Hesitation and rough idle

[Murdastylez15]

When I crank up my car cold, it runs fine. The idle is steady and my car continues to run great even after it get up to the normal operating temperature.

But after about 15 to 20 minute of driving, my idle gets really rough and stays below 600 RPMs. It continues to jumps from around 100 to 500 RMPs roughly. When I take off, it's hard to get my car going because it feels like it's going to stall. I am not sure if anyone else has had this issue before. But if you have the slightest clue of what's going on, please share your knowledge. Then I will know where to began to look for my problem.

[Josh]

What model and year is your car?

Sounds like it could be a couple of different things, PCV valve, EGR valve, vacuum leak perhaps, could be bad spark plugs/wires or coil/distributor. Is your check engine light on? have you done any work to the car at all recently? Just need a bit more history to help trouble shoot.

[Murdastylez15]

It's a 95 RS (4cyl) DOHC.

The check engine light isn't on. The only thing I've done lately after this problem began was change the spark plugs and wires. I haven't done anything besides that. Thanks for helping.

[Josh]

since you changed those I would probably start with the cap and rotor next. they get corroded, you might get away with cleaning them but may have to replace them. That car has an internal coil in the distributor and they have a tendency to go out as well. if that's not it i would start with PCV and EGR valves see if they are good.

OH one other thing, on the airbox there is a little vacuum line hooked into the side. If this is not hooked up it can cause a rough idle as well. They are known for braking off. This could be a cheep fix. happened to my car too.

[Murdastylez15]

Ok, thanks again for your advice.

I will start pricing and I will update you on the progress.

[SuperK]

Do you have any other issues, I.E. smoking or anything? sometimes issues can be related, such as loss of compression, etc.

My three suggestions would be vacuum leaks or the O2 sensor. O2 is easy to troubleshoot. Just unplug it and see if the issue persists in the same way. If you get a different result, then it's possibly a good idea to replace the o2 sensor.

Second is definitely spark related. You can get a small spark tester from your auto parts store super cheap and test the voltage coming to your plugs. the RS is not notorious for burning through distributors, but it's always a possibility, we've had some people have them die. You want to keep that possibility on the table.

Third would be vacuum as well. I guess just look over your hoses, and where they connect, see if anything is broken or whatever. some tape up their accordian tube as they say that cracks up fairly badly.

[Murdastylez15]

Ok. Yesterday a friend and I were just looking over some hoses and different connections. We noticed that the pcv valve was loose, so we replaced the pcv and the grommet. Figured even if it wouldn't solve the problem that it needed to be done and it was cheap.

I also cleaned the distributor cap and the striker from all the build up, since that needed to be done as well. The distributor, I'm ordering online and that needs to be replaced as well.

I will check out the O2 sensor as well today. There isn't anything smoking.

More symptoms I failed to mention earlier is that for instance if I try taking off in 1st gear it will continue to bog out until it gets to about 2500 rpms, and when I switch to 2nd gear while my rpms are still below 2500 rpms it continues to bog out.

Also, while in neutral when I'm having these issues, I could floor the gas pedal and it will bog trying to rev up and it will finally rev up after a second.

[SuperK]

Sounds like the Distributor or the O2 sensor. On my O2, mine didn't even throw a code when it went bad, but at higher RPM's the ECU shuts off the O2 sensor, I think it's like 3,500 RPM's. So I would get hesitation all the way till then, and like a switch, I regained the power.

[Dark_Rider2k3]

I'd say o2 as well. If you can get your hands on an OBDII tester try and see if you see any codes from that. I have had codes (though on OBDI) that did not show up unless i checked them (meaning my check engine light wasn't on but I still had codes...)

speaking of that, the o2 sensor code I think is a soft code and won't show up unless you check it yourself... I know I didn't know I had a bad o2 sensor and water thermosensor until I did my own code check (which cleared up my issues)

[SuperK]

95 4cyl is obd1 dark. so paperclip method is how you check codes not scanner

[Josh]

^^NICE!

So if all of that and your problem still isn't going away.. I would say it would most likely be a plugged catalytic converter there are two of them on that car.
OR
Another thing it might be if its bogging down like that could be the Fuel Filter. They are horrible when they clog up.

[SuperchargedK20Z3]

^^NICE!

So if all of that and your problem still isn't going away.. I would say it would most likely be a plugged catalytic converter there are two of them on that car.
OR
Another thing it might be if its bogging down like that could be the Fuel Filter. They are horrible when they clog up.

Hey guys, I have been helping Murda on his car locally.

What his car is doing is just idling low and shakes the car when stopped in neutral. Then at take off he is having to rev the car higher than usual to take off without completely bogging out. Also, if in 2nd gear or any gear in the lower RPM range the car has a lot of power loss.

He purchased a new O2 sensor that we are going to put in today. When the car was running and we unplugged the current O2 sensor it had no affect on the car. If the sensor was working wouldn't that affect the car when we unplug it?

We can also check the fuel filter today.

The thing is his car isn't doing this until it is warmed up. If the car is cold it is fine only after the car has been running a while is it doing it. What would be affected by temperature like that?

[SuperchargedK20Z3]

Just wanted to mention some other things...

I saw that "Josh" mentioned the vacuum line going into the air box. Well we noticed that line is not connected to anything currently because Murda is using an aftermarket filter and has removed the stock air box. Where does this line need to route to? It is a small/thin black hose that looks like it routes to the EGR Solenoid maybe??? I could be mistaken but it definitely used to route to the stock airbox and is now just hanging. This issue started happening long after he removed the air box though.

Having the A/C amplifies the issue he is having the revs constantly drop and go up drop and go up if the AC is on at all.

Murda feels like this all started happening after he wound out 1st gear going uphill. Was at a stop light on a hill. Could any damage of been done from strain on the engine going uphill?

Thanks for the help

[Murdastylez15]

Installed a brand new O2 sensor today, and there wasn't any difference with how the car ran. So I will be putting on the pout face to return it to Advance Auto.

I would really like to check the catalytic converter, but I would have to take it to a shop and have that done.

We also pulled the fuel pump out to check the filter and everything. Everything was very clear and no clogs.

The Chilton manual is sort of confusing me with the drawn out pics of the EGR valve and solenoid. Could someone give me any further information to the location and what I should be looking for.

Thanks for any assistance provided.

[SuperK]

just follow the small pipe from the exhaust manifold on the right, and it connects below the throttle body. the pipe starts above the O2 sensor and is _| shaped.

it's sounding like it's a distributor issue. Couple tune up ideas that always are nice to do, but not necessarily a cause is the fuel filter on the firewall, and the strainer on the pump.

But I'm leaning towards the disty going bad... You could always unbolt the catalytic converter from the down pipe, two bolts that are spring loaded... and see if it runs differently. If it does, then you know that you're not getting good flow through the cat, and can replace it.