'86.5 Running a little rough when cold
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From: South Florida
'86.5 Running a little rough when cold
OK, so I'm seeing this semi-frequently now, but not all the time. Also, keep in mind that "cold" right now where I am is in the '60s over night. Yes, you should be jealous 
Anyway, when this happens, the car runs rough, maybe like it's down a cylinder. It reminds me of the way it ran before I changed out my injectors, to be honest, with a lot of surging under mild throttle in the 2K+ rpm range. Once I've driven it for a bit, it ALWAYS cleans itself up. I've never had it continue past the first five minutes of driving or so.
Any ideas what might cause this? Since it seems so linked to operating temps, I was thinking the Temp II sensor, but I don't think I've seen anyone have these symptoms for that issue. I did check the sensor last year while chasing something else, and it was fine, so I will check it again, but I was wondering if any of you all have seen this before and found the root cause.
TIA
Anyway, when this happens, the car runs rough, maybe like it's down a cylinder. It reminds me of the way it ran before I changed out my injectors, to be honest, with a lot of surging under mild throttle in the 2K+ rpm range. Once I've driven it for a bit, it ALWAYS cleans itself up. I've never had it continue past the first five minutes of driving or so.
Any ideas what might cause this? Since it seems so linked to operating temps, I was thinking the Temp II sensor, but I don't think I've seen anyone have these symptoms for that issue. I did check the sensor last year while chasing something else, and it was fine, so I will check it again, but I was wondering if any of you all have seen this before and found the root cause.
TIA
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Check BOTH terminals of the Temp II to ground hot AND cold. Both terms should be roughly equal, >1000 cold, <300 hot.
Check spark plug wires and distributor caps. Could be condensation problems.
Have you adjusted the idle speed and CO? Surging is often a lean indicator.
Check spark plug wires and distributor caps. Could be condensation problems.
Have you adjusted the idle speed and CO? Surging is often a lean indicator.
Thread Starter
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From: South Florida
I haven't messed with idle speed and CO, since it generally seems to be very smooth (tbh idle reads a little high on my tach...hmmm)
I'll definitely check both terminals as you said...plug wires and distributors were done shortly after I got the car, about two years ago. I would hope they are still OK.
I was thinking it was probably lean too....it behaved similarly with old injectors, and would temporarily clean itself up with injector cleaner (that's what prompted me to replace the injectors).
I'll definitely check both terminals as you said...plug wires and distributors were done shortly after I got the car, about two years ago. I would hope they are still OK.
I was thinking it was probably lean too....it behaved similarly with old injectors, and would temporarily clean itself up with injector cleaner (that's what prompted me to replace the injectors).
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From: South Florida
Well, dammit. I'm measuring right around 2K, both sides, at ambient right now (78F) which is I think where it should be. I was hoping that would be the culprit.
Of course, I haven't started it yet, I guess if it runs fine this time I won't have proven anything...
Of course, I haven't started it yet, I guess if it runs fine this time I won't have proven anything...
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Check the vacuum level at the EZF. Should be >17"hg at idle, else vacuum leak(s).
When warm, bridge B->C on the test plug to check the uncorrected idle speed. You'll probably find it to be higher than 680, even if you turn the throttle body screw in all the way*, indicating vacuum leak(s) and/or the TPS idle switch not working/closing.
*7mm socket at front of TB, CW closes. Note that I found it best to have the TB bypass screw be at least one turn open for the S3 idle correction to work well. Also, setting the idle to 700rpm uncorrected helps too.
When warm, bridge B->C on the test plug to check the uncorrected idle speed. You'll probably find it to be higher than 680, even if you turn the throttle body screw in all the way*, indicating vacuum leak(s) and/or the TPS idle switch not working/closing.
*7mm socket at front of TB, CW closes. Note that I found it best to have the TB bypass screw be at least one turn open for the S3 idle correction to work well. Also, setting the idle to 700rpm uncorrected helps too.
