Ok. I'm getting very frustrated. I can get my car to start, and even run to the point where my timing can be adjusted; however, the entire engine shakes and runs pretty crappy and very rough, no matter how I adjust the timing. As soon as I adjust the timing to where it seems as though it runs smoothly, I hit the gas and BAM! It backfires through the exhaust. Do timing adjustments the other way POP! It backfires through the intake. I am running on all 8 cylinders finally after changing spark plug wires and leaning out the fuel mixture (I was way rich). I am getting good fuel delivery and spark to all 8 cylinders. I just cannot seem to be able to set the timing to where the car will run without it shaking so bad that it feels like it is going to fly apart! What is causing it to run so rough? Could the distributor be bad? I am thinking I am having some sort of timing issues. Yeah, Yeah, I know I need a custom chip, but surely my car would at least IDLE smoothly, right? Please help me.

 

Check your ignition coil. Your problem sounds exactly like the problem I had a few weeks ago. It's an easy and cheap fix. Go ahead ahead and replace the distributer cap and button. It should be less than $25 for all the parts

Eric

 

Did you adjust your valves? i had a similar problem when i swapped the 350 in the s10. I'd check your valves.

nate

 

I'm pretty sure the ignition coil is ok. It is an accel which I bought a couple of years ago. I will check the valves, although I've never adjusted valves. Is it difficult? How do I do it?

 

hate to step on anyone's toes but you guy's are way off, you can't adjust valve, the only you can get close to adjusting, if you wanna call it that is tighting down rocker arms, you have a electrical problem, it can be a number of things....one it could be your ESC module (Electronic Spark Control) its located on the drivers side firewall behind your fuel pump relay, also did you take anything apart or off the car, like the timing chain, did you remove the distributor, are the spark plug wires on the right terminals on the Dist. cap to match with the firing order on the cylinders ,a good haynes manual will illustrate this for you, also take all of your spark plugs out, rotate the motor to 0 degrees TDC, to find the exact point of 0 degrees place your finger on cylinder #1 spark plug hole while turning your crank (take your belt and crank pulley off ,take the crank pulley center bolt and screw it back into the crank all the way, this will be easiest to rotate the motor) the compression will pop your finger off abit, this is to make sure your on the compressing stroke of cylinder #1 when it stops your at TDC (top dead center) then take your distributor cap off look to see if the rotor piont is pointing at the #1 cylinder terminal , if it is your valvetrain and piston firing order is fine and your problem definitly lies along lines of a electrical problem if this doesnt work from what i stated contact me at Londonaftermid21@aol.com and let me know you result so i can get a better understanding of your problem, hope this helps,sorry again if i rained on anyone's parade



mike

 

Yeah, I was kinda leaning towards an electrical problem myself. I did exactly what you're talking about (finding TDC on #1) before I stabbed the distributor because I had it 180* out the 1st time. I guess that I could go back and check to make sure all the plug wires are on correctly, but I'm almost positive that they are. I was thinking that I could have a very bad ground somewhere. I've had several bad electrical problems with this swap. My ESC module is brand new. I replaced it with a 350 ESC. Hmmm... How do I check to see if my distributor is bad? BTW, cap and rotor are brand new, too. One odd thing I have noticed: when the dist. cap is off and I twist the dist. shaft slightly, my fuel pump primes. Is this normal?

 

Sounds like an electrical problem to me. Hey, don't rule out parts just because they're new. That's a rookie mistake.

 

Hey I had this exact problem Had the dist. in correctly and it just kept backfiring. I worked on this thing for weeks in the end the computer was bad..................Mine ran fine until I hit the gas and then BOOM. And the car never threw a code.


Brian

 

Backfire through the intake manifold is a timing and fuel lean condition usually. Either it's mechanical with the timing chain being way off or electrical. You said it's backfiring through the exhaust which means still WAY rich. When you run too rich you're more likely to get detonation which would make it run even worse. Try leaning out the fuel delivery a little more and adjust your base timing. Remember to disconnect the tan wire. If you can, get a friend with a laptop and build the winaldl cable for $6 in parts. That will tell you if you're having problems (knock), bad sensor that isn't giving an error code, maybe it's something simple like a spark delivery problem. Good luck and keep us updated.

 

same exact thing happened on my buds 79 t/a after we got done building that up.it turned out that he needed to buy a new distributor,as the stock one couldnt give him enough advance.so he bought a pertronix unit w/ adjustable vacuum advance and a mechanical kit already built into it,and after we got that all right,the car ran smooth as a babies rear.but its probably totally different for you since youre dealing with a computer instead of a carb.

