I did a search but didn’t really get a strait answer on my issue, I have a Redtop SR in my 89 coupe stock boost, and my problem started this past Sunday, when I start the engine the idle is super low and sounds like its missing when cold and as soon as it warms up after 15-20 mins of driving it runs perfect, even when im driving cold you can feel it bog down a little. I did some research and changed the Water Temp Sensor but it didnt solve the issue, my plugs are fine too! need help here guys again the motor runs great when warm but this is getting to me… Could it be the Idle Control Valve? or my Walbro? im lost
Does it do it at all when it warms up, or no? The coolant temp sensor sounds about right to me too, but evidently that wasn’t the problem if it’s still doing it.
Only other thing I could think of is the intake air temp sensor (which is built in to your MAF sensor, unless you’re running a stand alone/chipped ECU) could be fucked, but then it should do it all the time, not just when the engines cold…
Could be the ECU itself too I suppose. See if anyone would be willing to swap with you to test. I would offer, but I don’t have a stock ECU anymore.
no it runs perfect when warm, doesnt bog or anything, only when its cold. and yea its very wierd im gonna reset my ecu tmw, the only engine work i did before sunday was my power steering and i did unplug the MAF to remove my airfilter to get to the pump so i’ll make sure its plugged in right.
how cold is it outside when you have the problem?
I’m in Hamilton the coldest the past week was -5, so i reseted the ecu today plugged it out for about and hour and a half, dunno if thats long enough but it started up fine. Maybe its fixed or maybe the engine was a tad warm i’ll guess i’ll find out tmw morning.
same shit when i stared it tonight, could it be the coils being stupid when cold? cause i smell unburned fuel when the engine is bogging :s
when i start my redtop sr in the cold(negatives) it idles at about 1500 for a few minutes till it warms up then goes down to 820 and it purrs. why is this?
^ that’s the iacv, no? That’s what they are supposed to do…
this
gonna test my coils tmw, and my idle control valve i know these cant be the problem seeing how it idles fine when warm but i wanna start crossing stuff off the list. Im goona unplug my MAF and see if it idles fine for a bit, but im thinking i may need to borrow a stock ecu 
Couldn’t see it being a problem with the ecu. Check your iacv and maf. Also search online for an sr20det fsm. They have a big trouble shoot section on your problem along with others like it (hard start when warm/cold, rough idle when warm/cold etc. etc.)
^^ thnx! I’ll deff check it out im hoping its the MAF or IACV I want it to be an easy fix 
also check fuel pressure and check for intake leaks
Coils? Maf? ECU? Temp Sensor? Common… Problem was already stated above. IACV!!!
Think about it… the IACV is responsible for your cold air idle. So if your car will not idle when cold, but idles fine when its warm obvious its the IACV. If it were the MAF, you’d be fine until what, 2500 or 3500rpm? If it were the Temp Sensor then you’d have problems cold or warm. If the coil were toast or even near, it wouldn’t run proper when warm. If their was a fuel issue, again it wouldn’t run proper when warm. Same with intake leaks.
could be the iacv but… seen this problem a million times and its usually the air regulator its buried inbetween the intake plentum and the valve cover, easiest way to check if its punched is to take vicegrips and clamp the hose coming out of it. I don’t know the real purpose of the air regulator I’m guessing it was added to meet emmision’s standards in the early 90’s but id start there unless its been deleted already which case I would look at the iacv or an intake leak. Don’t know if its legal to upload photos from alldata so don’t sue me. I apologize if its not for the right engine but its the closest i could find.
If it’s bogging down/running rough when he’s driving too, how could it be the IACV?
And like I said, if it was his MAF, it would do it all the time, not just when it’s cold. Unless it’s an intermittent issue, in which case it would still happen when its warm, just not all the time.
As for the coils, it should be the other way around. Since it takes less voltage to make electricity jump the gap at the spark plug when the A/F ratio is rich (i.e. when the engine is cold and is dumping in fuel), it should give him problems when its warmer and under load.
Of course this is all speculation. Without having the car in front of me and having driven it, it’s difficult to diagnose these kind of problems over teh interwebz.
Sorry didn’t read that your motor was an SR, without any information or numbers it could be a number of issues. could be MAF try unplugging it and see if it runs better (will run of default table stored in ECU), doubt it would be fuel related unless you are hesitating at higher RPMs. Possibly be a coil, try spraying it with soapy water to see if its cracked. yes most SR got rid of the air regulator (or auxilary air valve) so i if it doesn’t have one, I would have to agree with Jedi and say IACV is the most likely route I’d start here. Take it off and see if there is a lot of carbon built up inbehind it you can try cleaning it with throttle body cleaner but I’d recommend replacing it.
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In theory yes, but its winter time and expansion contraction of contacts and parts as well as it takes much longer for moisture to evaporate due to lower temperatures. In winter coils are more subject to fail especially if they are cracked. During the winter the crack gets larger when cold also added moisture sticking around boom starts arcing then heats up crack closes a bit due to expansion moisture dries up and misfire disappears.
Could still be the MAF, because the car relies heavily on the MAF to control injector pulse width when it is cold. Due to the o2 sensor(s) being in open loop. When it heats up o2 sensors take priority and could mask a MAF problem.
Yes it could still be the IACV because the component could not necessarily be not working but sticking in its bore (aluminum intake contracts when cold, add carbon buildup to that now the pintle on the IACV gets stuck) this causes improper AFR car doesn’t know what is happening sees too much fuel not enough air since the O2 sensors are not reading because they are in open loop uses other sensors to crudely adjust AFR you give it gas it hesitates because it takes a min for the ECU to adjust. once again everything expands the IACV starts working again/ O2 sensor starts reading and allows better control over fuel and boom seems like nothing wrong. I have been working as a technician for a while now and get new surprises every day seen a lot of weird stuff impossible to really know without car infront of me or unless I have some voltage/ scantool readings of components.
Air Regulators function is to control the amount of airflow coming into the manifold while the throttle plate is closed etc… which in turns goes to the IACV to maintain idle. Unfortunately though its more common to cause high idle situations vs low.
Quick test would be to check the resistant between pins which should be 75ohm.
For the IACV, flash the ECU for fault codes. IACV is #25
Long Flash - 0.6 seconds on (the first digit)
Short Flash - 0.3 seconds on (the second digit)
Long Gap - 2.1 seconds off (used between codes)
Short Gap - 0.9 seconds off (used between digits)
There are two digits in each code. Count the long flashes, then the short flashes (only count how many times the light is ON) and you’ll have a 2 digit code. These codes are covered in the service manual.
thnx for the info guys its a big help this morning i started the car up again and i realised when the engine was cold and it was idling rough there was air being released from the BOV :s, I got the BOV from a guy who said it was tuned so it doesnt make sense, and the wierd thing about it is that when the engine is warmed up the BOV is fully closed.
Also check your ignitor chip ground. The unit itself has to be grounded to the body. Its an issue with the ca engines. Sand down whatever part of the engine bay your ignitor is on put down some dyeelectric grease and try it out.