Idle Speed Cold VS Warm

[sobamaflyer]

I'm going to tinker with this today and have been pulling in all the searches I can but maybe someone can point me in the right direction while I work.

I recently got my car, 3.0 '78 CIS engine, to start and idle on the 3rd crank (without ever touching the gas pedal). This was monumental in that it had previously taken 10+ minutes of fussing to get her running. A lot of this, I think, was creating a new, good epoxy seal around the pop-off valve that kept popping off, and richening up the mixture that I think was causing said popping in violent fashion.

Now after the car is fully warmed up (5 min on the highway) the idle wants to hang at about 1800-2000, if I turn it down to 1000 and let the car sit for 20-30 min and go to drive it again the idle is 500rpm-stalling out till it gets fully warm again.

So, am I still chasing vacuum leaks, am I missing a simple obvious part of this dialing in equation, some of both?

Hints and ideas welcomed and appreciated.

[1982911SCTarga]

Do you have a CIS fuel pressure gauge set? Knowing the system pressure, cold control pressure and warm control pressure are key diagnostic steps in terms of start-up and driveability issues.

Brian

[Scott R]

That's pretty normal on an SC with an incorrect mixture and fuel pressures out of spec. You will just keep chasing that adjustment around trying to compensate. Do as sated above, get your pressures measured, and you're going to need to get a way to verify the mixture.

[sobamaflyer]

Sadly, no, not yet. But they are on the list.

Apparently Google's search engine, plugging in Pelican, is a lot better than the board's search. After I posted this morning I tried that and came up with several helpful threads.

As of this moment I've changed my oil and bypassed my Deceleration Valve and she's acting "normal" again. I realize I'm chasing my tail here a little without a set of pressure valves to pinpoint specific malfunctions but I was able to make it better with the info I found this morning.

Thanks again Pelican ......I know I'm dealing w/ nothing new as the best threads I found were from '03 and '07. What did folks do before the internet?

[1982911SCTarga]

What did folks do before the internet?

We went to PCA meetings to learn how to maintain our cars and read Panorama for its technical content.

Brian

[boyt911sc]

sobamaflyer,

It seems you are having so much problem with your CIS engine. The '78-'79 SC's are the easiest to troubleshoot compared to the later SC's with OXS. I don't know how much you know about CIS but they are simple and easy to understand. It's about fuel pressure and vacuum.

If I were in your shoes, I would do the following:
1). Get a fuel injection fuel pressure gauge kit. This is mandatory for FI troubleshooting. If you don't have one, don't bother at all. You are simply doing guesswork and would depend largely on LUCK.
2). Check your WUR's control pressures versus time (zero to 15 mins.) This will give you the baseline data for your WUR.
3). If you have tweaked or alter the mixture screw setting without verifying the absence of unmetered air, you have added another variable to the problem.
4). Test for air leak/vacuum leak in the system. Not being able to find any leak does not mean you don't have a leak. So how do you do it? Perform a pressure test (5-10 psi of air or nitrogen). The test will show you whether it is leaking or not!!!! NO gueswork allowed for this test.
5). Check ignition timing, sparks, and battery charge.

It is very easy to make a CIS engine start even after a prolong hiatus. Keep the parameters close to spec and it would fire and idle right away. A small vacuum leak would still allow the engine to start as long as the air leak is not very significant to dramatically alter the stoich 14:1 ratio and make the mixture too LEAN!!!!. keep us posted.

Tony

[sobamaflyer]

Thank you Tony, the gauges are my next priority as I know I'm just guessing right now. I really appreciate the help this board provides but understand you all are guessing as much as I am.

Problem/Good thing is this is my toy, not my daily driver and it runs (after I get it going) fairly well. As of yesterday it actually gets going without an act of congress. What I think you have seen in my history of posts is that I manage to address one issue and seems to lead to another one. I refuse to take it to a shop knowing that I "can" get this relatively simple system under control, and would rather have the knowledge out of it.

