IDLE ISSUES - PLEASE HELP!!

ptravnic · 07-09-2001, 08:25 AM

I know there is lots of postings on this topic, I've read them and they have helped out greatly. But, I'm still having issues.

I've done a good deal of problem solving - here's the steps my father and I have taken: new plugs, new points/condensor/rotor, timed correct (although I'd be willing to pay a solid mechanic to double check the timing), all new vacuum hoses, new decel valve, new temp sensor 2 (it was bad), good cold start valve (wire was shorted but is now operating correct), thoroughly cleaned throttle box, new intake hoses & clamps (connects pipes to the air box), and welded the plenum (air box under air filter). Have used propane to test for leaks and am unable to find any. Have purchase a new diaphram (clamps onto the side of the distributor) - havn't yet installed it. The only things left to check or swap would be the pressure sensor (which I have yet to find a test for - although the ohms can be checked on the wiring), brain was swapped a couple years ago by a mechanic that I now believe didn't know what he was doing.

Now the symptoms my baby is having: Runs a very high idle when cold (1800-2200 RPM's). It does settle down to but does not stay at a steadyrate. Runs great on the highway - very responsive (as responsive as a 1.7L gets) but when I get off the highway I get a very low idle and oftenstalls. It seems that no matter how much I adjust the idle screw it still stalls when hot. I'm purchasing a new FI off a 73 from a guy inMichigan for $70 (bargain) but I fear that I will have the same problems even after I start swapping parts.

This thing is driving me crazy!!

bowlsby · 07-09-2001, 09:35 AM

Weird set of problems.

Variable idle usually means some sort of intake air leak or essentially a mixture problem. Checked all intake system hoses for leaks including the aux air regulator for proper operation? I suppose it might also be a small leak in the CSV or injectors, but that may not explain the low idle/dying.

Confirm the accuracy of dwell and advance settings, if you have a timing light and dwell meter. If not, get them.

The ECU and all FI system components should be confirmed as being the correct ones for your car.

Check here:

http://members.rennlist.com/pbanders/djetparts.htm

The MPS can be checked electrically (check for shorts to ground as well as proper coil resistance value), and pneumatically. Just use a vacuum gauge on the vacuum intake port and see if it will sustain a 15 inches vacuum. If it doesn't hold vacuum, or leaks down its bad, if it steadily holds 15 inches it should be fine.

Is the epoxy plug stil on the other end of the MPS or has it been drilled through? If its been tampered with, it may have been misadjusted. There is more information on one of the linked pages to the referenced website to help readjust it.

pbanders · pbanders's Garage

Quote:

Originally posted by ptravnic:
I know there is lots of postings on this topic, I've read them and they have helped out greatly. But, I'm still having issues.

I've done a good deal of problem solving - here's the steps my father and I have taken: new plugs, new points/condensor/rotor, timed correct (although I'd be willing to pay a solid mechanic to double check the timing), all new vacuum hoses, new decel valve, new temp sensor 2 (it was bad), good cold start valve (wire was shorted but is now operating correct), thoroughly cleaned throttle box, new intake hoses & clamps (connects pipes to the air box), and welded the plenum (air box under air filter). Have used propane to test for leaks and am unable to find any. Have purchase a new diaphram (clamps onto the side of the distributor) - havn't yet installed it. The only things left to check or swap would be the pressure sensor (which I have yet to find a test for - although the ohms can be checked on the wiring), brain was swapped a couple years ago by a mechanic that I now believe didn't know what he was doing.

Now the symptoms my baby is having: Runs a very high idle when cold (1800-2200 RPM's). It does settle down to but does not stay at a steadyrate. Runs great on the highway - very responsive (as responsive as a 1.7L gets) but when I get off the highway I get a very low idle and oftenstalls. It seems that no matter how much I adjust the idle screw it still stalls when hot. I'm purchasing a new FI off a 73 from a guy inMichigan for $70 (bargain) but I fear that I will have the same problems even after I start swapping parts.

This thing is driving me crazy!!

You've done a lot of good diagnostic work. I think Jeff's suggestion to verify the parts are correct using my web page is a good idea.

The usual cause of low idle and stalling when hot is that the idle mixture is too rich. What position is your ECU knob at? There is a little mark on the plastic surround, that is the "factory" position. How many clicks to the right or left of that position are you set at? Left is leaner, right is richer.

Brad Anders

John Rogers · 07-09-2001, 01:36 PM

Do you have the vacuum retard/advance ports on the distributor hooked up correctly? At idle the throttle connection with the vacuum should be pulling the distributor in the retard direction and the other one attached to the advance side of the vacuum pot.

Jim Smolka · 07-09-2001, 04:49 PM

Have you tested your auxilary air valve???
When the car is warm, you should be able to remove the inlet hose to the aux valve and no air should flow through.

JP Noonan · 07-09-2001, 08:15 PM

Also check the CHT sensor. If nothing else disconnect the wire from the CHT (and any in-line resistor, they go bad too) and ground the wire to see if it helps once the motor is warm.

