I failed emissions and I've heard doing both of these can help. To raise the idle, its some screw on the front of the TB, correct? Anything else need to be done in conjunction to that?

I did a search for how to retard the timing but couldn't really find accurate steps, all I know is its from the distributor. Any help would be appreciated

Also which one should I do first, or does it not matter?


Modified by es_squared at 1:03 AM 11/9/2008

 

why RAISE the idle.. i know in MD u want as littel "dirty" air going into the sniffer as u can.. raisein the idle would just put out more HydroCarbons and carbon monoxide?

 

To change the timing, loosen the three bolts on the distributor (10mm, I think). Rotate the distributor (top to the rear) to retard timing... However, with the knock sensor, normally, timing isn't an issue and the ECU will adjust the timing over time.

Second, idle - on the metal part of the air intake, right above where the plastic duct from the filter attaches, there is a screw that is facing the passenger side and is in-set into the casting. It is at the top and slighly to the rear. Loosen the screw (counter clockwise) to raise RPM.

How many miles does the car have? If you are over about 100K, I would recommend a new O2 sensor. This is often overlooked, but if you are getting less than 20mpg, and the car otherwise runs well, then this is the likely culprit. Your emmissions will be high if the both cases of either too rich or too lean fuel mixture and the output from this sensor directly affects this.

The sensor looks a bit like a spark plug on the exhaust pipe. In some it is fairly close to the engine, but on many (SI) it is under the engine just a foot or so before the catalytic converter. On newer models, there will be one after the CAT, but it is only there to make sure the cat is working. The first one does the real work. You can get an OEM for about $100 from Autozone, or a universal for about $35-$45. I have read elsewhere that the NGK brand is preferred as some see problems with Bosch (Although I find this a bit odd since Bosch is the MAN and invented much of the entire fuel system and emission controls).

I just recently bought an OEM for my '93 Lude on Ebay for $40 including shipping, although it was a Bosch, and it seems to be working well, but I've only had it for a couple weeks.

Last thing - after replacing the sensor, you need to reset the ECU to speed up it's "re-training". Just disconnect the battery for 15-30 seconds. You will need about 100 miles to get a good retraining. The ECU watches motor load, MAP pressure, RPM and O2 output and adjusts the mixture as you drive. Overtime, the mixture table gets adjusted to give you an ideal mixture over the operating range of the engine. (It's actually a pretty slick process).

 

The idle is controlled by the IACV and is set via the ecu. That idle screw only affects the IACV duty. In other words, if you adjust that screw any changes will be compensated for by the IACV and you idle will stay the same. Unless you program the ECU otherwise.

 

My cars too low so they only do an idle test on it, and raising the idle should show cleaner readings I believe.

duanes thanks a lot for the steps. the o2 sensor and basically everythings been replaced due to a rebuilt motor recently. Its also got 9:1 comp pistons but I wanted to ask whats the max I could retard timing safely? And how do I tell? Are there markings on the distributor ? Also I do these steps while the car is off correct?

 

motor is tuned? with low comp pistons you should have it tuned

 

I am not an expert, but I am pretty sure that the ECU on a '93 is not so smart and it is a much more 'manual' process.

I noticed that if the belt is off of the a/c compressor, when you turn on the air, the idle rises dramatically. The same thing happens if you are playing with the electric switch in the console at the bottom of the gear shifter (automatic). If you change the switch so that the dash thinks you are in gear, there is a rise in RPM.

I haven't replaced it yet (although I cleaned it), my Lude does not raise the idle enough whenever the first "load" is applied, such as putting it in gear. I watched the signal and the PWM is changing, but the idle does not respond. I think that inside the IAC, there are two springs and an electromagnet. The smaller spring has weakened some and is not opening the IAC at the bottom of the operating range. The "balance" of these two springs will stabilize and give a curve to the amount the IAC opens for a given signal change. If they don't have the right relationship, you will get either not enough rise or too much rise. I have not found any other way to influence the amount. If it was under CPU control, then the ECU would not need Electrical load sensors, gear sensors, etc - it would just regulate the RPM and be done with it.

