Unsteady RPM's

[BOC Jason]

Ok. So recently i've noticed that sometimes when i'm driving and i shift into neutral while coasting maybe 35 mph. My engine revs up and down from about 1200 rpms to 1550 rpms. Up and down, up and down...

Any idea's what would be causing this?

Thanks guys

 

[MadScientist92]

Check you water temp sensor. It's on the bottom of the radiator. The car will rev sometimes like that if that sensor is sending bad readings. Not 100% but worth a check. Also check the usual air and fuel stuff like; maf, TPS, CAS, etc..

 

[No_Skillz]

Check you water temp sensor. It's on the bottom of the radiator. The car will rev sometimes like that if that sensor is sending bad readings. Not 100% but worth a check. Also check the usual air and fuel stuff like; maf, TPS, CAS, etc..

Following this advice, what does your stock coolant temp gauge show? How fast do the RPMs oscillate?

 

[phillabaum03]

check the IAC. thats what they do when they go bad, or FIAC I guess is what their called on these cars

 

[BOC Jason]

Check you water temp sensor. It's on the bottom of the radiator. The car will rev sometimes like that if that sensor is sending bad readings. Not 100% but worth a check. Also check the usual air and fuel stuff like; maf, TPS, CAS, etc..

What would checking the sensor be? Like how would i know if it was sending bad readings of not, and also i'm not the best at abbreviations so i have to look up what TPS (throttle position sensor?? ) and CAS (cam angle sensor maybe?) is...

Following this advice, what does your stock coolant temp gauge show? How fast do the RPMs oscillate?

The coolant temp is just under the lower third line I believe.
and RPM's oscillate would be how fast is it reving up and down i'm assuming?.. about UP...2....3.......UP...2.....3.......UP...2....3.... if that explains it so basically it peaks every about every 3ish seconds.

check the IAC. thats what they do when they go bad, or FIAC I guess is what their called on these cars

IAC? or FIAC?





Also, i recently replaced my WP, Alt, and AC Belts about a week or 2 ago.... This in relation to that maybe? I had a hard time getting them to not squeal so basically i tightened the Alt belt tighter because there was no tensioner screw and hand tight wasn't good enough, and the squeal stopped.

Another thing though recently is that my dip stick has been shooting up and spraying oil under my hood (around power steering reservoir, valve cover, etc.) What could cause that?

I know this is a long one but i'm sure you understand my pain

Thanks!

 

[Twistaye]

Excessive crankcase pressure will cause the oil dipstick problem, there are plenty of topics already on that. And it does sound like it's your ISC, go to vfaq.com and do the test to check out your ISC if it tests out good then I'd try and adjust the screw inside the ISC, turn it all the way counter-clockwise till it's all the way out then re-install it. Had problems with the A/T stealth when I put it in neutral it would rev approx. 1500 rpms it was because of the ISC. Just figured I'd throw you a bone and see if it'll help out any.
http://www.dsmtuners.com/forums/newbie-forum/275958-trying-test-isc-because-bad-idle-problems.html
http://www.dsmtuners.com/forums/problem-diagnosis/267051-crankcase-pressure-oil-leak.html
Hope you get it fixed, keep us informed

Oh, and here's how to test your ISC:
http://www.dsmtuners.com/forums/newbie-forum/273307-idle-speed-control.html#post151306992

 

[oplix]

I had same problem. My throttle cable was loose. Make sure it's properly adjusted meaning it's not being pulled at 0% throttle.

 

[BOC Jason]

I just checked my ISC and i couldn't get any readings. I just got 0.00 on the pins which i've read that it meant it was bad.. But I hooked my battery back up and took her around the block and there wasn't any idle surge anymore so maybe the problem's gone.. Could it have been cause by a poor connection on the ISC fitting?

That still doesn't cause the 0.00 readings on the pins though. I have my VOM set on 200k.


As for the dipstick, I check the PCV valve and it was fine. The o-ring closet to the handle though is destroyed so i'm assuming that it's the culprit since there's no real snug fit in the tube. It still bothers me though because that means there's still pressure in the crankcase. And it hadn't shot the stick up before. It's only done it about 2 or 3 times now and i'm pretty sure i was driving somewhat aggressive. Any input?

 

[1LE]

As a side note, check and make sure the BISS is still there. I've blown a couple of them out of my car on boost...

 

[teamdsm95]

mine did the same thing and it ended being the throttle position sensor. just something to check hopefully not your problem, because they get quite expensive.

 

[BOC Jason]

It's not doing it all the time.
I got a bad reading on my ISC test so i'm hoping that's all the it is. Would it do it randomly if it was my ISC?

 

[toojung2die]

It's not doing it all the time.
I got a bad reading on my ISC test so I'm hoping that's all that it is. Would it do it randomly if it was my ISC?

I have three bookmarks for this problem. Hope it helps.
http://www.dsmtuners.com/forums/art...-fix-your-idle-surge-problem.html#post1591829
DmTaLoN's Idle Speed Control Test/Fix Page!
DSMISC Automotive (New ISC Supplier)

 

[steve]

That still doesn't cause the 0.00 readings on the pins though. I have my VOM set on 200k.

Please set the meter to the correct range and try again. Your measuring something that should be between 20 to 40 ohms, the 200 ohm scale would be correct not the 200,000 ohm scale.

If you get 0 on the 200 ohms scale, the ISC is shorted and will need to be replaced and your ECU repaired.

 

[BOC Jason]

Please set the meter to the correct range and try again. Your measuring something that should be between 20 to 40 ohms, the 200 ohm scale would be correct not the 200,000 ohm scale.

If you get 0 on the 200 ohms scale, the ISC is shorted and will need to be replaced and your ECU repaired.

yes! that's what i thought..i read one of your posts on another topic about this and itold my step-dad that it needed to be set on 200 (the lowest setting correct?) and after testing i noticed it was on 200k so i asked him about it and he said that it was right...(he's kind of older though...so he might have misunderstood me)

I'll have to go try the test again.

 

[BOC Jason]

Also, i just did a boost leak test and there was air bubbles coming from my BISS screw... does it need to be replaced?

 

[toojung2die]

Also, i just did a boost leak test and there was air bubbles coming from my BISS screw... does it need to be replaced?

Turn the BISS in until it gently bottoms out, exactly counting the number of turns. Then back it out completely and remove it. There's an o-ring on the BISS. It's a common size, replace it. Put the BISS back in and screw it in until it bottoms out and then back it out exactly the same number of turns you counted. Start the engine and see if the idle is still good. If everything is okay then put about a 1/4 inch of RTV in the hole above the BISS to seal it and prevent the BISS from changing adjustment. The RTV plug can be removed later if adjustment to the BISS is needed.

 

[BOC Jason]

Thank you! I'll definitely try that. I need to pick up another o-ring for my dip stick. One of them got completely destroyed... Would anybody happen to know the size of o-ring?