Reving problems

error_505 · #1 05-27-2008, 05:05 AM

98 Dodge Neon 2.0 DOHC

When I start it up, it revs to about 1900rpm. Drops to 90--1100 in a less than a minute. Barely, I mean very gently, touch the gas pedal and it revs to 2500 rpm, take about 1 minute to drop back down. Cant figure it out!!
Thanks for any help!!

das2123 · #2 05-28-2008, 07:40 AM

Your butterfly valve in the throttle body could have soot all over it causing it to stick some.

error_505 · #3 05-28-2008, 12:04 PM

Would I remove it and clean it, or spray something in it? I will check it out for sure.

das2123 · #4 05-28-2008, 01:40 PM

Take it off and give it a good cleaning.

error_505 · #5 05-29-2008, 08:54 PM

Removed the throttle body. cleaned. it was gunked up. replaced seal. replaced on car. and still the same thing. reving to 2000 on start and staying at 2000 now. touch gas pedal and engine revs to about 2800-3000.

Thanks for the advice though. The throttle body needed that cleaning. haha

das2123 · #6 05-30-2008, 08:26 AM

Could be the TPS (throttle position sensor) or the IAC (idle air control) motor. Both are mounted to the throttle body.

error_505 · #7 05-30-2008, 09:41 PM

Is there any way to test them?

demo_deven · #8 09-08-2008, 11:50 PM

Hey everyone, I hve a '98 DOHC and i'm having the same problem. I should mension its a demo derby car lol. I was doing a Figure 8 race and got like 5 laps in then on my first hit I only get to about 1,800 RPM and it hits the rev limiter. Idles fine cold or hot. If I touch the throttle gently, I can get about 3,000 RPM and let the pedle off and goes right back to idle. The only things I changed on this car is I removed the air tube going from the air box to the throttle body. Don't recall any sensors along that. The car ran perfectly fine until the first hit. Oh yeah if I start it after sitting for a few hours and rev it to the floor then it will go into the red zone (6-7000 RPM) and after 20 or 40 seconds just go right down to 1800-2000 and bounce off the limiter. I'm stuck! Also have the derby on Saturday so any help ASAP would be very appreciated. You said something about a cuple sensors on the throttle body...how would I test them? Like I said it's only a demo car she aint ging back on the road so something that is jimmy rigged will work only need it to run good for about 10-15 minutes

Thanks in advance! Deven.

das2123 · #9 09-09-2008, 07:15 AM

How does you air filter look?

demo_deven · #10 09-09-2008, 11:50 AM

Like I said, I removed the air intake tube going from the air filter box to the throttle body, so right now there is nothing attached to the top of the throttle body now.

das2123 · #11 09-09-2008, 11:57 AM

So it's possible you have sucked in all kinds of crap into your engine?

demo_deven · #12 09-09-2008, 12:03 PM

Yes it is possible...throttle body still looks clean though. You were saying in a previous post something about sensors on the throttle body, how do you test them? Also could you just disconnect them or will that cause the car to not run at all?

das2123 · #13 09-09-2008, 12:06 PM

TB would look clean cause all the crap is in the engine. Check the backside of the butterfly valve.

Sensors on the TB are the TPS and IAC.

demo_deven · #14 09-09-2008, 12:11 PM

OK i'll go have a look, maybe i'll just pull it off and clean it off. I'll keep you updated.

error_505 · #15 09-09-2008, 05:52 PM

I took off the throttle body and sensors. cleaned them up, added a new rubber seal. Had a vaccum leak also. All that and still reved up on me. I replaced the exhaust manifold gasket and it all works fine now. Good luck. Bout 2 hours to replace the gasket.

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