engine idling rough question
 

I have said my Land Cruiser is bullet proof. Well, it has been for a long, long time. I'm afraid this time it has come to haunt me. Got off the fwy and pulled up to a stop sign I felt the engine idling really rough to the point of of only 3-400rpm, I popped it in N, and gave it a few revs to clear its throat. No go, so I limped home. As soon as I give it some gas the roughness goes away but it lacks power like normal but it does drives ok. It has over 200k of trouble free miles on the original motor. Its time to spend some time and money on it. Its too dark to monkey with it now. I am thinking Ignition. I sure hope its just a bad plug. I restarted it once I parked it, and It had a bit of trouble starting but another try got it going. anything else I should look at before I take it in?

Jeff

anyone?

Is it newer than 1996? OBDII? CHeck engine light?

It could be just about anything from a plugged fuel filter to a bad sensor. There should be some information from the computer to tell you what it thinks is the problem.

yeah - need to know = will be much easier diag

rough at idle, clears up on run, might suggest a vacuum leak somewhere. Cracked hose or something.

How "rough?" Like dirty throttle body rough or misfire rough?

200k miles, ever change the ignition wires?

Its a 93. It feels like misfire rough. When I drive it, it doesn't feel smooth as the RPM climbs. That leads me to think its ignition. No check engine light on. I am going out to mess with it now to see if its a simple fix. The wires has been changed 40,000 miles ago. I am thinking cap and rotor or plugs, even all that has been changed at the same time. Keep em' coming gents.

Jeff

If it truly runs fine at slightly higher rpms, and not at idle, CONSIDER that it may have carbon build up around a valve stem making it 'stick' (or not seat completely) at low speed/pressure. Although it could be dozens of things. Once you've ruled out the more obvious, do a leak-down test.

When was the last time you got gas?

Bad tank?

Is the cap on properly? (That will usually throw a CEL though)

Look for burn-through on the wires, check vacuum hoses, Pull one plug wire at a time. Spray carb cleaner around intake...

A '93 will still have a lot of sensors on it. TPS is one that is suspect in this case. Or the parameters that feed info to the ECM that then tell the TPS what to do. Observe the TPS actions and see what it's doing. O2 can have something to do with it, too.

As much as we want to not like OBDII, it does tell you more.

O2 will cause an even poor running situation like decreased power - not a miss.

TPS could cause erratic throttle and poor running but not usually a miss.

it may be fuel injectors if it is not the spark bits

simple test is to un-plug the wire clip one at a time and note change/ no change
they due both plug up or leak
anyway it is free to check

an other quick check is ground wires
and connector plugs pop them open look for corrosion and spray on a little cleaner
again costs a little time and spray

Well you fix it then. I only know what has happened to me with an early 90's OBDI car.

Good gas, I run it once a week. No check lights on at all.

Sounds like my '92 Toyota 3.0 V6 I just got rid of. 182,000 miles...The cause was low compression (70-80) in two cylinders. A simple compression test told me all I needed to know....

Sorry didn't mean to offend. You could also be correct. Just helping the poster out. SmileWavy

Is that the 3FE engine? Could be the cap and rotor, or try and run some Seafoam into the brake booster vacuum line going into the firewall. Pour until it starts to smoke, turn off the engine and let it sit for 20 min. Start back up and blow that stuff out till it stops smoking (it's going to smoke A LOT).

I have the 1FZ EF engine. I have read about the Seafoam. So people use a funnel to force in Seafoam? I have always think about that. Have you try this stuff in your gas tank?

Possibly an EGR valve stuck open or not sealing when closed?

That should throw a code with the check engine light? What gets me is there is no check engine light. I am still thinking its something simple but just can't think of anything else.

It might throw a code but might not. It didn't on my obd1 Mazda. I diagnosed it by cutting a gasket which covered the EGR hole blocking any flow. My idle improved dramatically.

If I understand the CEL on OBDI cars, it only comes on in dire circumstances. It is not a sign to pull out your code reader. It's a sign to check the basics, like coolant.

A stuck smog valve would be a culprit as hardflex said.

Before dumping Seafoam in the thing, think about the cat. Better to find the problem directly, IMHO, of course.

EarlyPorsche, sorry, bad mood.

I depends on what sort of miss you have. EGR leak is sort of a weakening of firing, almost like it's running out of gas. Not a regular miss that a fouled plug or bad wire/injector would produce.

Common test of EGR is to apply a vacuum to the vacuum port on the EGR while idling. If the engine starts to die it's working. If it's leaking it's dieing on a smaller scale.

Unhook a vacuum hose (brake booster is biggest diameter) to the intake manifold and stick it in the open can and it will draw it out of the can and into the intake

It works well in the gas tank, but that's a completely different system getting cleaned