stutter and cutted off on freeway - CamaroZ28.Com Message Board


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Old 03-13-2018, 08:00 PM   #1  
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stutter and cutted off on freeway

Hey guys,oh man you gotta love these cars on my way to work today in morning,it started fine,accelerated nice,probably like 20 minutes into the drive on freeway before the exit one mile to go I had a hard stutter like 65 to 70 mph,i kept the speed low like 60 mph the car shutted off.

I pulled over to shoulder,i cranked it n fired right up n idled perfect,no roughness,or erratic behavior. I drove like 10 more minutes wasn't on freeway n car was fine. Got to work ok. After I got off car fired up fast,idled nice etc. Took streets home,nothing bad on way home.

Got home ok,in the garage I pushed gas to 5000 rpm no popping or hesitating,wot was good,i bought a fuel pressure tester,but I was gonna test fuel pressure,but the Schrader valve keep spraying fuel,released gas cap no hissing or pressure coming out.

Do I need to wait for car to be cold for testing,I'm sorry for long post,distributor is 3 yrs old,fuel pump 3 yrs old,icm coil 3 yrs old

94 camaro lt1,long tubes pace setter headers, all common mods,
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Old 03-13-2018, 09:40 PM   #2  
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Re: stutter and cutted off on freeway

Fuel spraying from the test valve does not indicate that proper fuel pressure is being held. To validate that, you will need to use a pressure tester.

Any codes?
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Old 03-13-2018, 10:22 PM   #3  
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Re: stutter and cutted off on freeway

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Fuel spraying from the test valve does not indicate that proper fuel pressure is being held. To validate that, you will need to use a pressure tester.

Any codes?
oh i know I need to use the tester lol I was implementing that I couldn't get the tester in because car was too hot,but I got my fuel pressure tester results.

as soon as i turn the key it primes to 42 43,then holds a lil bit but drops pretty fast.
I fired up the car pressure goes to 31,as I'm giving it gas it goes up to like 35 goes back to 31. I pulled the vacuum hose to regulator,put my finger to end of hose it goes to 45.

This is my first time doing the test,but Idk if there's anything wrong with fuel pump as I'm giving it gas on what the psi is supposed to be at with wot
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Old 03-13-2018, 11:34 PM   #4  
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Re: stutter and cutted off on freeway

The spec at idle, vacuum line off, is 43.5 PSI. But anything between 42-47 PSI is acceptable. When you reattach the vacuum line to the regulator, the rail pressure should drop proportional to intake manifold vacuum. An 8 to 10 PSI would be normal with a stock cam. Yours dropped 14 PSI. That's excessive. The manifold vacuum cannot be that high. May be a problem with the regulator. Itís normal for rail pressure to increase when the throttle is being opened (vacuum disappears), and to decrease as you snap the throttle closed (vacuum is high). But once the throttle is closed and RPM is back to idle, 31 PSI is too low.

Next fuel pressure test is to tape the gauge to the windshield, take it out on the road and take it up to 5,000+ RPM at WOT. Pressure should not drop below 40 PSI. Revving the engine in neutral does not place the engine under any real load. It actually needs to be working hard, accelerating the car.

When it stuttered and then cut off, did the SES light come on at any time? Have you scanned it for codes? If DTC 16 (Opti low res pulse loss) shut down the engine, it doesn't turn on the SES light, but the code would still be stored.
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Old 03-14-2018, 10:30 PM   #5  
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Re: stutter and cutted off on freeway

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The spec at idle, vacuum line off, is 43.5 PSI. But anything between 42-47 PSI is acceptable. When you reattach the vacuum line to the regulator, the rail pressure should drop proportional to intake manifold vacuum. An 8 to 10 PSI would be normal with a stock cam. Yours dropped 14 PSI. That's excessive. The manifold vacuum cannot be that high. May be a problem with the regulator. Itís normal for rail pressure to increase when the throttle is being opened (vacuum disappears), and to decrease as you snap the throttle closed (vacuum is high). But once the throttle is closed and RPM is back to idle, 31 PSI is too low.

Next fuel pressure test is to tape the gauge to the windshield, take it out on the road and take it up to 5,000+ RPM at WOT. Pressure should not drop below 40 PSI. Revving the engine in neutral does not place the engine under any real load. It actually needs to be working hard, accelerating the car.

When it stuttered and then cut off, did the SES light come on at any time? Have you scanned it for codes? If DTC 16 (Opti low res pulse loss) shut down the engine, it doesn't turn on the SES light, but the code would still be stored.
hey Fred,i got a better fuel pressure tester,the other one was leaking out the end in Schrader valve,ok I got 42 psi at prime,and it stayed there n didn't drop. I removed vaccum from regulator,went to 43.5. I taped the gauge to windshield pressure was at 44.
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Old 03-15-2018, 09:21 AM   #6  
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Re: stutter and cutted off on freeway

Scan for stored codes. Do not disconnect the battery.
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Old 03-19-2018, 08:22 PM   #7  
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Re: stutter and cutted off on freeway

I found out the distributor wire connection on left side of the engine connect part the pigtail wire was ripped up,i guess the previous owner must have ripped it up or tore it some how,because I never examined it. I put in a new wire.

Another thing to add the pigtail wire on the ignition coil had a bad connect on the pink wire,i had another pigtail wire and fixed it.

Then I took it out and fully running temperature,put it at wot and no more stutter.
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