Its starting to get warm in so cali and i am noticing that my car is starting to run like crap!

Once I get off the freeway, the car act as if it wants to cut off. It idles really low, and doesnt accelerate properly.

The car is a 73 1.7 Fuel Injection - stock. It runs fine when it is cold. This happens even when I dont drive the car hard.

Becoming quite frustrating. Once I cut the car off, it becomes hard to start.

Any recommendations?

Cylinder head temp sensor sounds suspect. Take an ohm reading with the neg at theground battery terminal, the positive on the cht. Souild read less than 100 ohms fully warmed up

Hum.. vapor lock ?? Just thinking out loud.

I have NEVER had a car vapor lock on me.. but it sounds about right.

B

What is vapor lock? Sounds like something out of a star trek movie.......

It is when the fuel becomes vapor (from heat) and cannot flow as a liquid. In Texas I used to run the fuel pressure around 29-30 PSI to help allieviate this problem. You may want to check your fuel pressure.

B

Im with Chris! Check the CHT!!! I just went through this with my car and the fix was the pot & resistor trick. Now it runs like a champ.

It sucks. I have a car that is running like crap cold..but runs great when warmed up (wifes car) The CHT measures within spec.

Anybody have the factory resistor they can sell me ??

B

I have an extra CHT for a 73 2.0, if thats what you mean. I believe it is the ...017

Nope. The 73 2.0's had/have a 300ohm resister in line with the CHT. I need one. I could do the whole measurement thing, but her car is bone ass stock and runs like a Swiss Watch (except when cold) so.. a stock part would be better than me going to Radio Shack for resistors.


B

Is it really as easy as a 300 ohm resister from Radio Shack? My 73 has the ECU that (according to PBAnders' D-Jet site) requires the resister inline with the CHT. I don't know which CHT I've got, but I know that it doesn't have a resister. Somehow I had the impression the a "ballast resister" was a little more complicated. My car seems to be running fine, but I'd like to know that it truly is "right".

To get things "correct" you need to know which CHT you have. One of them needs to have the 300ohm resistor and the other "supposedly" doenst need one. Porsche lists 2 part numbers. One for 73 2.0 and one for 74-76 2.0


B

Actually, it a 270 ohm resistor. Go to radio shack and get a resistor for $1, shrink wrap it and your are good to go. Of course, I spent $30 on the factory Wehrle resistor

I swear.. I dont know where I got 300. I told Mueller last night I thought it was 300 or 350. Maybe I'm thinking of actual head temps (300-350)

B

Is there a readable part # on the HTC so you can tell which one you have once you've removed it from the package?

Ernie,
The CHT you want has the last 3 digits of 017.You can kinda peek your head in theengine compartment and see the numbers, if your rubber gromet for the CHT is missing. Otherwise you need to take the CHT out to see. That is for the 1973 2.0L D-jet. You also want the Werhle (spelling might not be right) 270 ohm resistor. A radio shack one works fine, but you need to protect it with shrink wrap or something. I just bought the Werhle because I didnt want to mess with it.

To answer your question, yes, the part number is on the CHT.

I got a few of the resistors from RadioCrap.....a 200 and a 100 and then a bunch of 20s.....kept adding until it was where I wanted it....

so this pretty much sums it up huh-

the cylinder head temperature. I will go to Pelican tomorrow and pick one up.

Thanks.

hey NE14914,
are you going to the pomona swap this sun?

Mike that is why for the potentiometer! Once installed you can *dial* it in.

A 1.7L doesn't need a ballast resistor only the 73 2.0L.
If the car is running great cold and runs like crap warm I think its running rich. Check the plugs for a reading to see. Your MPS could be starting to leak due to cracks, as it warms up it goes richer. Put a vacuum gauge on to see if it holds a 15hg vacuum for 5 minutes. If it slowly leaks down its going, if it drops like a rock its toast.
Geoff

Wait, wouldn't it be leaner if it got hot?

Yes Ill Be there - Hope you get this thread. I have a limesh Green Teener.

Will be looking for you guys ....

If the MPS is starting to go the "loss" of vacuum is read to go richer.
High vacuum is 15hg which you have at idle, that vacuum pulls the diaphram against the idle stop.
No vacuum is at Wot and that read as full rich.
So loss of vacuum makes the MPS read richer...
Car is cold when starting up and needs the mix to be richer then it get hot and the mix should be leaner.
Geoff