Anyone else have this problem? Help

[2strokenut]

I have had this 93 4x4 supercab for about 4 months now and I freaking love it. The only thing that has been bothering me is a weird rough idle slash rev.

When I first got it the idle was rough and about 1200 to 1600 rpm is would run like it was misfiring, but no codes. It would vibrate and rock the truck thats how bad it was. I replaced the plugs wires filter thermostat cleaned IAC etc. I haven't changed the cap and rotor yet. It still did the same thing. What I did notice was that when cold ie, start up in the morning it would run perfectly. No rough idle no vibration. Then as it warmed up it would come back and do it again.

Now it has been doing it all the time even at startup. Not sure if its because its not as cold out or what but at the time it was getting into the 30s at night now its been high 40s so I dont know if the temperature has something to do with it.

I've noticed that around 12-1300 rpm it makes the worst vibration then tapers off and revs smooth after 2k. When it decelerates after revving it still makes the same erratic vibration around 12-1300 rpm. This to me is strange since its not firing on deceleration.

I have no codes. Hope I described the problem clear enough. I've been searching for the last few weeks and haven't quite found a problem like mine and most have codes.

Thanks

 

[fourwheelford]

Dirty or bad MAF or vacuum leaks are the first things that come to my mind.

 

[2strokenut]

Dirty or bad MAF or vacuum leaks are the first things that come to my mind.

Wouldn't those things throw a code or 2?

 

[fourwheelford]

Not always, thats why people have such a hard time diagnosing these problems. But high idles are usually unmetered air getting in through somewhere or air that is not being read properly do to a dirty sensor of some sort. Im not totally sure but it seems right to me. A could also be an injector issue or compression issue.

 

[2strokenut]

Not always, thats why people have such a hard time diagnosing these problems. But high idles are usually unmetered air getting in through somewhere or air that is not being read properly do to a dirty sensor of some sort. Im not totally sure but it seems right to me. A could also be an injector issue or compression issue.

Thanks man.

I checked the codes tonight and this is what I got:

KOEO:
176-(M) Oxygen sensor not switching - system is or was lean Left or Front HO2S - Fuel control

KOER:
I originally got a 136, 536, 538 but I did not turn the wheel, press brake and goose the throttle. After that all I got was 111, which is good.

So does this mean my O2 sensors are the culprit? I also noticed upon startup every time (warm) it would rev to about 1800 go down to 1400 then up a bit then down to 1100 then finally to idle around 800. Seems kind of strange.

 

[mitch4712]

MY truck kinda has the same symptoms did you get it fixed?