Please help. I recently purchased a 92 club cab 4x4 automatic
with 162,000 miles. The truck is bone stock with the exeption
of a muffler shop bent 3" system with a large oval car type muffler. The problem I am having is that the truck shakes
terribly at idle. The problem goes away just off of idle. I have
had the idle bumped up and this has helped but it is still bad.
I dont know if the exhaust system(muffler) is the culprit, too
much back pressure, but anyone who has any info on this
condition would be of great help. The truck is also getting
very poor milage,10-20mpg, and I have not noticed any smoke.Thank You for any help.

 

Sorry about your problem. To me it sounds like a dead cylinder. You can find it by loosening each injector line, say 1/2 turn, with the engine idling. WEAR SAFETY GLASSES!!! Start with #1 (front). Did it slow the engine down? OK, snug that one back up and move on down the line. Find the one that has no reaction on engine speed. That is the one to concentrate on. Remove that valve cover and check for valve lash ( being accurate is not important at this time), just make sure you can move the rocker arms a little when the valves are closed. If you find you have one that has no lash, loosen it until it does. Put it back together and see if that cylinder has come back to life. If it has, I would have a complete valve adjustment and compression check done to insure it hasn't been run too long like this and burned a valve. Enough from me, and welcome to the site! Jim

 

What is your definition of having the "idle bumped up"...???
Were is it now??

You may well have a bad injector which you will find using the loosen/tighten method mentioned above..
You may also try removing the injector nut, lifting it up a bit off the injector, carefully lining the injector line DEAD FLUSH with the injector top, hold in place and carefully rethread and tighten the injector nut.
If the line and injector top are not mated dead on, that can cause a nasty shudder/miss, and it gets worse when you put it in gear too....

Get back in here with some info and results...

bob.

 

Just in case you weren't convinced -- YES, to both of these responses.

Good luck!

 

Idle speed should be about 750 rpm while in Drive and your A/C is turned on. If you do not have a tach, I would then just try turning the idle up a little bit until it smooths out. Then go for a drive. I have noticed that my idle is a little HIGH when I can idle through a parking lot and I need to leave my foot on the brake to slow the truck down. It should just creep along at an idle. Since getting a tach, it is dead on for 775 rpm now. Anything lower and my teeth start to rattle.

 

Thanks for all of the great tips. I checked the injectors by cracking the nuts loose,
great tip on the safety glasses, Each injector caused the engine to run rougher.
I was hoping that this was the problem so I would have good excuse to upgrade
the injectors. I am going to have the valves adjusted just as a precaution. I have
not had time to check the injector alignment but will do so soon. This problem is strange because the engine appears to be smooth even though the cab is shaking. the problem is almost like a resonance so I question the exhaust.
I used an infer-red heat gun to check the exhaust manifold at each port and
each port was within 10 degrees of each other. I also checked the exhaust
system and found it to be 30 degrees hotter in front of the muffler than behind
it. I need to check a friends truck to see if this is normal. It seems to me that the
temp differance could be caused by too much back pressure. I also need to check
to find out what the idle speed currently is. I will get back with that soon. thanks
again for all of the great help.

 

Straight pipe it!...check the motor mounts for the heck of it too.

 

Sounds weird, hard to explain what you mean with bad vibration. My 93s flexplate just went south. at idle you could feel it through the floor like someone was hitting it with a hammer. at anything off idle it was smooth. pull off the inspection cover on the bell housing and look for matal dust and shavings.
Good luck. apache.

 

I finaly have a answer. I got rid of the vibration by replacing all of the engine and
trans mounts. The originals looked o.k. but after replacing them it went away.
I also installed a 4" exhaust system from Dodgepickups.com. it has made a
difference in power and fits well. Any suggestions on my next performance step.
Also does any one have any hints on installing a egt and boost gauge. Thanks to everyone for all of your suggestions. This site has been a huge help in getting
the performance out of this truck that I was used to with my last one(02 dodge
quad cab 4x4 ctd 5-gear xlt plus), I sold it to build new house, and shop, for
growing family. Who says that we dont make sacrifices. again thans fo the help.