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jimmers | Acceleration trouble | ||
Senior Guru
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After weeks and weeks of trouble with the vette it was finally running properly, so the lady and I decided to take it for a long drive to the beach. The car drove great all the way there and most of the way back. All of a sudden on the way back the car started to slow down. I couldn't accelerate at all. I'd push the pedal to the floor but nothing. I pulled over to the side of the road, put it in neutral and tried to rev the engine. Still nothing. I shut it off then back on and the problem went away. It drove great all the way home. I scanned for codes but came up nothing. My first thought was TPS, but it measured fine. Any ideas? I'd hate for this to happen again.
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Posted on: 2008/9/15 13:04
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Mekanic | Re: Acceleration trouble | ||
Registered Vendor
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tough one to diagnose for sure.
Start with the easy, ICM, coil, fuel pressure, ohm check the injectors |
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Posted on: 2008/9/15 13:51
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~Rich Polo LT4 Yea tho I walk through the valley in the shadow of rice, I shall fear no turbo, for torque art with me. |
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Schrade | Re: Acceleration trouble | ||
Elite Guru
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Yup - fuel pressure.
Check it static (motor off), idle with vacuum on FPR, idle with vacuum off FPR, and pedal down (gauge taped to the windshield). This last one you really need to do, to make sure of enrichment for acceleration... |
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Posted on: 2008/9/15 14:31
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LT5, Marc Haibeck ECM module, AUTOMATIC!!! |
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CentralCoaster | Re: Acceleration trouble | ||
Senior Guru
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Was the gas tank at 1/4 or lower?
I wonder if the fuel pump could've overheated or is failing intermittently. How long did you shut it off for before continuing? |
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Posted on: 2008/9/15 15:14
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1985 Z51, ZF6 |
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jimmers | Re: Acceleration trouble | ||
Senior Guru
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The injectors, fuel pump, coil and wires are brand new. They have about 200miles on them. When I pressed the gas pedal down it didn't even try and go. The rpms didn't go up at all.
The car had just under a full tank. When it happened I shut the car off and started it right away and the problem was gone. |
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Posted on: 2008/9/15 19:44
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Schrade | Re: Acceleration trouble | ||
Elite Guru
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Quote:
Pull your codes. Since the problem 'went away', it's probably electrical, and is stored in the ECM. |
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Posted on: 2008/9/15 20:07
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LT5, Marc Haibeck ECM module, AUTOMATIC!!! |
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jimmers | Re: Acceleration trouble | ||
Senior Guru
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I checked for codes lastnight, but there wasn't any!
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Posted on: 2008/9/15 21:24
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Matatk | Re: Acceleration trouble | ||
Webmaster
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Quote:
Is the filter new? Is the cap new? I would check fuel pressure as suggested. Matthew |
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Posted on: 2008/9/15 21:54
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2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP |
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CentralCoaster | Re: Acceleration trouble | ||
Senior Guru
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How is a filter or cap going to fix itself after restarting? That doesn't even make sense.
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Posted on: 2008/9/15 23:11
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1985 Z51, ZF6 |
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MK 82 | Re: Acceleration trouble | ||
Senior Guru
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Quote:
That is not a requirement for most armchair mechanics. I think it is a bad framulator! |
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Posted on: 2008/9/15 23:22
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96 CE Roadster LT4 |
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Schrade | Re: Acceleration trouble | ||
Elite Guru
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Quote:
Then let's go back to fuel pressure... Quote:
It doesn't matter if you have a new pump or not. If the regulator does not respond properly to increase vacuum, or if the vacuum is leaking somewhere, you won't accelerate. You have a problem accelerating? Check fuel pressure for increase pressure under pedal down conditions. Vacuum from pedal down must be correct to enrich fuel pressure for acceleration. |
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Posted on: 2008/9/15 23:48
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_________________
LT5, Marc Haibeck ECM module, AUTOMATIC!!! |
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Matatk | Re: Acceleration trouble | ||
Webmaster
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Quote:
I figured if the fuel filter is clogged, it will show signs of that under pressure. Turning off the motor may relieve pressure temporarily and possibly allow some contaminants to settle. I guess this was just my theory, but I've driven cars where one day they were perfect and the next day crap, all because of a dirty filter. Sorry we're not all perfect like you. Maybe one day I'll strive for that level of achievement. Matthew |
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Posted on: 2008/9/16 0:15
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2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP |
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Schrade | Re: Acceleration trouble | ||
Elite Guru
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Quote:
Alright there mr Coaster... Here's how that can happen (unlikely, but entirely possible) He's cruisin', the computer purges the evap cannister. His gas cap is loose. The system doesn't hold necessary vacuum. Since there's already vacuum leaks (possibly), he's not atomizing fuel well as it is. Additional vacuum loss puts him over the edge of 'running'. Power loss. Turn the motor off, the computer resets to 'not purging'. Flame suit on! Bring it! |
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Posted on: 2008/9/16 0:24
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LT5, Marc Haibeck ECM module, AUTOMATIC!!! |
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CentralCoaster | Re: Acceleration trouble | ||
Senior Guru
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I wasn't trying to flame anyone, just being terse. I was contemplating if the fuel system air pressure could cause issues, but it's tiny compared to the psi put out by the pump, and the evap system is a long shot, as you say. The debris one makes some sense, I've seen that happen in plumbing systems where it would flow fine and then block up under high flow.