Roland Kunz · 07-10-2001, 07:33 AM

Hello

You mentioned a new NTC I assume the one on the head. Now it is very important to check the NTC if it fits to the ECU. I think you will find the chart on upper pages and just check with the ordernumber in your billing.

Grüsse

ptravnic · 07-13-2001, 09:51 AM

great feedback, couple of follow up q's:

bowlsby - what is the CSV? probably should know what this atands for but... Also, I've checked the injectors, in fact I've got a spare set on a 71 1.7L I could swap. Plan on going through the test in Kjell Nelin's outline but won't be able to do that until next weekend (life sometimes gets in the way of 914 tinkering). Believe I have the timing correct but would like a professional to confirm - I'm willing to pay a couple dollars for this (any takers in the NYC area?).

pbanders: I'm diggin' the reference page you've set up. I had the ECU changed a few years ago - hopefully the replacement is correct - your reference page will help there... its tought to print though, i had to copy the page into word format (b/c the text in the web print out is light gray which is tought to read off a white page) but then the columns don't match up correctly - I will still be able to use it though. You mention the hot idle running rich if the knob on the ECU is mal-adjusted. This running rich idea may hold some water - the plugs are new (within a month) and the tips are black in color - is this a sign of running rich? Maybe the ECU knob is causing my problems? Most likely a mix of problems - I say this b/c each time I've found and fixed a problem another one is discovered. Eventually these gremlins are gonna all get scared away!!

john rogers: the vacuum retard/advance may be faulty - i bought a used one (known to be good) an will swap it this weekend. The hoses on the current are hooked up in the correct direction - my q is what would the symptoms be of a bum vacuum r/a

Jim S: I've debugged/cleaned the aux air valve but I'm beginning to question the cold start valve (5th injector). The car does idle down when it gets warm but I wonder if the 5th injector might get fussy when it runs hot for an extended period. Is this possible?

JP Noonan: what is the CHT sensor? - another vocab term I should know but don't (yet)...

Roland - I will make sure the Temps Sensor 2 is the correct fit for the ECU - figured on using Paul Anders pbanders) page for this reference.

ABOVE ALL, THANK YOU ALL FOR HELPING OUT A STRANGER - I HOPE TO SOMEDAY RETURN THE FAVOR.

Pete

bowlsby · 07-13-2001, 10:01 AM

CSV = Cold Start Valve
CHT = Cylinder Heat Temperature Sensor or TS2
TPS = Throttle Position Sensor
MPS = Manifold Prossure Sensor
ECU = Engine Control Unit (brain)
TS1 = Air temp sensor on air distibutor
TTS = Thermotime Switch

Sorry for the confusing lingo, we get too carried away sometimes

Black sooty plugs means the mixture is too rich.

I am able to print Pauls page easily by printing it straight off the Internet Explorer browser by using landscape mode. No shaded background.

Good Luck!

pbanders · pbanders's Garage

Some browsers have an option for "black and white" printing. Sorry the page design causes these problems, I'll look into possibly changing it in the future.

Brad Anders

ptravnic · 07-13-2001, 12:19 PM

thanks for the printer info - used IE and it printed out nice and pretty

pt

Dave at Pelican Parts · Dave at Pelican Parts's Garage

I've been staying out of this one because it sounds like you're getting all of the right advice and checking the right kinds of things.

The black spark plugs are a sign of rich running. Most especially, rich running in whatever load/RPM/heat regime the car was running at when you turned the engine off. Most likely, warm idle.

In general, you get the engine to run in a certain state for a few minutes (up to ~5), then you turn the engine off without letting it change state, pull the plugs and check the colors of the deposits. Black and sooty == too rich, grey/white == too lean, tan/brown == good. You can check the mixture at higher RPMs and loads than idle, but you have to be willing to shut the engine down without letting it come back to idle first. This means coasting to the side of the road.

I've done that once as a "sanity check" to make sure my air:fuel gauge was reading something near correct. It was.

--DD

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Pelican Parts 914 Tech Support

A few pics of my car: http://www.pelicanparts.com/gallery/Dave_Darling

Roland Kunz · 07-13-2001, 07:24 PM

Hello

I just have a feeling.

The ECU was changed to a newer unit ( with set crew on top ) but the head got the NTC from the early units. This will rich up mixture.

A way to simple test is to lower the pressure from 2,0 to maybe 1,5 bar to lean down.

Renewing the NTC is a task I allways pushed to the last. If it turned wrong it could make your day very long.

Grüsse

ptravnic · 07-14-2001, 02:15 PM

The parts combination on the car is correct, the brain matches the engine, pressure sensor, etc. Is Dave's way of checking rich/lean running the only method? Are new plugs required (for Dave's method) or can I just clean up the old (month old) plugs and do trial and error?

Thanks for all the good advice, the light @ the end of the tunnel is nearing.

pt

Dave at Pelican Parts · Dave at Pelican Parts's Garage

New plugs are not required. Just run them for a bit and see what color they are.

--DD

------------------
Pelican Parts 914 Tech Support

A few pics of my car: http://www.pelicanparts.com/gallery/Dave_Darling