I'd like to make a last ditch effort to fix this damned V6 before I call this guy back about his 305/700R4 to drop in my car. I ran about a quart of water through the intake to clean the carbon off the rings/seats/faces/cambers but no smoke and no gain... Just a horrible missfire for a few seconds...

Should I take the next step and buy GM Top Engine Cleaner? Or could I still have some other problem? My timing should be right, and everything checks out on the scanner... Could it be dying injectors? The scanner said injector loads were fine. Will they cause a car to struggle to accelerate at more throttle, but cruise ok, and get horrible MPG (15-16 city)...

FP is fine btw. MAF new, the snap-on scanner said o2 was fine (replaced a year ago), drivetrain geometry is correct, no excessive brake drag, tire pressure is fine, fluids are good, doesn't smoke (except wisps through PVC, but crankcase gases shouldn't be clear anyway), I pull anywhere from 16-19in/Hg at idle.

..:lala:

 

Did I miss a message? What happened? The car doesn't drive? I had a bad stumble once; turned out the cap/rotor was loaded up with a TON of carbon tracking. Another thing you could do is make sure the outer ring of the balancer hasn't slipped. If the outer ring slipped, what you think is "in perfect time" really isn't.

Engine off, remove the coil wire, remove the #1 plug wire. Put a phillip's head screwdriver in the #1 plug hole, and turn the crankshaft clockwise with a breaker bar & socket on the crank pulley. When the screwdriver stops raising up, look at the timing mark in reference to your timing indicator. Is it at 0 degrees advance? (It should be.)

If the balancer mark is nowhere near the timing indicator, then you've probably just found the TopDeadCenter of your exhaust stroke. Spin the motor clockwise again, so the screwdriver drops, and raises up again. This would be your power stroke... and see if the timing mark lines up to 0 degrees.

Another way you can determine power stroke VS exhaust stroke is to put your finger over the #1 plug hole. (I hear you can also stuff a rag into the plug hole.) When the piston is on it's power stroke, you'll feel pressure on your finger as the piston compresses the air inside the cylinder. (I hear the rag will blow out). Then you know you've got the power stroke, and could check TDC with a screwdriver.

Use the phillip's head screwdriver to keep from catching anything. You could visually inspect your balancer, too... if the rubber isolation ring is poking out from the balancer, the balancer is shot. I think I have a few messages up on "check balancer" and "balancer TDC", if you want to do a search for more info.

Oh and have you thought about a clogged catalytic convertor or exhaust leaks?

 

I think new modular is in order.
I think check fuel hoses, too.
Is the timing chain real old?
Like over 50-75K miles?
Don't give in.
Bring it to someone else, also.
NO NEED for top end cleanner.
You lack fuel, ignition or as Tom said, to much exhaust back pressure.
DON'T GIVE IN!
You'll find it.
Read my latest post (I did it my way...) about new computers & everything else, because a few wires were crossed.

 

Sorry Tom, didn't mean to be vague, you didn't miss anything.

What I ment was, "above cruising throttle, the car doesn't pull as hard as WOT should, and sounds like it is struggling."

The fuel pump is new, pressure is fine.

Ignition -module- is fine and new. "modular" is an adjective, not a noun.

The stumbling I talked about is what happened when I did the patented "water-trick" to clean the combustion chamber and other hot parts... I didn't get any vaporized carbon, just a bunch of stumbling missfire until the water burned off... (engine was hot enough to turn on fan)... I wanted plumes of smoke, and I didn't get any. It was disappointing.

I'll check the timing -again- tomorrow. This time without the light, I'll just move it around. I'll see if I can't walk off with the Snap-On scanner and take the car for a WOT run in it to look for knock counts... Either that or I'll ask to have it looked at by an OBD-1 scanner...

Is there any way to test ignition-coil output voltage? I don't want to believe my 8 month old Accel coil is crapping out, but I'll swallow it if it is...

Is there a surefire way to test the ECM to see if all parameters are functioning correctly?

How much are air/fuel ratio guages? Perhaps I'll check out my WOT air/fuel ratios with that... it would be a neat addition...

Have I missed anything else? (yes, the little stuff counts)...?

 

I just read weak high end power is also fuel pump.
You did replace the fuel sock right?

I doubt it's coil.
It would crap out and stutter, almost die.
This happened to me because I used a racing coil for a Chrysler instead of the correct SB Chevy one.
Bought it at a swap meet, made a mistake. Almost stranded me with this cute girl along the Pacific Ocean, on our first date.
Swap computers to see if yours is flaking out.
That's how I eliminated my ECM varible. Even did it in 100* heat & two wrecking yards to find the right ECM to swap in. I paid $40

 

Oh, at WOT... I thought you meant with regular throttle! Maybe you want to try a normal tb/intake cleaner (for fuel injected motors of course) to get rid of anything the water left behind. One problem with using water; you do clean off all the carbon, but you also remove carbon from the tops of the pistons. Yeah, that's usually good, but that carbon can increase the compression ratio a bit. And who knows if a big chunk of carbon broke off from the intake and is now clogging a valve? See https://www.thirdgen.org/techbb2/sho...hreadid=101558 for an interesting story by Vader...

 

WOT, which also includes anything more than crusing throttle...

Also, you'll note that there was no smoke from burning carbon. just wisps of white smoke from the tailpipes to suggest the water burnt off... no heavy clouds of carbon, nothing visible unless you ran around to the back of the car and looked...

Any water would have burnt off by now, I did a good bit of driving yesterday and today...

I think I narrowed it down to timing and or fuel though... Seeing as how it backfired out of the TB yesterday pulling out of my development... Only does it when it's cold I noticed. (note: I never really noticed it, because I cruise with the stereo up...)

 

Sluggish performance with all of that replaced? I'm going to say injectors unless the catalytic converter got plugged. My 85 got horrible gas mileage, drove okay but had no pickup. Turns out four injectors took a dump. put in a different rail with 6 injectors and mileage went way up performance out the ying-yang. Cruised to Ocean city MD from Elkton -- round trip used 1/2 a tank of gas

 

Alright, thats cool... I would say the same thing... I have another set, but... I need some time to get them in, I'm racing Saturday at E-town, and I'm working everyday between now and then... hmm... ****e! My mechanic is going to take a look at my ignition coils output voltage tomorrow, so maybe that will clear up that issue, I'll have him set the timing to 14*btdc regardless of what he says, and then we'll take it from there...

perhaps if I wake up -real- early one morning, I can have it all done before 4 o'clock..

Time to give a shout out to Rich J at cruizinperformance.com...