need ideas... my friends SC has an issue

Scott Long

Registered User
I drove the car tonight, and it makes boost but the damn car just doesn't go. I just tightened up some of the connections for the supercharger, and I checked all the vacuum lines, all are in tact. I just got the cooling system "burped" since he just bought it and the previous owner just changed the t-stat but I doubt they drilled the hole in the t-stat and I can guarantee they didn't vent the system after filling it.

The car is a 1990 SC aod. Removed air silecer, K&N cone filter, 70mm MAF, aluminum intake tube, cooling fan mod, and flowmaster cat back exhaust system.

Anyone have any ideas why the car is running like this?

We are going to do new plugs and wires, since I think they could use changed. But the car doesn't miss, shake, or shudder, so I don't think this is an ignition related problem.
 
about 5 pounds, but it doesn't seem to make any difference when it boosts or not the car doesn't go any faster. It will probably pull more boost when the car's revs get higher. It drives fine and shifts fine when you are at 0 but if you go higher the car falls on its face. Its not shaking like mine did when the plugs were bad. It actually sounds like the car is straining when it boosts. The blower screams, but the car just doesn't perform. You can rev it in park and it sounds fine, so maybe this is a transmission problem, although I don't feel the transmission slipping. All of the fluids are full. I'm stumped.

I guess we'll change the plugs and wires, and maybe I'll swap him my DIS module and see if that makes any difference.
 
MY '93 SC HAS BEEN DOING THE SAME THING FOR A LONG
TIME NOW...I CHANGED THE SC TENSIONOR PULLY TO THE
BIGGER ONE....SEEMED TO HELP...BUT STARTED DOING IT
AGAIN....IT COMES AND GOES....RUNS FINE UNTIL I GET ON
IT REAL HARD,THEN IT JUST KIND OF FALLS DOWN...LET UP
AND IT'S FINE...I DON'T KNOW IT'S DRIVING ME NUTS!!!!!
 
So many things.

Low fuel pressure.
new air filter (plugged intake)
pluged exhaust (cats?)

Make sure the air filter is clean.
Then check the fuel pressure. Could be running to low to produce power at higher rpms.
Then consider having the exhaust inspected.
 
I'M SURE IT'S NOT AN EXHAUST PROBLEM,IT HAS SHORT TUBE HEADERS,NEW DOWNTUBES WITH NEW CATS,NO RESONATOR,
AND NEW FLOWMASTERS.INTAKE IS AN OPEN K&N NICE AND
CLEAN...I ALSO PUT A 5% OD PULLEY AND A RAISED BLOWER
TOP ON IT..I'M LEANING TOWARDS FUEL PROBLEM...I CHANGED
THE FUEL FILTER...SAME THING...IT ALSO STILL HAS THE STOCK
FUEL PUMP...SO MABYE IT'S GOING BAD...LIKE I SAID IT COMES AND GOES...PEOPLE HAVE SAID TRY CLEANING THE MAS...
 
My friends car has a flowmaster cat back exhaust system, a bigger MAF, and a cone filter, aluminum intake tube, cooling fan mod, and all the fluids are full. The car ran fine up until a few days ago. We ran codes and nothing showed up in the computer so its not a sensor I don't think. Any ideas?

I'm currently changing plugs and wires, gotta get back to it, maybe it will help.
 
Guys..5 PSI???????....Ive never owned an SC (Ive had 3) that has boosted that low....Id check the built in bleed off valve..Maybe its stuck open....That would definately be why the car is a pig
 
The bypass valve is fine. We just changed the plugs and wires and it still runs good but performs poor. I am now thinking it has something to do with his transmission. The car goes into gear fine, shifts good, but under 2500 rpm it won't perform, it performs decent above 2500 rpm and but not like it should. My Audi would smoke it, and it shouldn't be able to.

The TV cable came loose from the throttle body linkage about a week ago and the guy driving put his foot to the floor and the tranny was slipping quite badly. We fixed the tv cable problem, by using the brass spacer and lock pin. I wonder if the damage was done when the transmission was slipping?

Any thoughts about it being a tranny problem? It revs up good in neutral but in gear you hit it and the boost won't spool up fast and the car is a dog, sounds like the motor is strained. But in park or neutral it will rev up and boost about 5 which is normal since it boosts more when there is a load on the engine.

Damn I'm greasy as hell from doing the plugs and wires. Gotta go jump in the shower. Adios!
 
MINE PULLS 10# OF BOOST BEFORE IT DROPS...IT RUNS FINE
75% OF THE TIME...THE CAR SITS IN THE GARAGE WITH A
TRICKLE CHARGER ON IT...I TAKE IT OUT EVERY 2 WEEKS...TO
MANY SCUMBAGS AROUND HERE...LIKE I SAID IT COMES AND
GOES...SOMTIMES SHE'S FINE...SOMTIMES SHE CHOKES...THE
PLUGS AND WIRES ARE NEW,CHANGED ONE YEAR AGO AND
SHE RAN FINE UNTIL A FEW MONTHS AGO..
 
Seems like you should beg, borrow or even buy a fuel pressure gage and check pressure at the shrader valve on the fuel rail. My experience here is NJ is "jaded" but I would never take a car to a trans shop unless I was sure it was bad. You may end up with a grand plus in you transmission and still have the problem. If the car doesn't give a code (and it is not the transmission) then usually it would be fuel flow or clogged exhaust.
Rock
93 SC 5spd & 89 SC AOD
 
I'm thinking fuel pressure, or maybe a leak between the charger and the intake. Maybe in the IC area. I also think that if it were the fuel pressure, then it would miss at high rpm's. By the way, what are the rpm's when it is turning 5 psi. My '90 jumps to 6 psi when I floor it from idle, 10 psi at 2000, and 13-14 psi at 4900.
Good luck, Biggin'.:confused:
 
I don't think any 90 SCs came with 70mm MAF what kind is on there? Sounds like a/f ratio not right going lean. If it was running too rich when it falls on it's face you should see black smoke out the tailpipes.

Jerry
 
SCREWEDBIRD said:
MINE PULLS 10# OF BOOST BEFORE IT DROPS...IT RUNS FINE
75% OF THE TIME...THE CAR SITS IN THE GARAGE WITH A
TRICKLE CHARGER ON IT...I TAKE IT OUT EVERY 2 WEEKS...TO
MANY SCUMBAGS AROUND HERE...LIKE I SAID IT COMES AND
GOES...SOMTIMES SHE'S FINE...SOMTIMES SHE CHOKES...THE
PLUGS AND WIRES ARE NEW,CHANGED ONE YEAR AGO AND
SHE RAN FINE UNTIL A FEW MONTHS AGO..
I hope you remove the battery cables from the battery before you put that charger on there, if not you may have fried the ECU. Computers do not like battery chargers of any kind!
 
same boat

I took mine to a trusted tranny shop to get a rebuild, since I've gotten it back there is a noticible power loss in the low RPMs. My friend in his avalon was able to keep up with me. Also i'm not able to peel out on the start unless its slick. When not using the OD I have more power bc the rpms get higher, but passing in OD right now is nearly impossible for me. I had more power when I was driving with 2 gears... what is up?
 
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