you have access to an external tach to verify what it's showing on the dash? Maybe it's an electrical thing instead of a low idle?
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Old 03-08-2010, 02:43 PM
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The odd time I get a slight miss, like the car is shut off for a split second during warmup at idle only, but that is only like one or two occurrences during warmup.

Idle doesn't surge at all, just really low. Haven't checked with a separate tach, but I have to keep my foot on the pedal to keep it running for the first 60 seconds or so, then OK on its own. Slowly the idle gets better and better as it warms up until it is at spec.

It is almost like the ISV isn't working at all and is in the closed position during warmup.

Originally Posted by Mike Frye View Post
Ted,

Probably a dumb question, but does it sound low (or does it miss) or does it sound OK but just shows lower than normal on the dash tach?

I don't think I've heard anyone have a low idle unless it was combined with a surge.

High idle=unmetered air
surging idle=could be almost anything including ISV
low idle=???

Most of the inputs on these cars raise the idle for different factors, but I don't think any of them lower it from the base idle.

Do you have access to an external tach to verify what it's showing on the dash? Maybe it's an electrical thing instead of a low idle?
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Old 03-08-2010, 03:18 PM
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Originally Posted by Cosmo Kramer View Post
The odd time I get a slight miss, like the car is shut off for a split second during warmup at idle only, but that is only like one or two occurrences during warmup.

Idle doesn't surge at all, just really low. Haven't checked with a separate tach, but I have to keep my foot on the pedal to keep it running for the first 60 seconds or so, then OK on its own. Slowly the idle gets better and better as it warms up until it is at spec.

It is almost like the ISV isn't working at all and is in the closed position during warmup.
Ah, well if you have to keep it running with the gas then that would confirm that the tach is accurate.

You have some non-standard setup things going on, like that induction thingy so it's going to be tough. How about your O2 sensor? Didn't you just do some exhaust mods? Is the O2 sensor new? Maybe a loose connection?
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Old 03-08-2010, 03:37 PM
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O2 is brand new and spliced in with butt connectors. Working fine as my AFR's are perfectly in the mid 14's in open loop when it is warmed up on my wideband (damn it is handy)! I think it is supposed to be in open loop on warmup so the O2 would be out of the equation anyway.

After I get home and I let it completely cool I am going to check the temp 2 values at the LH and EZF plugs and see where they are at. If I have a bad connection or a bad sensor that could be the cause.

Ya somewhat "non standard". You were right about adding the crossover wholly cow what a difference! Better fuel eliminated the detonation for now too, the car actually scares me at full throttle now (and that is a good thing)!

Originally Posted by Mike Frye View Post
Ah, well if you have to keep it running with the gas then that would confirm that the tach is accurate.

You have some non-standard setup things going on, like that induction thingy so it's going to be tough. How about your O2 sensor? Didn't you just do some exhaust mods? Is the O2 sensor new? Maybe a loose connection?
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Old 03-08-2010, 08:40 PM
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Adjust the base idle and see if that fixes the problem.
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Old 03-09-2010, 11:25 PM
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Default Update:

Pulled the LH and EZF connectors and checked the ohm reading of the temp 2 sensor at several temperatures and it is in spec. Hooked the 2 plugs back up, started the car cold and it idled perfectly. Weird stuff. I wonder if it will happen again, we will see.

Imre: I let it warm up and set the base idle as per your suggestion. It was only about 100 rpm too low, so now I am good there.
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Old 03-09-2010, 11:41 PM
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Ted...............John Speake professes that the LH & EZK connectors are selve cleaning...........if you now have good idle and thats thelast op you did then I'd sugest repeating the process (batt disconnect).

I just did this process stop when tshooting my hwy dead thread.
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Old 03-10-2010, 08:39 AM
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I just relocated my Maf from the normal location to under my fender. Now remember I have a adjustable Maf and when it was moved my WB showed rich really rich. It would start, idle would go up and down and after it went into closed loop it stabilized. I have adjusted it to compensate for it being a puller from a blower. What I gathered is that I set it up for my S/C using it's base line that it needed, when I moved it it all bets were off. This tells me that a window base line is needed when you modify your car and maybe the stock Maf may have an issue. I almost have it, but need a co-pilot to watch the A/F and boost to fine tune it but now it starts and idles normally. I can tell you the adjustment makes a huge difference maybe if your Maf is out of calibration after your Mods this is what is happening. Try the idle adjust per WSM by shorting the test connector after warmed up and go from there. A Co sniffer will help after you get it locked in to adjust the Co trim port.
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Old 03-10-2010, 08:43 AM
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Originally Posted by Tampa 928s View Post
I just relocated my Maf from the normal location to under my fender. Now remember I have a adjustable Maf and when it was moved my WB showed rich really rich. It would start, idle would go up and down and after it went into closed loop it stabilized. I have adjusted it to compensate for it being a puller from a blower. What I gathered is that I set it up for my S/C using it's base line that it needed, when I moved it it all bets were off. This tells me that a window base line is needed when you modify your car and maybe the stock Maf may have an issue. I almost have it, but need a co-pilot to watch the A/F and boost to fine tune it but now it starts and idles normally. I can tell you the adjustment makes a huge difference maybe if your Maf is out of calibration after your Mods this is what is happening. Try the idle adjust per WSM by shorting the test connector after warmed up and go from there. A Co sniffer will help after you get it locked in to adjust the Co trim port.
Cool idea. If you don't have a CO sniffer, Porken's Blink'r works really well.

Ted, let me know if you want to borrow one, I'm not using mine right now.

It's a really great tool to have. Once you use it you'll want to buy your own.
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Old 03-10-2010, 09:04 AM
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The LH2.2 has no constant power source. So there is no need to disconnect the battery when reseating the plug.
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