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1999 Pulling timing

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#1
Keith Novak

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My 99 has started pulling timing as it reaches the low end of operating temp, and I'm running out of possible sources other than changing the wiring harness.

 

It didn't do this last year.  I've installed a practically new motor with mostly new sensors that dyno'd well before installing.  I pulled the dash over the winter since this began as well.  I know it's supposed to pull timing at 204F.  I'm watching it happen between about 150 to 160F using an IR pyrometer on the heater hose coming off the back of the engine.  It pulls timing as much as 10* and is noticeably slow, not even being able to hold a draft from a good but not great car.

 

I changed the ECU with no effect (other than my fuel pump turns on normally now).  I changed the temp sensor on the back of the engine.  I've swapped out the throttle body and I've changed the top of the air box with the sensors there as well. 

 

I can see that the O2 sensors have been spliced together, and the one from aft of the catalytic converter is plugged in, but someone stuck some resistors in the wiring for some reason  Can O2 sensor faults cause the engine to pull timing?  Any other ideas here are appreciated.  I'm starting to run out of stuff to swap.  :help: 

 

Thanks,

Keith


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#2
Jim Drago

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Keith
Make sure there are no resistors in water temp wire from sensor to Ecu.
That harness runs above the engine between valve cover and intake.. I believe it is red wire with blue trace or vice Versa
Jim
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#3
ChrisA

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Knock sensor??


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#4
Ron Alan

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Keith...I cant offer any help but can you tell me how you know it is pulling 10 degrees of timing? Do you have a sensor wire? Or are you using a timing light on the crank pulley?


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#5
Keith Novak

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Knock sensor??

Nope.  That is NOT an easy part to swap out, but it still pulls timing at the same place.  The harness to the rear temp sensor is a short one so I'll try checking the resistance across the terminals. 


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#6
Keith Novak

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Keith...I cant offer any help but can you tell me how you know it is pulling 10 degrees of timing? Do you have a sensor wire? Or are you using a timing light on the crank pulley?

It's pulling up to 10 deg. 

 

I'm watching it with a timing light while I measure the temp with the pyrometer.  I'll get a steady timing of about 14* until the engine reaches just over 150.  Then, the timing gets more noticeably ragged as seen on the marks, and it drops typically to 8-10ish.  I say up to 10* because as I was trying to sort it, I played with the adjustable timing wheel a lot. Mine is a stock wheel that was slotted so you can set it to stock position, see it's dead at 10* and then when it's been hot, I've seen zero degrees advance at the stock position using the timing light.  Now that I've figured out right where the timing changes, I don't get it any hotter in the garage to see how much worse it gets. When it's up to full operating temp, you can't set it above 8-10, which is well off the marks cooler.


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#7
ChrisA

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#8
Keith Novak

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No this is my '99.  I wasn't able to figure out how to add a 2nd car to my profile.


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#9
ChrisA

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Ha! Just re-read your first post.

 

Do you have an OBD2 "live" scanner? That would let you see the temp. the ECU is seeing from the sensor along with many of the other engine parameters.


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#10
Keith Novak

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I don't yet but it looks like I need one.  Something's just not right and I'm running out of ideas and patience.  Is there one, or a specific type you'd recommend or stay away from?


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#11
High Chair

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Both of my 99s do the exact same thing however there is nothing wrong with them. Solid at 15 and as soon as it reaches 180 F the timing is reduced by 8/10 degrees as it switches maps.  If you put the car on a dyno and check it at WOT you will see the total timing is rock solid at 28/28.5 right where it should be. You can change all of the parts you want but you will not get it to stop doing it. I actually changed everything in my car (everything including all wiring) and it still does it. That is when it was suggested to take it to the dyno. The car make the same HP/TQ as the rest and the timing is right where it should be under a load all the way to read line. I never looked for a resistor as Drago suggested and that might stop it but under power it makes no difference. By the way I had multiple engine people look at it and all said they had never seen anything like it. That includes Ti-Speed and Jeff over at Auto Technics yet I have two cars that do the exact same thing and both with new Ti-Speed engines


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#12
Keith Novak

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Good to know that the map change doesn’t necessarily occur at 204 as others have reported.   That will stop me from chasing this forever.  I do know the car is down on power though compared to others.  It felt like it had no torque in 2nd and 3rd.  People who raced me even commented that it seemed very slow, and I have a lot of experience on the tracks where I discovered it and with the drivers I raced so I have a lot of data points to show me the car suddenly became a lot slower.  I do know someone who had this problem who fixed it with a new wire harness, although he's not sure if it was the harness, or the process of changing it that did something which fixed it.

