LEAN A/F Ratio

**Thorazine Shuffle** · 11-04-2006, 03:44 PM

Well I just got my car off the dynojet. The problem is, we had to abort my first run due to the fact that my A/F was at about 14.5... TOOOOO LEAN!!! The guy tuning my car got it down to a 12.6 which is great, but he had to drop the computer to a 10 to get that. Everyone agreed that the top end of the engine is carboned up, and this is what's causing the problem.

Does this sound right, or does anyone else have any ideas???

I'm going to take it back, and have the top end cleaned, and put it back on the dyno next week. I was just hoping for any other ideas if this doesn't work...

Please help...

By the way the car is bone stock.

**Thorazine Shuffle** · 11-05-2006, 10:15 AM

Anyone???

**Jims455** · 11-05-2006, 10:30 AM

could be the o2 is giving the ECM the wrong info

**Thorazine Shuffle** · 11-05-2006, 10:41 AM

I wish. We had a sniffer in the tailpipes linked to the dyno...

**shady milkman** · 11-05-2006, 11:00 AM

have you cleaned the maf and its sensors? possibly try a re-learn? sorry man thats all i got.

**96slow6** · 11-05-2006, 12:52 PM

what exhaust do you have? is it leaking? is the intake manifold leaking? major vacuum leak? those are my thoughts.

**Jims455** · 11-05-2006, 01:03 PM

Originally Posted by Thorazine Shuffle

I wish. We had a sniffer in the tailpipes linked to the dyno...

could'nt the ECM still be reading bogus input from the O2(like an overly rich cond) thus causing the ECM to lean the mix out. What about the MAF does it not tell the ECM how much air is entering the intake?

**Thorazine Shuffle** · 11-06-2006, 05:16 AM

Stock exhaust no leaks, no other leaks. I'm gonna swap out the O2s.

How do you go about cleaning the maf? I don't want to screw it up.

**djvaly** · 11-06-2006, 11:43 AM

I'm running lean too.. it makes better power but it ain't too good for the engine,,
@ the dyno, the guy had to do 10 mins in between runs.
he said he has to do a pro tune LS1edit to adjust the oxygen vs. fuel ratio etc.. I think that's all there is to it, unless you have a similar but different issue?

**Jims455** · 11-06-2006, 05:30 PM

you want to make sure the screen is clean and the wires are not broken or dirty. Spray some WD 40 on them and wipe them off they are fragile so be careful with them.

**Too Fast** · 11-18-2006, 09:03 AM

Originally Posted by Jims455

you want to make sure the screen is clean and the wires are not broken or dirty. Spray some WD 40 on them and wipe them off they are fragile so be careful with them.

WD-40 on the MAF? That will leave a film on the wire, eh?

**0rion** · 11-18-2006, 09:59 AM

Go to autozone and get MAF cleaner or radio shack carries a residue free electronics cleaner.
I would also put a bung in the exhaust closer to the engine and see what it says up there.
What mods do you have and did you guys calculate your duty cycle and check fuel pressure and things like that? How old is your fuel filter? Is it lean across the RPM band or just up top?
As far as cleaning the top end you can get Sea Foam and most parts stores and do it yourself.

**Thorazine Shuffle** · 11-18-2006, 10:21 AM

No mods. The a/f was about 14.5 acoss the board, which is cool at idle and even light throttle (from what I understand), but at wot....not good.

I haven't had time to work on it yet due to work, so I haven't been driving it.

I'll post up the dyno sheets later so everyone can see what I'm talking about.

**djvaly** · 11-18-2006, 10:41 AM

cool..

**01Z28M6** · 11-19-2006, 05:57 AM

Originally Posted by Thorazine Shuffle

No mods. The a/f was about 14.5 acoss the board, which is cool at idle and even light throttle (from what I understand), but at wot....not good.

I haven't had time to work on it yet due to work, so I haven't been driving it.

I'll post up the dyno sheets later so everyone can see what I'm talking about.

Hi. I would think the speed shop people know what they are doing but you realize a carbon build up wouldn't cause a lean a/f ratio; it would cause detonation and timing would be pulled automatically. Did they say if the full 15 degrees or spark retard was showing?

I've read that a tail pipe wideband reading is about .1 off but there are a lot of variables with that. I can say that my car was right around 14:1 on the dyno and they didn't abort any of the 3 pulls. The techs did say that there was probably more power available if I could rich-en up. I'm wondering what exactly was going on that they shut yours down and with mine nearly the same kept on going. I have a scanmaster display and I have never seen one instance of spark retard at open throttle. It makes me wonder if the dyno shop's wideband was correct. Please tell us how you make out.

**djvaly** · 11-19-2006, 09:27 AM

Originally Posted by 01Z28M6

Hi. I would think the speed shop people know what they are doing but you realize a carbon build up wouldn't cause a lean a/f ratio; it would cause detonation and timing would be pulled automatically. Did they say if the full 15 degrees or spark retard was showing?

I've read that a tail pipe wideband reading is about .1 off but there are a lot of variables with that. I can say that my car was right around 14:1 on the dyno and they didn't abort any of the 3 pulls. The techs did say that there was probably more power available if I could rich-en up. I'm wondering what exactly was going on that they shut yours down and with mine nearly the same kept on going. I have a scanmaster display and I have never seen one instance of spark retard at open throttle. It makes me wonder if the dyno shop's wideband was correct. Please tell us how you make out.

I'm confused, please clarify..if u run rich is better for the engine but u get less power, if u run lean is not good for the engine but get a few more hp?
is that correct?

**01Z28M6** · 11-19-2006, 09:52 AM

Hi, yeah lean to the point just before pre-ignition is more power but it is living on the edge at open throttle. A/F at 13 to 1 or a little lower is safer. If my engine was running as lean as the meter was showing, I should be getting some spark knock, at least at times. If they stopped your pull early the techs must have seen seen some detonation or were just being very careful not to toast your motor on their dyno.

I was just a little surprised to see they stopped at 14.5 unless it was on a trail to get learner yet.

**Thorazine Shuffle** · 11-19-2006, 01:33 PM

Yes it was activating the knock sensor at abot 5100 rpm. The ecm was also backing out the timing. Here are the pics of my pulls. The Blue is my first run, as you can see a couple of times the a/f got close to fifteen. What bothered everyone is, the a/f never changed. The second two runs, he had to drop his HP tuner to 10/1 to get the 12.5/1 ratio you see on the graph.

Today I cleaned the maf, and sea foamed my top end. Before you could hear detonation after 5500. Now I hear nothing and the car seems to pull harder. I'm going to take it to the dyno this friday to see if this fixed my problem.

**Thorazine Shuffle** · 11-19-2006, 01:40 PM

Oops the graphs....

**djvaly** · 11-19-2006, 06:01 PM

Originally Posted by Thorazine Shuffle

Yes it was activating the knock sensor at abot 5100 rpm. The ecm was also backing out the timing. Here are the pics of my pulls. The Blue is my first run, as you can see a couple of times the a/f got close to fifteen. What bothered everyone is, the a/f never changed. The second two runs, he had to drop his HP tuner to 10/1 to get the 12.5/1 ratio you see on the graph.

Today I cleaned the maf, and sea foamed my top end. Before you could hear detonation after 5500. Now I hear nothing and the car seems to pull harder. I'm going to take it to the dyno this friday to see if this fixed my problem.

let me guess,,ur car is stock, running 290rwhp.