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Chevy Caprice General and Technical discussion for the Chevy Caprice (1965-1996), which shares the B-Body platform with the Chevy Impala.

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Old 07-07-2010, 06:47 PM   #1 (permalink)
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89 Caprice Timing unstable, advances too much

Well here goes. Totally new to this site. I bought an 89 Caprice last year for a work car. It is a carbed 305. Well, this winter I took off the RH cylinder head as three exhaust manifold bolts were broke. Reinstalled everything and now after assembly, the thing will barely run after you plug the four wire connector back in at the distributor. During all of this stuff I did take the ignition module out and clean things up in there as there was lots of green gunk.

Here are some things I've discovered. It idles smooth and revs pretty good with the four wire disconnected. If I plug the four wire in the timing advances just a little, 3-4 degrees. However, if you crack the throttle at all it advances wildly and spark knock occurs. I am verifying this with my timing light as I am doing this. So, I said load and speed cause the timing to advance. So, I unplugged the MAP sensor and everything runs really smooth, even revs up nice instead of spitting and coughing. OK, bad map sensor. However, I backprobed the middle wire of the MAP sensor and 0.5V with engine off, key on, which would be the same as wide open throttle. With engine running I have about 3.9V at idle. Which seems pretty good. I just can't believe the MAP sensor is bad, however, if I plug the MAP back in at idle, with the four wire connected, it will just about kill the engine. My worry now is maybe the full MAP signal voltage is not getting back to the ECM.

It really isn't driveable without the four wire connected as you have crap for road power as there is no spark advance.

I have checked spark plug wire location and firing order 100 times. Also, checked to make sure the valves weren't too tight.

Any ideas anyone?

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Old 07-07-2010, 10:25 PM   #2 (permalink)
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I had a few late 80's boxes and I thought the emissions system was garbage, I ended up stripping them down to what I'd call a 1966 setup and it worked very well. That would be my way of solving the problem, I wouldn't go down the road of trying to restore the original system. You'd need a new carb, distributer, trans kit and I think that's about it. Used maybe $300 total.

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Old 07-08-2010, 10:43 AM   #3 (permalink)
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I would carefully check any wiring you even came close to when you took the head off, I would expect its related. Dinty is just very bitter about computerized vehicles, aren't you Dinty? hehe

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1978 Caprice Classic Landau
350 2-bolt, stock 4bbl
Stock rebuilt TH350
Edelbrock performer cam + intake
Dual 2 1/2" Flowmaster exhuast (waiting to be installed)
Edelbrock IAS Classic shocks
95 9C1 3.08 posi
4 wheel disc brakes!
16x8 American Racing Baja's with 225/60/16 Pirelli P4's

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Old 07-08-2010, 01:23 PM   #4 (permalink)
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I would carefully check any wiring you even came close to when you took the head off, I would expect its related. Dinty is just very bitter about computerized vehicles, aren't you Dinty? hehe
Yes, I am because I think it's a bullshit routine designed to keep us using the same wrong fuel so that a select few can get more and more filthy rich.

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Old 07-08-2010, 03:10 PM   #5 (permalink)
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Well yeah. Considering a girl I was in highschool with retrofitted her geo metro to run on water for her senior project, and it worked. I would say that they are screwing us just a little... Electric isn't so bad, they can still charge for that. The hydrogen models they are putting out bypass the water part, so they can charge for hydrogen. Hybrids... I won't even get into that! Needless to say, yes, you are correct sir. Plus, why is it that cars aren't getting any better mileage than they did in the 60's?

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1978 Caprice Classic Landau
350 2-bolt, stock 4bbl
Stock rebuilt TH350
Edelbrock performer cam + intake
Dual 2 1/2" Flowmaster exhuast (waiting to be installed)
Edelbrock IAS Classic shocks
95 9C1 3.08 posi
4 wheel disc brakes!
16x8 American Racing Baja's with 225/60/16 Pirelli P4's

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Old 07-08-2010, 03:54 PM   #6 (permalink)
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I don't understand the gas mileage thing. I remember a VW deisel getting 60 mpg around 1980. Yet most people are convinced that cars are way better now. Most people think my Caprice is an uneconomical gas hog, but if you figure I paid $800 for it 5 years ago and do all the math I'm sure it's probably less than 1/10th the cost of the best gas mileage 2010 model, plus safer and nicer to drive.

The electric cars get their electricity mainly from oil. Plus what would you do with all the old batteries? The first cop cars in NYC were electric but it's never really worked.

LPG is the way to go I think. We can make LPG from plants and there's tons already available. The problem I believe is that it would be a big deal to make all the fuel trucks, storage containers, gas stations etc... switch over.

You could convert a car like a RWD Caprice over for around $1K and there's almost no polution and from what I understand they go fast 'cause the compression can be higher than with 2010 gas.

Probably for the less than we've spent on the dubious wars we are in we could have switched the whole country's cars over and not have to buy any foreign fuel again.

The gas problem is political, not technological. The technology has been there for decades, but the common view is that we are waiting for some magic "breakthrough".

Sorry to rant!

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Old 07-08-2010, 04:10 PM   #7 (permalink)
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Yep, but the breakthroughs were made decades ago. Anyway, we should probably quit hijacking this thread, especially if its turning towards politics... I could go on forever about the lemming effect, sheep, whatever you want to call it.

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1978 Caprice Classic Landau
350 2-bolt, stock 4bbl
Stock rebuilt TH350
Edelbrock performer cam + intake
Dual 2 1/2" Flowmaster exhuast (waiting to be installed)
Edelbrock IAS Classic shocks
95 9C1 3.08 posi
4 wheel disc brakes!
16x8 American Racing Baja's with 225/60/16 Pirelli P4's

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Old 07-10-2010, 09:59 AM   #8 (permalink)
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Originally Posted by kingnutin View Post
Yep, but the breakthroughs were made decades ago. Anyway, we should probably quit hijacking this thread, especially if its turning towards politics... I could go on forever about the lemming effect, sheep, whatever you want to call it.

Sheeple! Na, I'd go back and check any grounds you may have left off the engine block or maybe by coincidence the ESC (Spark module) went bad? Make sure terminals are clean on all electrical connectors and that none are pinched or that the terminal pins in the connector them selves haven't been pushed out the back and aren't getting contact (this can some times happen with corroded or broken connectors or even from back probing the connector with a test light). Also a thing to remember is this, most of those circuits can't be checked with a test light - they're duty cycled not just a 12v supply, most are 0.5v reference signals and should only be tested with a multi meter. Doing so with a test light could actually damage an electrical component. So, tread lightly.

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