varying engine revving and stumbling

greybox · Post by **greybox** » Sat Jan 29, 2011 2:47 pm

(yes, I have tried the search function...can't find a similar problem)
2000 Neon LX-118,000 miles

Sat from March until June with very little drive time, then started getting driven regularly. New plugs, oil and antifreeze filled and checked.

Had a CEL for awhile but now that has gone away so that is good. Started when it would stumble, buck, stall but not quit. Now 90% of the time it drives fine BUT....

When cruising at a constant speed whether 35 or 65 sometimes the revs stick at 3000 when I lift my foot off. This lasts for maybe 3-5 seconds. It also seems to not like a sudden throttle input when its been cruising at a consistent speed.

I have found various threads that suggest vacuum leaks but it is so inconsistent it is hard to track. Is this something going bad or is a vacuum leak that isn't serious???

Any ideas?

heydockyle · Post by **heydockyle** » Sat Jan 29, 2011 4:12 pm

What was the cel?

Mine did this and it was a problem with the MAP sensor wiring being cut when it was wrecked. Take the map off clean it. Also take the IAC and clean it. Would be my first easiest suggestions.

greybox · Post by **greybox** » Sat Jan 29, 2011 8:18 pm

I never got a chance to check the CEL...it was there off and on and now has been gone for about a month, car has been running better too

I will check these though, thanks for the help. Might be a few weeks before I can devote the time and have the weather cooperate though.

Jenni · Post by **Jenni** » Sun Jan 30, 2011 1:37 am

sounds like probelms with the iac (idle air control) - that sits on the throttle body.
somewhere here is a how-to...

g_force58 · Post by **g_force58** » Sun Jan 30, 2011 3:34 pm

I was thinking the IAC as well. Mine did this to a degree when the iac was dirty. I would be interested in what the cel was. That could give a better idea on things. Leggoman, you mentioned cleaning the map sensor. How do you clean it? as far as I can tell mine is original and may have never been cleaned. Take the car to Advance auot parts and get them to scan the codes and write them down. If the battery hasn't died or been disconnected the code may still be in the ecu.

Post by **occasional demons** » Sun Jan 30, 2011 4:31 pm

Incorrect TPS voltage will cause the RPM's to hang at high idle, and if it isn't responding to sudden input, can cause some problems. I know with it unplugged, it will backfire in the IM with a sudden throttle opening.

When the TPS was bad on my Jeep, it would go bezerk just sitting there running. Anywhere from almost stalling to 4000 rpm. The throttle was closed. If the TPS is calling for more fuel, the o2 will go rich, so the PCM opens the IAC to lean it out. Thus you get some impressive revving.

greybox · Post by **greybox** » Mon Jan 31, 2011 12:18 pm

I am absolutely impressed with this forum so far and the quickness for help. I have been a VW and Scion man for years, first tim dealing with a Neon, but the support here is great.

It will be next weekend before I can get to cleaning it but I am anxious now that I have some input.

sidepipe87 · Post by **sidepipe87** » Mon Jan 31, 2011 6:02 pm

^well then go spread the word to the guys over on the vortex that the neon guys aren't really that bad

heydockyle · Post by **heydockyle** » Mon Jan 31, 2011 6:14 pm

sidepipe87 wrote:^well then go spread the word to the guys over on the vortex that the neon guys aren't really that bad

Yea but make sure you only say Neon. If you say srt they'll get all butthurt and make fun of us lol.

And to cleaning the map sensor off I just stick a paper towel up in it to get the oil out of it, and spray it out with carb cleaner, then dry it off.

sidepipe87 · Post by **sidepipe87** » Mon Jan 31, 2011 6:16 pm

They'll make fun of us either way and say we think SRTs aren't neons and we're douchebags with slow cars. I just summed up the vortex in one sentence haha

greybox · Post by **greybox** » Tue Feb 01, 2011 1:30 pm

A stock Neon has more power than any of the stock 2.0aba motors that came in mkIII or IVs....

The 1.8 and 2.0 ts are fast though but so is the SRT4 so apples to apples Neons are just fine...

(and they don't have the electrical problems VWs do...the whole reason I don't have VWs anymore)

r/tguy02 · Post by **r/tguy02** » Tue Feb 01, 2011 4:23 pm

we have a few electrical gremlins that show up time to time, but typically they're all from the MFS multi function switch.

Jenni · Post by **Jenni** » Wed Feb 02, 2011 10:27 am

g_force58 wrote:I was thinking the IAC as well. Mine did this to a degree when the iac was dirty. I would be interested in what the cel was. That could give a better idea on things. Leggoman, you mentioned cleaning the map sensor....

i think i said throttle position sensor?
map makes no sense - nothing to clean.

but the TPS is easily said a potentiometer like the volume knob in old radios.
you know them sizzling?
that is a dirty potentiometer.
in the radio it sizzles - in your car it gives wrong tps data.
so maybe you can clean it with contact cleaner spray...

Post by **occasional demons** » Wed Feb 02, 2011 12:07 pm

The TPS doesn't really come apart, and IDK if it would be worth trying to spray anything in there.

Jenni · Post by **Jenni** » Thu Feb 03, 2011 3:31 am

spray is cheaper than the sensor

(but i never tried yet if it is even possible)

greybox · Post by **greybox** » Fri Feb 11, 2011 3:57 pm

so I looked thru all the forums searches I could to see what the IAC actually looks like and how to remove/clean it and the only one I found was on an SRT$ and its this polished aluminum looking piece....I think I know where it is but all mine is, is a black plastic looking a shape with torx bolts...is this right and I am planning on just using rubbing alcohol and q-tips...

any photos would help too..thanks

titansxt · Post by **titansxt** » Fri Feb 11, 2011 7:52 pm

Don't use rubbing alcohol, try a carburetor cleaner. Link to my recent nearly the same problem.

viewtopic.php?t=55345&highlight=

It really likes to die around 45mph and 1500 RPMs while I'm cruising in overdrive. Once I get the first shudder from the engine around that speed, there is no recovery until the car dies and I restart it.

2 and 3 is the IAC, 6 is the TPS.

greybox · Post by **greybox** » Wed Mar 09, 2011 7:53 pm

So i finally got around to doing this..cleaned it good...(in the northwest you have to wait for dry days)...and then i put it back together. Worked good for about 2 days then 2 problems re-occuring.

1) the car will idle then just quietly die-has happened twice in 2 days so not constant

2) the car will hold idle at 3000 rpm or better-including the one time I took off down an entrance ramp and it held it almost 4000, spinning tires and all even though I only had it at 2500 when I started driving from the light at the top...

so the first one irritates me, the second one scared me and the fact that it bucks and jumps whenever it feel like it makes me want to kill the car...any help out there?????

greybox · Post by **greybox** » Thu Mar 10, 2011 2:36 pm

so finally had the CEL stay on long enough to get it checked..code p0340, cam shaft sensor...but at least now I know the IAC is clean...

Post by **occasional demons** » Thu Mar 10, 2011 2:43 pm

You can check the codes yourself, if you didn't know. Key on three times, (no starter) Codes will display on the odometer.

There is a how to for the cam position sensor.

greybox · Post by **greybox** » Thu Mar 10, 2011 3:11 pm

I did not know about the code thing...that is crazy! Thank you

I found the how to last night and then this morning even found a video on youtube for our exact cars...crazy what the internet has!

2GN.ORG

varying engine revving and stumbling

varying engine revving and stumbling

varying revs and stumbling

Re: varying revs and stumbling