 

I will get it on the dyno, but I have a few other ideas to check first, so it’s not just a trip to confirm what I think I already know.  I just bought a OBD reader for my phone that enables live monitoring so I can check and clear codes and see what the ECU is thinking when it pulls the timing, particularly the temp since mine changes at 150+ and not 180 or higher.   I’m going to check it with both the ECUs looking for differences between the two and see what that tells me first, and then see if I can detect a difference under power.


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#13
Jim Drago

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Keith

Make sure the butterflies are operating properly while on dyno.. It would definitely lack off teh corners if not working properly. lots are seeingthe check valaves and solenoid failing

 

Jim


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#14
Kyle Freiheit

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Keith. If you need any data points locally or want to use another car to look things over/test, I have a 99 street car here.

 

Kyle


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#15
Keith Novak

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It's handy seeing what the computer is thinking using the OBD II reader.  It tells me that the computer thinks the car is about 180* when it pulls timing from 10 to 3.5, but the actual measured temp at the temp sender, is only 150*.  That means that once it reaches normal operating temp of about 185, the computer thinks the car is over 200. 

 

I also noticed that the idle control valve is making an electrical buzzing noise when you turn the key to the run position, which I don't remember before.  More stuff to try and isolate I suppose.


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#16
ChrisA

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The OE temp sensor is in the coolant as it exits the head. That maybe more accurate than an infrared reading on the housing where it mounts or the heater hose. The housing will heatsink away some of its' temp to the head until that has stabilized and rubber hose is not a great conductor of heat. I've never seen it used as a heatsink  :) , so I would not trust that as an accurate reading of coolant inside of it.


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#17
Keith Novak

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I'm installing another sensor in the heater hose to find out.  The sensor I've used in the upper radiator hose is pretty innacurate which is why I used the pyrometer so far.


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#18
Keith Novak

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After installing the sensor in the hose coming out of the temp sensor housing, Chris is 100% right.  The hose does indeed like a heat sink and if you try to measure it with a pyrometer, at 180ish it will read 15-20* lower measuring the hose or even measuring the aluminum fitting for the sensor, than the sensor itself will read.  The Accutemp gauge read almost identical to the ECU up until the map change.  I watched the ECU timing read-out from the OBD II dongle and it switched at 176*F.  Comparing the ECU temp to the heater hose sensor, and the top radiator hose sensor, all 3 agreed but were higher than measuring the hose itself.

 

This is REALLY good news.  It doesn't look like a wire harness issue, at least on that circuit.  Now the question is, was the power issue related to the ECU that I swapped out, which definitely had something wrong since it kept the fuel pump running without a jumper, or something else.   It would be nice to have a dyno nearby, but until I can put it on one I can go through some factory manual diagnostic checks of other system, and perhaps a late night backstreet butt dyno run or two on back roads, while logging the OBD II data on my phone.


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#19
Keith Novak

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 If you put the car on a dyno and check it at WOT you will see the total timing is rock solid at 28/28.5 right where it should be.

 

I'm getting 23.5 at WOT according to the ECU.  Is 28-28.5 what the ECU is supposed to think, or do I add the 4-5 degrees of additional advance, in which case it looks about right now?


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#20
speedengineer

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I'm getting 23.5 at WOT according to the ECU. Is 28-28.5 what the ECU is supposed to think, or do I add the 4-5 degrees of additional advance, in which case it looks about right now?

You have to add the 4-5 degrees from the adjustable timing wheel to what the ecu reads via obd, so 23.5+4.5 so around 28 actual timing.

FYI, my 99 idle air control valve hums with key on too. I've just assumed it's normal.

*edit, or maybe I misread and you asking if you should add 4 degrees more on top of the 28? Time to go to the dyno ;)
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