Idle Screw/rpms/battery voltage.

[glowstang93]

I posted this in 2.3 tech, but I thought you guys might have a few thoughts too.


I tried something that I think will help some with my voltage drop when lights and defroster are on. I turned the idle screw in 1 1/4 turns to bump up the idle rpms. Doing this keeps my volts above 12.9 when the compressor kicks in. Awhile back when I was having ICM problems I had moved the screw some, so I may not have got it back exactly where it should have been.

It makes sense to me that if the idle screw is turned in, the rpms will rise due to the increased throttle. The rpms are still below the 1k mark, unless it is cold and its trying to reach operating temperature.

I have seen how to set the iac, but it just says to set rpms at 700-800. Doesn't say how to know for sure what the rpm's are actally reading, short of looking at tach.

I have a VOM hooked up to the cigarette lighter and will continue to monitor the voltage and rpms with the compressor and lights on. If its just lights on, no problems, if its just compressor, no problem, but both were making the volts go down to 12.3 when compressor kicked on.

Yes, I have a 3g, but its only a 95 amp, the only one I could find that the case was the right size and available easily.

Thanks in advance for any opinions or ideas.

 

[HISSIN50]

Sounds good Anthony. That's how I end up setting the base idle on some cars (especially automatics) myself - load it up with every accessory and the lowest hot-idle you normally see, and adjust away.

I'd note that if you have any amount of IAC duty cycle while making the adjustment, the idle might wander back towards the commanded idle eventually. I end up setting the hot, loaded idle (AC off) with the IAC disconnected sometimes, as the idle really cant go lower afterwards (the computer can increase IAC Duty cycle to raise the idle, but cant lower the idle if the IAC has zero Duty Cycle).

I'm sure you considered it, but O/Ding the alternator is another alternative.

Good luck.

 

[glowstang93]

Hissin, to disconnect iac would that just be unplug the electrical connection?

Also, I'm sorry but I didn't get your shorthand "o/ding" .

Sounds like I'll just have to wait and see how she reacts in regards to the iac and the commanded idle from computer. Thanks again for your response.

This has nothing to do with the post but I was finally able to get her washed and waxed yesterday, maybe the last time before winter

 

[superhuaman]

yeah, just unplug it. and o/d means overdrive, as in put a smaller pulley on it so it runs faster at idle.

 

[glowstang93]

Yea, after I stepped away from the computer I was thinking that was what he meant. To change to overdrive pulley, the belt length will change too right? I have seen where Steeda has them. How do you figure the belt length or will they know?

 

[superhuaman]

nah...if you have an automatic belt tensioner (my 90 2.3 did) it should make up for the pulley.

 

[glowstang93]

Wouldn't an overdrive pulley be bigger, making it harder to get belt to fit onto pulley?

 

[superhuaman]

no you want the alternator to spin faster, so youre getting a smaller pulley.

 

[glowstang93]

Duh
Ok, so the pulley would be smaller, making it spin faster, making the rpms to the alternator increase, decreasing the load from the compressor.
The tensioner took up the slack from the shorter distance on yours. Next question, where do you get one or where did you get yours?

Sounds like a plan since it only really has problems when the compressor robs it of the rpms.

 

[superhuaman]

you can buy them from most companies that make alternators, or i noticed some rebuilt alternators at the junkyard (on crown vic 5.0's and such) have smaller pulleys. i dont know why, but measure the diameter of yours, and then you will know you need something smaller. i dont know if i still have one, i will take a pic later if i have it.

 

[glowstang93]

Cool, its definitely an option for me to do if the idle adjustment doesn't work out. Its not really an issue most of the time untill winter hits or it gets really hot and i run the a/c.

 

[HISSIN50]

ASP and FFI both sell pulleys (amongst others). The prices on FFI (FordFuelInjection.com) look pretty good to me. When I was farting around with low idle and charge issues on the '94, I almost went with their OD pulley. Just crunch numbers to make sure you stay under the recommended alternator speed (16,000 RPM IIRC). I don't know what your crank pulley's size is, so I didn't want to assume anything.

The idle bump will probably take care of the issue, but it's nice to have alternative (like OD'ing the alt) ready to implement if needed.

Good luck.

 

[glowstang93]

Hissin, so let me get this straight.
Start the car, unplug the iac, adjust the idle screw with compressor/lights on, then reconnect iac?

 

[HISSIN50]

Hissin, so let me get this straight.
Start the car, unplug the iac, adjust the idle screw with compressor/lights on, then reconnect iac?

I'd let the car warm up. Then disconnect the IAC and get it to idle decently (do not have the AC on and do not turn the steering wheel - those items *should* require IAC assistance).

The idea is that with the IAC disconnected, the idle will not be able to go lower than where you manually set it at that time. Then when you reconnect the IAC, it might change the setting a bit, but it also again provides the compensation for AC, Power steering, etc.

Good luck.

 

[glowstang93]

I'm turning just below 1000 rpms after my 4 mile drive home at idle now. Voltage goes down to about 12.7 the lowest, but it doesn't stay there long at all now. Its probably about 3 seconds and then the voltge climbs back up to 13's. Much better, will keep watching it and see if any more adjustment is necessary, don't want to overdue the idle speed too much, like a little fuel economy

Thanks for your help everyone.

 

[glowstang93]

Well, its screwed up now

Drove home fine this morning and then this afternoon its idling rougher than rough. The exhaust sounds like open pipes. I tried to readjust idle, but this doesn't seem to be the problem. When I put it in gear, the engine runs even rougher.

I called my friend/mechanic and he thought since it was running rough in gear there was a vacuum problem, but then again this could be caused by the idle being set wrong, or a sensor, or who knows. The brake pedal isn't working too good either, its not getting any power assist.

Taking it to the shop tomorrow, or at least I'm going to try to drive it there. If not they have a trailer if I have to.

If you have any ideas, chime in. I know I am




Should have knows something was going to go wrong, it was that time again.

 

[HISSIN50]

A vac leak might have lead to the diminished idle in the first place. No amount of playing with the idle could make up for the issue.

A stockish 5.0 sees about 18-20" hg of vac at idle, but I don't know about your engine. It should be close to that in any case. I'd take a looksie.

Good luck bud.

 

[glowstang93]

Thanks man,

I was at my friend/mechanic's house tonight trick or treating with the kids and we talked about the vacuum leak a little more. He said it could even be a brake booster since I have noticed the brakes not having the assist too. I'm going to try to get it to the shop about 2 miles in the morning. If it leaves me stranded I'll be using the State Farm Tow Insurance, thats what its for

They will get it figured out, I have been taking my cars to him since 93 when I moved up here. Never has screwed me over or overcharged. My baby will be in good hands.

I'll post an update when I know more.

Why can't there be an after hours Emergency Room for Mustangs

 

[glowstang93]

Just got off phone with shop. A part has been ordered and should be in tomorrow. Something to do with the EGR and its like $70 for the part. Didn't get any more details than that. Should have her back tomorrow if all goes well.

 

[seijirou]

Yeah an egr valve being open when it shouldn't will defanently make her run and behave like crap.