


Car sputters when cold, then stops when warm.
#1
Posted 20 October 2009 - 12:25 AM

#2
Posted 20 October 2009 - 02:27 PM
Easy to tell if it's screwed up or not - start the COLD engine and immediately take an ohm reading across the contacts of the temperature sensor. If it reads about 300 ohms, the sensor is sending a signal to the EFI ECU that the engine is warmed up so consequently you are running lean until the engine actually warms up.
And check that the CTS connector metal female contact to the engine coolant temperature sensor male contact is clean and the wire is tightly held by the metal connector.
I would also check all of the engine vacuum tubing for cracks, tears or holes.
And do you have ANY ERROR CODES? See http://www.starquest...owtopic=28043 for an explanation of how to get & read 'em.
For What It's Worth.
KEN
Edited by Starfighterpilot, 20 October 2009 - 03:29 PM.
84 Starion ES RIP in 1987
66 Dodge Charger, Modified Original OEM 383/ 365 HP, 4-speed, Sure Grip, original owner, 113K HARD miles - Being Restored
76 Dodge PU, Modified 440/ 425 HP, 4 speed, Posi Dana 60 DIF, 675K Miles
#3
Posted 20 October 2009 - 02:48 PM
#4
Posted 20 October 2009 - 08:03 PM
#5
Posted 21 October 2009 - 10:30 PM
The CTS should read above 1500 ohms on a stone-cold engine. You don't even need to start the engine to test this... just pop the hood, unplug the CTS electrical connector (it's on the intake manifold near the oil dipstick, the connector is supposed to have a squarish rubber boot on it; most have rotted away by now) and measure the resistance between the two prongs of the sensor.
If the electrical connector going to the sensor doesn't have that squarish rubber boot - and doesn't appear to have a squarish section for the boot to attach to if the boot is rotted away - then you might have the wrong connector on that sensor. The sensor pins are crossed like a "T" shape; one of the sensors by the thermostat housing has a similar "T" shape on the 88-later cars. The CTS wire colors are yellow+green and black. The thermostat housing sensor will have a yellow+blue wire and yellow+white wire. The t-stat sensor connector also will be "T" shaped plastic with no obvious place for that square rubber boot.
If your engine runs bad when cold and suddenly gets better when there is heat in the engine - going from bad to good running quickly with no transistion - that sounds more like a vacuum leak on a vacuum circuit connected via the thermovalve. The thermovalve senses coolant temps; when they reach some point the valve switches ON or OFF. StarQuests have one thermovalve: it's by the thermostat, has two (very very fragile) vac ports on it. As a test, follow those two vac hoses to their OTHER ends and unplug them at that end. Cap the hoses & the ports they went to. (you could undo them from the valve but it's possible/likely you'd bust the fragile valve so we'll do it on the other end of the vac hoses) Now see how the engine runs hot and cold. If it's better cold, you've isolated the bug to this vacuum circuit. No difference? Restore the vac hoses.
Also, on a stone-cold engine, the ignition timing is supposed to be 15 deg BTDC. A few minutes later (in sync with the idle RPMs dropping a bit) the ignition timing will suddenly drop to the normal 10 deg BTDC. If your 10 deg BTDC "normal timing" is over-advanced, the extra 5 degrees on a stone-cold engine can lead to pinging/detonation issues. This is for folks not living at "high altitude" - this 5 degree advance will be present at all times for high altitude StarQuests (above 2500 feet or so).
Fuel injectors with less than optimal spray patters will cause worse cold-temperature running as well. When the engine is physically cold, the air+fuel mix flowing through the intake manifold may not stay mixed... the gas condenses out, especially if a lousy spraying injector did a lousy job atomizing & mixing the gas in the first place. Once the engine coolant gets warm - and puts some heat into the intake manifold - the gas will stay atomized better so the air+fuel mix actually reaches the cylinders. Atomized gas flowing through a stone-cold intake manifold is just like morning dew on your lawn: the gas condenses out into a liquid. That's why the manifold is heated in the first place... but it takes a few minutes to get heat into the manifold since the coolant is stone cold too for a while. This is the BIG advantage of port fuel injection: the injectors spray the fuel right into the intake valve openings, not into the intake manifold, so it has far less time to condense again.
mike c.
#6
Posted 21 October 2009 - 10:40 PM
One thing that I didn't do was check the gap on my plugs. Could that cause any of these symptoms?
#7
Posted 22 October 2009 - 01:03 AM
Then you will be 'In the promised' land. I just did this and boy what a difference after our frost hit my car need 30 seconds (or I start, smoke a cig and do the walk around the car) and im good to go.
#8
Posted 22 October 2009 - 07:22 PM
BTW - When your car is fully warmed and idleing for a few min. does it all of a sudden sometimes misfire/stumble just for a second? And can you hear a ever so slighty surge up and down by maybe 25rpm or so?
#9
Posted 22 October 2009 - 08:07 PM
jettajody, on 22 October 2009 - 07:22 PM, said:
BTW - When your car is fully warmed and idleing for a few min. does it all of a sudden sometimes misfire/stumble just for a second? And can you hear a ever so slighty surge up and down by maybe 25rpm or so?
Sounds like mine. I do have new plugs wires though. My fuel system could be the culprit. I think the fuel pump is original in the car. I did notice that sometimes when I shut the car off the pump will continue to run for like 5 seconds. Is that normal?
#10
Posted 23 October 2009 - 06:04 PM
scooterh72, on 22 October 2009 - 08:07 PM, said:
#11
Posted 24 October 2009 - 02:19 PM
Bad O2 sensor and ISC motor. I figured it might have been the ISC.
Two of the few things I have replaced on this rebuild.

#12
Posted 24 October 2009 - 05:20 PM
Drive Fast ~ Take Chances!
#14
Posted 24 October 2009 - 05:46 PM
stevieapollo, on 20 October 2009 - 12:25 AM, said:

Sorry, I feel like I hi-jacked your thread. Hope you are getting some good information like I did.
Scott
#15
Posted 25 October 2009 - 01:03 AM
#16
Posted 25 October 2009 - 12:44 PM
Indiana, on 25 October 2009 - 01:03 AM, said:
Well I had run the engine till it was fully warmed up and read the codes.......I then pulled the negative battery cable off for like 2 minutes to reset the codes. I then ran the car and one code went away (CTS, I just replaced it). I did run the codes with the engine running and pulled the O2 code. This still wouldn't apply?
#17
Posted 25 October 2009 - 01:09 PM
scooterh72, on 25 October 2009 - 12:44 PM, said:
#18
Posted 25 October 2009 - 01:55 PM
#19
Posted 25 October 2009 - 02:22 PM
Indiana, on 25 October 2009 - 01:55 PM, said:
Thanks for the clarification.
#20
Posted 02 January 2010 - 03:02 PM
Indiana, on 25 October 2009 - 01:03 AM, said:
I'll bet you can't read the word "Shift" anywhere on your keyboard. LOL. Don't get me wrong, I find all your input very valuable. I just think you use the "Shift" key TOO MUCH.

Slay the N00B!
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