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Posted by: toon1 Aug 17 2006, 06:44 PM

In my quest to find the hesitation problem. I think I have norrowed it down to the CHT.

The car stumbles, spits and backfires when cold. After it gets to operating temp it seems to go away and the car runs pretty darned good. I have done most of all the checks and most everything seems ok.

I checked the resistance on the CHT with the motor cold and it reads approx. 2145. I placed a lead of the ohm meter on the connector of the CHT and placed the other ohm meter lead on the cylinder head for ground.

the book I have says" approx. 3k ohm is good, if it's out of spec replace it".

Is this reading ok? Is the method I used to check the CHT ok or should I check the resistance at the ECU connector?

Posted by: rcrgrl Aug 17 2006, 07:28 PM

i thought it should be closer to 2k. and thats the method i used, for what thats worth...

Posted by: Dave_Darling Aug 18 2006, 09:29 AM

Method == fine.

Reading == OK; the exact number varies depending on the exact temperature of the sensor.

--DD

Posted by: toon1 Aug 18 2006, 09:47 AM

thank's dave, I wasn't sure if I would get anymore responses. I was reading the pennington book trying to trouble shoot and noticed that it mentioned, " if the cold start idle is not coming up check the CHTS". This is also another problem I am having.

whadda think??

Posted by: DNHunt Aug 18 2006, 09:58 AM

Check the connector for the cht to the harness. Old wires do break. May not be it but, it's easy to check

Posted by: toon1 Aug 18 2006, 10:12 AM

thank's, that is the one check I havn't done and was my next move. I am going to check it this afternoon.

From what I have been reading, the CHTS is not a factor once the motor is warm. If this is true, does the computer not read the resistance after everythig is at operating temp?

Would that explain why the car runs better when it is warmed up?

Posted by: Cap'n Krusty Aug 18 2006, 10:49 AM

It functions as a variable resistance GROUND for the ECU. No ground, no workee. I've seen numerous cases, BTW, where the female connector was pushed into the plastic insulator but only held against the side of the male lug, not inserted over it. Makes for an interesting laundry list of bad behaviors. The Cap'n

Posted by: rcrgrl Aug 18 2006, 12:10 PM

if the wire is broke the car won't start - ask me how i know

Posted by: jhadler Aug 18 2006, 02:21 PM

Uhm... I beg to differ... If the wire is broken, the ECU will consider the motor to be -really- cold, and go to full rich. No problem if the motor really is that cold. If not, it won't want to start very well (too much enrichment). Additionally, once the motor is warmed up, the ECU will be keeping the mixture at full rich and the motor will tend to flood and stall as soon as the rpms drop. Oh, and your mileage will -suck-...

BTDT more than once...

-Josh2

Posted by: Bartlett 914 Aug 18 2006, 02:27 PM

I had the same problems. Make sure the ECU is the correct one. I had one for a 73 and averything else for for a 74. There was a major change done between these years.

Mark