OEM ECU car does not want to start with cold temps

[IGGYWOOWOO]

I am stumped. I have owned this car for over 6 years now and thought that I had seen it all.

The Car:
94 APU TT (automatic)
OBD I ecu
MAP ECU piggy back
T-67 Turbo
HKS 264 Cams
Spark Plugs: Champion C63YC's that Jeremy Blackwell recommends. (Gapped at .025)
Idle AFR 14.7 - 15.1

The car just does not want to start. I can crank on it and the engine will just flood. I have to pull the ECU fuse and crank on it to get the fuel out of the cylinders and then put the fuse back in to start the car. The car will then Idle very rough at about 800 rpms until it hits operating temprature. Once the car hits operating temprature, it seems to run just fine. It boosts and easily breaks the tires loose at 16-17 psi with no miss at all.

I checked to see if the IAC was working and it was indeed changing to try to adjust the air into the car. Tonite the temp was 45 degrees outside and it took me over 15 minutes to start. I did have the car on a charger so I know battery voltage was not the problem.

Tonite the idle was so rough that I got a Code 14 (Ignition signal Code) so I ran a test on all of the coil connectors to make sure that all cylinders were firing. I had a good spark on all cylinders.

One thing to note was I started to notice the miss when the temps began to get cooler a few weeks ago. I thought that I would need to open the gap on my plugs to .030 to help idle. Well, the damn thing would not even start! I had to close the gap back to .025

Should I try a warmer heat range? Should I close the gap more?

Does anyone have any input?

Thanks,

Brandon

[Hefti2]

Could your water temp probe be defective? Other than that I would try to cross-check with another ECU to eliminate this possibility also.
Also check the spark of the plugs visually while cranking. If you see sparks this is not your issue.

I could not imagine anything else.

[IGGYWOOWOO]

I replaced the water sensors last year. I did verify a good spark on all plugs while cranking.

Would low compression in a cylinder or two cause this? I did a leakdown test on the car last year and everything was great.

[TE27Levin]

Well im going to go out on a limb here and say that champions are only good for lawnmowers and chryslers.

Is there anyway you can verify that your coolant temp sensor is actually good? Sometimes new ones can be defective...

[cwtt]

Could your water temp probe be defective? Other than that I would try to cross-check with another ECU to eliminate this possibility also.


I could not imagine anything else.

I would also agree. I know you said you replaced it, but I would double check it. Also check for shorts in the wiring.

My nissan did this as well.

[IGGYWOOWOO]

For reference, does anyone know which sensor is the gauge sensor and which sensor is the ECU sensor. The manuel does not mention the gauge sensor. Do they both test the same?

Thanks,

Brandon

[madman]

Ecu temp sensor is the two wire which is brown/black and blue/yellow. The sensor is located on the waterneck that your upper radiator hose is attached too. If your temp is around 45 degrees the resistance of the sensor should be 2 to 4 k ohms. Just check and see if its in the ballpark if it is your problem lies somewhere else. The temp gauge wire is only a one wire sensor and has nothing to do with how the car runs.

[IGGYWOOWOO]

It is about 53 degrees outside and I measured 2.9k ohms on the sensor, so I don't think that is the problem.

Thanks for the confirmation madman.

[IGGYWOOWOO]

air : check
fuel : check
fire : check
coolant temp sensor: check
fuel pressure: check

Question: should the IACV open during cranking?
Mine stays closed...

[normore]

Are you using the IAT sensor or the 2220 ohm resistor on the MAF input? If you are using the resister, the ECU thinks it is 70 deg F when it is actually colder and the startup fuel mixture will be incorrect.

[slither]

FWIW, when I was on low boost, champion plugs done better than ANY other I tried

[Hefti2]

Are you using the IAT sensor or the 2220 ohm resistor on the MAF input? If you are using the resister, the ECU thinks it is 70 deg F when it is actually colder and the startup fuel mixture will be incorrect.

But it would not lead to a suuper rich condition at startup, rather a leaner condition.
IGGY,
do you have another ECU by chance to check the issue with that?

I would also try othe rplugs just for the peace of mind. Maybe it is because ot them, maybe not.
Other than these two points I see no other solution almost.

[Silver Bullet]

Could be the tune on your map ecu. Also not that is your problem...but get rid of those champion plugs...absolute junk and you might want to raise your plug gap up a little.

