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Discussion Starter · #1 ·
I figured I would try and take a crack at this problem since it has still not been resolved and is starting to really be a nuissance. Background on the car at the bottom.

-I have been having a cold start issue ever since I installed my T28 turbo, 50# injectors, and a JZW tune a year and a half ago. I have had John take a second crack at the cold start maps after my original tune and he sent me an updated tune which improved the cold starting issues but still no cigar. Initially, it would have difficulty starting without stumbling around during cold starts or sporadic semi-warm starts but stayed relatively the same.

-Fast forward to this year; I replaced the coolant temperature sensor with a brand new piece from Eeuro with the hopes that it might solve the issue. It did not. The problem now is that if the car stays in a static or constant temperature while it is in the garage, it fires up cold close to stock and has no stumbling issues to note of. However, while it is at school outside, the car is subject to temperature fluctuations over the day and night times. It is at the point where if it is a cold start, the car will not start at all without a bit of throttle. This only happens during cold starts; it starts 100% any other time. Then I go home for the weekend and while the car is in the garage, it is like a switch is flicked and the car starts up great when cold. I bought another ECU to have sent to John so that he could tweak the cold start maps but when I tried that tune, the car would have even worse of a time to the point where I was not sure it would start a few times.


This brings me to a cross road in trying to fix the problem; I installed a new coolant temp sensor and it did not faze the problem, and am unsure what other hardware could cause poor cold starting? Then comes the question of the tune itself; is it possible that there are issues with the cold start map?

Thanks in advance for the help, it is always appreciated.

1996 900se, 36,000 miles on the odo, T28 turbo, 50# injectors, JZW tune, all supporting hardware. Fuel related sides replaced:

-new sparkplugs correctly gapped
-less than 5,000 miles on a new fuel pump
-new coolant temp sensor
-fuel filter replaced 10,000 miles ago
-no issues while driving
 

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Practically a new car, or so it seems:cheesy:.
Did you test the temperature sensor? And there are two of them.
50# injectors ? What is this??
And the fuel pump (FP), was that tested?
36,000 miles ??
Maybe not being driven has a negative effect.:evil:
Do check the purge valve and the EVAP system.
http://www.saabcentral.com/forums/showthread.php?t=111025
 

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Discussion Starter · #3 · (Edited)
Thanks for responding earthworm. I guess I should give some background on the car: my dad bought it new in 1996, and we moved overseas 6 months after for 9.5 years. It was stored at my grandfather's house in Florida where he maintained it and drove it sporadically. Once we moved back to the states permanently in 2006, it saw DD status and has been driven ever since. It is pretty funny to look back on the mileage from dealer records: 2003 saw 14,000 miles on the odo, now it has 36,000 miles on it. Anyways, you are right to assume problems arose due to low mileage. I have replaced in the last few years: AC compressor, convertible roof motor, brake calipers, brake discs, radiator, headlights, fuel pump, headgasket, a lot of rubber hoses, power seat motors, both o2 sensors, and a handful of other things. Yeah, the car is practically new for all intents and purposes.

I replaced the NTC coolant temp sensor but not the sender, should I give the sender a go? If the sender only for the temp gauge in the dash, I am not having any issues there. Also, once it catches it stumbles until you touch the gas it goes right up and idles normally with no indication it had any struggles previously. It is only on cold starts, no other issues with driveability otherwise.


50# injectors are fuel injectors needed for stage 5 (285whp)
 

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Discussion Starter · #5 ·
No kidding, I try to avoid driving unnessarily to keep the mileage reasonable but it is hard in California since you have to drive longer distances than when I lived in the NE. It has been a great car, but all these niggling issues really detract from the experience to be honest.
 

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Discussion Starter · #7 ·
I am going to try an IAT sensor and see if that will help a bit. Is this a logical part to try and replace? I have heard it contributes to the quality of startups so I figure I would run it by everyone to see if it is worth a shot.
 

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Well, there are a few things to consider:

A stock ECU will fire all injectors at the same time during startup to quicken the startup process.

When you step on the gas, you're not giving the engine more gas, but you're giving it more air. So it seems like you're getting too much gas at startup.

I just wonder if you have one or more leaking injectors, or if the ones you have are too much capacity for the tune.

The only way to be sure would be to monitor the A/F ratio with some test gear like an Innovate LM-1 or LM-2 at startup. And those (new) are pricey and need an extra bung in the exhaust... Ron
 

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Discussion Starter · #9 ·
Well, there are a few things to consider:

A stock ECU will fire all injectors at the same time during startup to quicken the startup process.

When you step on the gas, you're not giving the engine more gas, but you're giving it more air. So it seems like you're getting too much gas at startup.

I just wonder if you have one or more leaking injectors, or if the ones you have are too much capacity for the tune.

The only way to be sure would be to monitor the A/F ratio with some test gear like an Innovate LM-1 or LM-2 at startup. And those (new) are pricey and need an extra bung in the exhaust... Ron
It is a semi-custom tune, and was tuned specifically for the larger injectors and turbo. However, I had sent an ECU to my tuner a few times to try and improve on the cold starts and while it is much better than my original tune, is still having issues.

There are no injector leaks that I can see, the issue I think is the fact that my injectors are 50# ones and that maybe the tuner is not as familiar with them as they are with the green giants or the Dekka 630cc injectors and has not been able to properly adjust the cold start map accordingly.
 

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Do have the IAT (intake air temperature) checked. Do not replace, just check. It may well be OK.
Do not step on the accelerator during cold start, or any start-up.
This only adds unaccounted air which will lean things incorrectly.
Do have the ECU checked, its may not be processing the sensor info cottrrectly..
Also check for "unregulated intake air", this can mess-up things.
Another thing, the FP check valve. A test - pull fuse 17 then try a start, if the valve is good she should start and run for a second, using residual pressure.
Good luck:cheesy:
 

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Discussion Starter · #11 ·
I will check the FP check valve in a bit since that is the only thing I can really test while I am at school. Whar should I look for in terms of whether the FP is good or not?
 

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I mean leaking internally, as in contstantly spraying. Whenever the fuel pump is on, they may be leaking into the intake. You would not see that by looking at the outside. That's why I was also asking about the mpg. Add to that the color of each plug... Ron
 

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Discussion Starter · #13 ·
I mean leaking internally, as in contstantly spraying. Whenever the fuel pump is on, they may be leaking into the intake. You would not see that by looking at the outside. That's why I was also asking about the mpg. Add to that the color of each plug... Ron
Plugs all look as they should: slight black on the base with a cream color on the tips from burnoff. I average about 28mpg+ on the SID in mixed driving but real MPG is going to be around 23-24 due to the inability for the SID to differentiate larger injectors.
 
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