87 Bonneville dead

Heres the story: One morning I get up and go to work - car runs great. Get in car to go home and I notice its running on half power. Funny thing is, it runs smooth, no missing at all. Next morning same thing...go to work on what feels like half power. Runs smooth with no hesitation, sputtering or missing. After work, car cranks but no start. Fuel pump operating but pressure at fuel rail looks wimpy. Tow car home and replace fuel pump and filter. Now I have good pressure at fuel rail. So Now I'm feeling pretty good about myself..."all fixed". NOT! Still won't start. I have fuel, spark at all plugs, air, compression and every thing else I can think of. (plugs are wet which tells me my injectors are working)

Then one day while trying to start, it backfired with a loud loud POP! through the intake. Its never done that before. I dont know where to go next. Can a camshaft or crankshaft sensor cause this? Feels like a timing issue.

Really sounds like a Crankposition sensor or jumped timing. I had a very unusual problem like this because I lost the ground between H frame to engine. So a quick check that Block to h frame resistance is low (10 Ohms or less0 is free and can tell you if you still have a good engine ground.

did you ever hear a rattling noise in the engine, especially at idle? That would indicate a broken timing chain tensioner, or possibly a bad harmonic balancer.

did you ever hear a rattling noise in the engine, especially at idle? That would indicate a broken timing chain tensioner, or possibly a bad harmonic balancer.


how many miles on the car? if the car its got more than 120,000 i would suggest checking the catalytic converter clogs up just disconect th exhaust from behind the engine and cranck the engine like that if the catalytic converter its bad the engine should run

did you ever hear a rattling noise in the engine, especially at idle? That would indicate a broken timing chain tensioner, or possibly a bad harmonic balancer.
It had been making more noise than usual. Sounded like valve tappet noise though. I did pull the valve cover and checked location of piston and valves by positioning #1 piston at TDC compression stroke and both valves at their closed positions. Could not detect anything that was out of the ordinary. But I admit this test may be crude and inaccurate.

One day its working fine with full power. Next day, runs on half power but also runs smooth with no missing or sputtering. After that it doesnt start at all. Its got to be a timing thing but I'm just not sure where to go next. Thanks.

did you ever hear a rattling noise in the engine, especially at idle? That would indicate a broken timing chain tensioner, or possibly a bad harmonic balancer.
Today was such a nice warm day I decided that with the help of my sons I would push the bonneville over to the other side of the yard and get it out of the driveway for now. Just for the heck of it I turned the key to try and start it. yep, you guessed it, it started. I could not believe it. This time I listened closely and yes it does make a rattling noise at idle. Ran it around the block and it died just around the corner from where I live. Pushed it home and parked it. Won't start again. So now what? Is the timing chain hard to get to? Do I need to pull the engine? Jeff

Check the balancer on the crank first.

Check the balancer on the crank first.
When checking the balancer, what am I looking for? I am not familiar with this.

Look for the outer section of the balancer coming apart from the rubber isolator to the inner portion on the crank.

Checking the balancer is the easiest as I suggested earlier and Max just confirmed. If you grab the serp belt with your hands and you can move it back and forth real easy, the balancer is shot. You should see the outer metal ring moving independently from the rubber center section attached to the crank. Since the outer metal ring has the reluctors on it that pass through the crankshaft position sensor for timing purposes, this will throw off the timing. If the balancer checks out, try rotating the engine using the center bolt. If it can be rotated more than a couple degrees back and forth (don't turn the engine backwards once you feel resistance), the timing chain tensioner is gone and there is too much free play in the timing chain. This will cause the static timing to be off, and the noise is causing the knock sensor to signal the computer to retard timing, making the situation even worse.

Thanks maxwedge and richtazz. Hopefully I'll find some time this weekend to check it out. I'll be surprised if that is not the problem. I'll let you know what I find.
jeff

Harmonic balancer checks good. The rubber is still intact. I tried the timing chain test and yes it feels like that could be the problem. As I rotate the crank I can hear a definate "clank" (chain sound) when it comes to the end of its travel. Both directions.

How do I go about tearing into the timing chain? I can change waterpumps, starters, alternators and things like that, but this timing chain thing is going a little deeper than my experience. My son needs this car for transportation to work. The sooner I can get a response the better. I appreciate the help so far. Jeff

The biggest obstacle is getting the harmonic balancer out of the way. If you have a good repair manual, it sounds like you have the skills to do the job. It's pretty time consuming, but not beyond the DIY with decent mechanical skills and a few brain cells to rub together.

Harmonic balancer...piece of cake! Took my half inch impact with 1 1/8 socket....bolt came out easy. Grabbed the balancer with my bear hands and pulled it right off without breaking a sweat. The only thing that was time consuming was waiting for the air compressor to build pressure.

All this talk about how to remove the harmonic balancer...kinda funny. Oh well,I guess some people have it and some people don't. Of coarse, now the real work begins.