LS surging idle throttle blade hole

[K5Rob]

Have you checked for vaccum leaks?

However, would vacuum leak not cause a HIGH idle? Mine is low to the point of stalling (which it does)

I would still like to check. I dont want to spray carb cleaner all over the place. I have an appt with a tuner ($350 - ouch, way more than I would like to spend) but would like to check as much as possible first

 

[JBswth]

However, would vacuum leak not cause a HIGH idle? Mine is low to the point of stalling (which it does)

I would still like to check. I dont want to spray carb cleaner all over the place. I have an appt with a tuner ($350 - ouch, way more than I would like to spend) but would like to check as much as possible first

A slight vacuum leak would cause a high rough idle, but a bad one will cause a low idle and frequent stalling. Spraying carb cleaner is probably the best way to find it. You could spray gas, but that is very dangerous.

J. B.

 

[K5Rob]

A slight vacuum leak would cause a high rough idle, but a bad one will cause a low idle and frequent stalling. Spraying carb cleaner is probably the best way to find it. You could spray gas, but that is very dangerous.

J. B.

Both valve covers have a line that goes to the intake. Used the top intake port. Getting 16” of vacuum at idle, when its idling smooth.

I am getting 90 psi of fuel pressure with key on, not running, and 100 psi when running at idle. The gauge only goes to 100. I am running a Wix brand filter/regulator from Summit. Should it even run as good as it does with 100 psi???

 

[TotalyHucked]

Both valve covers have a line that goes to the intake. Used the top intake port. Getting 16” of vacuum at idle, when its idling smooth.

I am getting 90 psi of fuel pressure with key on, not running, and 100 psi when running at idle. The gauge only goes to 100. I am running a Wix brand filter/regulator from Summit. Should it even run as good as it does with 100 psi???

You need to get that sorted out, 58psi is where LS's need to be

 

[Ricko1966]

I have not, Would anyone know where the port on an LM7 is that I can hook a vacuum gauge to?

The first place to start with a vacuum leak is a can of starting fluid* (not brake clean) or a propane torch (ask how) oil( too messy) anyway spray anywhere vacuum could be leaking in and see if the idle pics up,if you find a spot where the idle pics up you find your leak. More complicated would be a pressure test or a smoke test.. Pressure test seal off your throttle body,set your shop vac to blow attach it to your tailpipe turn it on,go spray soap and water everywhere looking for bubbles,like finding a tire leak. BTW I actually use bubble wand solution, dish soap and water works though. I've never owned or needed a smoke tester,I've heard of people smoke testing with a cigar,again I've never needed a smoke tester.

 

[Ricko1966]

However, would vacuum leak not cause a HIGH idle? Mine is low to the point of stalling (which it does)

I would still like to check. I dont want to spray carb cleaner all over the place. I have an appt with a tuner ($350 - ouch, way more than I would like to spend) but would like to check as much as possible first

Take a propane torch,put a piece of hose over the end so you have like a 12 inch or so flexible extension,like the straw on a can of wd40. Turn on the torch,but don't light it. Run your hose around any areas that might leak vacuum, a vacuum leak will draw in the propane and speed up the idle.

 

[Hunter79764]

Both valve covers have a line that goes to the intake. Used the top intake port. Getting 16” of vacuum at idle, when its idling smooth.

I am getting 90 psi of fuel pressure with key on, not running, and 100 psi when running at idle. The gauge only goes to 100. I am running a Wix brand filter/regulator from Summit. Should it even run as good as it does with 100 psi???

Yeah, that's an issue. Check if you have a clogged return line from the filter assy, and get a new filter.

Alternatively, if you have an 87 with TBI, you should have a full length return line anyway, and a high pressure fuel filter. I much prefer the return style fuel rails if you have one, the Corvette filter/regulators can cause issues sometimes. Note, your tuner will need to know which style you have, and it may be worth swinging by his place to show him the truck and let him verify a few simple things like this ahead of time.

 

[K5Rob]

Got fuel pressure straightened out with an adjustable regulator. Ditched the jenky corvette regulator. Had the pcm tuned for the mild cam and all is good now, running great.

 

[Hunter79764]

Good deal. The corvette regulators are good at keeping things simple, but man, they can cause some issues some times. And hopefully the tune didn't lighten your wallet too much.