I have my stock 1.7 running pretty well lately with all the work I've put into it. Only one obstacle remains:

When the outside temperature is warm, the car runs well and is very smooth. But when the temp drops below 50 the car stumbles a bunch unless I really get on the throttle. To me, it feels like it runs too lean when its cold.

I've done the archival research, not many threads that address the outside temp as opposed to the engine temp.

What do you think? bad temperature sensor? vacuum leak amplified by cold weather?

Nobodys got anything for me??? car no likey cold temperatures...anyone anyone, bueller, bueller....

Some factors to consider for temperature dependent mixture:

AAR, is it working or lettingin too much air/not cclosing
Cold start valve, is it hoked up (although it is supposed to only work at like 35 degrees)

Not coming up woth anything else off the top of my head. But basically, if it is lean then something temperature dependant is leaning out the mixture.

Is this only on warm up or after it is already warmed up as well?

Thanks for the reply Dr. Evil, very helpful.

It seems to NOT be dependant on whether the engine is warmed up or cold, just the outside temperature. It runs better when its warmer, but the stumbling is still there.

Temp Sensor I (or is it II), the one in the plenum is the sensor for incoming air. Check the wire for that one as well as the sender itself.

Does the idle drop down as the car warms up? (AAR working?) I can't really come up with anything that would be outside temperature dependant. Is it at idle, or all across the rpm range? If just at idle, you could try turning the ECU one notch richer. This is a tricky one.

Good luck,

Don't ya just love summer? So much sun shine and FI problems

Well, gonna need to run some tests.
-Plug AAR and see what happens
-Check your MPS for leaks
-Check CHT fo propper range
-Look at spark pluggs, what do they tell you?
-Check spark
-Check cap, points, rotor, wires

Do easy first and post findings. This should whittle you down to a cause.

Concept:
Stumbling is gonna likely be fuel delivery or spark delivery. I am assuming your valves are correct as well as your timing. Fuel delivery can be skewed by air ingress (so you check your AAR, and vaccume lines) and by your electrical fuel metering (MPS, TPS, FI points, injectors).

Spark issues can be caused by plug wires, coil wires, points, condensor, rotor, cap, fouled pluggs adn a dizzy shaft with play in it. Oh ya, check your dizzy shaft, too.

Also, check grounds on your injectors (big lump of white wires going to connector thing on one of your case bolts.

So far I am assuming D-jet as well.

Ooo, thats a good one that I forgot. If you need one I have one in pristine condition I think.

This is great thanks guys. Here's some more info:


- Regardless of the outside temp, upon startup it acts like so:

1) Car fires right up, idles around ~1500rpm and runs pretty good
2) Then, it seems like the cold start goes off and its idles pretty low rough for the next couple minutes but still runs alright.
3) As it warms, the idle goes back up to normal (~1000) and when the engine is hot sometimes I adjust the idle slightly just so its dead on 1000.

So regardless of outside temperature, this pattern seems to stay constant: 1) runs good on startup 2) just after idles rough 3) as it warms idle returns to normal


Here's what I've done in the past month


- Fuel pressure checked its right where it needs to be
- Points replaced with pertonrix
- Most vacuum lines were replaced, but I need to clamp them all and see if that makes a difference.
- Yes its a stock D-Jet


So it sounds like the Temp Sensor I is the next thing to check....

On your 1,2,3 listing above this sounds like normal 1.7 Djet operation. Will idle slightly rough between AAR closing and before engine is up to temp. John

alright....so I stopped at the local auto store on the way home, picked up a ton of clamps and dropped them on the vacuum lines with reckless abandon. I clamped EVERYTHING DOWN!

Took her for drive in the crisp evening air and she was running like a top! I guess I should have done that first before posting but thanks a ton guys, you rule!



I'm going to post some nice pics I got in a separate thread