When she's cold she runs real rough!

P-DUB · 10-18-2006, 02:10 PM

OK, the never ending Battle with my car! Here we go, 73 FI 2.0. Just put in a new temp sensor and a used brain. It coughs, chokes ans stutters when under acceleration when cold. Idles about 2K. When warm, it quits, and idles about 1k. It takes 4 - 5 minutes to get to the point where it is not embarrassing to drive. At least it's drivable and i don't smell like a Texaco! Any ideas on the coughing and choking when starting cold? Clear up when warm and runs like a champ!

hardflex · 10-19-2006, 06:12 AM

do you have the ballast resistor in line with the CHT sensor?

P-DUB · 10-19-2006, 06:23 AM

I am not sure. How do i check? For the most part I have been having a mechanic work on it, but i am about done with that. Too costly, and still not getting anywhere.

hardflex · 10-19-2006, 07:06 AM

i think it's inserted between the CHT sensor and the wiring harness connection. It's just a resistor, the increased resistance would make the car richer thruout the temp range, but the effect would be greatest at startup. The Temp sensor that goes with that setup is getting harder to find, I think, so mismatches could have occured somewhere. Before the Net and all the knowledge it made available, It bought a resistor at Radio Shack, put a couple of crimp on connectors, and inserted it.

That setup was in use in the early 2.0's, I'm not sure if your car had it or not. There's another thread going along similar lines you should read too. PBanders page has a lot of good reading, and you can compare part no's to see that they are all correct.
Check the MPS # too, since they're expensive and hard to find, it could have been replaced by one from a VW or something, although if it runs good when warm it's probably near to right.

P-DUB · 10-19-2006, 07:16 AM

Thanks for the help, I will continue (my so far) never ending battle!

hardflex · 10-19-2006, 07:21 AM

When you say "i don't smell like Texaco" that sounds too rich... is it belching black smoke too?

P-DUB · 10-19-2006, 03:09 PM

No, I was referring to my gas cap/fuel line problem i just got fixed. No smoke at all. It runs great when warmed up, idles about 1500? I need to work on that, and it runs like dog chit when it's cold. I will put my new vacuum lines on when then get here, and then go to something else if that doesn't fix the problem. I am thinking it's the CHT. Just had a new one installed, now it doesn't work at all (never registers the car getting warm)? If i new where it was, i might try taking it out and replacing it or?

hardflex · 10-19-2006, 03:15 PM

you can check them with an ohmeter.... check it cold, then as it warms up too... it's screwed into the head on the right side under the battery between the spark plugs. look for a wire going in right there.

P-DUB · 10-19-2006, 04:02 PM

Does this require the extension with the corner ground off and the deep socket trick?

hardflex · 10-20-2006, 06:08 AM

to remove the CHT, you need the extension ground off. But you can measure the resistance with the CHT still on by just touching the wire with one Ohmeter probe and a ground with the other.

P-DUB · 10-20-2006, 07:10 AM

I will see what I can do. i think I found it. Is there supposed to be a rubber grommet in the hole and then the wire goes through the grommet? If so, the grommet is there, but has slipped out of the hole and hanging on the wire!

hardflex · 10-20-2006, 09:06 AM

yeah, the grommet just seals the cyl. tin for max cooling

Bleyseng · Bleyseng's Garage

You need the 017 CHT witha 270 OHM resistor for the 73 if it still has the 037 ECU and a 037MPS. Look at the numbers on all the parts as a 73.2.0 is a one year deal and usually is not all the right parts which causes problems like this.

Geoff

hardflex · 10-20-2006, 10:58 AM

Geoff's got it. On the bright side, I believe this setup was sold by Auto Atlanta as a "high performance" max power FI setup.

P-DUB · 10-20-2006, 11:08 AM

I am not too worried about max power right now, i would be happy with a little power when it's cold. Some times it idles right other times it idles high, and i am still thinking vacuum hoses. i got them yesterday, and that was going to be my date night tonight to see if that helps. Any other ideas?

1. cold start, starts, then dies.
2. restarts, starts and idles rough until you give it the slightest amount of gas, and then revs high (probably normal for being cold).
3. warms up and runs good, sometimes it idles where it should with the occasional dip down to nothing, other times it idles about 15K.

Should I trade it in for a Cayman or try to work on it myself?

hardflex · 10-20-2006, 11:58 AM

go to this page, scroll about 2/3 to 3/4 way down, and read about CHT and Ballast Resistor.

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

Thank you again, PBanders, for that resource!!!

P-DUB · 10-20-2006, 12:21 PM

Now we are getting somewhere. My mechanic told me he put in a new temp sensor but left the resister out. Where would i get one of those and how do i install or hook it up?

hardflex · 10-20-2006, 12:29 PM

Pelican doesn't list one. Call em and ask, they might know.

If that fails, you can make one easily with parts from Radio Shack.

P-DUB · 10-20-2006, 12:34 PM

Do i just need the resistor and put it in line with the connecting wire?

hardflex · 10-20-2006, 12:45 PM

yeah. I bought a resistor, crimped a male and female slip connector on each end and inserted it. you are shooting for 270k, but in a pinch anything 250-300k will work to see if it improves it dramatically.