85 ? bad spark knock

[stepNstone]

I havent had it but a few days. It has run fine but yesterday i was
running along about 65 mph. it felt like it was running out of gas then it went on
down the road just fine. I got to my exit and when i took off from a stop i got on it going into second gear. It then spark knocked real bad I mean Real bad.
I let off and it went on. I tried to duplicate the problem and wouldn't do it. I have noticed the idle is very erratic on the car sometimes its high sometimes it
is very low. It does run rich but i was contributing that to the guy has the cats off of the car. The air pump hose on the passenger side is also cut off. I assume it went down to the cats. Now today i went to get on the interstate and the car did it again (spark knock real bad) any body have a idea where to start?
Thanks.
also where is the fuel filter on this car? I am not real familar with this thing yet.

 

[stepNstone]

another ? about the car.
At what temp without the ac running should the electric fan kick in? And is there a way i can make my fan come in at a lower temp?

 

[Vettefan87]

Yes you will smell a gasoline type smell running no cats since there is nothing there to burn up unburnt fuel, and yes that air pump hose goes the main cat, don't hook the main cat up without the air tube or you will burn up the cat.

About your spark knocking issue I would definetly check your base timing which should be 6 degrees before TDC. If it is not that you might want to back it down a little and try it. You might also consider buying a new knock sensor, I am not sure how to test them to see if they are good or not, but I don't think they are that expensive either.

The fuel filter is on the passenger side. If you are at the front of the passenger side door and look underneath the car it will be right by that fuel rail. When I did mine I removed the little aluminum cover that was covering it. I think they are two 10mm bolts and then you are good to go.

There are a couple things you can do for you fan. Factory setting is 230 degrees, way to hot for my liking as well. There are a couple things you can do for it. One you can order a switch from Mid America which turns it on at 180, or you can get a Hypertech Thermo master chip that will turn the fan on at 175 degrees, and off at 160. Hope this helps.

 

[WhalePirot]

It sounds like some rube started messing with a very sophisticated machine w/o a clue. One wonders what was done besides the chopping up of the clean air parts. Probably, the car was modified, which messed up the mixture, clogged the CAT, so he pulled all that stuff off, then got frustrated and sold it.

The fan cut-on change depends on whether yours is an early or later '85. The earlies used a temperature sensor on the right cylinder head (which can be changed to a lower 'trigger') while the laters had the ECM trigger the fan. There are many threads about this topic and your fuel pump questions.

The car has two fuel filtrers. One is a sock-like filter inside the tank, on the pump intake pipe. The other is mounted to the frame, about under the passenger's right foot. I fail to see how this is your problem. It sounds like a bunch of advance is being added, unless there is a mechanical problem.

This is still an internal combustion engine and the basics of yore apply. If you are to work on it, you will need more tools to diagnose, like a fuel pressure gauge and (I like to use) a vacuum gauge. You can drive the car with them connected and taped to the windshield so you can see the readings, if necessary.

The fuel pressure can indicate if your pump or the filters need replacement; can check leaky injectors, etc. The vacuum gauge is useful for many, many diagnoses.

 

[vetteboy86]

Are you on a fresh tank of gas?

 

[Moonunit 451]

Knock sensor = 50 bones.

 

[stepNstone]

Well i know where the knock is comming from or atleast i hope. It was filled up with reg unleaded (87 octane) ....

 

[stepNstone]

. The earlies used a temperature sensor on the right cylinder head (which can be changed to a lower 'trigger') while the laters had the ECM trigger the fan. There are many threads about this topic and your fuel pump questions.

You are talking about the passenger side? I know the one on the driver side is for the temp gauge but mine does have a sensor on the passenger side also above the last cyl. Is the the one you are in refrence to?
I don't mean to sound like such a tard .. I am very mechinacaly inclined but am a tard when it comes to these new computer crap motors lol.

btw is there a way to make it run good without all this computer crap since the previous owner already took off the cats and the air pump? It runs good but as far as the rest of the stuff?

 

[WhalePirot]

You are talking about the passenger side?

Yes.

the passenger side ........ Is the the one you reference?

See above...

I am very mechanically inclined but am a tard when it comes to these new computer crap motors lol.

Now, now. We are (were) all 'tards' until we learn(ed). The computer does the same things as other components on the older engines, but does them better and more precisely.

Is there a way to make it run well without all this computer crap since the previous owner already took off the cats and the air pump?

If you study and learn the system (that other crap) you will appreciate the help that the computer can give you. The basics still apply, as I have said over and over, and need to be squared away before trusting the ECM's codes.

Many here have Vettes that absolutely SCREAM, while running full smog gear and the stock ECM; some with a re-programmed chip. In my case, I updated the wiring harness and the computer, added a custom PROM and have a nasty-a** 406 that drives nicely about town and idles smoothly, albeit with the lumpiness we all love, at just under 900 rpm. THAT, would not be possible w/o the computer on this engine.

I suggest you spend some time learning to search (above button) and read what has and hasn't worked. Quick cars are expensive and these are all that and more, but all are more costly than necessary if we don't learn from others. This forum is excellent as such a tool.