One question - will a vacuum leak cause the car not to rev over 1000rpm? That really is my biggest concern - the rich issue is a problem, but I can't get the damn thing to rev....

 

You seem to have more than one problem. However it appears you are looking for one quick answear. I totally agree that you have a vacuum leak somewhere. Now that may be a line a gasket an intake manifold etc. As to the being rich. When car is running do you see black (I mean dark black) smoke from the exhaust pipes? I can only guess but from what you say the car ran fine for about 40 miles and an then crapped out. In my experience if the carburation is extremly rich the engine will actualy flood out even when running. In other words too much fuel is as bad as too little. It may be the rich problem will go away when you find the vacuum leak but don't bet on it. Good luck in finding your problem but don't trap yourself into thinking something is right or good that traps you in a small box that you wiil have to get out off before you can see the big picture. Please let us know what you finally find because in this way you help us all in the future.

 

That pig rich, it might. Solve the obvious problems before you go chasing shadows. Why worry about what might be, when you have problems you can see. Maybe fixing them will clear everything else up.

RACE ON!!!

 

I'm not sure what you guys are saying...

Yes, I do feel like I'm chasing my tail and changing too many part to not have any positive results...

I plan on going over every vacuum hose tonight - but like I asked before... will a vacuum problem keep the car from reving more than 1000 rpm? If so, I wont look any further than the vacuum.

I know I have a vacuum problem - But, do I have another issue with the limited rev?

LIMP MODE - could this be a possibility??

You guys are giving me great information and I thank you very much!!

This is what I have replaced since the problem started:

O2 Sensor
MAP sensor
Spark Plugs
Plug wires
Cap
Rotor

Now I have someone telling me to change the O2 sensor to a 3 wire...

I'm not spending another penny until the vacuum problem is solved - am I going in the right direction?

Thanks for the help!

 

i have definitely been there! hang on - you'll get it eventually!

at any rate, in my limited experience, i have never seen a vacuum leak keep a car from going over 1000 rpm. that certainly doesn't mean it couldn't happen, but i really doubt it.

how is your air filter? could there possibly be something blocking your intake duct? could the intake duct be collapsing when you try to rev it? just a few more easy things to check. good luck!!

 

A vacuum leak, unless it's enormous, shouldn't prevent the engine from revving above 1000 RPMS.

Here's what happens: any vaccum leak that occurs down stream (after) the MAF is air that isn't getting measured by the MAF. Consequently, the system will be very lean. This very lean condition will eventually hurt the engine so it has to be corrected.

If you have a downstream vacuum leak, the 02 sensor - assuming it's sending feedback to the ECM AND the ECM is accepting that data - will send back a lean condition signal. The ECM then adds more injector pulse timing trying to correct the lean condition.

Don't leave any vacuum ports UNBLOCKED, even if you "think" it's okay to do so. Plug 'em all.

You've fallen into the same trap that many others have in the past; changing a lot of parts and STILL not correcting the problem.

Changing to a three wire (heated) 02 sensor isn't going to SOLVE your problem. All a heated 02 does is allow the sensor temperature to remain at or above the 600 F needed for the ECM to accept it's input. If the 02 temp falls below 600F, the ECM ignores any 02 input and goes into open loop during which time it operates off pre-programmed maps in the PROM.

Even in open loop, though, the engine will still rev above 1000 RPMS, UNLESS there's something else wrong.

An 02 dropping causing the sytem to drop out of closed loop usually only occurs when long tube headers are installed which causes the 02 temp to fall below the 600F AT IDLE. Only if your current 02 ISN'T working properly, will a heated 02 help solve the problem.

A data logger, like Diacom, ScanTool, etc., will immediately show you where to look for the source of your problem. It'll show which sensor numbers are out of normal operating range. I can't stress this strongly enough: get a data logger, you'll be using it time and time again.

I agree, first track down and plug all vacuum leaks. A vacuum leak will skew many of the other sensor numbers. We can then move on to diagnosing any other problem you may have.

Keep us posted.

Jake

 

The filter is new - but its not even on the car now.... I even removed the tube from the t-body to the breather box - no effect..

 

Now we're talking!!! tell me what data loger to buy and I will get one on the way!!

I've looked at several, but really have no idea what one is better until I own one.

Any suggestions with model numbers?

 

There are several different ones on the market. Hopefully guys will post about the one they use and how well it works, etc.

Wht you need is one that gives real-time data as the engine is running.

AutoZone sells the ScanTool which isn't too expensive. I've never used one, but there are a lot of Forum members who do. Maybe they'll post their assessment. I'd visit AutoZone and read the package info on the ScanTool to see if it does what you're looking for it to do.

Diacom works in conjunction with a laptop and is kind of pricey, in the $600 range, last time I checked. I don't think it's worth the cost since all you're looking for are the sensor readings.

Diacom's what I have. If you're looking to have your PROM re-burned sometime down the road, Diacom has the ability to save all the traces (cold start, hot start, idle, part throttle, WOT, etc.) to give the person re-programming the PROM the info needed to enter the needed changes.

Jake

 

I bought my ALDL cable from ALDLcables.com and downloaded TT datamaster it is free for 20 scans the cable was $30 and if you are inclined you can make a homemade one your self. My scans have shown me some problems that I am working on now like one O2 being squirrely and a slightly lean condition due to improper program of chip after putting FMS injectors in. Check Scan&tune for more info on this subject.

