poor running 84

[MoeJr]

John the computer is on the passenger side of the dash. You should see it as soon as you look up under the dash. Not bad to get to at all. If you cannot get anyone to help you down there you can ship it up or trailer it up here and I'll have my crossfire guru get that puppy running. He did mine almost 5 years ago and have not had any trouble with it.

Moe

first let me say thanks to all the input and help, however its beyond my control now. did jumper A&B no codes, never had codes with car running
and no jumpers. tried to start this am big big backfire at rear TB
i did notice with ignition on rear IAC kept going on and off i approx
2-3 second intervales nothing from front IAC. im beginning to think
computer not hooked up or bad no BUBBA bad boy.
im really in a rural are here in va. these guys think a crossfire
is a campground term, HA,HA. i am tryin to get someone here from
a chevy dealer who i spoke to and knows these campfires i mean
crossfires, little joke there. computer on drivers side correct??
hard to get to??? THANKS ALL--------JOHN

 

[chevyagain]

thanks moe, sometimes if you stay away from it for a day, that helps
i have taken out distributors before, never had a problem. i just want it to run again for awhile so i can set the timing up again but im dead in the water now--------------john

 

[Buccaneer]

Sorry for not replying yesterday back on this, but got side track on the CFIV forum.

Bill's suggstion on the ECM may be a good point and another place to check. You should get a CEL with the key ON, not running. If not, you have ECM issues or related. Make sure the bulb is not burned out as well. You can also test that via the ALDL connection.

As far as the backfire goes, I would say that you still have either a vacuum leak somewhere as suggested or the timing is way retarded and maybe even a coil or module wigging out which may not be showing up with a CEL.

You could also have a lean condition, but I would lean towards the other options first unless you have a modified motor and running a different ECM and may have a mis-tune and leaned out the VE tables too much.

It's all about a logical process of elimination. If you have a GM service manual, use it, it has a lot of good info in there.

I would be very interested in the outcome of this issue.

 

[chevyagain]

ok guys, heres where i am, finally got it back up and running, friend came over with scanner, showed no codes, reset timing, reset TPS sensor, idles good, still one problem, under load or in drive or even just revving up
im still gettin a bad, bad, fireball backfire through rear TB, maybe
vaccum leak again, OH NO, just went through that, i thought with
plenum gasket change. ok guys bring all input, almost got it

 

[Buccaneer]

Glad to see that you are making some head way. How many miles are on the car? You may still have a vacuum leak and an ignition issue under load. Check that coil and module.

What was the TPS and timing set to before you adjusted it...just curious?

 

[chevyagain]

thanks buccaneer, heres where im at,looked over engine found rear
IAC LOOSE AS A GOOSE , now, i had replaced the one on the front
TB but not the rear. the rear was shot sheared off threads, replaced with new one now engine just cranks and cranks no fire whatsoever
dont think its getting air at rear TB is there a setup procedure

 

[Buccaneer]

the rear was shot sheared off threads, replaced with new one now engine just cranks and cranks no fire whatsoever
dont think its getting air at rear TB is there a setup procedure

OMG...there's a lot of things going on with that motor it would seem. Glad to see that you're finding problems slowly but surely. I'm concerned on your statement that the threads were sheaded off and you replaced with a new one. I would think that would mean that the TB body is trashed since it is only cast medal and the IAC is a bit tougher. Slightly confused on your statement.

No, there really isn't a setup for the IACs. There is a measurement, but as long as the pintle is pushed all the way down before installing the IAC you will fine. The IAC/ECM will reset itself after a short cruise over 40mph. Odd that the motor doesn't start now.

 

[wishuwerehere82]

You are going to have to isolate the problem closer for us to help you.

Is the ignition firing the spark plugs? A timing light will flash if the plugs are firing.

Do you have fuel spraying out the injectors? It will squirt twice when the key is turned on, and 4 times , alternating between the front and rear TB's for every full rotation of the crank when cranking the engine.
If it squirts when you turn the key on, but not when you crank it, the Tach signal is missing. Check the connections at the distributor wiring harness.

 

[chevyagain]

had engine running fine, night before last, got up next morning, cranked
bacfire at rear TB, cranked again never started, as i said rear iac
was shot, loose, threads sheared off at base of iac, new iac today
cranks, no attempt to start, spray good. scanner inicated good
vaccum, no codes, timing set right when running
will recheck this pm and get back
PM, just checked no spark, new cap, coil, ignition module
when i replaced coil i used a MSD, module was aftermarket, new but not msd, could coil kill module

where do i go from here????? noticed some sort of condensor in dist????? maybe????

 

[wishuwerehere82]

I bet you have some corroded contacts on your Batt. and Tach connectors on the distributor. It very important that the 3 wire connector from your ignition module makes good contact to the coil.
Clean them up with some emory cloth or fine sandpaper.
And pop the cover off your coil, and makes sure the spade lugs on the coil wires aren't pushing up into the distributor when you plug the connectors in. Also check to see if the spade connectors are crimped solid to the primary wires to the coil.

