19 replies to this topic

[stevieapollo]

My 88 Starion doesn't run well when it's cold. However when it warms up it runs muich better. Is this normal, and can I do anything to improve this.  Mods are... Walbro fuel pump, KDM hardpipe kit with cooler, 16g turbo. When I first aquired the car it did not have this problem, until I did the mods, it then started running odd. Is there anything I can do? I want to avoid going back to stock. Everyone says that the hard pipe kit with the 16g turbo makes it run awsome! But this isn't the case for me   Stock actually ran better. Or KDM messed up my car lol.

[Starfighterpilot]

It could possibly be your engine's coolant temperature (CTS) sensor causing the problem. Normally if this sensor fails it makes the engine run like doggie do do when warmed up. But maybe it is screwed up the other way.

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.

[scooterh72]

Mine does the same thing and I have a brand new CTS. Haven't messed around with it lately. Probably will look at it this weekend.

[scooterh72]

Awesome. I guess I should have checked these codes sooner. That is an excellent piece of information on the link. Will certainly do this on the weekend.

[mikec]

Define "doesn't run well when cold."  Does it idle at low RPMs?  Does it shake?  Just not have any power?  Bucks when boost pressure builds?  An engine that doesn't have 1200 to 1500 RPMs at stone-cold startup idle probably has a bad CTS or bad idle speed controller (ISC) mechanism.  If your idle RPMs jump to 1500 after cold startup, and slowly but smoothly drop to normal (950 or so) after a few minutes the CTS is basically working.

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.

[scooterh72]

On my car (86) it idles higher in the 1200 to 1500 range on cold start up and will idle down after awhile. If I start it up and attempt to drive it is will buck and sputter. It seems that once the overall temperature of the engine, by going off of the guage in the dash, reaches 1/4 and above it seems to run pretty good. I do have a new CTS, all new vacuum lines, new injectors and hard pipes on all. I do need to check engine codes this weekend. I am planning on checking timing, tps and isc reset as well.

One thing that I didn't do was check the gap on my plugs. Could that cause any of these symptoms?

[Dcrasta]

Scooter if you havent now is a good time to do the full winter tune up if you are going to be driving I would get the stock heat range plugs, new rotor and cap, clean or replace the air filter and oil, check coolant levels and mix, check water pump belt and battery, and reset the TPS/IDLE SPEED CONTROL (Oh and timing).

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.

[jettajody]

I have the same identical problem you have bud! I have narrowed my issue down to dieing fuel system, bad plug wire, and possible temp sender switch [ not sure if its related ], but is cracking loose. I will let you know if I find the bug.

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?

[scooterh72]

jettajody, on 22 October 2009 - 07:22 PM, said:

I have the same identical problem you have bud! I have narrowed my issue down to dieing fuel system, bad plug wire, and possible temp sender switch [ not sure if its related ], but is cracking loose. I will let you know if I find the bug.

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?

[jettajody]

scooterh72, on 22 October 2009 - 08:07 PM, said:

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?

I don't think so bro... You can even hear my pump. it's quiet as a mouse, and stock......

[scooterh72]

Ran codes today.

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.

[Dan]

Now get that car fixed so you can enjoy it before the snow falls!

[scooterh72]

Dan, on 24 October 2009 - 05:20 PM, said:

Now get that car fixed so you can enjoy it before the snow falls!

NO kidding......but we have already had some snow this year. Phooey.

[scooterh72]

stevieapollo, on 20 October 2009 - 12:25 AM, said:

My 88 Starion doesn't run well when it's cold. However when it warms up it runs muich better. Is this normal, and can I do anything to improve this.  Mods are... Walbro fuel pump, KDM hardpipe kit with cooler, 16g turbo. When I first aquired the car it did not have this problem, until I did the mods, it then started running odd. Is there anything I can do? I want to avoid going back to stock. Everyone says that the hard pipe kit with the 16g turbo makes it run awsome! But this isn't the case for me   Stock actually ran better. Or KDM messed up my car lol.

