Shutter and loss of power/boost

C

Cobra330

Registered User
Ok I'm lost here I just got the car running and drivable. I took it for the first test run in the middle of January and it ran great. I parked it so I could finish my radio wiring (nothing is powered yet) decided to bring it home in February and when I shifted from 1st-2nd, and then 2nd-3rd, etc.. It developed a massive shutter through the car. The shifter shakes while driving. It also had some type of power loss not sure if it the fuel or ignition system.

So I parked it thinking it was the plugs and wires I put in before I reinstalled the engine. I have since brought it to work and got it on the lift noticed the exhaust was hitting one of the braces under the car fixed that. I check the engine and trans mounts all were fine. So then I put the new plugs and wires into it which sucked balls. Took it for a ride and still has the shutter and power loss but while driving I notice the boost dropped from almost 14psi to like 10psi. I have had a few people go for a ride to see what they thought. I was told it could be the pressure plate, it could be something in the suspension, or even in the drivetrain. It's driving me crazy. I am suppose to bring it back in the shop this week to drop the trans to check the clutch flywheel and clutch slave cylinder.

It has a 94 complete engine, new Autozone clutch, fuel sending unit, accel 30lbs injectors, Taylor wires, auto lite plugs, and a accel coil. Also I'm using a 93 harmonic balancer on the 94 engine not sure if that could be a problem. It's just weird that the car drove fine the first time I mean at least without the shutter, it did have the power loss though. Please if anyone can give me a clue to what it might be. Thanks John
 
I would guess an extreme lean condition. Probably a vacuum leak that occurs only under pressure, so look for something after the outlet of the blower (including the outlet) and into the intake manifold.
 
Mike8675309 said:
I would guess an extreme lean condition. Probably a vacuum leak that occurs only under pressure, so look for something after the outlet of the blower (including the outlet) and into the intake manifold.
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Ill check it. I am leaning towards tensioner spring though. I am also going to check the fuel pressure to see what its showing. Thanks
 
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90tbird4.7l said:
94 complete motor? what year supercharger? 94-95 had 36lbs injectors
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Yes the complete motor. Supercharger is out of a 94. I know the 94-95 ran 36lbs injectors but Im running the 93 computer so I put in factory 30lbs injectors. Should I be running the 36 lbs injectors?
 
Ok the shutter i felt was actually Clutch chatter. Next is the power loss. Had a guy at work go for a ride and he drove it and at WOT the thing fell on its face. Once the clutch is in and back together im going to check my fuel pressure at the rail. May be a fuel issue, also going to check all the super charger tubes.
 
Ok update fuel pressure was at 32-35lbs. I did a fuel volume test and it was sad. It took about 45 mins. to fill a 5gal gas can. So I just got a 190lph fuel pump from SCP, it did fix my fuel volume problem but still had the same fuel pressure. I did disconnect the vacuum going to the regulator and it went to @ 44lbs. I was told that if I disconnect that and it spikes then the regulator is working, but could it work and be off calibration? It's not an adjustable regulator so any help here would be great. Thanks.
 
The proper fuel pressure is 39 psi above manifold pressure. When the engine is running, the engine vacuum is deducted from the reading on a gauge that reads against atmospheric pressure. If your engine is making 15" Hg of vacuum at idle, that equates to about 7 psi of negative pressure. So the reading against atmospheric pressure will be about 32 psi.

The pressure should also rise as vacuum decreases, and when boost starts to build. Each 1 psi boost will increase fuel pressure by 1 psi. At 5 psi of boost, fuel pressure should be 44 psi above atmospheric.

If you want to check the pressure with no vacuum influence on the reading, just do it with key on, but engine off.
 
S_Mazza said:
The proper fuel pressure is 39 psi above manifold pressure. When the engine is running, the engine vacuum is deducted from the reading on a gauge that reads against atmospheric pressure. If your engine is making 15" Hg of vacuum at idle, that equates to about 7 psi of negative pressure. So the reading against atmospheric pressure will be about 32 psi.

