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Discussion Starter #1
I have an issue, an issue i have seen other Saab'ers write about, to where after letting a fully warmed up car sit for 25-35 minutes and upon starting it again it will misfire. Restarting outside of that window no noticeable problems can be felt. The problem seems to be getting increasingly worst, as today it even stalled (restarted no problem).
There is 167K on the clock.

I have been trying to fix this for a good six months and the following has be done.

Replaced all six plugs and coils (bosch).
Replaced the EVAP valve, twice.
Checked and retighten all clamps on the intake side (from the air filter to the throttle body)
Cleaned the Throttle Body
Checked all the vacuum lines (hard black pipes)
Went through and checked the connectors below the LH headlight and battery area
Installed new battery
OHM the CPS, within spec's (i think it was 910 ohms)
Checked the grounding (battery to frame to engine)
Cleaned the ECM connectors
Changed both the MAF and the pressure/temp sensor



My thought is something (a sensor?) is breaking down with the heat from the engine when turned off. I just can't figure it out.
I had the TECH2 connected when it happened this morning, it did throw a CEL. It was P0300, P0302-P0306, she was misfiring really bad. No surprise with these.
It is hard for me to interpret any of the readings as they are jumping all over the place do to the misfiring. The one that was steady was the fuel pressure, it displayed 2.56Bar.

The only odd thing i came across was when i tried to O2s Response self test, it fails due to "Engine Load is out of Range". Tried this about 7 times, same result failed. I went to self test the O2s thinking maybe the sensor 1 was going bad.

My next thought was to change the intake gaskets, tho this is a guess.

Any ideas?
Any pointers on what I can check using the TECH2?
 

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Discussion Starter #3
Replace CPS.
If this will not help, replace ECU.
Agreed, after this morning-had a hard time starting. Never had an issue always started right away, today no start on the first key turn.
CPS is on order

any tips on replacing it on a V6?
WIS is showing to remove the Downpipe
 

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Mine is doing the same with exception of no codes being thown. My mechanic was thinking vapor lock. My fans are not working, waiting for cooling fan relay to come in. In the meantime I've been opening the hood to let it cool down and car now starts after sitting 30 minutes. Are your fans turning on?
 

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Discussion Starter #6
Mine is doing the same with exception of no codes being thown. My mechanic was thinking vapor lock. My fans are not working, waiting for cooling fan relay to come in. In the meantime I've been opening the hood to let it cool down and car now starts after sitting 30 minutes. Are your fans turning on?
Interesting idea, I will check. Are you staying your fans never come on?
I do remember in the summer, after parking the car and removing the key, the fans would run for a couple of mins. This is normal, tho I don’t remember this happening in the fall/winter months as the engine wouldn’t get hot enough.
 

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Discussion Starter #7
I has some time to double check the cooling fans. They are both working (all four stages) via the TECH2. I also double checked that they come on via the temp sensor, they do. When the temp got to 102c they came on and if the temp was >103c and I turned off the car the fans stayed on for 420 secs.
I did find some interesting, the RH fan is black while the LH fan is white. The RH fan puts out a lot more volume of air compared to the white LH fan.
Not sure if it is designed this way or if that fan is on its way out. The LH side fan airflow is over the battery area, coolant overflow tank, ABS, etc.

Is there anyone that can check their Aero for the amount of airflow on each side and reply back?
It is a long shot, but worth checking.
 

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Agreed, after this morning-had a hard time starting. Never had an issue always started right away, today no start on the first key turn.
CPS is on order

any tips on replacing it on a V6?
WIS is showing to remove the Downpipe
Did you check the 2 ground wires on the ECU? While you’re there verify all pins are intact and straight on the 2 ECU wire looms.


Sent from my iPhone using Tapatalk
 

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Discussion Starter #9
Did you check the 1 ground wires on the ECU? While you’re there verify all pins are intact and straight on the 2 ECU wire looms.


Sent from my iPhone using Tapatalk
thanks for the reply and the idea.

As for the grounds, a couple of weeks back I found the ground wires (one think and one thin) one loose and the other one not connected to the ground lug but under one of the mounting bolts. As well as I found two out of four mounting bolts missing. All is back the way it should be and now it ohms .2 from the ECM to battery ground. Tho all of this didn’t resolve the problem.
The ECM pins are all straight and both connectors were cleaned.

I will give an update on the CPS in my next post, as I replaced it Saturday.
 

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Discussion Starter #10
Quick update, sorry for the typos using the Iphone.
Replaced the CPS over the weekend. The job went smoother then I thought it would.
Started with removing the rear cat, the three mounting nuts were rusted to hell. Broken the first stud but was able to remove the next two. Had to pound on a 12mm socket into the rusted 13 mm nut. Had to heat the broken stud to be able to remove it with the vise grips. This was the hardness part.
The WIS states to remove the two cat brackets, this isn’t necessary. Found this out after the fact.
The next step was to remove the CPS heat shield. The first bolt, 15mm I believe, is visible and is on the bottom of the shield. The second bolt is a 10mm and is hidden from view. Located on the top left side of heat shield, gotta go by feel on this one. Once they are both removed, the shield can be moved and the CPS can be seen.
One 10mm bolt and the CPS can be removed.
So far the results have been positive, there would have been three time to where upon starting the car it would misfire..it didn’t. So I got my fingers crossed this will solve my problem.
once I have more news, good or bad, I will update this thread.
A couple of pictures
272159
272160
272161
272162
 

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Looks like you could get at it without removing the cat. Might be a bit more of a PITA but doable.

Have a new CPS sitting on my bench and have been meaning to put it in. I only have hard starting once the car is filled up and hot. Just replaced the coils and EVAP purge valve this morning.

In to hear how it goes for you, hopefully this fixes it!
 

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Discussion Starter #12
If you do replace it with the cat in place, let me know how it goes. I have a 2007 Aero that has a similar problem. My plan is to move forward with replacing the CPS on that one as well when the part arrives.
thanks for the reply.
 

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Discussion Starter #13
Quick update, not as I hoped. Still seeing misfires on re-starts. As the same as before replacing the CPS

I moved forward with pulling the intake and having the fuel injectors cleaned. Waiting for them to come back from the shop. I will update once completed.
 

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Mine always did this in the summer. One good WOT pull through second gear and it would go away. My theory was vapor lock in the fuel rail. Since these engines don't have a return style (circulating) fuel system the fuel in the rail gets heat soaked after shutting the car off. Makes sense with the very specific link to time after shut off when it occurs. One good pull brings enough fresh fuel into the rail to cool things off. Just a theory.
 

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Discussion Starter #15
Hey Garrett Charger,
That is a interesting theory, vapor lock. I did watch the fuel pressure rise from 1.5bar to 3.4bar after turning the car off, took about 15 mins.

Now you got me thinking about heat wrapping the fuel rail. Found this, hook and loop seam. Has anyone used this before?
heat shield

Wish i knew prior, i would have ordered it and wrapped the rail while installing the injectors.
 

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There is a big 7-pin connector near the atmospheric pressure sensor, disconnect it and check both sides of the connecter .
 
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