I know, i know, this isn't the right forum to post it in but this forum seems to be the best and has the nicest and smartest people here :) Since this is a street racing forum, i'll uh, make it relate kinda too it with this statement. "I can't race anyone with this problem i got, so, here it is" :(

Okay, i drive a 1992 Chevy Caprice that use to be a cop car. It has 214,000km on it. It is also an automatic with a race/cop tranny. For the past several months I've had this problem. Which happens only once and a while, never when i want it too when i show people :(. Anyways, when I'm driving around, the rev's drop and I loose lots, if not all power from the engine. Even though my foot still has the gas depressed. This happens while stopped, accelerating hard and slow, traveling fast and slow. It happens in cold and warm weather. It has been happening a lot today so it is starting to concern me. When it loose's power, it's like the engine has dropped from an 8 to a 4 cylcinder. I tried flooring it and it slowly accelerates. I'm use to flooring it and getting kicked back in the seat. The car also starts to shake and viberate once and a while when this happens. Sometimes i'm driving along and it just happens. Then, after a few seconds (feels like minutes), everything is nice and dandy again.

I have, well my dad has, talked to mechanics and they don't seem to know why or understand the problem. Well one said to change the fuel filter, which i did, and it didn't help :( It has very recently had a oil change aswell. I've checked all the fluids and they seem alright (Although the tranny is running in the hot section of that metal rod you stick in to test the level, is that good or bad? That was done after driving for 5 minutes if that matters). A tune up had been done in the middle of august, about a month ago, and they changed the distributer cap, spark plugs and spark cables. Among other things, but i don't have the list with me. We also put in regular fuel, the cheap one. It already costs us $80 or so for a fill up of the cheap stuff :( So i don't want to try the more expensive stuff yet.

When I get the chance and I feel and see the problem, i'm going to put it in neutral and rev it and see if I still have the problem. This might help me find out whether it's the engine thats screwing up or something else like the tranny.

EDIT: I also don't know to much about cars. :( It also has a full tank of fuel.

I would have the transmission fluid changed to start off with.

I used to have a Dodge Charger that would do that sometimes. I couldn't figure it out and it never did it when I could show anyone. I sold it :lol2:

Do the electrical accessories start to mess up too when it does it? If so maybe you have a bad connection or ground somewhere?

Well it's not the tranny, i rev it and it just sputters. It's so bad, i can't even drive anywhere now :( I'm thinking it might be the oxygen sensor kicking the bucket and giving wrong readings, or the fuel pump is messed up or something like the engine isn't getting the fuel it wants :( any more ideas? if not, i'll just try some stuff and hope for the best.

EDIT: The electrical seems fine, all the lights light up and the speedometer lights up. I'd sell it, but who'd buy a car with 214000km ? :)

I'm willing to bet that you've got dirty fuel injectors, for starters. Run some STP through the system and see what happens. There's also the EGR valve. That could be it. And, as you've been thinking, the fuel pump may be sour.

An O2 sensor doesn't seem likely, but it's worth a shot. Get your hands on a computer diagnostics tool and see what your car's comp can tell you.

I am a mechanic, your description of the problem is excellent, but a problem like this can be very difficult to find with the car in the shop, over the internet is almost impossable.

To start with it could be a fuel delivery problem, you have already replaced the filter which is the first step, but the problem could be with the fuel pump(s), fuel inlet "sock", fuel pressure regulator, fuel pump power circuit (relays). Other areas to look are the air MAFS (mass airflow sensor), knock sensor, plugged catalitic converter, bad engine grounds for the injectors, ....

I have seen all of the above cause symptoms similar to what you are describing. Start with a logical diagnosis, fuel supply and pressure, would be the best place to start.

Good luck

A weird thing happened today when my dad was driving the car. He went over some bumps when the car was struggling and all of a sudden it got it's power back. Then, a few more bumps and railroad tracks later, it lost it's power, right after he went over a railroad track. So, we're guessing that something could be loose or a little off and the odd bump knocks it back in place or out of place?.. Also, after 60 km/h, it seems to run fine. :screwy: I don't know if it was just luck or it actually matters. Also, it seems that when you put the pedal down the acceleration increases as you depress the pedal (oviously :) ), but anything past a certain point, like halfway depressed. Anything past that halfway mark doesn't increase the acceleration.