I guess I read a lot of tech posts where it seems like people replying didn't read the first post. My apologies. |
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Posted on: 2008/9/16 3:21
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1985 Z51, ZF6 |
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jimmers | Re: Acceleration trouble | ||
Senior Guru
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I'll check my fuel pressure as Blade_1 stated and see what happens.
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Posted on: 2008/9/16 19:47
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Matatk | Re: Acceleration trouble | ||
Webmaster
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NP. I think the bottom line is we all want to figure out what's wrong and help out jimmers, and that's what we are all striving for! Matthew |
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Posted on: 2008/9/16 23:56
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_________________
2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP |
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jimmers | Re: Acceleration trouble | ||
Senior Guru
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Well it happened again tonight, a few times actually. I turn it back on and it goes for awhile. I checked the fuel pressure the other day and it was fine, both at idle and when driving. Now tonight after it stalled on the driveway I started it again and opened the hood. The fuel pressure was about 7psi lower then normal, and 2 injectors were really loud when pulsing. I put my finger on them and I can really feel the tapping. Does this mean anything? I'm going to go scan for codes again.
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Posted on: 2008/9/19 23:44
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CentralCoaster | Re: Acceleration trouble | ||
Senior Guru
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Personally I think many of the replacement injectors are louder. Perhaps it's because the injectors are a bit longer and bottom out against the intake base which makes it transmit more noise. A fix for this is putting washers between the fuel rail and base. This is especially a problem with some of the aftermarket intake baseplates. Also I've heard of this binding the injector housings up and causing them to stick open or shut.
Keep in mind everytime the injectors shut, the fuel is still flowing towards them, and it hits this now dead end, and slams into it and makes a pressure spike. This tranlates to noise and vibration at the injectors and fuel lines. If the injectors aren't bottomed out, they should be cushioned a bit from this shockwave (water hammer) by slight movement of the orings. |
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Posted on: 2008/9/20 0:11
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1985 Z51, ZF6 |
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jimmers | Re: Acceleration trouble | ||
Senior Guru
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Quote:
The injectors were never noisy until yesterday. Now two of them are really bad. Is this a sign that the injectors could be bad? |
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Posted on: 2008/9/20 15:49
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Mekanic | Re: Acceleration trouble | ||
Registered Vendor
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Usually they don't make noise unless they don't have fuel in them. But that would cause all of them to be noisy.
They may be clogged, or they may be bad injectors. |
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Posted on: 2008/9/20 15:57
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_________________
~Rich Polo LT4 Yea tho I walk through the valley in the shadow of rice, I shall fear no turbo, for torque art with me. |
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Schrade | Re: Acceleration trouble | ||
Elite Guru
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Do the ohm test for your injectors. There's a video sticky of the test in CF C4/tech/perf. Do the test cold, AND HOT...
It might take you 10 minutes to do it, if you take your time. |
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Posted on: 2008/9/21 0:16
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_________________
LT5, Marc Haibeck ECM module, AUTOMATIC!!! |
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Transfer |
anesthes | Re: Acceleration trouble | ||
Master Guru
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Quote:
You won't accelerate? That's pure nonsense. The amount of fuel pressure pulled under vac is very minor. -- Joe |
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Posted on: 2008/9/21 1:11
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Schrade | Re: Acceleration trouble | ||
Elite Guru
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What happens if you don't get fuel enrichment?
