motor running lean at idle?

560 Views 14 Replies 4 Participants Last post by T-BONE-92, Aug 27, 2009

T-BONE-92

Discussion Starter · Aug 24, 2009

89 fox. car runs lean at idle. pulled plugs and they are very white. veh has a autometer afr gauge. sometimes it doesnt read at idle, other times it sweeps from lean to stoich on the gauge. under medium to heavy throttle. the gauge is right on the line between stoich and rich. reciently bought the car, and dont know alot about efi. gt40 tubular intake, b cam, shory equal length headers, cai. stock injectors and fuel press. reg. offroad exhaust. aod with nonlock up converter. and 4.10s. i dont know what the fuel press. is, dont have a gauge on it. idle is good now, thanks to another board member. just lean. thomas

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turbostang

· #2 · Aug 24, 2009

First - toss that guage. It does NOTHING and is no where near accurate.

Next, a "stockish" EFI car ,99% of the time, will have white plugs - that's what they are tuned to do.

With that cam, I can promise you this - it's anything but "lean" at idle. Put it on a dyno and TUNE it. Be prepared for shitty numbers with the AOD. I'd bet 220RWHP.

Mustangman_2000

· #3 · Aug 24, 2009

narrowband a/f gauges are worthless. you don't know what your a/f ratio is at idle because it oscillates back and forth constantly going rich to lean. your spark plugs are white because cylinder head temps are too high. could be low fuel pressure or too much advance. could be a cooling issue.

you need a wideband to monitor your a/f ratios accurately. and why don't you start by turning up the fuel pressure a bit and check your timing. and maybe clean the maf with some crc maf sensor cleaner.

turbostang

· #4 · Aug 24, 2009 (Edited)

Mustangman_2000 said:
narrowband a/f gauges are worthless. you don't know what your a/f ratio is at idle because it oscillates back and forth constantly going rich to lean. your spark plugs are white because cylinder head temps are too high. could be low fuel pressure or too much advance. could be a cooling issue.
you need a wideband to monitor your a/f ratios accurately. and why don't you start by turning up the fuel pressure a bit and check your timing. and maybe clean the maf with some crc maf sensor cleaner.

Man, you are going to have this guy pulling his motor out telling him this stuff!

The sparkplugs are most likely white because THEY are too hot, as in - a hot plug range, or a wide gap or both!

If the car runs good, I'd skip all the b.s. and go straight to the dyno to check it out.

If it idles good, leave the MAF alone.

If the car has good power at WOT, the fuel pressure is probably a non-issue.

Get it on the dyno and make a few pulls with a wideband attached, it will tell you all you need to know without putting any parts on it. Have an allen wrench, 1/2" wobble socket, and a timing light handy to make a couple of quick adjustments...

Mustangman_2000

· #5 · Aug 24, 2009

You have some good points, but I mentioned a cooling issue because I've had frosted white spark plugs directly related to overheating.

I tossed out possible causes as this is the internet and all you can do is try to get someone in the right ballpark. Without seeing the spark plugs or car in person you can't make a definitive diagnosis.

He's new to the EFI game, so he's gonna learn quickly that the first thing you do is throw that narrowband a/f gauge in the trash for starters.

OP- Good luck on fixing your problem.

T-BONE-92

Discussion Starter · #6 · Aug 24, 2009

it has stock autolites in it. and ive set the timing to 12, with the spout unpluged.also car runs 160 170 temp. ive been putting the the dyno off, dont have the cash right now. i will get it on there hopefully this month. do i need to get a chip done with mods done to car?

T-BONE-92

Discussion Starter · #7 · Aug 24, 2009

turbostang. you think i should try a colder heat range plug for now. till i get it on the dyno. if so just one or 2 heat ranges colder? thanks.

turbostang

· #8 · Aug 24, 2009

I honestly dont think you even need a dyno tune, there's not enough done to that car to necessitate it - Fox's have gone a LONG time without tuning aids anyways.

You can adjust the fuel pressure up some, but you really need a guage first.

If it's detonating, I'd gap the plugs lower than what they are or put colder plugs in it. The first choice bieng gapping the plugs down some.

T-BONE-92

Discussion Starter · #9 · Aug 24, 2009

here is what the plug looks like, not actual but just like it.

http://www.tirinda.sk/adrian/quad/sparkplug/wwwP1080428.jpg

im going to try and get it on the dyno this weekend. and i dont hear any detonation. thanks for all your help. thomas

T-BONE-92

Discussion Starter · #10 · Aug 27, 2009

put 1 heat range colder plugs in it yesterday. still havent had it on the dyno yet. but plugs have alittle color to them now. and the car is running still strong. also fuel pressure is 41 with vaccum unpluged. thanks again guys.. will get a narrow band on it soon. thomas

turbostang

· #11 · Aug 27, 2009

T-BONE-92 said:
put 1 heat range colder plugs in it yesterday. still havent had it on the dyno yet. but plugs have alittle color to them now. and the car is running still strong. also fuel pressure is 41 with vaccum unpluged. thanks again guys.. will get a narrow band on it soon. thomas

Fuel pressure is pretty good, it just depends on what it likes on the dyno. Don't fall into the trap of lean is mean on the dyno, and remember that when yuo take the car off of the dyno it gets MORE lean. So, if it loses some power because you have it "richer" than you normally would, that's fine. On the road it will pick it right back up.

Oh, and you are supposed to be ditching the narrow band, which is what you already have. You need to be putting a wideband ON it.

T-BONE-92

Discussion Starter · #12 · Aug 27, 2009

think its still sittin in my trash can. took it out after yall told me to get rid of it. thanks again. thomas

dustin

· #13 · Aug 27, 2009

I'm not sure that you're understanding the difference between the guages. On your narrowband you have a bar that lights from green to red and just goes back and forth. On a wideband, you have a digital readout that displays your air/fuel ratio.

turbostang

· #14 · Aug 27, 2009

dustin said:
I'm not sure that you're understanding the difference between the guages. On your narrowband you have a bar that lights from green to red and just goes back and forth. On a wideband, you have a digital readout that displays your air/fuel ratio.

Exactly. A narrowband 02 simply reads on and off.

A wideband reads a range from, say, 0-5V. 0V bieng dead rich, and 5V bieng dead lean.

T-BONE-92

Discussion Starter · #15 · Aug 27, 2009

yea, i meant wide band. my bad. was late when i typed narrow band.lol. thanks again for the help.

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