How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Virtual Wrench Your Own Question
Virtual Wrench
Virtual Wrench, Chevy Mechanic
Category: Chevy
Satisfied Customers: 14618
Experience:  35 years Master Mechanic
2617050
Type Your Chevy Question Here...
Virtual Wrench is online now
A new question is answered every 9 seconds

Chevrolet Impala SS: I have a 1996 impala SS. When I press

Customer Question

I have a 1996 impala SS. When I press on the gas peddle, there is no power behind it. It just doesn't move. RPM's barely move. When it first happened the car slightly sputtered and wouldn't go over 40mph. It got worse and won't move at all. I changed whole distributor, wires, and spark plug. My battery is new. OBD2 codes p0335 and p0336 came up when I ran a diagnostic scan. I replaced the crankshaft position sensor and ensured that it wasn't too long to where it'd be hitting. The car runs idle smoother but not top notch. No longer sputters but just doesn't move. I'm thinking I have to check the PCM but and unsure to where it is and how to check it. I have a multi-meter tool. What do you think? And how do I check the PCM?
Submitted: 1 year ago.
Category: Chevy
Expert:  Virtual Wrench replied 1 year ago.
Hello,
This doesnt sound like the PCM, it sounds more like a restricted cat converter. When they start breaking up it restricts the amount of exhaust that can get out, and if air cant get out, it cant come in.
Do you know if it has the stock converter still?
Customer: replied 1 year ago.
I was told it had a new one in already.
I forgot to mention that after I had changed the wires and distributor the car ran perfect for about 30 min. The. When I slowed down and tried to pick up speed again is when it started not accelerating
Expert:  Virtual Wrench replied 1 year ago.
Thanks for that info,
The thing about the converter is that when it heats up, the material inside swells up and slows the flow.
What you can do first just to rule it out (or in) is to remove the O2 sensor that goes into the exhaust forward of the converter and it will relieve any back pressure if the cat is plugged. Then take it for a drive and see if it improves.
Can you do that and get back to me. I really feel it is worth it to try because if it were a problem with the PCM it would have set a code.
Customer: replied 1 year ago.
The code that comes up on my OBD2 is p0335 and P0336. I didn't see any of the causes having to do with the Cat converter which I why I never would have guessed. I'm actually not working on the car at this precise moment so I can't try it at this moment. But I will try it and get back to you when I do. Thank you. If I remove the O2 sensor like you said. The car would run just be momentary like before?
Expert:  Virtual Wrench replied 1 year ago.
Hi,
After you remove it you would notice a big difference in power right away and it would stay that way. It wouldnt run good then bad, off and on. I wouldnt ask you to remove it if i didnt think it was worth a shot bud. It's just that i have seen SO many act like yours is doing that i really think its worth a shot. Also, sometimes if you smack the bottom of the cat when its cold, you can hear pieces rattle around...not always but something to do also.
Take your time and get back when you can..
LJ
Customer: replied 1 year ago.
Ok. Will do. Thank you. I'll get back to you when I can.
Expert:  Virtual Wrench replied 1 year ago.
Fair enough. Regardless of the outcome, we WILL get to the bottom of this.
Have a good night my friend!
LJ
Customer: replied 1 year ago.
The guy I got the car from said it could also be the fuel filter or pump. He said it could be the engine not getting the right amount of gas pressure to accelerate. I was just wondering your opinion on that.
Expert:  Virtual Wrench replied 1 year ago.
Hi,
Sorry i missed you last night.
The fuel pressure and filter were the next things i was going to have you check. Go ahead and replace the fuel filter because you have no idea how long its been in there, its just good maintenance anyway.
These fuel pumps are known to have problems so you can do a fuel pressure test by connecting a gauge on the test port on the fuel rail. It has to be real close to 45 psi and no lower than 41. If you dont have a gauge autozone will loan you one for free with a deposit.
It might read ok at idle so rev the engine and check it because they can fool you. Sometimes we have to drive the car with the gauge attached to the windshield to see what the pressure is at when its acting up...pain in the ass but sometimes it has to be done.
Let me know what you find with the O2 and fuel pressure. My PC is acting up so i am trying to fix it so it might take a bit to get back to you.
Customer: replied 1 year ago.
Ok. Thank you.
Expert:  Virtual Wrench replied 1 year ago.
You are welcome.
Customer: replied 1 year ago.
Just tried the O2 sensor. It won't even let me reverse out of my garage. Goes into gear, but when I gas it, it doesn't move.
Customer: replied 1 year ago.
Same as it was before.The fuel filter turns on but I haven't had a chance to check fuel filter. Waiting for the car to cool down now. Same p0335 and p0336 codes coming up. If fuel filter is fine I'll go down to O'reilly's to rent a fuel pump pressure gage.
Customer: replied 1 year ago.
Can you think of any other possibilities?
Expert:  Virtual Wrench replied 1 year ago.
Hi,
Buy a crank sensor also. Usually when they fail it wont even start but thats what the codes point to. Other than the fuel filter and pump is all i can think of off hand.
Let me know tomorrow. I have to leave.
Best>
LJ
Customer: replied 1 year ago.
I have a new crankshaft position sensor in already. That's one of the first things I replaced because of the code. But I'll check the pump and things. Then I'll let you know updates tomorrow. Thank you
Expert:  Virtual Wrench replied 1 year ago.
sounds good

Related Chevy Questions