Is it definitely a CAS problem?

[gordonq45]

Hi,

My aged Q45 is back for help!

Last year, my 90 Q45 had an engine light on problem that was not steady (see the thread "Try to understand my aged Q45"). At that time, I can not make conclusion what problem it was because the ecu code was not available.

Now the same problem pup up again. The car stalls on the road several times, but I can restart the car by press the gas paddle harder and drive the car with engine light on. The RPM is not stable that jumps up and down with the engine light on, especially at around 2000 RPM. I checked the ECU twice that shows the same code as 11 (one long and one short). I cleared code from ECU memory after first time to make sure the result is new code, not left from before.

Please help to make some suggestions:

Is it definitely the Crank Angle Sensor problem?? I read several threads on this forum with similar symptom and each one had little different reason such as MAF, fuel pressure regulator etc.

If it is the CAS problem, what is the proper action to fix it? rebuld? repair or replace it?

Can I do it by myself or I have to send car to a shop? If it can by done by DIY, I can call Joe for the parts. What is the procedure to remove the CAS?

Thanks,

[Q45tech]

Check/clean both connectors on CAS [the easy one on the body and the harder one with a dangle and connector under the front decorative cover.

[gordonq45]

I'll do it today. It there a better way to clean the connectors? Do I need some special chemical?

Thanks,

[Q45tech]

Not to say that CAS and MAF don't fail, but at $500 each , you try other things first.

[gordonq45]

Thanks lot. It is a very good catch from the Q45tech.

I checked both connectors of the CAS. The flat pins inside one connector socket are rusted. I sanded the pins and reconnected.

I also checked the connector of round object at up left of the CAS that may be the sub-CAS, I'm not sure. That connector has rusted pins too. I did the same cleaning.

I drove few miles for a testing, so far so good. I'll monitor the situation and post the result.

Thanks again.

[Q451990]

Good job! To prevent more corrosion, be sure to pick up a tube of di-electric grease at your local auto parts store. Unplug the connector and put some of this stuff on the pins.

Heath

[gordonq45]

Thanks for the suggestion. That is a good idea. I'll put di-electric grease on the connetors.

[gordonq45]

I believe the CAS problem has been fixed after cleaning up the connectors and putting di-electric grease on them. It has been few weeks and has no problem so far. THANKS AGAIN FOR EVERYONE'S HELP.

One exprience can share with you!

Last weekend, I can not start my car after refueling my car and back to my home. I searched the threads about this problem that most point to fuel pump problem. I use the same philosophy provided by Q45tech to check the wire first. I open the back trunk and disconnect and reconnect the connectors of fuel pump and fuel controller ( I DO checked the connector pins and they are ok, not rusted) . The problem is gone after reconnect them. So far it is ok.

SO, WE CAN/SHOULD CHECK THE WIRE AND CONNECTORS FIRST BECAUSE THE CAR IS GETTING OLD AND CONTACT COULD BE A PROBLEM.

One more issue on my car is idle. The idle is pretty low if the gear moved to Drive/Rev position, about 500-530, after the engine reaches to normal tempreture. At P/N position, the idle is ok, about 700.

Please give a suggestion to find out the reason of this issue.

Thanks,

[Q451990]

I'd pull the FPCU and check the internal electronics for overheating. I've seen two now that the connector is fine, but the transistor-looking parts inside are toast. If the pump is humming when you're below 1/2 a tank and you can hear it at idle - you have a problem! If moving the connector around fixed your problem then you are running on very borrowed time and could be stranded at any time...

The idle problem could be fuel pump related, but is probably due to a dirty throttle body, plenum, intake runners, etc. A quick cover-up is to adjust the AAC valve (back of plenum near firewall) by turning the screw out a turn or two. Definately a cover-up, but it'll help for a week or two until you have the intake cleaned.

Heath

[Q45tech]

Slow idle usually means that the air flow is restricted [assuming someone didn't fiddle with air adjustments.

The IAC normally should show a 10-15% duty cycle when engine warm.

75-80% under throttle plate, 10% from IAC bypass screw setting opened 2.5-3.0 turns], and 10-15% from the extra air the IAC solenoid allows.

Since the leakage around the throttle plate is 75% of air, a little dirty oily crud can make major changes in idle speed.......the ecu tries to correct with IAC solenoid duty cycle.

Back yard mechanics open the bypass screw instead of cleaning the throttle body and IAC passages.........getting everything out of whack.

[gordonq45]

Sorry everyone, my response is so late. I haven't get a chance to put my hands on the car yet. Possible in the next few week I'l try to find time to work on that.

Thanks for everyone.

Gordon

[Q45tech]

Members should acquire a used FPCU as a trunk spare. You never know when you might need it especially if your unit is over 7 years old..........mine finally failed at 14 years out lasting 3 pumps.