Kevin in Atlanta

Prior to top end refresh idled 1000-1100 failed emission with high Nox. Failed smoke test miserably.

Refresh comprised of replacement of every hose and the elbow to the MAF, new plugs, cam cover gaskets with new seals in the cam cover all the vacuum related lines and elbows and properly rerouted the lines. Used hose clamps everywhere I could. It is sporting a newly re-calibrated MAF. Even swapped that and idle did not change.

I tested the ISV before I installed the manifold and I heard it click when I allied 12v.

Post refresh sidles at 1800 and drops to 1500. Yikes!

For grins and giggles I disconnected the MAF and the idle is perfect. I did not expect that.

Maybe there is a small air leak that I made bigger?

Mrmerlin

Kevin here is how your ISV works, they can freeze up from corrosion if yours old I would suggest to swap in a new part .

https://rennlist.com/forums/928-foru...?highlight=ISV

what is the coding plug being used by the computers?
verify it in the WSM
I had idling issues with an engine swap and the coding plug was partly to blame

Kevin in Atlanta

Well, manifold is not holding pressure so I need figure out why that is. This exactly what was happening before the top end refresh. So, I am going to have to pull the manifold. I can pressurize the manifold out of the car, right?

Herman K

Replace the flappy and throttle valve bearings and install the ones with seals on both sides - I found the plastic elbow on the DS (connects to the brake booster) broken at the base after a top and refresh which caused the high idle - Other disconnect the battery ground for 30 minutes or run an adaption mode if you have a hammer available.

Kevin in Atlanta

I think I found the leak. I plugged the vacuum line that runs into the fender and tried to pressurize the intake and this time I could hear the leak at the front of the engine. So, I wrapped some Teflon tape around the dipstick to rule that out and the hissing persisted - I think it is at the solenoid valve at the front of the engine. I am going to pull it and look.

Mrmerlin

that solenoid valve will leak when its not energized as it has to release the vacuum to the flappy.

that said.

maybe you have the lines swapped as there shouldnt be any leaks at the supply side of the valve.


The supply side is the vacuum source from the engine,
the output is the side that has the leak till the valve is energised open, and then redirects the vacuum to the flappy,

NOTE once the valve is DE energized then the flappy port is then opened to atmosphere,
thus the flappy returns to its rest position.

Kevin in Atlanta

Sorry - Hold on I have used the incorrect word. The hose with three ends runs from the lower manifold to the oil filler and along the front of the engine to a plastic device with a black connector. That is where I am hearing a leak. There may be other leaks. At least now I can hear them.

Mrmerlin

the thicker hose with 3 ends is a venturi , this device will increase the vacuum at the side that goes towards the booster,
it is used so no matter what the throttle position is there will be adequate vacuum available to the brake booster and the vacuum supply canister.

NOTE there is a O ring inside the venturi, it pulls apart.
it would be a good idea to replace it.

use DC111 on the new O ring so it will stay soft and create a better seal.

Lizard928

Stan,

He is referring to the hose on the front of the engine. Not the side I believe.
It connects to the filler neck and the eec valve.

Mrmerlin

Ahh thanks Colin I reread his post and yes your correct.

Kevin in Atlanta

We are pulling the intake tomorrow. Used a hose to locate the leak at the front PS of the lower manifold. Think there is a problem with the gasket between the upper and lower halves or leaking hose.

Mrmerlin

its common for the intake manifold to ride up onto the water bridge on the passenger side front,
this will let it leak,
loosen the intake bolts and slide it away from the water bridge

SeanR

Just finished a top end on an '87 that had the exact same symptoms. It had been done by Micky and Mouse down in Houston along with some other work and nothing was done correctly. The culprit was the ISV they installed. It was stick wide open, it would click with power applied but the rotator was not moving. Yanked the intake and put in a known brand ISV and all works good.

Beware of crappy parts from not known places.

Mrmerlin

Ahh yeah, I heard about that Micky and Mouse ouitfit ,
did not know where they were located though.


True story went to pick up a U haul trailer,

walked in and found a greasy alleyway strewn with rusted worn out engine and suspension parts,
the roaring jet heater was going full blast and a smokey diesel haze filled the air.
It was 12 degrees outside with snow on the ground.

Upon this , I see 2 fellas with greasy clothes attacking a McPherson strut and installing the top mounting pad to the strut piston.

2 fellas in cleaner clothes were also standing watching this display of mechanical aptitude ,
as they were the proud owners of the new struts that were going to be installed into the family Buick.

Meanwhile Josie the guy with the air gun places the top nut onto the hapless strut,
and then his gifted helper IDK who, stands the unit up then holds it while the gun finds its home on the top of the strut.

The next thing made me totally cringe.

The helper quickly picks up an 18 inch pipe wrench and fits the wrench in between the spring coils, and neatly grabs the piston with said wrench.

Now a slight clanking is heard, as this fine piece of precision pipe holding tool grips the highly polished shock piston about 4 inches from the top of the body of the shock.

Meanwhile Josie is now giving the shock nut a go with the pneumatic gun and the pipe wrench is beginning to grab the piston and create new polished grooves into it.

My heart rose up as I saw this display of mechanical aptitude taking place, I was speechless , I was stammering ,I was dumbfounded.

Holy flunk what where these hapless individuals doing with these tools and who taught them how to use them.

Meanwhile Ben N Jerry,the owners of the new Buick shocks didnt seem to comprehend the ramifications of the polishing that was taking place on the piston rods of these new shocks.

All I could do while shaking my head in disbelief was lean over and and say,
it looks like your getting new shocks, I hope they last.

He nodded his head with some kind of unfathomable question,
as I think deep down he was also trying to figure out why a pipe wrench was being used on his new pistons,
and the new polishing marks that said tool was leaving.

At this point I thought it wise to be quiet ,
as its quite possible for these new shocks to be swapped out for a set thats not leaking after a few short miles.

Thats when I saw the big sign on the wall,....

Dumb Dumbs, auto repairs.........


Holy ship............ true story,
all to pick up a U haul trailer

Kevin in Atlanta

I looked and the base of the 91 waterbridge and it is bigger than the 87's. There is plenty of distance between the 87's waterbridge and the intake. None on the 91. Hard to see if there is contact. Will loosen the bolts tomorrow and see if the intake moves back at all. I want you to be right!

I can't help but think that if you are right, that this was original issue that brought me to doing the refresh in the first place.