94zgreenmachine

iTrader: (2)

Can a broken valve spring cause a map reading, at idle, to read as if it were at WOT?

I already know of the problems/damage a broken valve spring can cause, I am working thru that. The valve never dropped, the keepers were still in it.

I had a reading of almost 90KPA @ idle. The broken valve spring wasn't heard till Datamaster was hooked up and showed high MAP DTC 33 and spark retard(3* to 4*). Most likely the valve hitting the piston......At that point we got a little closer to the engine.

skinnies

iTrader: (33)

When I had a 918 break on me, my brakes went to junk(ie high map/low vacuum). It didn't hurt the valve or anything, just barely kissed the piston.

94zgreenmachine

iTrader: (2)

I've done a leak-down test. I quit the test after I got it to about 5% leak. Anything above 15% should be considered for tear down and inspection. I spun the valve along the seat, by hand, and could feel nothing. It spun smooth so I am throwing the new spring on and am going to hold my breath. It broke at about 1500rpms.

ADM

What springs are you running?

94zgreenmachine

iTrader: (2)

Pac 1220 Big block Bee-hive spring. About 175lbs on the seat, 375 on the nose. It wasn't coil bind. Looks like a defect in the spring. It peeled back and broke.

I'll post a pic tonight, works internet filter is horrible......

94zgreenmachine

iTrader: (2)

Here is the pic:

ss.slp.ls1

iTrader: (36)

I would hope you didn't get any metal shards anywhere inside the engine.

94zgreenmachine

iTrader: (2)

The spring looks to be complete when the 3 pcs are put together...

94zgreenmachine

iTrader: (2)

Yes, A broken spring can cause a high Map reading. I replaced #3 intake and it is all better now. I can even get the car to idle, imagine that

Hope this will help someone down the road....