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Posted on: 2008/9/21 1:33
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_________________
LT5, Marc Haibeck ECM module, AUTOMATIC!!! |
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anesthes | Re: Acceleration trouble | ||
Master Guru
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Quote:
Your fuel enrichment comes from your acceleration enrichment table, and power enrichment table depending on throttle position, throttle rate, and MAP signal. The fuel pressure regulator is designed to pull some fuel pressure off when the manifold is under vac. This is designed so the fuel pressure remains the same ratio relative to manifold pressure. -- Joe |
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Posted on: 2008/9/21 1:57
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CentralCoaster | Re: Acceleration trouble | ||
Senior Guru
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Quote:
Yup. If you've got 20" of vacuum at idle, it'll pull a whopping 20" of fuel pressure. That's less than 1 psi. |
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Posted on: 2008/9/21 4:52
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1985 Z51, ZF6 |
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Schrade | Re: Acceleration trouble | ||
Elite Guru
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Oh.
Ok... So let me ask the question again, since I didn't see any wording that answered it... What happens if there's NO FUEL ENRICHMENT? answer will be something like: "If there's no fuel enrichment, ________ ." |
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Posted on: 2008/9/21 15:16
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_________________
LT5, Marc Haibeck ECM module, AUTOMATIC!!! |
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jimmers | Re: Acceleration trouble | ||
Senior Guru
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Ok well I've been playing around all day so far and heres what I found.
I start the car the fuel pressure goes up to about 45psi, then dies. The fuel pressure goes down to 0. Once it dies the fuel pressure goes back up to about 45psi and I can start it again. So it's completely loosing fuel. When I turn the ignition to on the fuel pressure stay's steady at 45psi and slowly goes down. That makes me beleive that my injectors are fine and not leaking. Could it be the FPR, or a vacuum problem? |
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Posted on: 2008/9/21 15:51
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Mekanic | Re: Acceleration trouble | ||
Registered Vendor
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If your pressure is leaking down after priming the rails then its either a stuck injector or the check valve on the pump
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Posted on: 2008/9/21 15:56
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_________________
~Rich Polo LT4 Yea tho I walk through the valley in the shadow of rice, I shall fear no turbo, for torque art with me. |
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jimmers | Re: Acceleration trouble | ||
Senior Guru
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Quote:
Forgive me if this is a dumb question but shouldn't the pressure slowly leak down if the car isnt running even though I primed the rails? I'm a little confused. |
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Posted on: 2008/9/21 16:58
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Mekanic | Re: Acceleration trouble | ||
Registered Vendor
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no, you should keep pressure LONG after shutting off the car, or priming the rails with the engine off.
By LONG after, I mean I've been sprayed by the schrader valve after the car has been off for over a week |
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Posted on: 2008/9/21 17:02
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~Rich Polo LT4 Yea tho I walk through the valley in the shadow of rice, I shall fear no turbo, for torque art with me. |
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jimmers | Re: Acceleration trouble | ||
Senior Guru
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Quote:
Oh, I was under the impression that it takes roughly 30min for the fuel pressure to bleed to 0. |
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Posted on: 2008/9/21 17:13
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jimmers | Re: Acceleration trouble | ||
Senior Guru
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Quote:
I understand that an injector can be bad. What I dont understand though is why the car dies instantly. If a few injectors were bad it should still run but rough, correct? |
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Posted on: 2008/9/21 17:18
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anesthes | Re: Acceleration trouble | ||
Master Guru
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Quote:
Why? it has nothing to do with the fuel pressure regulator as I stated. It's in the computer. (enrichment) And if the FPR was not raising fuel pressure with map changes, it would probably accel faster because it would lean out a hair. (and I mean a HAIR) We all know a slightly leaner edge makes more power. Well. most of us know that. (unless it detonates) -- Joe |
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Posted on: 2008/9/21 17:47
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anesthes | Re: Acceleration trouble | ||
Master Guru
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Quote:
The fuel pressure dies or the car dies? Quote:
I think your pump is failing. I think it can prime to 45psi but cannot maintain, but I also don't completly understand what you are describing. How long does it take to fall when you prime it? (key on)? My TPIS AFPR would hold pressure for about 2 weeks. My holley regulator holds it for about 2 minutes. heh. -- Joe |
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Posted on: 2008/9/21 17:50
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jimmers | Re: Acceleration trouble | ||
Senior Guru
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Quote:
The fuel pressure and car dies. The fuel pressure will go down to 0, and then the car dies. But right after the car dies the fuel pressure goes back up to 45, then I can start the car again. Quote:
It takes about 20min for the fuel pressure to fall to 0. |
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Posted on: 2008/9/21 18:01
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anesthes | Re: Acceleration trouble | ||
Master Guru
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Quote:
Well... When the car dies the ECM energizes the fuel pump so it re-primes. The oil pressure switch keeps the fuel pump energized as long as their is oil pressure, and the ECM keeps it energized as long as their is reference pulses. It could be a bad fuel pump, though they normally just die. The drop in fuel pressure suggests the injectors are in fact firing. Since they are firing, you MUST be getting distributor reference pulses since that is how they fire. I wish I could get my hands on the car. -- Joe |
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Posted on: 2008/9/21 18:49
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jimmers | Re: Acceleration trouble | ||
Senior Guru
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Quote:
Thanks for the help! Is there anyway to test the fuel pump for sure? I'd hate to get another one and not have it solve the problem. |
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Posted on: 2008/9/21 18:56
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jimmers | Re: Acceleration trouble | ||
Senior Guru
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Well I went outside to test for 12v at the fuel pump wire and it started right up and ran fine. It ran for 10min before I shut it off. The fuel pressure is holding steady still. Now I'm really lost.
