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post #1 of 12 Old 08-15-2015, 10:54 AM Thread Starter
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Folks - engine shudders and shakes initially at startup

Upon startup - You can watch the tach and see that the computer is making adjustments for about 10 seconds and then she idles fine. Upon restart later it may do the same thing, or, the symptom may be more brief or non-existent. No codes...copper autolite oem/rec plugs are 2,000 miles. I have changed ecm boards w/no change. Sensor? Clean the throttle body? Replace plugs anyway/brand? All ideas appreciated...thanks

Last edited by jimmytroy; 08-15-2015 at 10:54 AM. Reason: sp
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post #2 of 12 Old 08-17-2015, 06:04 AM
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Re: Folks - engine shudders and shakes initially at startup

If the problem is only on initial startup after sitting the first thing I would do is verify you are getting proper fuel pressure on startup.

If the pump is weak or there is a bleed down problem it make take a few seconds as you are describing to get the proper fuel pressure.

As far as your TB, if it is dirty/carboned then Yes, clean it.

CHECKING FUEL PRESSURE
https://www.turbododge.com/forums/f4/...-93-turbo.html

THROTTLE BODY/AIS MAINTENANCE
https://www.turbododge.com/forums/f4/...automatic.html

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post #3 of 12 Old 08-17-2015, 06:20 AM
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Re: Folks - engine shudders and shakes initially at startup

Misfire at startup?

Maybe a plug is being fouled by antifreeze or some other fluid and clears up after a few seconds.
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post #4 of 12 Old 08-17-2015, 08:07 AM
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Re: Folks - engine shudders and shakes initially at startup

Im having the same problem. I'm hoping this gets resolved. Mine does the same thing. It feels to me like a fuel feed issue. It takes a bit to crank it over and she finally starts. Once started I'll get a shake and noise, followed by almost stalling out. Once it evens out she drives fine for hours. I'm convinced its a fuel pump TBH. Will let you know if I get mine fixed before you!
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post #5 of 12 Old 08-27-2015, 02:05 PM Thread Starter
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Re: Folks - engine shudders and shakes initially at startup

Quote:
Originally Posted by NAJ View Post
If the problem is only on initial startup after sitting the first thing I would do is verify you are getting proper fuel pressure on startup.

If the pump is weak or there is a bleed down problem it make take a few seconds as you are describing to get the proper fuel pressure.

As far as your TB, if it is dirty/carboned then Yes, clean it.

CHECKING FUEL PRESSURE
https://www.turbododge.com/forums/f4/...-93-turbo.html

THROTTLE BODY/AIS MAINTENANCE
https://www.turbododge.com/forums/f4/...automatic.html
I passed step 1 and got the 57 with the ASD actuated and 80 w/return line pinched and the 57 holds after disconnect. Now I'm trying to understand the steps from line 2c and 2d. The word "as" in "as you deactivate the pump pinch..." is not clear to me. In what order do I do what, in other words? I previously mounted a fuel gauge permanently just before the fuel rail - is that a sufficient location to take these readings?


2C)Re-Pressurize the fuel rail and as you deactivate the pump pinch off the return line, if pressure now holds replace the FPR.
(Always remove and check the FPR vacuum line for raw fuel, if fuel is found replace the FPR)
D)If pressure does not hold repeat the fuel rail pressurization and this time as you deactivate the pump pinch off the fuel inlet line.
If pressure now holds replace the fuel pump.

Last edited by jimmytroy; 08-27-2015 at 04:26 PM.
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post #6 of 12 Old 08-27-2015, 05:43 PM
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Re: Folks - engine shudders and shakes initially at startup

If you deactivated the ASD and pressure held when the pump was turned off you do not need to go any further in your fuel pressure diagnostics.
The additional diagnostics only needed to be performed if the pressure dropped quickly after the pump was turned off.

The only other thing I would advise you to do is connect the fuel pressure gauge after the car has sat overnight and see how long it takes fuel pressure to build when cranking after sitting overnight and what fuel pressure is reading running when the "idle shaking" problem is happening.

Remember, rail pressure will drop 1 PSI for every 2" HG applied to the fuel pressure regulator with the engine running.

