1996 Chevrolet Truck very rough idle.

Tiny
SHUFF2249
  • MEMBER
  • 1996 CHEVROLET TRUCK
  • 5.0L
  • V8
  • 2WD
  • AUTOMATIC
  • 170,000 MILES
Have changed plugs, wires, aic valve, egr valve, cleaned mass airflow sensor and throttle body. Still Idles very rough and a lot worse when in gear. Much better when accelerating. Please help.
Do you
have the same problem?
Yes
No
Sunday, March 9th, 2014 AT 5:59 PM

8 Replies

Tiny
OBXAUTOMEDIC
  • EXPERT
Hello,

Ok, unless you forgot to mention it you didn't replace the Distributor Cap & Rotor.

I would remove the cap and take a look inside if the electrodes are corroded or worn down replace both.
Was this
answer
helpful?
Yes
No
Sunday, March 9th, 2014 AT 7:08 PM
Tiny
SHUFF2249
  • MEMBER
Thanks for the reply. Changed the cap and rotor and truck idles much better. However after it warms up, while still idling much better, the rpms go down and I can hear the occassional ping again. Anything else you might recommend.
Was this
answer
helpful?
Yes
No
Sunday, March 23rd, 2014 AT 1:33 PM
Tiny
OBXAUTOMEDIC
  • EXPERT
Ok, is engine light on? If so could be the Knock Sensor, it is suppose to control the ping.

The knock sensor is located on the engine block, cylinder head or intake manifold. This is because the function of this sensor is to sense vibrations caused by engine knock. The PCM uses this signal to alter the ignition timing and prevent detonation. It will compare this information with its preset tables to identify an engine knock or ping. If a ping is sensed it will retard the timing to protect the engine from this damaging pre-ignition.

The knock sensor is a piezoelectric sensor that contains a piezoelectric sensing crystal and a resister. This crystal creates a small amount of voltage when shaken. This sensor takes advantage of this unique property.

Symptoms: The symptoms of a bad knock sensor usually show up at highway speeds or under a load. Be clear that this sensor effects the ignition timing of an engine. The vehicle will have a loss in fuel mileage and acceleration especially at highway speeds. The customer may complain that the vehicle's engine doesn't feel right. Some COP coil on plug systems use strategies that cancel cylinders, see the manufacturer's manual for special instructions. Some of these are located on the cylinder heads under the intake manifold. The vehicle's computer will detect a bad knock sensor, set off a code (P0325-P0332), and enter fail safe mode.

KS Location

On left side of engine block, below exhaust manifold, forward of starter.

Other cause could be low Octane you could try adding an Octane Booster to see if clears it up.

Question - Has anyone mess with the distributor, remove the hold down bolt or removed the distributor?
Was this
answer
helpful?
Yes
No
Sunday, March 23rd, 2014 AT 5:32 PM
Tiny
SHUFF2249
  • MEMBER
Thanks for your reply. The check engine light does not come on. Actually drives much better when driving on highway and does not have the ping. Could it be caused by carbon build up and, if so what is the best product to uze.
Was this
answer
helpful?
Yes
No
Sunday, March 23rd, 2014 AT 5:51 PM
Tiny
SHUFF2249
  • MEMBER
Oh sorry. Nobody has messed with the distributor.
Was this
answer
helpful?
Yes
No
Sunday, March 23rd, 2014 AT 5:52 PM
Tiny
OBXAUTOMEDIC
  • EXPERT
I use SeaFoam pic attached, also check the vid on use...

http://www.youtube.com/watch?v=vRAV5ln5cUc
Was this
answer
helpful?
Yes
No
Sunday, March 23rd, 2014 AT 5:55 PM
Tiny
SHUFF2249
  • MEMBER
Thank you.
Was this
answer
helpful?
Yes
No
Sunday, March 23rd, 2014 AT 6:01 PM
Tiny
OBXAUTOMEDIC
  • EXPERT
No problem. If you would once you are Satisfied with results please click on the User Satisfied button at bottom.
Was this
answer
helpful?
Yes
No
Monday, March 24th, 2014 AT 7:37 AM

Please login or register to post a reply.

Recommended Guides