The idea of the bad engine ground for the injectors could be the problem. I went camping this summer with the car and when we started it up to leave it wouldn't start. So we popped the hood, checked a bit and tried again. I heard the worst sound ever, a loud banging knock :( The problem turned out to be that some of the spark plug wires were touching other ones and when the electrical charge went down one it also went down the other and caused the piston to misfire :( But the problem i have now happened before this. That was just a horror story for your reading pleasure. :)

Also, thank you guys very much for your help. I haven't solved the problem yet as i've had no time to work on the car with school and a bunch of other stuff. Also, my dad doesn't like me doing the stuff by myself, so i'm stuck waiting for him to get free time aswell. But this weekend i will do some major work on it. I'm going to try most of your suggestions, well, the ones that don't require diagnostics because I don't have the equipement for that. And as of right now, i don't know who does.

I think i will look into the manual i have of the book and check out how to do the things you guys have suggested. I will also flip over to the troubleshooting part and maybe see if that can help me. Oh well, atleast i have an excuse to work on the car now :)

I'll keep you posted after the weekend is over about what happened. Hopefully she starts to run good again :) Got to love the huge 5.0's and the roar of the engine when you let her loose :)

EDIT: I will be doing the STP thing tomorrow.

My dad was having the same problem with the LandRover its fixed now but we did so many things done were not sure what fixed it.

maybe catalytic converter?????

Good luck with that, bro. My '94 Cougar had a similar problem with the transmission. I never figured it out cuz it got wrecked.... :D

Alright, i have some good news and some bad news. As an update for this problem. Well i'll start with the good news. If you don't want to read below and want the summary, read the last paragraph.

The good news. The problem has been constant for the last few days so we managed to have a few mechanics voice their opions. They all suggested cleaning the throttle body and checking the catalytic converter. But, we have found the problem ! or a likely cause or maybe it's just the lack of my car smartness. But today we took of the air filter and all that stuff to expose the throttle body and spray some cleaner (yes, it's throttle body cleaner, not dish soap :)) into it (As perscribed by a mechanic). At the same time, we noticed that one of the two fuel injectors was not spraying any fuel. Problem? i think so. So my dad reved it and still nothing coming out. But man was it loud and boy did it suck air in. Man, if i wasn't paying attention i probably would of been sucked in :lol:

Now the bad news. Since we think the problem is the one injector being sucky. We probably won't be taking the catalytic converter and exhaust pipe and muffler off anymore (thought it could be back pressure) and reving it. I really wanted to hear the v8 roaring without anything muffling it.

So, the assumed problem is one injector is not injecting. The solution... thats where you guys come in :) We used the STP, but no luck. We'll be doing workon the car this wednesday, so quick suggestions would be good :) We'll be talking to a mechanic or two tomorrow for some ideas and will probably read up a bit. But, if you want to voice your ideas, feel free too. :)

i am glad to hear about this i just registered today on christmas. i have a chevy caprice1992. it has a 305 in it throttle body. im experiencing the same problems. i had the catylitic converter removed, tune up, o2 sensor, iac valve, tps sensor, knock sensor, ignition coil and module, esc module, fuel pump and filter and pressure regulator, valve caver gaskets, and replaced plugs with bosch platinum2's.i have no idea what it is but i dont want to waste money taking it to the shop.every week ill go outside to start it and it wont start just keep turning and the injectors wont spray. i either have to unplug the the harness to the timing over the passenger valve cover to start it which always doesnt work. when it doesnt i have to spray either down the throttle body.some times either wont work so i have to unplug the harness over the valve cover. it shifts rough, misses, runs rich, accelerates rough and sluggish, and it idles up and down on a cold start. i have the sam symptons as the user that started this page has. anyone know whats going on.

Sorry but we don't have to many chevy's kicken round down here, we do have the Holden V8 that run multi point injection. The fact that you could see the injectors suggest it is the central injection type. You may find that only 2 injectors will fire and the other 2 kick in under extreme acceleration, like a 4 barrel with vacuum secondary's.
I had 2 different Holden V8 efi's with very similar problem. One was the fuel pump. As the brushes wear down they start to struggle to stay in contact with armatuer. Try getting someone to bang pump with hand while engine running.
The other was the optical pick up in the distributor, as this both triggers the spark and injectors. If the Chev has a crank angle sensor you might try that. The optical pick up in the holden's does the job of crank angle sensor too.

Good luck.

Starting and losing power then gaining it back sounds like a TPS, I have a 305 TBI in my truck and when the TPS was bad used to do that, but if you think its the injectors theres a way to fix everything with the fuel at once pretty much, just get a new TBI from a junk yard... Shouldn't be too much money and just take it with all the sensors still on it so you don't have to worry about those either.