Setting timing and reducing backfires? (Two issues)

I've made a few posts lately about fueling problems and stand alone computers. I have two more issues/problems YAY!

1. How do I set/verify the ignition timing? I have the CAS but everything I read on stealth 316 doesn't really help. Will it be in my service manual? (I don't have access to my service manuals at work). It idles cold at about 2000RPM. I hoping that if the timing is off I can fix some RPM issues.

2. The car is backfiring. Alot. REALLY loud. My O2 sensor is reading about 1.04 Lambda. If I richen up the tune a wee bit would it help the backfires? It is sitting with only the downpipe on but I don't think that would cause any backpressure problems because the tiny td04 turbos should supply enough backpressure. Also could the timing be causing backfires too?

I don't mind letting it warm up with a high idle but the backfires are stupid loud and Im afraid harming the engine. I don't think that its a vacuum leak causing the high idle because I fixed all those I could find and it brought the idle down from ~2700RPM.

This website has been a big help in getting this car running and I'm hoping you guys can pull through again. I'm hoping you guys teach me enough so I can be of help in the future.

You need a timing light to set the timing, but you won't be able to set your timing right until you get the car to idle the correct curb idle. I'd double check the throttle body adjustments to start.

Use a Timing Gun to set your ignition timing VIA cas... Do not set it cold. wait till the car is at running temps, and proper idle... Cold idle @ 2000 rpm sounds about right, should go to about 1100, then settle around 800 once hot.

The backfires, are they between shifts or just off throttle letting the rpms wind down?

my VR4 off throttle even at low rpm has lots of gurggles, bubbles, and pops you can hear especially when cold. The car is made to run rich-er while cold. Back firing isn't necessarily a Bad thing depending on the manner in the condition...

The stock idle specs never are supposed to go above 1500 RPM even in the coldest conditions.

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Originally Posted by Forest Gump

The stock idle specs never are supposed to go above 1500 RPM even in the coldest conditions.

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I was told the same thing.

As of backfires it backfires just Idleling at 2k. It sounds like a gunshot. If you look under the car while it does it there is a literal fireball. Thats what makes me think there there is a timing problem.

The 1.04 lambda was on a run when it wasn't really backfiring. I think if I richen it up it should help prevent the backfires (I hope). I also just read my standalone manual and I can set it in "timing adjust mode" which automatically sets all computer controlled timing to 0 so that might help me figure out if its a timing issue for the backfires.

Thats a wall of text pretty much saying the samething over and over I think.

I'll try to get the video posted to youtube but tis on my friends phone so we'll see how that goes.

Back fires with flames out the exhaust = unburned fuel igniting in the exhaust. If the 2000 rpms is constant. Not just start up then your probably have a big vacuum leak or its your tune. Did u try the basics first. Check for leaks. And adjust your biss.

I've checked for leaks. I guess there could be a couple left. I wasn't going to adjust the BIS until it was warm to get it to the right idle. When I had a big vacuum leak it idled at 2700. I'll check the ignition timing and then give everyone an update.

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Originally Posted by Bleu

I've checked for leaks. I guess there could be a couple left. I wasn't going to adjust the BIS until it was warm to get it to the right idle. When I had a big vacuum leak it idled at 2700. I'll check the ignition timing and then give everyone an update.

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You are pressure testing to check for leaks, correct?

I have a little shitty PVC thing for boost leaks, but that shouldn't be necessary for looking for vacuum leaks. The only leaks I need to find are post throttle body right now. This is a MAFless setup encase I never mentioned it

adjust the BISS 1-1.5 turn out from full in, should at least get you able to adjust it. use a timing light to see where ignition timing is set right now, I bet the CAS is wayyy off. Get it somewhere close to TDC and the backfiring will stop if it isn't mechanical timing issue. That should settle things down enough to run through the actual adjustment procedure. Don't trust wideband on open downpipe depending on where its at.....there are reversion waves that come back up the pipe, so I'd be weary of readings of a wideband less than a couple feet from the end of a pipe at low load.

When you say get the CAS to TDC you mean just loosen the nut and rotate it counterclockwise until it stops? I hate asking stupid questions like this. :Doh:

EDIT: Another thought: Won't retarding the timing too much also have the ability to cause backfires? Or is that more of a carb thing?

Yes...too far retard will cause after firing. You hook timing light up and shoot the crank pulley, adjust either way until the marker is roughly tdc or a little before. The goal isn't to set the timing but to make the engine stable enough to go through the factory procedure. Do not adjust gas all the way to the stop.....if you reach a stop before you can gain control of the timing.....your mechanical timing is off and you need to check your cam and crank gears.

Roger. That's what I figured you meant but just had to be sure since there is still so much I don't know about these engines.

Retarded the CAS a wee bit and it really helped the backfires. Might retard it a tiny bit more and then hook up some more exhaust and we'll have to go from there.

Also, does anyone know where to go if the MAF harness connector isn't getting juice? Kind of related since my IAT sensor only reads 220º

Retarded the timing more and the backfires are almost nonexistant. Does anyone have a picture of the stock timing map to compare my computer to?