Hi all, I'm wondering if any one could help me with a problem I have. When either cold or hot my engine runs at 1600RPM. I have looked for any air leaks, all the hoses are new. The only things I can find are the following - After removing the throttle body I noticed the surface the gaskets sits on is uneven due to powder coating so I sanded this area back to bare metal and it is a lot flatter, this had no effect on the RPM. When the engine is cold I can block of the air hose going to the cold running injector and the revs come down to about 1200RPM, as the engine gets warm the cold running injector stops operating as it should. The air intake valve on the side of the throttle body is wound fully in but the valve does not appear to seat properly, when I hold it up to the light I can see gaps both side of the valve, is this normal?
The other thing I noticed when holding the throttle body up to the light was the butterfly valve in the throttle body has gaps around most of the sides of it when closed, is this normal or is this an indication of wear?
In the butterfly valve is a hole approx. 3mm. When I block this off the revs come back to 1100RPM which is getting closer to what it should be.
Any one have any thoughts on this please?
Thanks Steve

Appears you have a vacuum leak somewhere, its typically indicated by high idle.

Those things you mentioned may be contributing. Is your AAR functioning properly?

Couple ways to check:

Spray carb cleaner at possible leaks and see what happens to the RPM, or put a blower in the exhaust pipe (engine off) and put soapy water on possible leak sites.

Thanks Jeff I will go and try the carb cleaner and check the AAR. I will report back with findings.
Steve

Had same problem with the 2.0 liter

Turned out the TPS wasn't tight and had vibrated a depression in the rubber membrane/gasket that sealed it to the intake manifold.

Had to replace the gasket and tighten down the TPS, ran like a Top!

Thanks for that, pardon my ignorance but what is the TPS?
Cheers

Throttle Position Switch

Throttle Position Switch/Sensor.

It's also a very boring report...


https://www.youtube.com/watch?v=Fy3rjQGc6lA

To there is no rubber gasket on a 2.0. There is on the 1.7 and 1.8 but the tps won't rub against it. The tps does not mount to the intake manifold. It mounts to the throttle body which mounts to the plenum. Pure bs.

I think he was referring to the throttle body itself, which has a gasket between it and the air plenum. Not a common leak point, but could happen if the throttle body is not torqued down.

There is no gasket between the TPS and the throttle body.

I don.t know if you are running the stock distributor or not...I had a similar issue and it turned out to be the diaphram in the vacuum advance pot on the dizzy.

Also I would check the advance plate on the dizzy to make sure it isn.t sticking.

My point exactly. He doesn't know a tps from a throttle body from a plenum from an intake manifold from his ass. Yet he spouts crap out the wrong body opening.

Great point. The advance weights need 1 drop of 30 wt annually to keep them lubed...when they hang up they can cause rough running. Not sure about a high idle.

Thanks for the input, TPS seems OK from what I can work out. AAR seems to be Ok as its working when the engine is cold and as it warms up it starts to turn off. I will check the dizzy, it is the stock unit, will also check the vacuum advance, what's the best way to check vacuum advance, by removing the vacuum hose going to the dizzy?
Found a vacuum leak around the throttle body/plenum gasket due to uneven powder coating on the plenum surface and the cold running injector gaskets missing so put gasket RTV on, still leaking some were will keep looking.
Thanks

I looked through your thread but couldn't tell if you have DJET or LJET. I'll assume you have DJET.

Have you tried the carb cleaner method to find the leak? Spray everything especially interfaces between manifold and head, all lengths of hoses as they may be split anywhere along their length.

High idle for DJET is caused by vacuum leak. The vacuum advance can only cause high idle if it is leaking. Same with the MPS (manifold pressure sensor). Check MPS and vacuum advance with a vacuum pump.

I used a brake bleeder vacuum pump sold at Harbor Freight. Tested all vacuum holding components on my DJET FI. My MPS had a massive leak. Vacuum advance on the dizzy also had a big leak.

HF Brake Bleeder

If you don't have access to a vacuum pump, use a human vacuum pump. Worst case, put a hose on the MPS and vacuum advance and suck on the hose. Once you create a vacuum, put your tongue on the hose. The unit should hold vacuum.

2L is Djet. I wouldn't suspect the MPS because a leak there would cause it to run rich, not fast.

You can also take an unlit propane torch and probe around. When you hit source of leak there will be a drop in idle. It may not be a huge drop but you should notice it.

If you can get hold of an evap smoke machine that is a great way to hunt down leaks.

The TPS can be mis-adjusted and prevent the throttle (butter fly) from closing all the way. It holds it open a little which of cource creats a high idle.

Check the adjustment, if you have not already.

I have seen the distributor advance stuck advanced and cause a high idle.
Many people forget to lube the distributor advance as part of maintenance.

Jim

Yep


Quick way to check is use the aforementioned HF pump...take the dizzy cap off and pull vacuum on the advance pot and them the retard pot if you have one. See if the advance plate moves fully and that tje diaphram will hold vacuum. Best way to clean and lube the dizzy is to take it out of the car. IMH experience.

...there is a small ball bearing under the plate IIRC.

Good luck.

10-4,

that was the reference.

Thanks every one it will take me a couple of days to look into these suggestions. I will start with purchasing a vacuum pump then check the dizzy.
Cheers

Like others have said, tps and mps won't make it idle higher. Vacuum leak will

Over-advanced timing will also make the idle faster as well. That and vacuum leaks are the two main causes in D-jet cars.

One odd leak I have had (and others as well)--there are two supports inside the manifold. They're tubes going from the top to the bottom surface, inside the chamber. They can crack where they join up with the top or bottom of the manifold, which results in a leak.

--DD

No need to use a vacuum pump,put a long piece of hose on there suck on it and check the movement on the advance plate,it you block the hose it should stay put,release suction it should snap but to rest,if the movement of the advance plate is sluggish the dizzy needs to be cleaned or you may free it up by turning the rotor back and forward and use a little lube.
Put the lube down the top of the shaft after removing the rotor.
These later aircooled distributors such as yours have a real habit of sticking up on the advance plate ask me how I know....I used to overhaul them.
Is this the car you had imported to NZ that Mc Mark restored??,seem to remember that.
Good luck from a fellow kiwi
P.S. make sure your timing is spot on.

I'm curious why the MPS couldn't make the idle higher. When I re-installed the FI on my engine, the MPS wouldn't hold vacuum at all. Thus a huge vacuum leak.

Does it matter where the air is getting in?

If the MPS is leaking, yes the engine would likely run richer. If air is getting in as well there is more air and more fuel = ???

When the mps diaphragm fails it goes full rich. With no extra air it floods with fuel. If your vacuum hose is leaking you get extra air and a higher idle. Kinda like the aar. A controlled vacuum leak. I could be wrong (done that once or twice) but that is my experience.