RyanPerrella

Well the engine is in the car, its all back together and it was finally time to throw it off the cliff to see if it flies.

No oil or water leaks, there is an exhaust leak in the center of the car where the claps are for the CAT.

One issue, and I dont have a clue what it is. When it fires, it goes into a nice idle, then after about 10 seconds, the revs drop to like 300, when i step on the throttle a bit there is obvious hesitation. I have started it 3-4 times now and it is always doing this. Is this the 4 cylinder mode, what would trip that if it is?

I am wondering if this is fuel injection or what? I havent a clue, ive never experienced anything like this. I am suprised it continues to even run idling so low.

Any ideas on what i need to check?





another note, the car has painted exhaust manifolds, after running for a couple minutes there was some smoke coming from the bottom of the cam covers on both sides ( right by the manifolds) Is this the paint burning off? I had expected there to be some type of paint burn off, it dosent really smell like anything, not oil or fuel is this just pretty typical when you paint an exhaust manifold and it heats up for the first time?

RyanPerrella

also i had expected some noisy lifters at first start up, but wow were they loud, it quieted considerably after about 15 seconds, and i expect it to get quieter still after i put some miles on it.

RyanPerrella

Another note,

When the engine drops in revs shortly after startup (approximately 10-15 seconds) the engine starts to shake to the point that the headlamps vibrate. I think this vibration is the result of the low engine rpm, but its something that i thought should be noted.

SwayBar

Congrats on your rebuild!

Go to your Techncial Publications, specifically the one named:

928S4-928GT Fuel and Ignition system.pdf

Starting on page 18, it describes the 'Ignition Circuit Monitoring' circuit which first appeared in 1989.

Skipping forward to page 23, there is a section labeled 'Switching Delay', which sounds like what your car is doing:

"In order to avoid erroneous switching of the ignition ciruit monitoring relay due to imbalanced cooling of the stopped engine, the relay is blocked for approx. 18 sec whenever the engine is started again."

Backing up to page 22 under 'Operation' reveals how to check for sure if that indeed is the problem by looking at the red and green colored diodes in the relay.

BTW, a slightly smoking engine after any engine-work is normal, as well as clacking lifters. What all did you do to the engine?

RyanPerrella

Engine was torn down to the crank, everything but the crank was removed, everything replaced but the main bearings.

What Technical Publications, I am not familiar with this?

RyanPerrella

Ok, based on your tip i tried to start it again and it idled for 15 or so seconds and then i noticed a green light by the CE panel, I think it was coming from the larger clear plastic covered relay directly under the LH and EZK brains.

I saw a green light and the engine died. This was the first time it killed itself. Previously the revs would drop and i killed it after a few seconds

SwayBar

The ones that come on the Jim Moorehouse CD's.

If you do not have the technical publications, then get out your workshop manuals and goto page 24 -19, Test Point 10, Injection circuit shut down.

SwayBar

Yep, that's 'Injection circuit I shut down', from page 24 - 19.

That indicates you have a problem with cylinder-grouping 1,4,6, and 7.

RyanPerrella

I just realised that the temprature sensors on cylinders 4 and 8 are not plugged in. I am pulling the air filter box to plug these in and will report when i get that done.

SwayBar

This will be an easy fix for you!

justin

update?

RyanPerrella

That was it!

Simple enough. The 2 temp sensors were detached, plugged them back in, fired it up and it idles nicely.

Now off for a quick spin around the block

justin

Good luck!