i need some CIS help. starting to give up :(
 

ok, first off, i have checked my CIS pressures. they are all perfectly within spec

cold: 31psi @ 65 degrees
system; 69psi
warm; 53psi
and the system holds at rest pressure for one hour @22psi
(at this point i removed the gauge and buttoned everything up)
PO installed MSD and all the acoutrements with it.

car runs fine, starts great when cold BUT, when it is warm, it starts up perfectly fine, but it chugs and chugs at around 300-500 rpm. sometimes if i try to feather the gas, it does baby pops in the airbox. eventually, the revs come up, and i can motor away happily. i gotta get this fixed. AXing with all the hots starts can get annoying, and embarrassing. i thought it may be my accumulator, or check valve, but doesnt the good "at rest" pressure eliminate this? i am stumped.

cliff
PO did a tune up one year ago.

maybe ignition related.

Fuel accumulator issues are typically when the car is hot and the car will not start. Does your exhaust smell like fuel? Have you tried removing/replacing the relay under the pass seat? Do you have another CD box you can test with? Sounds like a fun one....good luck!!

-B

Just a thought,

This is purely speculation, but maybe your injector seals are leaking air. If the seals are leaking more with the engine warm, it would cause a lean mixture at high vacuum pressures at idle.

Sounds like an accumilator.

AFJuvat

yea, i was gonna toss in a new accumulator and check valve because they are both relatively cheap and easy to install. but i dont want to start chasing this with new parts. that could kill me, at least my wallet. still, the good residual pressure should eliminate these two items.

john, i considered a leaking injector, but maybe a seal is more probable. thanks.

Vash,

Have you checked the operation of your AAR?

I am also wondering if your cold start valve is leaking.

Have you checked for smooth movement of the sensor plate?

Be careful of those baby pops Cliff. That's how mine started and look at what I'm doing now!!!! I was lean and my wallet is angry.

Just last weekend, I replaced my fuel pump and accumulator and had the same problem. I then dicked around with the mixture and idle screw settings with only minor improvements.

I checked my point settings and they were way out. I reset the gap to .012" and it ran and started way better. Then I reset my mixture and idle screw and now it runs better than it ever did since I bought the car. The warm idle is still a little bit rough (missing on 1 cylinder) so I think I may have one bad injector.

Have you checked things like the temp switch, throttle position switch, and frequency valve?

Could be ignition but that would not be my first choice.
I agree your tests rule out typical warm start problems (check valve, accumulator, etc).
From your description is sounds like when you start it warm the mixture is way off. Popping through the intake usually means lean, but I'm not sure in this case.
As previously stated, vacuum leaks are the first and obvious possibility. Then I would look at your cold start injector, AAV, and thermovalve.
If the fuel injection thinks the engine is cold when it is actually warm, it would add too much fuel.
When an engine is started hot, the air is not as dense, which usually makes it run a little richer than if it was started cold. If the mixture is already too rich, that would make it worse.
The next time you start it hot and it stumbles, pull the air cleaner off and carefully lift the air sensor plate a little bit. That will basically add more fuel without adding more air.
If the idle gets better, you are too lean. If it gets worse or dies, it is already too rich.
If it's too rich you need to figure out why and correct it.
If the cold start injector leaks, you could compensate a little with the mixture adjustment which would work OK when cold but not when warm.

I have the same problem, when i first start the car, usually when it is cold, it will idle low, 500 or so, and the usually within a few seconds come right up to speed. If i give it any gas, it will pop and usually die. I just let it do its thing and not touch throttle and it works fine. I have a 83 CIS motor which i modified the CIS to remove the Lambda in a 78 though.

I suppose you could pull the injectors, have them cleaned and tested, then replace with new seals.

Even if all of the pressures are correct it may be possible that the injector(s) are bleeding down pressure in the lines between the fuel distributor to the injector itself.

When you go to restart the engine at a warm temp (meaning without the cold start valve functioning) one or more injector line is repriming itself and maybe causing your symptoms.

Just a theory, YMMV. Good luck.

Cliff, if you need to drop the motor, lemme know. After next weekend I'll be an expert! ;)

Check the AAV its easy, first check for voltage with the car running then pull it and run 12 volts to it and see if it closes all the way. Easy to check for vacuum leaks with the carb spray method, I assume you did that. I think that will work on Injector seals too.

Oh check the diaphragm on the decel valve if you have not. its easy too.

if i recall correctly, another quick check is to simply remove the oil filler cap while running..it will let a lot of air into the sytem and should kill the engine, but if it's running extremely RICH, it probably won't die. anyone else recall the details of this check?
ryan

No, it should stumble a little when you remove the cap, but not die. That's because of the whatchamacallit in the soft oil line that reduces the flow.

If it stumbles and pops and then dies when you give it more gas (air actually) -- it sounds lean. While it's stumbling and popping can you pull down on your throttle plate and see if it picks up.

vash,

I had the same problem with my 81 SC, with the symptoms you describe on your original post.

The problem was a fuel leak on one of the metal fuel lines that ultimately connects to the fuel accumulator. It wasn't apparent to me, however, until I replaced the fuel accumulator and filter.

Since your problem is prominent during warm/hot starts, I would strongly suggest you change your accumulator and filter (especially if you think they are old components anyway), as you had originally intended to do based on the relatively low cost of replacement vs. other more expensive fixes. This is based on the simple fact that the accumulator plays a key role in fuel pressure during warm starts.

From what I have researched, messing with the fuel mixture is somewhat delicate, and should probably best be left to expert.

Again, this is just my $.02 and is based on my personal experience with this issue.

Good Luck.

J L