 

Thanks, I'll take a look at both of them..

UPDATE** Just installed a new ECM and it did nothing.... Checked the codes with my handy Auto Zone scan tool (key that looks like a divot tool) and no codes...

Now to the vacuum lines... I don't know how well this will work, the damn thing will only run if the booster is disconnected

I'll keep you posted!

 

Sounds like your rich condition maybe causing your engine to load up and not letting it rev. You may want to track down the running rich problem first, it may make finding that vacuum leak easier.

 

I thought you weren't going to spend any more $$ until you solved the vacuum leak. What's up with that!?

I keep posting: Throwing parts at a problem "ain't" the way to go about it. Oh, well.

If the engine runs with the power brake booster hose disconnected, there's your source. At least one of them.

I now suspect the plastic booster is cracked and leaking vacuum. You need a strong drop light and maybe even a mirror to examine the booster without actually having to take it off. The firewall side is a prime suspect location.

With the hose connected have someone step on the brakes and listen for a hissing sound. You may even be able to feel the crack with your fingers.

Mine had a crack that was longer than 6" on the firewall side of the booster. Exhaust heat kills 'em.

The other possible locations are: the hose leading to the plenum from the booster and/or where the fitting screws into the plenum.

I'm assuming your setup is similar to mine.

Keep us posted.

Jake

 

Jake - If I was told to throw $20.00 in the intake - I would do it at this piont....

I checked the brake booster for cracks and found nothing... what I did find out was; If I remove the brake booster vacuum line the sucking will go away after a few seconds (vacuum hose open) The car will rev a little higher when I rev it up slow (about 2000 rpm) and then will back fire through intake if I hold it there. If I plug off the vacuum tot he booster, the sucking sound comes back and the car rev's the same way but runs rougher.. The hose does go to the back of the plenum and it does have a fitting that screws into it, but it not leaking or cracked either..

The distributor has not been out of the car, so I don't have it out of time anymore than it can be turned - and I've turned it both was (advance & retard) to get it to run, but it just wont!!!!

What next??

 

Ok... I give!

I'm going to buy a scanner before I go any further..

I've checked and double checked eery vacuum line on the car - no leaks
I checked the brake booster - no leaks or cracks
I have replaced - ECM, TPS, Wires, Cap, Rotor, Plugs, O2 sensor, MAP sensor and even tried my spare control module - still runs like crap and no real change in anything...

I have looked around and it seems like the best value is the AUTOXRAY EZ-SCAN 3000 @ $249.00 shipped is the best deal.

I know this won't fix my problem, but it will sure make it alot more simple to pin point - right?

 

I just read in another forum of a similar problem and it ended up being the coil. Check your coil wire in a dark garage for arcing. I would not waste that much money on a scanner unles you are going to use it a lot suggest what I did above. Datamaster is a GOOD program and it will give you the same info. Someone in scan and tune will be able to look at your data and tell you if anything is a miss.

 

I see in your mod list that you have "no emissions", does that include no cats? If you don't have cats, disregard the rest of this post but...

If you were running super rich, it may have loaded up the cats to a point where you have no flow to speak of. It would also explain the backfiring when you get it to 2K. You may have such a restriction that anything above idle just can't get rid of the exhaust gas quick enough.

Just my .02. Good luck!

 

I explained the sucking noise stopping in a previous post. With the brake booster hose connected, and the sucking sound present, stick a hose, such as a heater hose, to your ear and play the other end around the engine in search of the source of the noise. You would be crazy to spend a nickle on a scanner or anything else until you solve the known problems. Once the vacuum leak is corrected, any other problems will be easier to track down. Also, at least temporally, dial the fuel pressure down by about 10 psi.

Redeasysport,
A coil won't cause a sucking noise.

RACE ON!!!

 

CFI-EFI - I'll try that when I get home tonight... and I did turn the AFPR down to 40 psi. - is that low enough?

On a Mustang (I know more about the Fords - for now...) it has a vacuum tree on the firewall - Does the Corvette have anything like this?

At least with the Ford, I have a place to start from... With the Corvette, there are many vacuum hose's routed all around the motor - does anyone have a diagram of vacuum routing available?

I have come across so many little stupid things that "might" have caused the problem, but when they are fixed - no change is evident..

I did do some research on the "LIMP MODE" It looks as if it was in limp mode, it would still run and rev fine - limp mode just bypass some sensors to make it home... So I have ruled that out...

So - I will go home tonight and try yet another search for a vacuum leak..

I'll keep you posted!

 

CFI-EFI,

The sucking noise was present before the car fell on its face - could this vacuum leak have caused a sensor to fail due to the rich problem? I was reading in my service manual - to properly set the TPS, you must first put the computer in diagnostic mode (jump wires A & B) and then unplug the IAC - leaving the IAC extended.. Then set the TPS to .45 - .50v - Is the is the correct pocedure?
I did not do this and I have not looked at the IAC valve... Correct me if I'm wrong, but isn't the IAC a computer controlled "Air Leak"?

I will check for other vacuum leaks (I don't want CFI-EFI to whip me ) but should I also check the IAC as well??

CFI-EFI has been a great help and has offered some great advice as well as the other members who have posted ideas - Thats what makes this forum GREAT!!

I'll keep you guys posted as to my progress!