Also check the contacts on the two modules in the distributor for dirty or loose contacts. Or loose ground screws. The ignition advance module should have thermal grease on the back of the heat sink to the distributor.

About the condensor: make sure that it it grounded to the distributor body It should have a star washer under the screw head for good electrical contact.
You have some sort of an intermittant contact that is working one day and not the next. We could be here for a while.:W

 

[Buccaneer]

One more thing to tag onto the ignition is that it's a good idea or rule of thumb if you will to use the same manufacture of the coil and module and replace them as a set.

It would seem that you "may" have multiple issues going on and some are intermittant. Like "wishuwerehere82" has said...we could be here a while on this one. Keep plugging away and eventually you'll get it right.

 

[chevyagain]

if you guys ever saw the movie CHRISTINE this is her sister
maybe all this backfiring in the past was an ignition problem
to begin with, sure is spooky. just wondering if anybody has gone through what i have, from the beginning of my posts

 

[John Robinson]

I would like to tell you a story. In 1956 I had a 55 Olds. I took it to a garage for a tune up. I had the wires, plugs, cap, rotor, and coil replaced. Picked up car for a trip from Detroit to Parkersburg, WV. It would not run over 55 MPH all the way to Parkersburg. Took the car to another garage and we checked every thing again and again with a sun machine. Could not find anything wrong everything tested just fine. Finally out of desperation I opened the trunk and handed the mechanic the box of old parts that were taken off in Detroit. We replaced the new coil with the old and all the problems were solved. My point is just because it's a new part it may not be a good part.

I am wondering if someone might have adjusted the valves and over tightened one causing the backfire when the engine does run. As for the starting and not starting I agree you probably have a bad connection somewhere. Loose battery cables will cause a start no start condition.

 

[wishuwerehere82]

I am wondering if someone might have adjusted the valves and over tightened one causing the backfire when the engine does run. As for the starting and not starting I agree you probably have a bad connection somewhere. Loose battery cables will cause a start no start condition.

That's what I'm thinking too. At idle, the lifters aren't pumped up much, but as the RPM increases the lifters get pressurised and BANG! Then the knock sensor retards the timing, and shuts it down.

 

[gmjunkie]

I am wondering if someone might have adjusted the valves and over tightened one causing the backfire when the engine does run. As for the starting and not starting I agree you probably have a bad connection somewhere. Loose battery cables will cause a start no start condition.

Yes or maybe the valve seats are receding,I've seen this before and lately!!! I was told it was older type seats that aren't as hard as newer ones,But My BB just did it again!!!But they at least lasted 60,000 miles this time!!

 

[chevyagain]

seems this gets more involved than i want it to be, valves and all
someone got into this car and has it messed up. found fuel pump relay
off firewall wires look bad might have been laying on or near exhaust
manifold, can salvage, but if anyone knows where i can get the
harness end or plug with pigtails to plug into relay let me know
again thanks for the input, looks like we have a bestseller book here
DEAD IN VIRGINIA-----------JOHN
oh by the way gmjunkie scanner looked good really no issues real good vaccum
and coolant sensor ok, uncanny. im still thinkin about the msd coil
and aftermarket module, see i bought the module first when it wouldnt
run right then i hit it with the coil, might try old module PM

 

[chevyagain]

put back old ignition module, started right up, little shakey, but started
what does this tell us, replace with matching MSD module???????

 

[wishuwerehere82]

You might try the old module and old coil combo if you think the MSD coil is blowing the ignition module. Or you may have found the intermittant connection by replacing the new module with the old. Hard to tell without swapping the modules back to see if the new one still works or not.

Still blowing fireballs?

Don't be afraid to adjust the valve backlash. it's very easy to do and may cure the backfire problem.
I prefer the dynamic method. First remove one valve cover. Hook up a vaccuum gauge to the port on the front TB that is hooked to the EGR valve so that you can monitor the manifold vaccuum.
When the engine is idling, loosen one rocker arm nut one at a time until the rocker arm starts to clatter. Then slowly tighten the rocker arm nut until the vaccuum gauge reads the highest reading. Usually about 1/2 to 3/4 turn from the clatter point. If it goes up and then drops, you went too far. So loosen it and start again.
Then proceed down the head to the next one, and so on, until you have all of them adjusted for that side of the engine. Then put the valve cover back on and do the other side.
You will be surprised at how much the vaccuum increases by doing it this way as opposed to preloading the lifters by spinning the push rods and tightening 1/2 turn after they get tight.

I increased my manifold vaccuum from 18" to over 21" by using this method. What it does is maximize the valve lift to it's optimal running height and eliminates any variation in preload from lifter to lifter.

 

[chevyagain]

no fire balls, old coil tossed, will just get new msd module, i think im close
now, who knows, might not start tomorrow, never know what
christines sister has in store all i need is for the radio to go on by itself

 

[wishuwerehere82]

If you hear this, drop the keys and run!!!:L
http://www.youtube.com/watch?v=LYjPoCEAafM