Drifting
Joined: Oct 2010
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From: Centerburg, OH
I know the '86.5 is a different bird than my '88 (I also have an '86.5) Check my post here for some other info. Since I changed so many components, I really couldn't say what my main issue was except 90% sure it was the broken hose on the ISV. Symptoms were very much like yours.
https://rennlist.com/forums/928-foru...when-cold.html
https://rennlist.com/forums/928-foru...when-cold.html
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From: South Florida
Whoops, somehow I missed the most recent bits of advice. I will do these things. I did want to report back that the Temp II sensor swap (I figured why not, it's 30 years old) did not seem to fix the problem. I still run rough (rarely rough enough to get the bucking/surging at light throttle though...usually it just sounds off/rough and feels weak). One thing I've noticed though, which I didn't really notice prior to the sensor swap (doesn't mean it has changed, I just didn't notice it) is how abruptly it fixes itself as it warms up. When my temp needle gets to just below the lower middle line (it usually runs between the two lines) it is almost as if a switch is turned. Suddenly it's butter-smooth and everything is running correctly. Something is not being done correctly, whether it's due to vacuum leaks or whatever, and then suddenly, some transition is detected and it's fine.
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From: Under Cruella's Thumb
Sounds like something to do with cold running if it suddenly fixes itself when warm. I know my car runs differently when it's cold...revs a little slower, etc. I was going to suggest injector cleaner...
Maybe you are a little lean...give the pot on the MAF 1/8 turn clockwise...you can always put it back.
I mess with the MAF pot quite a bit...I have a system for adjusting it without having to take the MAF off...works pretty well...
Flexible carburetor adjuster...with the hex head JB welded to the end...have the MAF pot facing front wards..then use a bent coat hanger to jiggle it in there...then a screwdriver to help remove it...I can take pic of you want let me know..
Maybe you are a little lean...give the pot on the MAF 1/8 turn clockwise...you can always put it back.
I mess with the MAF pot quite a bit...I have a system for adjusting it without having to take the MAF off...works pretty well...
Flexible carburetor adjuster...with the hex head JB welded to the end...have the MAF pot facing front wards..then use a bent coat hanger to jiggle it in there...then a screwdriver to help remove it...I can take pic of you want let me know..
Drifting
Joined: Oct 2010
Posts: 2,271
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From: Centerburg, OH
Whoops, somehow I missed the most recent bits of advice. I will do these things. I did want to report back that the Temp II sensor swap (I figured why not, it's 30 years old) did not seem to fix the problem. I still run rough (rarely rough enough to get the bucking/surging at light throttle though...usually it just sounds off/rough and feels weak). One thing I've noticed though, which I didn't really notice prior to the sensor swap (doesn't mean it has changed, I just didn't notice it) is how abruptly it fixes itself as it warms up. When my temp needle gets to just below the lower middle line (it usually runs between the two lines) it is almost as if a switch is turned. Suddenly it's butter-smooth and everything is running correctly. Something is not being done correctly, whether it's due to vacuum leaks or whatever, and then suddenly, some transition is detected and it's fine.
https://rennlist.com/forums/928-foru...when-cold.html
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From: Under Cruella's Thumb
Coat hanger bent. Below is a flexible tool for adjusting mix on carburetor. I JB welded the correct size hex head to fit in the MAF pot.
View of MAF with pot facing towards front of car...
Basic set up..tool goes in and use wire to help lift flexible shaft into alignment to push into MAF pot.
I use a long flathead screw driver to help remove the tool from the MAF pot.
Thread Starter
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From: South Florida
Ahhh...that's very helpful, thank you. I have a little flexible tool like that but not sure it's quite long enough. (Quiet, peanut gallery!) I've never actually adjusted the MAF thing...
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From: Under Cruella's Thumb
Using the method I can increase/decrease voltage (as a constant across the map) to give more or less fuel....I find a little tinker with it every few months generally helps..
For any change on the pot, you will need to accompany that with minor adjustment on the idle bypass screw or you may find the car idling at an incorrect speed or idle recovery from rpm deceleration changes...
For any change on the pot, you will need to accompany that with minor adjustment on the idle bypass screw or you may find the car idling at an incorrect speed or idle recovery from rpm deceleration changes...
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From: Bloomfield, MI
HF sells a small Screwdriver kit with an attached flex end and it comes with many attachments for less than 8 bucks, it works great for doing this. It was posted here a few years back:
http://www.harborfreight.com/hand-to...set-93916.html
http://www.harborfreight.com/hand-to...set-93916.html