[IGGYWOOWOO]

Good points. I will change the plugs when I get home today. I have had my MAP ECU and done all of my own tuning for a couple of years now. Not sure how you would tune for start up? Maybe add more fuel at real low rpms?

I do have the temp sensor locked down with a resistor, but can plug in the sensor that came with the map ecu. I will try that as well.

One other thing to note is when I started noticing my car getting harder to start a few weeks ago, I pulled my plugs and gapped them to .030. The car did not even want to start! I had to put the gap down to .025 and the car would start with some misfire. The car would then warm up and run just fine.

[Kruso]

$5 says its not the plugs. I have the SAME EXACT problem which happened the second I installed my MAP ECU. Its something within the tuning in MAP ECU.

[IGGYWOOWOO]

Well... I have changed the plugs, verified that my air temp sensor is locked at 2.1 k ohms, verified that my tps seems to have the right output. I have also verified that the timing belt has not slipped. I have checked a couple of ground points on the engine and that looks good. One thing that I have noticed is that it trys to start, but just will not. I figure that cranking on it as much as I have would yield wet plugs, but I have pulled them and they are dry!

I watched the follow me table on the MAP ECU and have added a shitload of fuel to those cells with not much difference. She wants to start damnit!

I have been running on this tune for a while and have been using my MAP ECU for about 3 years now.

[IGGYWOOWOO]

I have tried almost everything with exception of swapping out the ecu.

I pulled all coils and turned them upside down with spark plugs gounded in all six. I cranked it and saw a good spark on 5 so I replaced the one with the weakest spark. and she still will not start. The grage now reaks of unburned fuel so I can tell that the injectors were injecting fuel.

Does anybody have a loaner obd 1 auto ECU?

[Tricky-Ricky]

I do have the temp sensor locked down with a resistor, but can plug in the sensor that came with the map ecu. I will try that as well.

The car would then warm up and run just fine.


Why have you got a resistor in the ECU water temp sensor circuit?

Has the MAP ecu got a water temp adjust map that you can + or - fuel from depending on temp? if so then that will be you're problem, sounds too rich to me.

[Martin F]

It is about 53 degrees outside and I measured 2.9k ohms on the sensor, so I don't think that is the problem.

Thanks for the confirmation madman.

Don't just check the resistance at the sensor, also check the voltage at the ECU. I believe the manual gives a voltage range.

[IGGYWOOWOO]

I was refering to the air intake temp sensor.

I may have found my problem though.

LOW compression!

I will have my compression test results this morning.

[Kruso]

Is bypassing the MAP ECU and going back to MAF an option? I would try that before trying to swap the ECU.... its only a wire swap.

[IGGYWOOWOO]

Well, I found low compression realy throughout the entire engine. I found: 125, 50, 75, 150, 125, 50. I have not put oil in any of the cylinders yet, but I bet my problem is rings. I rebuilt the head a year ago.
The weird thing is that I drove the car home and was none the wiser.

I would think it would still try to start.

Kruso, I can read the output from the MAP ECU on my Blitz SBC id. The signal is normal from the MAP ECU although I would try a MAF if I still had one.

[TE27Levin]

Your cylinders are probably just completely washed down. I would still suspect something else leading to that problem.. Change the oil too. its probably all gas.

[Kruso]

Well, I found low compression realy throughout the entire engine. I found: 125, 50, 75, 150, 125, 50. I have not put oil in any of the cylinders yet, but I bet my problem is rings. I rebuilt the head a year ago.
The weird thing is that I drove the car home and was none the wiser.

I would think it would still try to start.

Kruso, I can read the output from the MAP ECU on my Blitz SBC id. The signal is normal from the MAP ECU although I would try a MAF if I still had one.

I live in Sugar land, I have a spare MAF that you can borrow to test this out, sent you a PM.

[IGGYWOOWOO]

Your cylinders are probably just completely washed down. I would still suspect something else leading to that problem.. Change the oil too. its probably all gas.



Agreed. I do however think it is time for a new engine as mine has a shitload of miles on it. I am really thinking it could be the ECU. The problem literally got worse every time I have cranked on the engine. It does not even sputter any more like it did when this first happened.

[IGGYWOOWOO]

Well, I put a little oil in all cylinders and repeated my compression test. I do indeed have two blown cylinders. Here is the kicker: I put everything back together and the bastard started right up! WTF. I have been fighting this for a week! Oh well, time for a new engine and perhaps an aftermarket ECU.

Thanks for all of the help guys!

Brandon

[Kruso]

What were the compression test results?

