Running out of parts, and patience

ddukes

Registered User
91 super coupe, won't idle for crap, rebuilt engine, now has new IAC, cam sensor, crank sensor, dis module, hard to start, acts like the timings off, but its not, no fault codes either,
 
I hear 'ya, man.....my crank sensor is off and I have to keep on re-adjusting to get it to start.

First, I would try to hunt down a vacuum/ boost leak. The idle being way off would seem to point towards that.
 
Good morning


What is the vacuum gauge reading at idle? Greater than 15 hg? Like 1FSTBRD stated look for leaks.


See this: http://www.35thatr.org/Tips/SCAirLeaks.htm


I use a can of @WD-40 and spray around theses areas. If the idle suddenly increases you found your leak. Don't forget the supercharger hat/top.


Some other areas I would check:


-- PCV connections (valve cover to intake duct, the "Y" metal line at the passenger side firewall next to the A/C accumulator).

-- Bypass valve line for cracks/leaking.

-- EGR regulator lines or EGR pipe to exhaust manifold (the bellows) for cracks/leaking and or damaged/missing gasket if applicable.

-- Charcoal Canister solenoid hoses/lines (underneath front passenger bumper) for cracking/leaking.

-- Intake duct/clamp for security.

-- HVAC hoses/lines at firewall for cracking/leaking.

-- Underneath the the instrument cluster for a cracked vacuum gauge line leaking.

-- Throttle body, Plenum manifold gaskets missing or damaged.

-- Fuel pressure.


Good Luck.
 
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Are you sure? Because the computer will normally act very quickly to smooth out the idle, making it very difficult to detect any change, I think.

Ken

I usually use Carb cleaner - same concept...if there is a leak the engine will Rev up.


Also for what it's worth...I recently replaced the front cover gasket on my '89...installed new Cam/Crank/DIS and installed a Powerbond Harmonic Balancer at the same time. Set #1 at TDC...set cam sensor by eye ball to the correct degree. Car wouldn't start...unplugged the Cam sensor and did the 3-5 crank method where the car will start off the EEC base tuning...ran like a top. May want to give that a shot also...timing could be off even tho you feel as confident as I did that it was right. It's a simple enough test as you just have to unplug the sensor.

-Tim
 
I can verify that a vacuum leak can be difficult to find with just spraying the hoses down while the car is running. I connected a hose to the PCV line that runs into the back of the plenum, and blew into it, manually.......a good set of lungs will find the leak. You'll hear some air escaping at the throttle body, but that's normal. I had a small vacuum leak in one of the plenum hoses......spraying fluid/ water while the car was running had otherwise yielded nothing.
 
Every time mine becomes hard to start, I find a vacuum leak somewhere. Definitely smoke test it to locate the leak.
 
Wires

Real dumb idea that's easy to mix up, did you double check the plug wire connections at the coil pack? Myself plus several others have mixed them up before. Instead of 123456 it's something like 123465.

Other posibilities,
Vacuume leak
Bad plugs right out of the box, seen this with the Bosch brand
Broken wire to any sensor,
Egr valve, may be stuck if she's been sitting for a while. Remove the valve and install a blanking plate (or use a piece of flat gasket material with no holes and reinstall the valve). If the valve is stuck open, it's similar symptoms to a vacuume leak.

Best luck,
JJ
 
OK , new computer, thought it fixed it , but now its doing the same cranking like its kicking back or out of time,! Starts fine sometimes, other times, mostly when it is hot, it acts up, no vacuum leaks, good fuel pressure, you name it, its new, is there someone in southern Illinois, or western ky, that is qualified to work on it?
 
The coil shouldn't be breaking down when hot (or not to my knowledge).

It still sounds like you have a vacuum leak.

Triple check for vacuum leaks (including the vacuum tree behind the return plenum by the firewall). I'd mentioned in posts above, the vacuum leak that I had a couple of years ago was miniscule and hard to find. The car running and spraying water on the hoses yielded nothing....no dying out, no leaks, nothing. With the car not running, I sprayed the hoses and then connected some PVC hose to a connection on the back of the plenum and blew into it (there's more than enough pressure in a good set of lungs to find a leak), and sure enough, some bubbles had came out of one of the hoses on the intake plenum.