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Posted on: 2008/9/21 19:38
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jimmers | Re: Acceleration trouble | ||
Senior Guru
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I went for a ride around the block, stalled on me. I kept starting and starting it before it finally stumbled home. Stalled on me on the driveway a few times. I hit the fuel pump and it seems to help a bit.
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Posted on: 2008/9/21 20:16
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jimmers | Re: Acceleration trouble | ||
Senior Guru
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I hooked up my 12v light to the fuel pump source again and started the car.
The light will turn on while the car is running. When the car stalls the light will remain lit, and turn off about 2 seconds later. So I guess the pump is getting a good 12v source. Seeing as how the pump dies before the light, I can assume that the fuel pump itself is bad. Correct? |
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Posted on: 2008/9/21 22:25
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anesthes | Re: Acceleration trouble | ||
Master Guru
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Quote:
If the fuel pressure is dropping BEFORE the light goes out, then I'd guess the pump is failing. I had a boat once, that would run for a minute or two and the engine was die. Mouse in the fuel tank kept getting sucked into the pickup. Fuel pressure would drop, engine stall, then the mouse would float away from the pickup and I'd be able to restart the engine. Food for thought. Anyhow. if the fuel pressure IS in fact dropping it's pump related. Rule out ECM, FP relay, etc since you have good power. If the fuel pressure is NOT dropping, i'd move my bet to ignition. -- Joe |
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Posted on: 2008/9/21 23:25
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jimmers | Re: Acceleration trouble | ||
Senior Guru
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Quote:
Thanks for your help! The fuel pressure does drop to 0 psi before the light goes. I think I narrowed it down, but I'd love to know for sure. Are there any other tests I can do to know for sure? |
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Posted on: 2008/9/22 0:48
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anesthes | Re: Acceleration trouble | ||
Master Guru
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Quote:
If it was a no start you could do a volume test. I think you either have a failing pump, strainer, filter, etc. I'd replace all since the cost is so low and get on with it. -- Joe |
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Posted on: 2008/9/22 0:58
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jimmers | Re: Acceleration trouble | ||
Senior Guru
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Quote:
The funny thing is that it was all replaced about a month ago. Thanks for your help again. |
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Posted on: 2008/9/22 1:22
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Ramrod | Re: Acceleration trouble | ||
Senior Guru
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I ain't no Guru, but mine did the same thing with a dirty fuel filter and fuel pump filter, was sucked up into the pump???? Changed both and it's been 12 months since, cheap fix maybe?
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Posted on: 2008/9/22 4:39
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_________________
1996 LT-1 DynaSpark Opti, Tapered Rear Wheel Bearings, SS Brake Lines, Speed Bleeders, MC Bias Spring, Hawk HPS Pads, MSD Wires,NGK Iridium, lowered, etc. |
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anesthes | Re: Acceleration trouble | ||
Master Guru
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Quote:
My mouse + boat story was a hint that something could be sucking into the strainer. Who knows. Might just be a 'master' brand pump from autozone failing. Seen that enough times. -- Joe |
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Posted on: 2008/9/22 11:08
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jimmers | Re: Acceleration trouble | ||
Senior Guru
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Well it turns out my fuel filter was the culprit. Something inside broke and when under pressure blocked the line. Again thanks for everyones help!
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Posted on: 2008/10/8 22:03
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Matatk | Re: Acceleration trouble | ||
Webmaster
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Quote:
Thanks for the update! Good to know the solution to problem for future reference. Matthew |
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Posted on: 2008/10/8 23:12
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_________________
2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP |
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TommyT-Bone | Re: Acceleration trouble | ||
Chair-man of the bored
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Quote:
Thanks for the update! Follow-ups are great. |
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Posted on: 2008/10/9 0:02
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crash | Re: Acceleration trouble | ||
Guru
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what year and how many miles on it is the cat oem
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Posted on: 2008/10/9 1:29
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