So for today, I'm off to town on a gorgeous fall day and hopefully I don't have a new "what's it doing now" post for tomorrow

[longhornchris04]

A few more tips for diagnosing...

1: Hard starting may be due to the accumulator not holding pressure. With fuel pressure gauges you would see this as the pressure will fall quickly on shutdown. A quick test without pressure gauges is to check the pressure on the air-flow plate after shutdown. If it the plate is 'free' then the system isn't holding pressure when off, and you need to check your accumulator and fuel pump check valve. IMPORTANT: If the plate does have resistance, don't hold it up for any length of time, as it will activate the injectors and flood your engine.

2: Unless its a warm day, 5min of highway probably isn't enough to get the system 'warm.' Assuming your WUR is working properly, 15min should be enough for the electrical heater to do its thing... if not then its a question of how quickly the engine heats the bi-metallic element.

3: An easy vacuum leak test is to remove the oil cap which creates a vacuum leak. Ideally this will cause the engine to change drop RPMs but not stall. If it doesn't then you probably have a more significant vacuum leak and have tuned around it.

Good luck.

[sobamaflyer]

Cool! 1 and 3 aren't problems I have then The plate does have a bit of pressure and the idle definately drops when I take the oil cap off.

I live in S. Alabama, "Warm" may be relative term here

....Happy to report I just came back from a 40 mile round trip of mixed highway, traffic and back roads. Glenda was a perfect lady all afternoon. Seems the Decel Valve is the culprit and multiple posts indicate my car can live without it....we shall see but for now it's capped off.

Gratuitous afternoon pic completely unrelated to the topic (except maybe she was idling nicely at 1k rpm at the time?!)

[longhornchris04]

I've lived all over the county... and warm certainly is relative. Its currently 'warm' for Ohio, a year ago I would have said cold (Los Angeles), and 6 years ago DAMNED COLD (Texas).

Oh, and she's pretty, but missing her hood crest.

You can try lowering the idle bypass a bit once warm and see how she behaves the next day (when cold). Just remember how far you adjusted it in case you have to undo the adjustment. You shouldn't have to adjust the 3mm to change the enrichment, just close off the bypass slightly.

Of course if she's behaving herself, then idling 200rpm high shouldn't hurt anything except perhaps your city fuel economy.

[sobamaflyer]

Originally Posted by longhornchris04

Oh, and she's pretty, but missing her hood crest.

Thanks she's missing much more than a hood crest if you start studying hard but seems those all need to be after the pressure guages on the wish list

[longhornchris04]

Oh, another item for your wish list (if it isn't on there already) is the front lip spoiler.

When I got my 911, it had the tail but no front spoiler - handled like a dream below 60, but started to get skiddish above that, especially on LA's segmented concrete freeways. 90mph was... entertaining. Anyway, lip spoiler helped plant the front end, and the car is much more composed at speed, even in heavy cross winds.

Only downside is the ground clearance isn't as good... well worth the price if you ask me.

[sobamaflyer]

It is. I've found just what you report. I found a full tank of gas helps, empty and above 80 seems a little squirrelly. I'm also in need of a decklid upper latch and it's disturbing to watch the tail flutter just a little at very high speeds. I can't imagine that it is possible for it to come up between the weight and aero pressure but?

Is it normal to be pulling close to 4k rpm at those speeds in 5th or do I have a modified transmission?

[longhornchris04]

At the 65mph speed limit I'm around 3k, if I push it up then I'm around 4k at 90. Unfortunately every road in Ohio is 65mph or lower, the state troopers are everywhere, and a bright red car sticks out.

As much as LA traffic sucked, the road were surprisingly empty at certain times and I almost never saw a cop.

