Rough Idle After Driving-2.7L

I am having a rough idle issue with a 1995 Tacoma 2.7L.

The engine has 200K on the bottom end and about 50K on a head gasket/head job.

I first noticed the rough idle after coming off the interstate and coming to a stop and it would usually clear itself up after shutting the engine off. This would only happen only occasionally at first.

Now I can short the battery terminals and restart which will get rid of the problem until I run it back down the road. A few minutes of driving will cause the issue. I can run it forever idling and sitting in the driveway with no issues and once it starts I can turn the engine off and come back the next day and still have the issue until I short the cables.

I have replace the plugs, and cleaned the MAF and throttle body. There are no CEL codes.

Unplugging the MAF after it starts runing rough only improves the idle slightly so I do not think it is the MAF.

Catalytic converter and o2 sensors have about 50K on them.

Has anyone ever experienced this? Any Ideas?

Thank you in advance for any info.

 

I have a 1993 4cyl. Last time I encounted a bit of a vibration at idle I was due in for adjustment of the pushrods. My understanding is that my engine has solid lifters. When I idle rough again I will schedule it again.

 

I think I found my problem. There was a vaccum leak on the side of the throttle plates that does not have vaccum until the throttle is opened. I guess the small amount of unmetered air that would come in while driving was affecting long term fuel trim to the point where it would not idle. Each time I reset the ECM it would clear the long term trim and it would run fine until the ECM tried to adjust and the long term fuel trim would get back out of whack. The earlier incidences of rough idle following interstate driving could have been unrelated.

Thanks,
Charles

 

That wasn't it.

It ran great for a longer period of time but that was not it. Also I am noticing that shorting the cables could have been coincidental as well because today after driving I was not able to get it to run better after shorting the cables. When it is idling rough it it accelerates as if it is loading up but it still has plenty of power. The last time that it ran this way it was the head gasket.

I guess compression tests and leakdown tests will be next. It passed compression tests before with a bad head gasket but the leakdown bubbled the overflow reservoir.

Anyone have any other suggestions?

Thanks,
Charles

 

So I figured out that the rough running/rough idle only occurs after having my foot into it which points to something that is failing under stress. I dropped in another distributor last night that I had laying around and drove it like I stole it for 30 miles to work this morning with no issues. I am keeping my fingers crossed.

 

Keep the post going..i have this with my 96. Just had u tuneup done too..no fuel filter change tho..mayb should have. Shouldnt they have said something bout my distributor?

 

Definetly replace the fuel filter. An engine straining to pull fuel through a dirty filter will cause that problem.
Replace all of your vac lines, hunting for leaks is a waste of time on an engine that old.
Is that engine coil on plug, or coil pack? In the dark, mist the coils and wires(coil pack) with water and look for arcs. If coil on plug, did you replace the insulator boots? They will arc out, and you won't see it.
Remove the air induction hoses, stick a flashlight inside the hose(in the dark) flex the hose and look for leaks.

 

Soozin,

Are you still having issues with your Tacoma? If yours does have a distributor and you are experiencing the same issues as I was then I would not suggest spending the money on a distributor without having someone troubleshoot a little more. I happened to already have a whole distributor from a previous engine swap. The ignition coil is in the distributor along with a pick-up coil which appears to be a cam sensor. My guess is that the sensor inside the distributor was bad becasue I would expect misfire codes if the ignition coil was bad.

Charles

 

I believe his is neither type of ignition system you mentioned. He mentioned that he installed a replacement distributor to test. I agree with you that a fuel filter would be a good idea to consider. especially if it has not been changed for a while.

 

Missed that. Plugs,wires, cap, rotor, vac lines=smoooth. Fuel filter is normally a stall issue, but cheap insurance.