Violent shaking on cold start!
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Senior User
Joined: Sep 2003
Posts: 184
Likes: 0
From: Ohio
Violent shaking on cold start!
What is going on?!
Lately my 92 4.0 a4ld shakes fairly violently on cold start and tries to die on me. I have to tap the accelerator several times to keep it from dying, and the van continues the hard shaking until the engine warms up. After that it's fine.
This has been happening on cold start only no matter what the outside temperature is.
The tranny was rebuilt a couple of moths ago; regular oil changes; tune-up last year; decarboned last week.
What could be causing this to happen?
aerostargal
Lately my 92 4.0 a4ld shakes fairly violently on cold start and tries to die on me. I have to tap the accelerator several times to keep it from dying, and the van continues the hard shaking until the engine warms up. After that it's fine.
This has been happening on cold start only no matter what the outside temperature is.
The tranny was rebuilt a couple of moths ago; regular oil changes; tune-up last year; decarboned last week.
What could be causing this to happen?
aerostargal
Lead Driver
Joined: Oct 2004
Posts: 8,062
Likes: 35
From: Central Oregon
The mass air senser, senser just before the TB on the intake, may be dirty. When my 90 4.0 started something like that I would give it rap, and it would smooth out. I did replace it soon after and no problems with now.
Post Fiend
Joined: Apr 2005
Posts: 5,720
Likes: 5
From: Washington state
Try cleaning the Mass Air Flow sensor, 3" long aluminum cylinder that connects top cover of air cleaner to long black air flow tube, spray with electrical contact cleaner or aerosol fuel injector cleaner, has a narrow vertical port in center that has exposed heated electrical wires which become contaminated with dirt, oil, chemicals, etc. No longer supplies correct signal to PCM computer.
Also clean I.dle A.ir Control located on the top or side near the front of the throttle body with same sprays. May be plugged/contaminated, affects idle performance, controlled by PCM. Ferd states in service info the IAC is not cleanable/serviceable--replacement only. Unplug when cold and check how the engine starts, if better starting and running cold with IAC disconn.--replace IAC.
While you have the cleaner spray out and hood up, clean throttle body plate area, dirt and contamination build up in narrow gap areas between plate and body, affects idle performance.
Also clean I.dle A.ir Control located on the top or side near the front of the throttle body with same sprays. May be plugged/contaminated, affects idle performance, controlled by PCM. Ferd states in service info the IAC is not cleanable/serviceable--replacement only. Unplug when cold and check how the engine starts, if better starting and running cold with IAC disconn.--replace IAC.
While you have the cleaner spray out and hood up, clean throttle body plate area, dirt and contamination build up in narrow gap areas between plate and body, affects idle performance.
Last edited by 96_4wdr; Aug 10, 2005 at 12:59 PM.
Post Fiend
Joined: Apr 2005
Posts: 5,720
Likes: 5
From: Washington state
my 4L Aero hates that cheap Fed EPA/ corn farmer pure grain alcohol 200 proof they pollute real gas with in the winter time. more gas booze is coming compliments of the NonEnergy bill =lower fuel mileage again.
My mileage drops 2-3 mpg on the corn liquor rockgut and is really gutless.
My mileage drops 2-3 mpg on the corn liquor rockgut and is really gutless.
Post Fiend
Joined: Apr 2005
Posts: 5,720
Likes: 5
From: Washington state
Since we don't know what was used or how the carbon was cleaned by the mechanic, I would spray clean the tb plate closure area, do not wipe this area on the throttle body throat, some are coated with a substance that improves high velocity air flow, tb teflon?.
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Laughing Gas
Joined: Jun 2004
Posts: 1,240
Likes: 3
From: Dallas, Texas
Check the Pressure regulator too. I found a small leak in mine. It would take 2~3 times too start when the tank was half full or less. It started fine when full or close to full. Showed no problem when I check regulator. It had a small hole that would leak down when it set over night.
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Hopefully you are not seeing more than normal white smoke coming out the tailpipe. That and the rough starts was the first signs that I had a coolant leak in one of the heads. But at 200K miles, who am I to complain! Good luck!