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Hey guys this is my first post i hope i do justice explaining the situation.
So i have a 94 Chevy 350 5.7 gas engine 2WD. I’ll explain the rev problem first. I’m somewhat illiterate in car talk but I’ll do my best. So I noticed this problem in the winter because that’s when your vehicle brakes down. What goes on is when you start it, it starts and sometimes just dies right away from the cold. But what usually happens is it starts and than revs up to around 1000 RPM than will drop down to barley running, than back up, and it would shudder and die. I thought it was the cold but once the engine gets started and is warm the engine still fluctuates. You usually have to drive it in order for it to stay running, but even then the RPMS will drop and almost stop running when you hit the brake to stop at lights. What is really strange also is when you hit the throttle and there is no power, like I could floor it while driving down the road or take off from a stop sign and no power, and then all of the sudden launch like it should. also on the hwy its really tough to get up to speed and stay there as well. So it fluctuates when your driving as well.
What has been done: The fuel pump, spark plugs, spark plug wires, air filter, are all new. One mechanic hooked it up to the computer and said he found nothing. The idle air control valve is new as well.
Not sure if this one is related, but the cruise control stopped working a while ago in the way that when you step on the brake to take the cruise off stopped working. So i had to use the switch to take off the cruise. But now the the cruise can be off and when i step on the brake to stop the pedal just pushes back and the engine revs right up as if the cruise is still on trying to bring it back to speed. (its happened at stop lights and stop signs and its flippin scary, i once went around a corner at 70 kph) So i kinda want to get it fixed hehe. It happens intermittently. So i have no idea there.
I hope thats enough info I can answer any other questions.
Alright so just to add on that the distrbutor cap and rotar were replaced with the stuff listed above.
and mister “mechanic” didnt want to waste his time on a vehicle with as many km on it as mine.Also a question only a total noob such as myself would ask is: how can you tell if you have a carburetor or fuel injection. and are there vacuum hoses on both? sorry i have no idea how a vacuum system works, is there any good sites that explain this stuff, cause i cant seem to find a
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I’m wondering if you have some sort of vacuum issue related to your cruise control and/or brake booster. I notice on my little beater delivery car, when i pull up in front of a customer’s house, and after putting on the handbrake and releasing the brake pedal, the engine surges because the brake booster isn’t demanding vacuum anymore. This is pretty stretchy, but what you said about the pedal and the engine surge reminded me of that. I’ll have to do some digging.
Welcome to the forums!
+1 for checking any vacuum related issues.
Did the ‘mechanic’ check for fuel pressure at KOEO and KOER before replacing the fuel pump?
Also, you never stated if the distributor cap and rotor were ever changed?
Here is a good video Eric make on checking for voltage leaks –
http://www.youtube.com/user/EricTheCarG … -U9WqJfaJs
I would even start to look at possible timing too. How many miles are on the vehicle?
http://autorepair.about.com/library/pic … 460lib.htm
I found this poking around. Honestly, I don’t know alot about the cruise control system on that vehicle, but there are some related parts to what you described. Most notably was the vacuum line that went to ‘brake switch vacuum release valve’ that I saw.
I don’t think the system was much if any different in 1994 models.
There are a couple of suggestions I’d like to make. The first is to check for vacuum leaks as suggested, in fact the engine is somewhat famous for intake gasket leaks so this would be an excellent place to start your search. Vacuum leaks can cause all kinds of problems. The second thing I would like you to check is the brake light switch, check your brake lights and make sure they are working. Not only does the switch send a signal to the brake lights but it also sends one to the cruse control unit as well as the engine computer to raise the idle a little when you brake, if there is a problem here and the computer does not see that you are getting a brake input signal it might ‘mess up the idle’ as a result.
As to your question on fuel injection, you can pretty much say that anything made after 1990 is fuel injected as that is about the time it became cheep and emissions laws dictated that vehicles needed more accurate fuel controls. The easiest way I know of telling the difference is to look at the intake manifold, if you see just a throttle plate then it’s fuel injected but if you see an assembly bolted to it then it’s likely to be a carburetor, I say ‘likely’ because some fuel injection systems LOOK like carburetors but that’s a whole other post. Here is a video that I did on the basic parts of the engine that might better explain what I’m on about.
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