ScottyG

A friend has a 98Z that has a bad bog at ~5500 rpms, and recovers within a couple of hundred rpm’s and runs strong right up the limiter. It’s not a dead miss, but more of a soft, sudden bogging down.

AutoTap shows 3 to 4 degrees of KR.

It’s essentially a stock 6M car. All it has is a catback, lid, and a Granetelli MAF.

Three different MAFS, including bone stock, screened MAF have been tried.

A couple of AIR system codes have popped up, but they come on at lower rpms. No other SES codes.

O2’s are 870 to 900mv.

Fuel pressure stays constant before, during, and after the 5500rpm bog.

This did not appear in conjunction with any mod.

He’s about to go nuts… any ideas on what to look at or try?

gwj

Soft lifter or a bent pushrod r/2??
I suggest this b/cz u usually don't see this from an A4.
AIR codes should not affect performance.

gwj

Ooops, didn't see the KR. KR has some effects sometimes that don't show up in other parameters.
FWIW, this seems to be a fairly common prob /w these motors, never seen a "1 thing cure all".It always sounds like valve float/bounce but is hard to quantify, especially when it picks up again at higher rpms.

SS SLP2

iTrader: (8)

Had like problem for 1 1/2 years wasted several hundreds and many hours trying to correct problem
did solve problem, was under drive pulley, have had many in the know say some LS1 with stock pulley may do same thing at times >>I know for sure my problem was the under drive pulley which I was running for the 1 1/2 year of problem
just my $ 0.02 Johnny

ScottyG

Hey Johnny..

Good to hear from you.

You're alignment on my car is doing well... car tracks perfectly and no tire wear.....but you already knew that, right? <img src="gr_stretch.gif" border="0">

I'll pass the pulley info on to my buddy. I'm almost positive that he is running the stock pulley. I have my original unit I could give him to try.

See you at the Silsbee cruise in June, maybe?

Cool Z

After I fixed my pinging problem, I was still loosing power at 5600 RPM's. To make a long story short, that little lag was - 45+RWHP on the dyno. It would run strong lag at 5600 then get its power back and pull like mad to the rev limiter. The problem started out intermittantly then became a constant occurance. I replaced the valve springs with LS6 springs after having checked every possible cause. Low and behold it solved my probs!!! <img src="gr_grin.gif" border="0">

Patman

Try the plugs first. I had a set of TR6s foul out on me that exhibited that kind of behavior.