Weird Starting Problem ... Need some advices

W

White_Hair

Premium Member
Premium
Location
Vancouver, Canada
Hey guys,

I start to have a weird starting problem with my FX in a very random way.

I drove to a gas station getting some thing cold to drink. The weather was pretty hot, like 25C.

I started the car. The car fired up without a problem and right after I fired up the engine, all the rpm dropped down to 0. and all the lights show up like you turn your key to the "ON" state. I was like WTF. Shut my car off and fire up again, everything is fine with no difficulties of firing up.

However, I did notice one thing quite frequent that I started up my car with a warm engine, the rpm revs up when the engine is fired up and then it dropped down to like 500 rpm immediately then climb back to the normal idle rpm.

The car is at 130,000 km. The spark plugs were changed around 100,000 km. I only use 94 octane with all the maintenance done regularly. Battery voltage is at 12.6V.

Tried with a ODBII reader, but cannot reproduce the same problem and no error codes stored in the ECU. It has happened twice within 1 month.

Any advices are welcome and much appreciated. :smile (2):
 
I'm no expert but sounds like maybe a dirty MAF Sensor or possibly a faulty O2 Sensor. Hard to say without it throwing any trouble codes.
 
Thx MTN_FX for the info. When I connect the ODBII reader to the car, one of the O2 sensor voltage always remains constant unlike the other 3 with varying voltages. Could that be the sign? I am not the expert in things related to O2 sensor. Perhaps someone can chime in with some info about O2 sensor voltage?
 
turbocad6 said:
sounds like a dirty throttle body to me, def the first thing to do is clean the throttle body.
Click to expand...

That is also possible. I did do some cleaning the throttle body about 3 months ago for the first time in 7 years owning the car. :tongue (2):

But I will take a look again and see if it needs some more cleaning. But weird thing is, I only have this random problem at starting up, but it is fine driving around.

Do you think is it time to do some mod with the TB? Found this on the ebay: http://cgi.ebay.ca/DNA-90MM-CNC-Bil...r_Truck_Parts_Accessories&hash=item230774d8dc

:wink (2):

Thanks John.
 
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I realized I start to have all these issues after I left my FX in the garage with the battery disconnected for 1.5 months. Should I just go ahead with the relearn procedure? I am not really good with pedal dances.

If taking the TB off, do I need to have a new TB gasket?

Also if I failed the Idle Air Volume Learning (Throttle Position Learning), do I have to re-do the Accelerator Pedal Release Position Learning and Throttle Valve Closed Position Learning?

Sry about bunch of questions. Just wanna be prepared before I actually touch the TB.
 
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Update:

I cleaned the throttle body by removing it and did a thorough cleaning. I also did the entire re-learn procedure following Jeff's instruction and I did see the check engine light blinking and stay on, then I release the pedal and turned the car on within 3 secs. I am pretty sure the re-learn was done correctly.

However, now car is acting more weird. Idle seems fine around 650, but the car shakes as the idle is very rough and rpm starts to drop at idle and seems the car is going to stall.

I guess I need to replace the TB now. :tears:
 
I doubt you ruined anything, probably just knocked it out of calibration. read up on all the reset procedures & try again or have a mechanic hook up a scanner or consult II, worse case should be it needs to be reprogrammed. how did you clean it? I'm sure you were careful?
 
I took the TB off the plenum to clean. It was a difficult job with small alien key and seized bolts. I ended up cutting my finger pretty deep when my hand slipped I cleaned it with the CRC TB Clean Spray thing i bought at local automotive supplier. When I cleaned the TB by moving the plates, I was doing it very careful, there was no snap close. I slowly released every plate movement to ensure there is no sudden close. But I might press the valve to hard?

I also noticed that when I stop at the light or slow down toward the intersection, the sounds from the engine like down shifting, but the tranny is already settle, and then if I leave the car idle for about 20 secs or more, the idle became rough and dropping and seems like the car is about to stall and the engine starts to shake a bit.
 
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fxlr8 said:
Did you make sure you have no vacuum leaks and all sensors are plugged back in?
Click to expand...

All sensors are in place. I got no SES or any other warning lights. Just the idle is very rough to the point that my car is about to idle. However, I did not replace the TB to plenum gasket. I just apply some oil on that gasket for better seal. I hand torque the TB bolts to whatever I can, it was quite difficult with small alien key.

I am guess I probably did not wait exact 20 secs on the last second step in the relearn procedure. I probably rev my engine too soon.

Right now, I have my battery disconnected, MAF cleaned. I will tried to do it again tmr morning.

The plates in the TB are dis-colored, is there any coating on those plates? If I am still hving the same problem after the re-learn tmr morning, I will try to visit the stealership or get my TB replaced.

Do you need to do the re-learn after the TB is replaced? How about those bored TB? Any significant benefit?
 
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Tried redo the learning procedure again. Idle rpm seems fine. However, if I leave the car idle for about 20 secs. The car starts to shake like detonation is not correct. the rpm drops below 650 and car is about to stall.

I also noticed when in full automatic mode, slowing down the car approaching stop, the downshifting becomes more noticeable than before.

Is there a way of check leakage between the TB and plenum. I didn`t replace the gasket, but I tied it to the max i can, don`t know if there is a leakage.
 
Update:

Problem is fixed. I went to get a code scan at the shop my buddy works. It was P0300 - Random Miss Fire (if I remember the code correctly).

There is a leakage at the TB gasket. Replaced it and everything works fine.

Few tips I like to share with people intend to do the TB cleaning -


1. The Idle Air Volumn Learn Procedure:

- In the steps that you will have to full press and release the acceleration pedal within 5 seconds and wait 7 seconds after that. Make sure you start counting the 7 seconds after the previous 5 secs has elapsed. DO NOT count start to the 7 second wait time right after you finish the last pedal release. That will increase your chance of getting into the learning mode by a lot.

2. Removing TB and Cleaning:

- Always try to replace the gasket instead of using silicon. Don't try to save couple bucks on a small gasket. Pretty much all silicon seal will end up leaking after a while due to heat and vibration, no matters if it is rated high temp or not (advice my mechanics friend). It will save you a lot of headache.

3. Tips on Checking Air Leaks on Intake Paths:

- If you noticed weird idle drop and random miss fire symptoms like I do after the TB cleaning, install and learning procedure, having your car engine running and spray the TB cleaner around the TB gasket location or another intake hoses or paths you have re-connected, except the filter itself. If you notice engine responses different (like reving sound, or louder engine operation sound) during idle when you spray the TB cleaner, that is where the leakage located. A tip that many may have know but good to know for newbie like me. :tongue (2):

Again glad to learn a few tricks on working on my FX. :smile (2):
 
White_Hair said:
Update:

...
- If you noticed weird idle drop and random miss fire symptoms like I do after the TB cleaning, install and learning procedure, having your car engine running and spray the TB cleaner around the TB gasket location or another intake hoses or paths you have re-connected, except the filter itself. If you notice engine responses different (like reving sound, or louder engine operation sound) during idle when you spray the TB cleaner, that is where the leakage located. A tip that many may have know but good to know for newbie like me. :tongue (2):
...
Click to expand...

That's a great old school trick. You can also use it to diagnose vacuum leaks elsewhere in the system, not just @ the TB. The plenum gasket, PCV lines, and either of the two lower manifold gaskets just to name a few. :tup:
 
if you don't want to spray a combustible liquid all over your engine you can do the same thing with a propane tank with a hose attached to it. glad you got your problem solved. so is it back to fine with even the original problem solved?
 
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