[boyt911sc]

Originally Posted by sobamaflyer

Thank you Tony, the gauges are my next priority as I know I'm just guessing right now. I really appreciate the help this board provides but understand you all are guessing as much as I am.Problem/Good thing is this is my toy, not my daily driver and it runs (after I get it going) fairly well. As of yesterday it actually gets going without an act of congress. What I think you have seen in my history of posts is that I manage to address one issue and seems to lead to another one. I refuse to take it to a shop knowing that I "can" get this relatively simple system under control, and would rather have the knowledge out of it.

So for today, I'm off to town on a gorgeous fall day and hopefully I don't have a new "what's it doing now" post for tomorrow

sobamayer,

Obviously, the reason you posted this thread was that you needed some sort of help and guidance to find or solve your problem. We all do that!!!!! The readers are trying to guide you identify the situation you have now. To proclaim that these guys are just doing queswork just like what you are doing simply shows the arrogance in you!!!!

CIS troubleshooting is simple and fun!!!! It becomes tedious and difficult because you don't know how to do it or have limited knowledge of the subject. If you don't know it then comes the guessing game that involves luck. Would you bring your car to a mechanic that depends of on luck to fix your car?

Every symptoms of your problem/s could be tested and verified without guessing. In your case, you have cold starting problem. Ask yourself what could possibly affect it? There is a big difference between doing a systematic analysis of the problem and working hard!!!! Good luck.

Tony

[sobamaflyer]

Wow?! I'd like to think I willingly assert that I know relatively little which is why I ask for possible things to check, not sure how that came across to you as arrogance? I'm going to assume you woke up on the wrong side of the bed, mis-understood my statements, saw a drop in your 401k, something....

I accept that I don't have Gauges to test components at this moment and that adds a huge variable to getting any "real" help. I actually purchased a set from somewhere and after a month of backordered status I cancelled it.

If anything maybe I misspoke or you mistook my intentions, but my indicating fellow Pelicanites were performing guesswork was because I cannot provide quantifiable data that would lead to better suggestions (and I think I mentioned this several times?). What I did find in searching through outside search engines were several instances of symptoms similar to my own with suggestions as to what to check, which I did, and which helped......that was what I was looking for yesterday morning.

[boyt911sc]

obamaflyer,

Please accept my sincere apology!!!! I re-read your post several times and it still come clear to me differently. My sole intention in sharing my limited experience with CIS troubleshooting is to reduce to minimum the guesswork!!!!! I've driven more than 200 miles to help fellow members in their CIS for free and would be willing to do it again.

Where are you located in MD? PM me it you need some assitance. I'll be more than happy to drive over and show you the rope. Soda and snacks would be sufficient. Have you heard about grumpy old men?

Tony

[sobamaflyer]

Tony, your (and everyone's) help is always very appreciated I promise. The last thing I ever want to come across is arrogant or ungrateful because nothing is farther from the truth! I know just enough to be dangerous about a lot of things but this is the first time I've ever tinkered with any kind of FI and am happy to admit it up front.

I wish I could take you up on your offer, I'd happily pay for the gas AND snacks but I live in S. Alabama and I think that'd be quite a haul for you . I plan to take your advice order a[nother] set of pressure gauges so the next time my car starts acting up I can report back with true data when I ask for help.

Just for the record it's entirely possible it was me that got up on the wrong side of the bed this morning and got defensive.......

[boyt911sc]

Sobamaflyer,

I have mistakenly identified you for the guy next door from Maryland!!!! You have an early SC and they very easy to troubleshoot. The picture below is a running '78 SC motor (like yours) on a homemade engine test stand. Notice the CIS fuel pressure gauge attached?



When you get the pressure gauge kit, practice measuring the fuel pressures without running the engine. Familiar with that procedure? Get us the numbers and we'll start from there.

Tony

[sobamaflyer]

Originally Posted by boyt911sc

Sobamaflyer,
When you get the pressure gauge kit, practice measuring the fuel pressures without running the engine. Familiar with that procedure? Get us the numbers and we'll start from there.

Tony

Thank you! And I will definitely take you up on that.

Cool open air engine bay, that would make it a whole lot easier to work on