[IGGYWOOWOO]

With oil in the cylinders: 150, 55, 135, 80, 150, 55 respectively.

I will do a leakdown test to make sure the problem is not the head gasket or valves, but both of those were replaced or rebuilt last November. I think it is probably time for a new block and oil pump.

B

[JeremyBlackwell]

For those of you who think Champion Race Plugs are "Junk", have you actually done before and after testing of them versus NGK? We have :)

CHampion Race plugs are MUCH better than NGK or any other comparable plug we have used. On BPU cars we routinely run 0.035" to 0.040" gap with no missing and many thousands of miles more lifespan than NGK. On AEM cars at ~17psi we run about 0.030" due to AEM's inferior wasted spark set up on 6 cylinder cars. Compared to NGK the Champions offer much better idle, throttle response, slightly cleaner emissions to to better combustion, etc.

Also, here is a detailed write up I did on the plugs. If any of you with NGK plugs get tired of constantly changing them and running tiny plug gaps, give us a call as we have these plugs in stock :) Remember, Champion plugs are listed as OEM direct replacement plugs for 80% of new cars, and come factory in the Viper, etc.
http://www.speedforsale.com/supraparts//product_info.php?cPath=36_42&products_id=571&osCsid=kggt0p86klb38n9h8f4lljumf2

Here is a picture of a CHampion Race PLug that came out of one of our customer's 1997 BPU Supras with 18,000 miles on them:
http://www.speedforsale.com/supraparts//images/DSC04856.JPG

[Altezza576]

Ecu temp sensor is the two wire which is brown/black and blue/yellow. The sensor is located on the waterneck that your upper radiator hose is attached too. If your temp is around 45 degrees the resistance of the sensor should be 2 to 4 k ohms. Just check and see if its in the ballpark if it is your problem lies somewhere else. The temp gauge wire is only a one wire sensor and has nothing to do with how the car runs.

Would this sensor cause a car to not start? Mine just broke and now car wont start.

[madman]

Would this sensor cause a car to not start? Mine just broke and now car wont start

If you completely broke the sensor off it wont run but normally when they go bad they usually just run real bad due to wrong coolant temp info to the ecm especially under cold starting conditions....

[Altezza576]

If you completely broke the sensor off it wont run but normally when they go bad they usually just run real bad due to wrong coolant temp info to the ecm especially under cold starting conditions....


http://www.supraforums.com/forum/showthread.php?t=518927

Stupid me broke it completely off during cam swap. :chairshot

[slither]

Great post Jeremy, your findings were the same that I had.
Silver Bullet, I assume you have done testing to determine for your use they were "junk"? :dunno:


For those of you who think Champion Race Plugs are "Junk", have you actually done before and after testing of them versus NGK? We have :)

CHampion Race plugs are MUCH better than NGK or any other comparable plug we have used. On BPU cars we routinely run 0.035" to 0.040" gap with no missing and many thousands of miles more lifespan than NGK. On AEM cars at ~17psi we run about 0.030" due to AEM's inferior wasted spark set up on 6 cylinder cars. Compared to NGK the Champions offer much better idle, throttle response, slightly cleaner emissions to to better combustion, etc.

Also, here is a detailed write up I did on the plugs. If any of you with NGK plugs get tired of constantly changing them and running tiny plug gaps, give us a call as we have these plugs in stock :) Remember, Champion plugs are listed as OEM direct replacement plugs for 80% of new cars, and come factory in the Viper, etc.
http://www.speedforsale.com/supraparts//product_info.php?cPath=36_42&products_id=571&osCsid=kggt0p86klb38n9h8f4lljumf2

Here is a picture of a CHampion Race PLug that came out of one of our customer's 1997 BPU Supras with 18,000 miles on them:
http://www.speedforsale.com/supraparts//images/DSC04856.JPG

[IGGYWOOWOO]

I have to agree with Jeremy and Slither, the champion racing plugs are the best that I have ever used in my car hands down. ( I have tried just about all of them)

FWIW I am swapping in a new engine right now. Should be up after Christmas.

B

[Altezza576]

Not for nothin, but I have had great luck with Lexus/Toyota GS400 OEM plugs. I bought a new set from the toyota dealer back in 2004 and the same set I purchased has been in every turbo motor I have run, from my IS300 to the Supra.

I highly recommend them.... to this day the gapping is dead on and they look as clean as the posted pic of the champion plugs up there ^^^^^^