The pressure should also rise as vacuum decreases, and when boost starts to build. Each 1 psi boost will increase fuel pressure by 1 psi. At 5 psi of boost, fuel pressure should be 44 psi above atmospheric.

If you want to check the pressure with no vacuum influence on the reading, just do it with key on, but engine off.
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Ok I put my gauge on it and I saw how the pressure went upto 39-40 psi in neutral. I did take it out for a quick ride and the problem was definitely the pump. The fuel sender I bought lost it's flow. Thanks for the help.
 
OK i have changed out the DIS. Still no power, it feels like the timing might be off. I have gotten the mark on the balancer to meet up on the pointer on the front cover but when the car is running the timing gun shows like i don't know between 20-30 degrees BTDC. So umm now what, other than taking off the supercharger to get to the valve train? Any suggestions? :confused:
 
You said you are using a 93 SC computer with a 93 SC balancer on a 94 SC engine, so I'm assuming you are also using an early model crank sensor. Not even sure if the late model block has mounting provisions for the early model crank sensor that you should be using, so I'm curious how you mounted the crank sensor. Did you use the entire ignition system and wiring harness from a 93 SC on the 94 SC engine ? What car is this motor in ?

David
 
Cobra330 said:
OK i have changed out the DIS. Still no power, it feels like the timing might be off. I have gotten the mark on the balancer to meet up on the pointer on the front cover but when the car is running the timing gun shows like i don't know between 20-30 degrees BTDC. So umm now what, other than taking off the supercharger to get to the valve train? Any suggestions? :confused:
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The timing should jump around at idle. That's the main way the EEC controls idle speed.

If you pull the SPOUT (SPark OUTput) plug that is in a wiring connector right above the AC compressor, what does the timing change to? It should lock at 10 degrees BTDC with that plug out.

I thought you had a fuel problem. Is that fixed?
 
David Neibert said:
You said you are using a 93 SC computer with a 93 SC balancer on a 94 SC engine, so I'm assuming you are also using an early model crank sensor. Not even sure if the late model block has mounting provisions for the early model crank sensor that you should be using, so I'm curious how you mounted the crank sensor. Did you use the entire ignition system and wiring harness from a 93 SC on the 94 SC engine ? What car is this motor in ?

David
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The car is a 93 and I am using all the wiring and timing cover from the 93. The engine is out of a 94.
 
The '94 long block used - did you make any changes to the timing or was it pulled from one running SC and used in your '93? If so I wouldn't think timing to be the issue.

Also to clear up any concerns the '94 Longblock works fine on an earlier model as long as the front cover and electronics are used from the '93 just like you've done. There are internal differences with rods n pistons but nothing that causing a drivability issue.

-Tim
 
S_Mazza said:
The timing should jump around at idle. That's the main way the EEC controls idle speed.

If you pull the SPOUT (SPark OUTput) plug that is in a wiring connector right above the AC compressor, what does the timing change to? It should lock at 10 degrees BTDC with that plug out.

I thought you had a fuel problem. Is that fixed?
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When I pulled the SPOUT connecter I could see and hear a change but it didn't look like it changed at all using a timing gun. I did change the fuel pump the first pump had no volume. The new pump had way better flow, but when I went o take it out for a ride it fell on its face. So I am back to figuring out what is wrong.
 
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Tim Groth said:
The '94 long block used - did you make any changes to the timing or was it pulled from one running SC and used in your '93? If so I wouldn't think timing to be the issue.

Also to clear up any concerns the '94 Longblock works fine on an earlier model as long as the front cover and electronics are used from the '93 just like you've done. There are internal differences with rods n pistons but nothing that causing a drivability issue.

-Tim
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I put new gaskets, timing chain, balancer and my old cover on the 94 long block and thats it.
 
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i know this would probably be to easy but when i bought my first sc it would fall on its face,loose power on boost,if i can remember correctly.Changed every d--n sensor and come to find out the mass airflow sensor wire had a small amount of dust or oil on it cleaned it and that was the issue the whole time.
 
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