 

Sounds to me like your distributor module (inside the distributr itself) and/or the pickup coil is busted. Therefore, you are getting no advance at all by the ECU and the spark advance you set it at initially is the advance you will have ALL THE TIME UNDER ALL conditions. that will cause the problems you are having. replace the distributor module and pickup coil, maybe 35 bucks for all the stuff from GM dealer. OEM stuff is fine. OR drop a known good distributor in to see if that's the problem.

Getting any codes???

 

It could be a defective fuel pressure regulator, especially if you're still running the stock tbi. I had alot of similar problems with my Blazer ('90 tbi 5.7L) to the point where I had to take it off the road for the winter it got so unreliable. It was extremely hard starting hot or cold and when it finally would kick over it would surge violently in open or closed loop, while missing/backfiring and stalling. It ran better with the MAP disconnected, but still crappy, and would bearly run at all with the EST in bypass. I had performed all the tests in the service manual and the regulator looked ok, but just for the hell of it i swapped it with another one and now it runs perfect. Who knows...? Well good luck

 

I've never experienced a bad dist. (thank ***) but personally it sounds more to me like it's either the cam timing is off (timing chain jumped or not installed with the timing marks correctly aligned) or the distributor is off a tooth or two (or maybe even three).

When he advances or retards the timing, it is only then when he gets the backfire thru the exhaust or intake. That would mean it's firing when an exhaust or intake vavle is open, respectfully.

Question, how much are you advancing or retarding the timing before she backfires (either way)? If you are advancing (or retarding) the timing only a small amount before it backfires, that would be a good indication that the cam or dist if off.

Mike

 

So two questions:
1) How do I know if my dist. is a tooth or 2 or 3 off?
2) How do I fix it? Do I have to actually stick a screwdriver down the dist. hole and turn the pushrod for the oil pump? Or is there another way?

 

If your timing light shows the marks on the balancer and timing tab lining up, its not "a tooth off".

If you aren't using a timing light, get one!

 

Just because the timing mark on the balancer lines up with the marks on the timing tab does not mean that the entire valve train is in time. It only means the the SPARK timing is in time with the crank shaft. However, if you are getting very poor performance and/or backfiring through the exhaust or intake, it means that the cam is not lined up (or in time) with the crank.

Did you do any mods to the timing chain (ie, replace with new or did you swap a cam). How many miles is on the timing chain?

When did this start happening? Did you do any mods to the motor? Was it running fine one day then all of a sudden it started acting up?



Later...
Mike

 

Well, the engine is a rebuilt 350 from a shop that really knows what they're doing, but I guess it is possible that they made a mistake. All the valvetrain components are brand new, so unless they just installed the cam or timing chain incorrectly, I don't see how it could be any of the valve train components. I am really leaning towards the distributor. It is the one that came stock with the RS, so it could be bad. BTW, I do use a timing light! As far as the backfires go, I don't have to adjust the timing very much either way before it starts to back fire. This just started happening. Before I changed the spark plug wires, the car ran crappy, but it wouldn't backfire like it does now after minor timing adjustments. I would guess that a rich condition combined with a bad distributor that is perhaps a tooth or two off is the most likely cause, since the engine is practically brand new (unless, of course, the machine shop really screwed up). What do you think? Oh, BTW, how do I fix the distributor if it IS a tooth off? Thanks for the help guys!

Oh yeah, I ocassionally got a code 43 under WOT before this problem

 

Given that you just changed your wires, I would say you got them crossed some where or got a bad wire. You can verify that each wire is working with you timing light.

As for your error code:
<U>https://www.thirdgen.org/newdesign/faq/thirdgen.shtml</U>
<B><font color =blue>43. Low voltage at electronic spark timing circuit</font></B>
There is an entire code chart there.

The low voltage will reak havok on your ignition system, especialy with that high output coil. Just think of voltage as a tube. The smaller the voltage or tube, the less amps can flow through it. Your coil needs more amps than a stock one. It would cause misfiring and definatly cripple your car.

 

jdrobley : Thats not what they mean by low voltage.

The low voltage is the signal from the EST module to the ECM. This signal is normally a steady voltage. When knock is detected the EST module lowers the voltage to tell the ECM. If the ECM detects a low voltage for more than 5 seconds Code 43 sets.

Code 43 also means failed knock test. The ECM spikes the timing high and listens for the engine to knock. If the EST doesn't sense any knock it triggers a code 43. The purpose of the test is to make sure the EST/Knock circuit is working.