Spun

OK, so I have been working the intake over and over again chasing vacuum leaks and have the last one down to the throttle body bearings. She runs, but you can tell there is a leak.

What is odd is after 30 min of driving she turns off. I can crank it for a few seconds and then same thing. If I wait about 30 min, I can drive her for another 15-20 then same thing. I would say it acts like it is over heating, but the temp on the engine is good. When it reaches the last white line, that is when it turns off.

I have replaced both knock sensors, temp 2, and the crank position sensor. I did not replace the hall sensor.

Could I be getting one side of the engine hotter than the other?
Could it be a faulty temp sensor?

help please... I would like to nail this down before I put her back together again... though I am getting good and fast at it...
Emerald

Ducman82

bad fuel pressure dampener?
hard start with HOT....

Spun

She will fire up fine, but if I try to drive, she dies again.

It was good before the refresh, but I did have it coated when the did the other items... I could have hosed it...

brutus

When it "shuts off" does the fuel pump run ??? You may have a marginal relay which after it gets hot no longer holds the points closed. Can be any one of three small 53 relays or possibly your big ignition monitor relay. They all can turn of the engine at any time.

Spun

Hmmm... I have new 53s, I should go change those. I did put in an 044 pump, so I could have just been lucky enough for both issues to show at the same time...

I think I have a spare ignition relay as well. I will swap them one at a time.

To be sure, the relays to check would be?:
IV Ignition Relay X
XVI Electronic ignition system
XX Fuel pump
XXV LH jetronics

?

John Speake

Check whether you have a spark when the engine stops. The symptoms you describe are often related to a faulty CPS.

Dean_Fuller

Is this an auto? Crank movement?

Spun

Yes auto, not crank issue... already tested that when I was putting this girl together before...

Well, many of my boots are shot on connectors, but I replaced the Crank Position Sensor... the other was shot to hell... would this make it stop as the car warmed?

SeanR

Did I read correctly that you had the FPR or the fuel dampeners "coated"? Hope you mean painted and not powder coated. That might just ruin the internal diaphragms.

Dean_Fuller

Are there any other odd electrical issues...like windows or headlights not working some times. Could this be a bad ignition switch?

Why do you think its hot?

brutus

Actually when ...." I would say it acts like it is over heating, " cars do not stop running when overheated until it gets so bad that it is detonating rattling all the time and then the piston rings basically melt and there is no compression .....and it never will run again.
You need to figure out what is missing....fuel spark when it stops running.

Spun

Not powder coated, but anodizexd. The coating was very corroded... But why would it run good for 30 min until the engine temp got warmer than standard cool?

The headlamp relay (up and down) went out, but I think that is due to the painters... they did a few other things I have had to fix... otherwise, everything is good.

As far as hot, because if I let it sit for 30 min, I am good again. I do not have a fuel pressure issue of venturi type action again... so it just seems to be related to thermal when the car got to a certain temp, it stopped... might be non related... just a starting point of thought..

I thought I had read somewhere... where I cannot locate, that if the motor heated up uneven that there was a sensor that would shut the motor down. Problem is I cannot remember where I read that or if it was for a 928... brain has been fried of late.

I have the vacuum issue licked now, so I will bolt the rest together tomorrow AM, swap out all of the recommended relays and drive it for a while to see if it happens again.

She ran great until I messed with the intake ... vanity will get you every-time....

John Speake

There have been crank sensors that failed when hot, when cooled down the engine would run again. These were usually old sensors.

Suggest you check for spark when it won't start.

The problem may not be related to the work on the intake. Check out the 3 vital relays, FP, LH and EZK. Swap for known good ones to test. Fuse tester type relay can be swapped for a "53".

Spun

Yeah, that is what I have been starting to think. Nothing like randome issues to make the diagnoses more fun

I will swap those and thank you. Hopefully I will know today if these ideas work... If not, at least we know what it is not

Emerald

worf928

First remove the airbox and MAS.

Apply a vacuum hand pump at the vacuum port to your two fuel dampeners and fuel pressure regulator. They should hold vacuum. If they do not, then that will be part of the problem as fuel will be sucked into the intake through the vacuum lines. Also, if they do not hold vacuum, your hand pump will be full of fuel and so will all of the vacuum lines from the 5-way connector and you'll need to replace all the vacuum lines and rubber elbows connected to the 5-way or be sorry later.

Under the FPR and rear dampener, check that the two LH ground points are connected, clean, and tight. A bad or loose LH ground will cause the problem you describe.

Never mind - you DID replace the CPS. Last, when you did the intake refresh you should have changed the CPS. It's a know time-related failure point.

Really last, an intake leak at the throttle shaft bearings cannot cause the symptoms you describe if everything else is right. Worst case a leak at the bearings might contribute to a slightly-high idle.