Erratic AF and Inj DC/ Help!

[Louie L.]

Guys ,
I need help figuring out a problems that just started with my GN.
I run a WB B2B unit.

The car was running perfect to include idleing very nice. I pulled out of the drive way and not 100 ft from the house the motor begins to stumble badly. Before i can get back the car stalls several times and smells rich.

Plugged the laptop in and i notice that the ECM is commanding any where from 1.6 to 2.5 or more at times INJ DC. Its very eratic jumping up and down. The WB shows a corresponding erratic reading anywhere from 9.5 to 11.1 AF The map is also making big jumps and the Vac gauge is barely making 10in and almost vibrating(15 normal) When it was running right It was right on or abouts 13.0 AF.

At 1st i found plug number 6 fouled, now all are.New plugs went in, killed them before i could figure it out.

I have taken all the fuel out available through the ACT and Coolant correction tables as a experiment . Still idleing rough, the AF went up slightly in to the 12.5 AF but continues to run rough.

When it started to act up , the laptop was not pluged in. No changes had been made for weeks to the car or tuning. Fuel pressure is as previously set and hasnt changed.


Can you give any suggestions? Will the cam sensor cause such a problem?

Help?

 

[TurboJim]

Sounds like a loose connection somewhere. Maybe coolant temp sensor ground?

 

[Louie L.]

Jim,
Thanks for the reply. That was gonna be my next suggestion. BUt where to start? Both Coolant and air temp sensors are reading correctly and steady.

 

[quickstrike]

What battery voltage reading is the dashboard showing? Is lower than normal or same as always? Have you done any work to the car prior to all this? even something very minor? Just thinking this happened to another car I know and he found it to be a small ground wire that attaches to the frame not connected.(usually from the neg side of the battery)

Just tossing out ideas
Randy

 

[Louie L.]

The battery is showing proper voltage with NO voltage correction. The box is wired straight to the bat.

 

[Louie L.]

 

[bobc455]

I gotta wonder if it's something mechanical- cam jumped a tooth, leaking exhaust manifold (cracked header? blown gasket?), etc.

-Bob Cunningham
bobc@gnttype.org

 

[quickstrike]

I would agree with the previous.

Have you been checking all the engine basics? vacuum gauge fuel pressure gauge, compression or leakdown? how bout something as simple as coil or coil wire finally quit. I only say that because I just finished buying a new coil. My left me stranded at the track. one minute it was fine the next the car would barely idle or start and was just flooded with fuel.

Sorry I am not much help, its hard without being there.
Be nice to borrow a FAST ECU for a minute to see if that had any effect wouldnt it?

Randy

 

[Craig Smith]

If a vacuum gauge is showing low vacuum, then I would expect the MAP sensor would also read high. This would do exactly what you are describing. If the vacuum gauge bounces around a lot, it sounds like you lost an intake gasket.

 

[Louie L.]

Thanks for the advise guys, we are on the same page.Ok here is the latest.

We did a leak down of the motor last night and found no problems, nice and tight.

For giggles we did a new coil pack and module,New cam sensor and plug wires also and checked the cam sensor. Ive gone through the whole harness and rechecked all connections. Found nothing weird there.
I keep finding the #6 plug way fouled up.

Ill be swapping ECUs in an hour and seeing if thats the problem.

Im thinking that the vibrating vac gauge is telling me something. I was originally confused cause the INJ DC was jumping around so bad, but i guess that would have everything to do with the erratic vac.

 

[quickstrike]

keep us posted.

curious to know what it is.

Randy

 

[Louie L.]

VALVE SPRINGS


Hartline Performance to the rescue. Cal gave me a box of valve springs and a spring tool and told me to go home and check the valve springs , especially that number #6 cylinder.

Presto, the exhaust spring was broken right in the middle but had stacked it self , with the break on the back away from view. There was no tension past 1 turn of the spring tool!.Replaced the single spring and Voila, back to normal. Was all done in 20 mins.

Thanks to all that helped Me here, im out to drive my baby out to dinner.

 

[TurboJim]

Hmm, you did say the vac gauge was vibrating....but neglected to mention it was bouncing in sync with a miss.... that would have made all the difference in diagnosing your problem.

Little things like that tid bit make our online diagnosis' more accurate.

Glad you found the prob