Sorry, I feel like I hi-jacked your thread. Hope you are getting some good information like I did.
Scott

[Indiana]

Don't pay any attention to that 02 code, the motor first needs to be fully warmed up to even check the 02 "code" and the motor MUST remain running also.  All the other codes are with just the key "on".  The idle motor, it won't work if the throttle cable is TOO TIGHT.  Loosen the jam nut on the throttle cable at the throttlebody and back it off so that you can move the cable in and out of the housing, just because you can move it up or down that isn't good enough it could still be way too tight and that prevents the throttleplate from fully closing and its at this time a tab on the linkage pushes closed a switch on the end of the idle motor so the ECU can control it.  If you could check everyone car you'd find 80% of them have throttle cables that are too tight and cause this problem.  It would seem that when they are put back on or adjusted they are to be that way so you can hit wide open throttle, well trust me there is plenty of pedal left to do that will a lot of slop and slack in the cable at idle.

[scooterh72]

Indiana, on 25 October 2009 - 01:03 AM, said:

Don't pay any attention to that 02 code, the motor first needs to be fully warmed up to even check the 02 "code" and the motor MUST remain running also.  All the other codes are with just the key "on".  The idle motor, it won't work if the throttle cable is TOO TIGHT.  Loosen the jam nut on the throttle cable at the throttlebody and back it off so that you can move the cable in and out of the housing, just because you can move it up or down that isn't good enough it could still be way too tight and that prevents the throttleplate from fully closing and its at this time a tab on the linkage pushes closed a switch on the end of the idle motor so the ECU can control it.  If you could check everyone car you'd find 80% of them have throttle cables that are too tight and cause this problem.  It would seem that when they are put back on or adjusted they are to be that way so you can hit wide open throttle, well trust me there is plenty of pedal left to do that will a lot of slop and slack in the cable at idle.

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?

[jettajody]

scooterh72, on 25 October 2009 - 12:44 PM, 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?

The only thing I have ever seen a bad O2 sensor do on any car was give a lil' bad MPG.......

[Indiana]

The 02 code happens, it doesn't mean the 02 is bad.  If you have open exhaust or large exhaust with little restriction a non heated 02 will show that code all the time, it doesn't mean the ECU isn't still using the 02.  A stock system will show that code at different times its normal.  The explanation is in the service manual.  There isn't much corection from the 02, the difference in air fuel ratio from a dirty injector throws the air fuel ratio out of the range of what the 02 could tell the ECU to correct anyway.  If the range is so far off that's a voltage feedback to the ECU and it just thinks hey its bad lets throw the code.  I don't read those retarded codes I never have its like using a crystal ball and asking it what you had for breakfast.  The service manual and a volt meter is all you need, you won't use those codes or that plug at all.  Is your car 100% stock?  If its not the first thing you do is IGNORE that 02 code.

[scooterh72]

Indiana, on 25 October 2009 - 01:55 PM, said:

The 02 code happens, it doesn't mean the 02 is bad.  If you have open exhaust or large exhaust with little restriction a non heated 02 will show that code all the time, it doesn't mean the ECU isn't still using the 02.  A stock system will show that code at different times its normal.  The explanation is in the service manual.  There isn't much corection from the 02, the difference in air fuel ratio from a dirty injector throws the air fuel ratio out of the range of what the 02 could tell the ECU to correct anyway.  If the range is so far off that's a voltage feedback to the ECU and it just thinks hey its bad lets throw the code.  I don't read those retarded codes I never have its like using a crystal ball and asking it what you had for breakfast.  The service manual and a volt meter is all you need, you won't use those codes or that plug at all.  Is your car 100% stock?  If its not the first thing you do is IGNORE that 02 code.

Thanks for the clarification.

[Rexkrazy]

Indiana, on 25 October 2009 - 01:03 AM, said:

Don't pay any attention to that 02 code, the motor first needs to be fully warmed up to even check the 02 "code" and the motor MUST remain running also.  All the other codes are with just the key "on".  The idle motor, it won't work if the throttle cable is TOO TIGHT.  Loosen the jam nut on the throttle cable at the throttlebody and back it off so that you can move the cable in and out of the housing, just because you can move it up or down that isn't good enough it could still be way too tight and that prevents the throttleplate from fully closing and its at this time a tab on the linkage pushes closed a switch on the end of the idle motor so the ECU can control it.  If you could check everyone car you'd find 80% of them have throttle cables that are too tight and cause this problem.  It would seem that when they are put back on or adjusted they are to be that way so you can hit wide open throttle, well trust me there is plenty of pedal left to do that will a lot of slop and slack in the cable at idle.

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!