Rough Idle

[DeanoDeano]

I have a 98 Ranger, 4.1 liter, manual tanny. It runs rough at an idle. Over the years I have replaced the plugs, wires, coil and EGR valve. Nothing seems to help. It runs fine at speed. Any input is appreciated

 

[Uncle Gump]

I moved this to the 4.0L forum... will get better views.

Does the idle want to ramp up and down in RPM?

 

[DeanoDeano]

Thank you. It does not ide up and down. It just grumble/rumbles at idle. Does not matter iffy it is warmed up or not.

 

[Uncle Gump]

You say it runs well off idle and just cruising?

Does it start at higher idle then settle down to running like crap?

 

[DeanoDeano]

You say it runs well off idle and just cruising? Yes

Does it start at higher idle then settle down to running like crap? No, it does not have a high idle phase. It has a normal idle speed, and runs idles rough no matter whether the engine is cold or hot.

 

[Uncle Gump]

It kind of sounds like your IAC solenoid isn't working.

 

[sgtsandman]

I’m inclined to agree. There should be a high idle until it warms up some then it will work it’s way down to a regular idle. The Intake Air Control Valve doesn't sound like it’s operating correctly.

It is possible that it’s just cruddy from years of operation. You could pull it and take a look. If it looks cruddy and clogged or partially clogged up, you could try cleaning it first and see if that fixes the problem. If it looks pretty clean, time to replace it.

Keep in mind, new parts don’t necessarily mean it’s a good part. Especially if it’s an aftermarket part. So, don’t immediately assume that wasn’t the problem if it doesn’t fix it.

There is a way to test operation and proper voltage but I don’t have that information on hand. So, don’t want to give you bad information. You would want to check the voltage to make sure the IAC is getting the correct signal before replacing anything. No point in throwing a part at the problem if it’s a wiring issue. A new part won’t fix bad wiring.

 

[DeanoDeano]

I’m inclined to agree. There should be a high idle until it warms up some then it will work it’s way down to a regular idle. The Intake Air Control Valve doesn't sound like it’s operating correctly.

It is possible that it’s just cruddy from years of operation. You could pull it and take a look. If it looks cruddy and clogged or partially clogged up, you could try cleaning it first and see if that fixes the problem. If it looks pretty clean, time to replace it.

Keep in mind, new parts don’t necessarily mean it’s a good part. Especially if it’s an aftermarket part. So, don’t immediately assume that wasn’t the problem if it doesn’t fix it.

There is a way to test operation and proper voltage but I don’t have that information on hand. So, don’t want to give you bad information. You would want to check the voltage to make sure the IAC is getting the correct signal before replacing anything. No point in throwing a part at the problem if it’s a wiring issue. A new part won’t fix bad wiring.

Thank you Mr. Sargeant and Mr. Uncle. I pulled the IAC and it didn't look too cruddy, but I filled the open ports with carb cleaner and let it sit for about 5 hours. Gently cleaned it with q-tips amid reinstalled it.

Immediately the idle revs went to about 2500 and it would not throttle down even when fully warmed up. The check engine light came on.

I replaced the valve and idle dropped back to 800-900 revs and the idle is smooth.

 

[Josh B]

Awesome Deano

 

[sgtsandman]

Thank you Mr. Sargeant and Mr. Uncle. I pulled the IAC and it didn't look too cruddy, but I filled the open ports with carb cleaner and let it sit for about 5 hours. Gently cleaned it with q-tips amid reinstalled it.

Immediately the idle revs went to about 2500 and it would not throttle down even when fully warmed up. The check engine light came on.

I replaced the valve and idle dropped back to 800-900 revs and the idle is smooth.

Glad you got it fixed. Sorry cleaning the valve didn’t fix it. I tried to save you money.

 

[DeanoDeano]

Thank you gentlemen! O always try repairing or cleaning a part if I can, $75 at AutoZone......$35 ON aMAZON. iI didn't want to wait and I didn't think to look on Amazon until I had already bought it.

I have a the 5 speed manual tranny, at 202,000 miles I am having some shifting issues....I need to go find and read the relevant threads.

 

[Josh B]

You might pick up a pointer or two on my Going Full Circle thread, specially the one about making sure it's in neutral

 

[sgtsandman]

Thank you gentlemen! O always try repairing or cleaning a part if I can, $75 at AutoZone......$35 ON aMAZON. iI didn't want to wait and I didn't think to look on Amazon until I had already bought it.

I have a the 5 speed manual tranny, at 202,000 miles I am having some shifting issues....I need to go find and read the relevant threads.

When was the last time the fluid in the transmission was changed? And was it real Mercon V?

I’ve found the aftermarket stuff doesn’t shift as well as the actual Mercon. I’ve also found that shifting noticeably changes after about 30,000 miles. A drain and fill fixes it every time.

 

[DeanoDeano]

When was the last time the fluid in the transmission was changed? And was it real Mercon V?

I’ve found the aftermarket stuff doesn’t shift as well as the actual Mercon. I’ve also found that shifting noticeably changes after about 30,000 miles. A drain and fill fixes it every time.

I bought this truck for my son 20+ years ago when he was headed to college. About a year ago, I was literally popping open my computer to take a look at craigslist and truck trader to see if I could find something to haul shit around and have something to play with - and he texted me from up in the Bay Area (I'm in LA) and said " Hey Dad, this truck just sits out in front of my house and I almost never drive it - do you want it back? Pretty good boy, right?

All of that to say, I don't have the maintenance records on it, but I would venture to say that that fluid has NOT been replaced recently. I am confident of my abilities to drop it and fix whatever is needed - but swapping out the fluid sounds like GREAT place to start.

I will do that and keep you posted

 

[DeanoDeano]

I bought this truck for my son 20+ years ago when he was headed to college. About a year ago, I was literally popping open my computer to take a look at craigslist and truck trader to see if I could find something to haul shit around and have something to play with - and he texted me from up in the Bay Area (I'm in LA) and said " Hey Dad, this truck just sits out in front of my house and I almost never drive it - do you want it back? Pretty good boy, right?

All of that to say, I don't have the maintenance records on it, but I would venture to say that that fluid has NOT been replaced recently. I am confident of my abilities to drop it and fix whatever is needed - but swapping out the fluid sounds like GREAT place to start.

I will do that and keep you posted

any opinions on whether I should drain the case and then put a quart of so in and re-drain in an attempt to get any "extra crud" out of the tranny?