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post #7 of 12 Old 09-04-2015, 01:38 PM Thread Starter
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Re: Folks - engine shudders and shakes initially at startup

changed the plugs to champion RN12YC and as of 10 starts still no shudder...old plugs were only 3k

however, still runs hot ... and there is a squeal (like a belt) about a third of the time when I start it...does this sound like it could be the water pump?
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post #8 of 12 Old 09-04-2015, 07:26 PM
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Re: Folks - engine shudders and shakes initially at startup

The squeal on startup sounds like a loose belt.
Have you verified actual coolant temp yet?
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post #9 of 12 Old 09-05-2015, 06:11 PM Thread Starter
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Re: Folks - engine shudders and shakes initially at startup

Quote:
Originally Posted by NAJ View Post
The squeal on startup sounds like a loose belt.
Have you verified actual coolant temp yet?
I verified that the fan cuts on when the temp needle is at 6 oclock...when I am moving down the road the needle sits at 7 or 8 oclock and can rise to 5 oclock when I am stopped at a light in mid-day. Should the temp reading stay in more constant position. (I drilled a hole in the new thermostat as specified on other posts and maybe that's why the fluctuation)

I saw the pic of the backprobe on the CTS and it was not clear...are each of the leads connected to a side of the sensor? Why am i trusting the back probe reading volts to chart for the true temp...seems like an infrared therm would be useful? I'll get the data off the backprobe...what does one slip into the connector wire ports, paper clips? It looks tight and I don't want to force in the meter probes if they are too big. Do I begin my readings from cold startup and let the thing run till it maxs out?

Tried to tighten the alt/wp belt and it seems to be at its max (can twist the belt by finger 180 deg and the sliding bolt has no more room to travel)...cleaned black dust from the pulley...perhaps the effort made a difference...will install a fresh (presumably shorter) belt. Could the water pump be seizing and causing the pulley to not turn properly...looking into weep with magnifying glass shows no sign of fluid yet. I'm suspecting the water pump but the other posts do not reveal a test. Will have a chem block test on the head on wed by a local pro (free). I tried the test myself with AZ loan materials but do not trust my ability to discern a color change.

I am fighting the tendency to assume the squeal, running hot, and stumble are all from the same problem- a leaking head. I am a true rookie doing my best to keep this on the road (I've had it 15 years)-many people like my td minivan. Thank you for your patience.
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post #10 of 12 Old 09-08-2015, 06:40 AM
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Re: Folks - engine shudders and shakes initially at startup

Quote:
Originally Posted by jimmytroy View Post
I verified that the fan cuts on when the temp needle is at 6 oclock...when I am moving down the road the needle sits at 7 or 8 oclock and can rise to 5 oclock when I am stopped at a light in mid-day. Should the temp reading stay in more constant position. (I drilled a hole in the new thermostat as specified on other posts and maybe that's why the fluctuation)

I saw the pic of the backprobe on the CTS and it was not clear...are each of the leads connected to a side of the sensor? Why am i trusting the back probe reading volts to chart for the true temp...seems like an infrared therm would be useful? I'll get the data off the backprobe...what does one slip into the connector wire ports, paper clips? It looks tight and I don't want to force in the meter probes if they are too big. Do I begin my readings from cold startup and let the thing run till it maxs out?
The gauge on the dash is not accurate and never has been and never will be.
In the summer time my gauge reads at the 3/4 mark when the fan cycles on and in the winter it only goes to the 1/4 mark before the fan cycles on but coolant temp has been verified to be the same and correct, she has done this since new.

The CTS is actual coolant temp that is used by the engine controller for fuel and fan control, that is where you need to read coolant temp.
Pretty simple procedure to backprobe the sensor connector and connect a digital voltmeter.
You can use paper clips or backprobe pins.
Backprobing allows you to connect test equipment without causing damage to the terminals.
Fan should cycle on at 212 degrees, if the temp drops and the fan cycles off you are not running hot.

Does not matter what temp is when you start reading temp, you are looking for max temp when the fan cycles on.

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post #11 of 12 Old 09-08-2015, 06:45 AM
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Re: Folks - engine shudders and shakes initially at startup

Quote:
Originally Posted by jimmytroy View Post


Tried to tighten the alt/wp belt and it seems to be at its max (can twist the belt by finger 180 deg and the sliding bolt has no more room to travel)...cleaned black dust from the pulley...perhaps the effort made a difference...will install a fresh (presumably shorter) belt. Could the water pump be seizing and causing the pulley to not turn properly...looking into weep with magnifying glass shows no sign of fluid yet. I'm suspecting the water pump but the other posts do not reveal a test. Will have a chem block test on the head on wed by a local pro (free). I tried the test myself with AZ loan materials but do not trust my ability to discern a color change.

I am fighting the tendency to assume the squeal, running hot, and stumble are all from the same problem- a leaking head. I am a true rookie doing my best to keep this on the road (I've had it 15 years)-many people like my td minivan. Thank you for your patience.

Alternator belt sequel on these cars are a common problem that can be caused by a...
1)Loose/Worn Belt
2)Alternator Mount Bushings Worn or Isolator Bracket Worn.
3)Rust/Dirt/Grease/Oil in the Pulley

There is no test for a water pump.
It is either noisy, leaking or the pulley is loose.
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post #12 of 12 Old 12-28-2016, 11:36 PM Thread Starter
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Re: Folks - engine shudders and shakes initially at startup

ngk plugs make a big difference at startup
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