The reason why I'm still wondering if there's a small, almost undetectable vacuum leak is because my car didn't run well when it would start to heat up (ie: when the temp gauge would start to register movement). It would run great when starting it cold, and it would run pretty good when it was at full operating temps (though a little erratic in the idle). When trying to start the car up when it was hot, it would be more difficult to start, and would crank weird......like the battery was dying. This was pretty embarrassing, since the type of quick, in and out trips to places like 7-11 would result in the hesitant starts. Another crank or two would always get the car up and running. But it did feel like the timing was off, like what you are describing. And at stoplights during the periods when the engine would just start to heat up, I would have to have one foot on the brake, and the other on the accelerator and have to keep the idle RPM's up a little higher than they normally would be, otherwise the car would stall and die out. I kid you not!

I had replaced the hose clamp on the problematic hose/ connection.......the guy who had the car before me had tried to tighten it up when it had somehow formed an oval sort of shape instead of a round shape. It sealed up well enough--but not well enough under pressure. You may just want to buy new hose clamps at all the connections coming off of the intake plenum.......for a couple of bucks, you'll have the assurance that they're clamping well. Another thing that I've noticed is that the smaller hose clamps can get damaged pretty easily if they're torqued too much.....the grooves on the clamping part get distorted and bent and they may not really torque down too much.
 
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The coil shouldn't be breaking down when hot (or not to my knowledge).

It still sounds like you have a vacuum leak.

Triple check for vacuum leaks (including the vacuum tree behind the return plenum by the firewall). I'd mentioned in posts above, the vacuum leak that I had a couple of years ago was miniscule and hard to find. The car running and spraying water on the hoses yielded nothing....no dying out, no leaks, nothing. With the car not running, I sprayed the hoses and then connected some PVC hose to a connection on the back of the plenum and blew into it (there's more than enough pressure in a good set of lungs to find a leak), and sure enough, some bubbles had came out of one of the hoses on the intake plenum.

The reason why I'm still wondering if there's a small, almost undetectable vacuum leak is because my car didn't run well when it would start to heat up (ie: when the temp gauge would start to register movement). It would run great when starting it cold, and it would run pretty good when it was at full operating temps (though a little erratic in the idle). When trying to start the car up when it was hot, it would be more difficult to start, and would crank weird......like the battery was dying. This was pretty embarrassing, since the type of quick, in and out trips to places like 7-11 would result in the hesitant starts. Another crank or two would always get the car up and running. But it did feel like the timing was off, like what you are describing. And at stoplights during the periods when the engine would just start to heat up, I would have to have one foot on the brake, and the other on the accelerator and have to keep the idle RPM's up a little higher than they normally would be, otherwise the car would stall and die out. I kid you not!

I had replaced the hose clamp on the problematic hose/ connection.......the guy who had the car before me had tried to tighten it up when it had somehow formed an oval sort of shape instead of a round shape. It sealed up well enough--but not well enough under pressure. You may just want to buy new hose clamps at all the connections coming off of the intake plenum.......for a couple of bucks, you'll have the assurance that they're clamping well. Another thing that I've noticed is that the smaller hose clamps can get damaged pretty easily if they're torqued too much.....the grooves on the clamping part get distorted and bent and they may not really torque down too much.

I have 20 inches of vacuum at idle, and can see no leaks, everything is clamped, runs like a striped ape once you get it started.
 
I have 20 inches of vacuum at idle, and can see no leaks, everything is clamped, runs like a striped ape once you get it started.

I had 20 inches of vacuum at idle too, and everything looked clamped. It drove me nuts because there was enough annoyances of not starting well when hot, and erratic idling. But then it would behave under other circumstances. You need to do some sort of pressure test or smoke test to really rule it out, because a tiny vacuum leak can be a major problem--it's small enough that the car will generally run, but it's not big or obvious/ visible enough for one to really identify it as a problem.
 
I've got an evaporated smoke tester. I just found a leak on mine today. You should bring it up so I can have a look.
 
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