engine revs itself

stephanieASTRO · Post by **stephanieASTRO** » Thu Jun 07, 2007 8:51 pm

Hey everyone!! my van when in idle, weather in park or drive, is reving it's self. It doesn't stall but it will rev as if someone keeps pumping the gas. I had to do air care and failed the 3rd time. The only thing I failed on was the Carbine monoxide, other wise I passed everything with flying colors. EGR, oxygen censer, ECM, spark plugs, leads, cap and rotter all replaced, and I even cleaned the combustion chambers with cleans. And I still failed. I found a crack in my bran new distributor cap, could that be a problem? I don't think it is. A guy told Sanja that it could be the fuel injecters. Spitting out too much fuel for the engine to burn causing carbine?!? I'm not willing to spend $400 on something that works fine. Is there a way I can test them at home?? I'm fresh out of college so I'm flat broke. My van has 239,000 K's on it.

Kidhauler · Post by **Kidhauler** » Thu Jun 07, 2007 9:13 pm

Hey Steph

It could be a leaky intake gasket that is causing the revving problem. Usually this is caused by the base gasket under the TBI leaking. A easy way to check for a leak is spray carb cleaner around the base gasket this will swell the gasket and seal the leak and the van should idle fine untill the gasket dries out and you will know if it is leaking.

As far as the fuel injectors spitting too much fuel that would cause a Hydrocarbon failure as hydrocarbons are unburnt fuel.

Hope this helps

Kevin

stephanieASTRO · Post by **stephanieASTRO** » Thu Jun 07, 2007 10:40 pm

okay I'll try that! Thanks!

peter · Post by **peter** » Fri Jun 08, 2007 2:36 am

If it's a CPI, it could be the spider assembly leaking, no?

BLAZER · Post by **BLAZER** » Fri Jun 08, 2007 5:00 am

Peter, usually when the CPI system springs a leak, it runs like garbage, worse at idle, and will smell very strong of gas.
Stephanie, I would tend to believe it is a vac leak somewhere, like kidhauler stated, under the intake, TBI, or just maybe a vacuum line somewhere. That would sound reasonable in that it is revving up and down trying to compensate for the leak.

Water Boy · Post by **Water Boy** » Fri Jun 08, 2007 7:49 am

S~

Can you post your van info?
It will help those who can help....

Someone · Post by **Someone** » Fri Jun 08, 2007 7:58 am

Stephanie... this is a reply from Matrixx that I posted for him at AS.com

Hi Stephanie
That's a very broad spectrum Stephanie How were
the Old plugs when you changed them, reading plugs can tell you alot on
how the motor is running. The easiest and simplest way is to have a good
look at the injectors themselves while the motor is running. You will
see if it's dropping to much gas in the motor by small anatomized
droplets (raw gas) that's the easiest Stephanie I have found. If it's
Droplets of gas going into the motor that you can see with the eye, then it
needs to be rebuilt. If you can't see any raw gas going into the motor,
then you need to look at a Vacuum Leak, Bad Temp Sensor, or Bad MAP
Senor are the common causes, You mentioned the EGR was replaced so I
didn't mention it. Also, How old is your Cat?
Testing the Temp Sensor:
2 Wires: 1-Yellow 1-Black
Yellow wire (5-volts Cold) and will drop in voltage when the coolant
temperature rises.
Ohms should be:
13,500 ohms at 20 deg F
7,500 ohms at 40 deg F
3,400 ohms at 70 deg F
1,800 ohms at 100 deg F
450 ohms at 160 deg F
185 ohms at 210 deg F
These are coolant temp readings.

Testing the MAP Sensor:
3-Wires
Gray- (5 Volt reference)
Light Green- (MAP Signal)
Purple- (Ground)
Idle speed- 1-2 volts
Wide Open Throttle 4-4.8 volts
Elevation- Under 1000 ft. should read at or Less than 3.6-5.2 volts

IAC Check:
4- Wires
Terminal A- Light Blue and White
Terminal B- Light Blue and Black
Terminal C- Light Green and White
Terminal D- Light Green and Black
Testing:
Terminals A to B (40-80 ohms)
Terminals C to D (40-80 ohms)
Terminals B to C (Infinite ohms)
Terminals A to D (Infinite ohms)

Also I believe you have whats called a "Tuning Valve" in your Manifold
for that year. You need a Command tool to diagnose it, but would be
worth the time to have it checked.

