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Rough Idle

jeepsrock said:
Are you saying that i should use a multimeter and check the battery voltage during idle ?

pete
Click to expand...
Yes just somethng to check. Let it idle untill it starts doinking up then check the voltage at the battery.
 
I still have an idle that "hunts" once in awhile, but it does not seem to be getting better or worse, regardless of what is done. I will say one thing about the O2 sensor, after I changed it, and let the truck idle for a while, it seemed to "hunt" a little bit less, but you REALLY had to pay attention or you would miss it. I noticed that overall, the idle is the same, but when you whack the throttle, the motor revs. a LOT quicker, and I had to relearn how to drive the thing because now it will actually get up and go, AND it will do it while going uphill in 5th gear with 3.07 gears, and 235/75/15s' on it. NICE to be able to pass the old folks on sunday. LOL

It just occured to me to may-be, I have a lifter going soft, or may-be a bad cam lobe. Will check that, and post reply. A soft lifter could cause a stumble at idle, due to lower oil pressure than at running speed (on the road, trail etc...).
 
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Well my oil pressure is about 20 at warm idle (after 10-15min of driving) and is usually anywhere from 35-65 at all other times. The o2 sensor was replaced with a premium bosch one from napa. (look at first post for list of replaced items)

I pulled codes using the dash lights and all i got was code 12 and 55. 12 is battery disconnected and 55 is end of list. pretty meaningless huh.

As far as checking my vacuum all i need to do is spray carb cleaner all over the vac lines..right ? Even tho the tps is about a month old can it be bad ? Is it possible that the IAC is suck or something , or would this produce another result ?

pete
 
650 is OK, try pulling you vacuum lines one at a time and plugging the inlet with your finger and see what happens.
Double check your plug wires, just to make sure they are seated all the way down on the plug and there isn´t a gap between the contact and the plug head. I´ve seen a bunch of guys pull plug wires by the wire (especially number one) instead of the boot and slide the contact farther into the boot, the spark then has to jump a gap before making it to the plug.
A little dab of non water based lube of some sort (I use silicon spray) sure helps the boots go on easier and makes it easier to tell by feel, when the plug wire contact clamps the plug head.
A sticky IAC usually causes a too high or to low idle. Which can be a sometimes thing.
How bad is the miss, I had one 87 (fairly cherry) that had a slightly rough idle for years. Nobody ever did figure out what it was. I always figured it was internal motor balance.
 
i know it sounds wierd, but I just got done changing my exhaust manifold for one that is not busted up, an dnow my idle is STABLE at about 700-750 rpm. I think that my manifold gasket was a little bit toasted and that caused my wierd idle. HTH
Ren (rapidly becoming used to working on the wierd and not supposed to be on there stuff).
 
ren said:
i know it sounds wierd, but I just got done changing my exhaust manifold for one that is not busted up, an dnow my idle is STABLE at about 700-750 rpm. I think that my manifold gasket was a little bit toasted and that caused my wierd idle. HTH
Ren (rapidly becoming used to working on the wierd and not supposed to be on there stuff).
Click to expand...
That makes sence, some cylinders are running lean while others are ok, computer tries to make adjustments and can't.
 
Well an update for everyone.

I just checked all the intake manifold bolts that didnt even budge at all. I also sprayed carb cleaner on all the vacuum lines i could see which didnt have a darn effect.

I checked all the spark plug boots for connectivity and they all snapped when i repushed them in.

I did unplug the IAC motor while the engine was idleing expecting it to die if i stresed the PS pump by turning the wheel or turning on the AC. I unplugged it turned on the AC, turned the wheel and the idle was unchanged..Am i too understand that the IAC is stuck since with it or without it nothing different is happening ? Or is supposed to actuate at a different time ?

Pete
 
I think i may have had something happen to me that may be a bit related. Yesterday i drove the jeep from LA to Bakersfield and on the way there is an area about 10 miles that is very hilly and strenious for any car. I had the AC on and as soon as i would go up the hill the AC vents would cut out, my thinking is that their is a vac leak that i cant find. Eventuall i had to turn it off as the temp was increasing bc of the hilly highway (went to white line b4 red). After the hills i turned it on and it worked ( the vents were open) , it seems to be effected when under big load.

Any ideas ?
pete
 
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Read the whole thread...i am talking about issues that can be effecting my rough idle. I mention the AC vent issue bc maybe thats a sign of a vac leak ? ?

pete
 
jeepsrock said:
Read the whole thread...i am talking about issues that can be effecting my rough idle. I mention the AC vent issue bc maybe thats a sign of a vac leak ? ?

pete
Click to expand...
A vacuum gauge is a great tool, you need to get a good one, it's is likely you have a leak around the intake manafold. The one I have is called a compound gauge, it has "0" in the center so the same gauge reads down to 30" vacuum and up to 60# of pressure. Just one question though, when you say the A/C quit, do you mean the vents went closed or the air just turned warm?
 
I just re checked the manifold bolts and they are very tight. I was able to find 5 bolts 3 on top and two annoying ones on the bottom.
When i talked about the AC i meant the vents quit blowing.

I will go pick up a vac gauge , sometime soon.

pete
 
Well actually i havnt been able to track it down. At the moment it happens when it wants and where it wants. Like i said i ran that techron concentrate cleaner and its possible that it helped a bit. I think it just may be a vacuum leak, that i cant trace. I havnt really tended to the situation as i have a bigger issue with overheating a bit.

pete
 
pete,

i was just searching, and i am in the exact same boat you are in.

i have a rough idle that is great initially, and then every 8 seconds or so it will drop to 100 rpms for a few seconds and then it will recover itself back up to about 800 rpms or sometimes it will just die. i have noticed it is a lot more noticeable when cold (below 210° F). if i have it in drive it will just bog the engine or act like i am not giving it gas.

i also may have a slight overheating issue--at least my gauge shows it flucutates between 210° -240°ish. and get this, i just replaced the radiator, hoses, and thermostat last weekend!!

i am almost certain mine is a faulty sensor (temp sensor maybe sending wrong temp to computer or MAP sensor???). i just have to figure out what. and maybe the water pump (the only thing i didn't replace, darn)?

Please update on issue.... does it happen when it is less than 210°F?
 
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