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Discussion Starter · #1 ·
Been awhile since I've posted 2 any Z site and this is probably a 1st time for posting here but I've gotta problem that has me STUMPED!!

1991 Z-24 3.1 V6 5spd
Crank pulley, Down Pipe, HI Flow Cat, Full Exhaust
FastChip installed
Run 91-93 Octane
130,000 Original Miles

When I was getting on the highway last week very fast thru a corner my car ended up dieing on me, felt almost as if the throttle cable had snapped in that the gas pedal had no effect on the engine RPM whatsoever. Figured I may have run out of gas since I was goin 2 get gas and had about 2.5 gallons left, friend got me gas so I was able to get 1 gallon into it but nothing, after awhile the car started would idle but any time I blipped the throttle it would die.

Car was towed home.

Some Symptoms I've noticed

- Next day car started fine but blipping the throttle would cause it to die but I was still able to get it into our garage and onto the lift.

- You can start the car whenever the engine is cool or cold but when it is warm or has already stalled out not always able to start it right away.

- The car will sometimes be idleing fine but then without warning, just die.

- If you press the gas to the floor it will increase in RPM by about 1000 drop 1000-2000 (depending on the rpm you started at) and increase again by 1000 drop the same amount and then go up by the same amount, repeating itself untill it stalls or you let off the gas.

- Blipping the throttle still causes it to want to die or to die and it sounds like the car is gasping for air.

- Only when the car is off and the ignition in the ON position, the Check Gages (NOT CHECK ENGINE) light illuminates, will go off, come on, go off, and come on, and sometimes stay on but the gages read normal

- I've smelt unburnt fuel from the exhaust for a few years now but have alwasy passed emmisions and only smells at startup (running a FastChip Chip)

- For the past 2.0 months the idle at startup has been kindof ruff as in when you step on the gas it does not have a smooth sound but would clear after a minute or so to the point where it sounded normal

What I have checked and what has been replaced
I've used an AutoXray ScanTool for GM Vehicles set up to scan the 91 Z24

Fuel Pressure - OK
Fuel Pump - New, less than 6000mi
Fuel Filter - New, installed today, 0mi
Fuel - added 2.5 Gallons of 93 Octane
Fuel - added STP Fuel INJ Cleaner
Air filter, 10" K&N Cone filter, Cleaned, less than 2000
NO Obstructions in air intake or TB
PCV Valves removed 7 years ago, No Problems
ECM - Checked with known Good
Mem Cal - Checked with known Good
CPS (Crank Pos Sen) - Checked with known Good
MAP Sensor - Checked with Known Good
MAP Hose OK and when disconnect will set code.
Ignition Module checked with known Good
Coils Tested and alll 3 are within SPEC
New Plugs and Wires less than 2000mi
TB was cleaned and regasketed less than 2000mi
IAC Motor checked with known good
All vacum lines from TB were checked for cracks, still need 2 look at the ones going to the charcol canister
Cleaned TB with STP TB Cleaner
TPS registers proper voltage and shows correct throttle angle %
CTS and IAT temperature readings when compared are within limits
O2 Sensor, fairly new less than 4years old (LOW MILEAGE) adjs itself accordingly when engine is running.

SO WHAT IS IT?

I will not rule out ignition or fueling problems, could it still be the pump even though its a new BOSCH?

ANY IDEAS or what I can check next would be greatly appreciated, I know someone has delt with this before,

Thanks every1 for your help and ideas

- PETE :pimp:
 

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Discussion Starter · #3 ·
That was something I was going to get back to tomorrow when I could have my dad read the gauge while I tried blipping the throttle.

I forgot to add before that if I push down on the accelerator pedal slowly and gradually feed in throttle it will increase in RPM, its just that when you blip it, it dies out.

We were also going to lift the car up on the lift and place it in gear and under load and see what happens to the fuel pressure.

I got the factory service manual in front of me and was going to read on how to test the FPR, so no I've never replaced it, are these known to go bad on CAVYs?
 

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Discussion Starter · #7 ·
While under load I can't remember what the PSI was, I'll have to ask my dad........but nothing struck him as odd and he's been wrenching on cars since uhhhhhh LONGTIME

I placed the car in 1st gear let out on the clutch gave it gas to gradually bring up the RPMs then I slowly applied the brakes........as I fed it more gas after awhile it just cut out...just died

Before I got the car towed I was able to start it and coast in 1st gear.......but after doing that for awhile the car will start to buck (assuming thats the correct term) .......... Once I get this sorted out (why the car won't run) I'm going to try the OEM chip and see if it does the same thing since I don't remember the car doing that until I started running the "FastChip".
 

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Discussion Starter · #8 ·
Well I uh removed the EGR and YUP it affected the idle.........it went WAY THE HELL UP..it dipped and then shot right up....I never waited for it to die out I just shut the engine right off..............NOW as I write this you know whats interesting is that if I blipped the throttle the car either dies or wants to die........but with the EGR removed from the car and after a few seconds (what seems like anyway) the RPM's shoot way up but then come back down.......not sure if it would die out this way but its just wierd that they would actually climb that fast without the car wanting to stall/die...........well i suppose the plenum will be coming off to do a thorugh inspection for internal obstructions, vacum leaks, FPR lines, and injectors........Service manual says that if fuel is present in one of the lines (Vacum?) going to the regulator then you should replace the regulator.......I HOPE there is and it fixes my problem
 

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Discussion Starter · #9 ·
Haven't taken the plenum off yet but I did make a blockoff plate 4 the EGR vavle 2c if that would have any effect on idle/blipping the throttle.......if it did it was barely noticeable.......Gonna remove the plenum later in the week after I get my Mirage put back together....this was suppose 2b done already but then the Z decided to BA B1TCH!!!!!
 

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Let us know what you find when you get your plenum off.

The reason that the engine rpm's went off with the EGR off is because the engine was getting air through the EGR hole in the plenum and not through the TB. (You probably already knew that though).

Brad
 

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Discussion Starter · #11 ·
When it did that I asked myself......WHOA!!! why the hell did it do that?....about 3-4 Seconds later........OH YEAH its like I had my foot to the floor and the Butterfly Valve was COMPLETELY OPEN.

If not EGR valve didn't set a CEL and Removing the Pig-Tail didn't set the CEL.....and COMPLETELY blocking off the EGR didn't set the CEL........wonder how you get the CEL to go off?

I know with the TECH 1 Scan Tool you can energize each of the 3 Solenoids and observe the reaction on idel to see if the EGR is functioning properly.

Lookin 4 one of those used on EBAY for my CAVIS' and the Buick Riviera.

I'LL definitely post what I find.............My dad found a link that has GM Mechanics online certain times and days during the week........gotta find out when this is.............Oh well at least the car starts and runs (good or bad?).
 
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