PS: You didn't mention if you failed by much or not, did you fail the
CO's at "Idle" or "Speed" test or both? Could you post the readings if
it's not to much trouble? Only the readings you failed, Thanks.

BLAZER · Post by **BLAZER** » Fri Jun 08, 2007 10:29 am

From her inof on AS.com, she has a 93 4.3L Z motor so she is TBI. You do not have the tuning valve as posted by matrix so don't worry about that.
I'm still betting on a vac leak somewhere.

NotDadsW41 · Post by **NotDadsW41** » Fri Jun 08, 2007 10:33 am

A TBI engine with a hunting idle and signal impending fuel pump failure as well. But I'd bet on the gasket under the TBI myself too...

stephanieASTRO · Post by **stephanieASTRO** » Fri Jun 08, 2007 11:45 am

Here is my air care results, This is what I failed:

Carbon Monoxide

allowable: 12.4300

vehicle reading: 17.2511

average passing: 7.3330

They only make me do the driving test, they have never made me do the idle test.

When I took my old spark plugs out I looked at them carefully, They appeared to be normal. It's a grayish tan on the side electrode and on the center electrode. It does appear to have some carbon on the plug but only a light amount. My cat is about 4 years old .

My van is a 93 Z 4.3

Before I did the air care test I was watching my fuel injectors and they seem to be spraying normal but I will look at that today. I'll also study the TBI and hoses for any leaks.
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stephanieASTRO · Post by **stephanieASTRO** » Fri Jun 08, 2007 1:06 pm

well I looked at my TBI tower (fuel regulator part) it was cracked at the base. Not a small crack, the screw that holds it down was cracked right off. But when I started the van up it didn't rev up and down and I couldn't wiggle the tower. But the gasket didn't look good. So I hope that this is what is causing the van to fail aircare and to idle funny. I haven't taken it apart yet because I'm going to wait for my dad to pick me up the new part. I'll still check for a vac leak just to make sure. As soon as I get it replaced I'll let you all know.

Thanks so much for all your info and help everyone!!

dragonvan · Post by **dragonvan** » Fri Jun 08, 2007 4:33 pm

Sure sounds like a vacuum leak to me. Spray a LITTLE carb cleaner around the intake gasket, TB gasket, and vacuum connections and lastly the brake booster if you have a vacuum booster. When you find the leak, the idle will change. Go slowly as to not get too much carb cleaner all over (it's flamable!) and to give yourself time to hear the idle change.

Matrixx · Post by **Matrixx** » Tue Jun 12, 2007 8:34 pm

Hi stephanieASTRO
Yeh that's right out the window steph. You shouldn't have any problems finding that one. Definitely check for Vacuum Leaks and also check the IAC as well. If your timing is off, that can contribute to some of it but not all of that. It "could" be a combination of things leading up to the readings you have. Check for Vacuum leaks and also check what Someone posted for me up above. Please keep us updated, thanks.

PS: Thanks Someone very much for your help in posting that for me SO, much appreciated.

Matrixx · Post by **Matrixx** » Tue Jun 12, 2007 8:52 pm

Ooops.

Matrixx · Post by **Matrixx** » Tue Jun 12, 2007 8:52 pm

Hi stephanieASTRO
Hmmm, Just an Off the wall thought If everything has been checked from above and is in good shape, is to have a look at your Coil. How old is it by the way? If you have a weak Coil it will give off alot of problems that your not aware of, these coils usually don't just quit, they gradually die off because of the Heat Build up in such an enclosed space. It's something to definitely look into "If" you didn't find anything mentioned above to check first. Hope this helps. Please keep us updated, thanks.
Coil Check:
http://www.autozone.com/az/cds/en_us/09 ... oPages.htm

Chevy & GMC Vans

Chevy & GMC Vans

engine revs itself

engine revs itself