I've been tracking this gremlin for 2 days now...

I think have found the problem, but I don't know where to go from here..

I pulled the codes and I found #13 = O2 sensor.. I replaced it and the code is gone, but the problem is not...

The problem - The car will start and run (very rough & rich) and will not rev over 1000 rpm.. I can gently raise the rpm to 2-2200, but thats it..

The T-body is making this loud vacuum sound - So, I disconnected the brake booster and the PCV and the sucking noise goes away - the car still runs... Still wont rev, but sounds a little better..

This thing is driving me crazy!!

The car has new and recently installed:
Headers - 52mm BBK T-Body, Holley AFPR, MSD 8.5 wires, Cap & Rotor, O2 Sensor, Smog Pump Elininator, No Emissions, No EGR w/ brock off plate, Corsa exhaust, Hypertech Coil, New TPS, T-Body water bypass and New Spark plugs (this may also be a problem) - After I installed them I noticed the parts store gave me the plugs for the LT5, I have the L98.... The plugs are the same, except for the heat range - that shouldn't keep it from reving though.... The LT5 is FR5LS The L98 is FR2LS The LT5 is a colder plug (I Think) - either way, it should run and rev if the gap is correct... right?

My last resort is the ECM, but I'm going to be piz'd if thats not it either!!

 

You have removed and replaced alot of parts. Have you forgot a vacuum line somewhere.

 

The hissing or sucking sound you heard is a vacuum leak. For thing on the agenda is to track down the cause of that leak. TPI engines are very sensitive to vaccum leaks.

Check that the connection of the power brake vacuum hose to the plenum is tight and not leaking.

"5" is a hotter plug than the "2". "2" may be too cold; I'll bet "3" would be better though. But even so, the engine should run and rev with any of the three.

Look further for any other vacuum hose you may have left disconnected. I use water when trying to tack down a vacuum leak, a change in idle speed or smoke out the exhaust IDs the source.

Others recommend an unlit propane torch or even spray carb cleaner.

Have you checked the TPS voltage?

Jake

 

I have used carb cleaner with no results... The TPS is set at .5v

Could a blocked off vacuum line or bad PCV give this effecy?

 

No, there's no blocked vacuum hose that I know of that could cause that. If the PCV is disconnected, about all you'll see is blow-by coming from the valve cover opening(s), and may be gasket leaks at some time in the future due to the pressure buildup.

Even if the fuel pressue regulator hose is blocked, the pressure will increase not decrease.

There are a LOT of places a vacuum leak can occur. That's why I use water, and plenty of it.

Intake manifold to head, runner to intake, runner to plenum, TB to plenum, injector to intake, fuel tank vent hoses, cruise control hoses , fuel pressure regulator hose , vacuum port under TB, power brake hose to plenum and to booster, IAC to TB, TB to passenger side valve cover (part of the PCV system), EGR gasket, accordian between MAF and TB, cruise control hose to break pedal switch, just to name some of them.

It may take some time but you'll eventually find it.

Jake

 

I suspect it has to do with the new work. It usually does. The first thing that comes to mind is a vacuum leak, associated with the TB change. Could there be a gasket that was incorrectly installed? The other item, is how rich it is running. A vacuum leak can cause that, but have you checked the fuel pressure with the new AFPR? I'll bet a bundle that the problems are related to the new work. If these suggestions don't reveal a problem, go back over everything.

RACE ON!!!

 

Just checked the Fuel Pressure again - 48 psi at idle and will climb to about 60 psi or little more when I try to rev it before it dies out..

I did leave something out in the first post - after all the mods were complete (less the sensors) I did drive the car about 40 miles before it started this "no rev crap". It was running rich and it did have old plugs in it when it started running like this, I figured it was due to the bad plugs.. That is when I installed the plugs, wires and sensors.

When I turn the key on the fuel pressure will go to 45-47psi, when the car is running, it is aroud 48 psi and when I rev it (2k rpm is all it will do) it jumps to 60 psi - Should I count the fuel system good and move on to the vacuum trouble shoot?

 

I know you said they are new, but have you checked any of your spark plugs to see how they are burning.

 

Not as of yet..... I'm trying to go around that - they were a beotch to install!


What I don't understand is; the car seems to idle better and the sucking sound goes away when vacuum lines are removed - it would seem that it would run bad and make the sound when the lines were open

could I be losing fire when the rpm pics up and that is why it dies out? If so, what would cause that??

 

I would lower your fuel pressure, 48 psi is kind of high for an L98. When you did the throttle body bypass did you cap off the ends at the throttle body? Did you reconnect all the vacuum lines to the right location. Just some thoughts

 

No, the ends are still open... I figured it was just a water bypass through the T-Body - Would it cause a problem if it was open? It's just water, no vacuum - right?

I would say "yes" to putting the vacuum lines back in the correct location - The EGR vacuum I just blocked off at the sensor / relay

vetster86 Thanks for the link, but thats the same as what I have in my sevice manual...

I have asked this question in several post and have yet to be answered... what is "Limp Mode" and how does it work on the L98 computer? and if it is in Limp Mode - how do I know??

 

ttt

 

Any chance you put the hose from PCV to the wrong nipple on TB.? With all those nipples in your face it could be possible to get distracted

 

Doesn't the nipple from the pcv(drivers side) attach to the intake between the runners? Get the right plugs in for a start. Def. sounds like a vacuum leak somewhere.

 

hey scoop, did your revelation find fix the problem?

 

You are correct, i mean't the fresh air intake on pass side but called it PCV as it is part of PCV, just not the valved portion

 

cuisinartvette - It goes into the t-body and yes it's in the correct spot (connected to the t-body)

Sleazy Rider - Nope made no differance at all... (the dist. rotor was not tight and one of the bolts was completely out - still in the rotor, but not screwed in)

I think I'm going to just buy a an ECM... That is the only thing I haven't replaced..

 

the lt5 plugs that you put in are hotter that the fr2ls by 3 heat ranges.. it probalby is not your problem but i would get them out..

 

The "sucking sound" is air rushing through a relatively small opening. When you remove the vacuum hoses, the air takes the path of the least resistance and quits sucking air through the noisy leak. It idles better with the vac hoses disconnected, because they admit additional air to help burn the super rich mixture you have with everything buttoned up. Find and plug the vacuum leak, and turn down the fuel pressure by a BUNCH and you will be well on your way to solving your problems.

RACE ON!!!

 

I did change the plugs out to the correct plug - just to make sure that wasn't the problem - it wasn't...