 

its not tuned yet, im waiting on a reply back from my tuner. I only failed by about 30 points for HC which is why im trying to see what tweaks i could make to pass it. I just need to now how much I can retard the timing temporarily? And if the distributor has marks on it to tell how much im retarding by.

 

I've played with the distributor position a little bit on my '94. As far as I could tell, you can retard timing by rotating the distributor toward the front of the vehicle as far as it will let you before the engine starts to sputter, then turn it back away from that point enough to stop sputtering. IMO, that would be your sweet spot if you wanted least ignition timing set.

 

You are right on the timing - I looked at mine again - top to the front to retard.

FYI: There is a square hole (port) about 1/2" by 2" on the block, 10" below the distrib on the front of the engine. If you pull the plug out and attach a timing light on the first cylinder (driver-side piston), and shine it in the hole, you will see a mark on the flywheel and a pin and notch (like pistol sites) on the block. During a normal idle of ~750-850 rpm - you just adjust until the sites line up with the mark. It seems like there was something else that had to be done (put a jumper somewhere or have the emergency brake pulled - can't remember-, but I think that this is pretty close.

Timing lights are not too expensive, or you can rent one locally (I think autozone rents stuff like that as well)

 

fantastic, i appreciate the replies guys. One last question.. when adjusting the timing from the distributor.. this is done while the car is off correct?

 

I actually make the adjustment with the engine running.

First disconnect the IACV plug; this is a gray plug directly behind the engine between the intake manifold and the fuel rail. The engine should come to a low idle. Now when you turn the distributor fore or aft you should hear/feel the idle of the engine adjust with the ignition timing.

After you set the distributor where you want it. Plug the gray connector back in. The check engine light should have illuminated. Turn the car off and back on again and the code should clear and you're done.

 

On a side note. I failed emissions a week and a half ago here in Texas. Here were my numbers:

25 mph
2679 rpm
Standard > Current
HC 132 > 126 PASS
CO 0.73 > 0.41 PASS
CO2 > 14.8 NOT TESTED
O2 > 0.3 NOT TESTED
NOx 945 > 615 PASS

15 mph
1870 rpm
Standard > Current
HC 136 > 192 FAIL
CO 0.76 > 0.61 PASS
CO2 > 14.4 NOT TESTED
O2 > 0.6 NOT TESTED
NOx 1045 > 1681 FAIL

I replaced plug wires and plugs, NGK wires and NGK Iridium IX plugs, and retarded my timing slightly.

I had advanced my ignition timing a while back and I felt like I gained a lot of low end power by doing so, it just really feels like it pulls better with advanced timing; but apparently it also makes the cylinders run hotter and with higher compression which promotes the formation of NOx.

Here's my retest from today:

25 mph
2103 rpm
Standard > Current
HC 132 > 33 PASS
CO 0.73 > 0.07 PASS
CO2 > 15.2 NOT TESTED
O2 > 0.0 NOT TESTED
NOx 945 > 63 PASS

15 mph
1894 rpm
Standard > Current
HC 136 > 41 PASS
CO 0.76 > 0.15 PASS
CO2 > 15.1 NOT TESTED
O2 > 0.0 NOT TESTED
NOx 1045 > 94 PASS

Pretty crazy what a difference timing seemed to make. At least now I don't have to drop any extra money on a new cat or an O2 sensor


Modified by K-Litt at 2:30 PM 11/11/2008


Modified by K-Litt at 2:32 PM 11/11/2008

 

nj is prob just like mds system. if u only failed hc by 30.. u should of just got back in line and tested it again. and insted of holding at 2500, cheat and hold 2100 u prob would of passed. those machines are soooooo sensitive. u prob go just go back and pass

 

Per the earlier question - timing is adjusted with the car idling in park, with the parking brake pulled. (I think the brake causes a "test" mode or something). The timing light is a strobe light that attaches two wires to the battery ( pos and neg) and then one wire that goes in line with the spark plug wire on cylinder number one. This causes a brief flash when the plug fires. You shine the light into the rubber covered timing hole on the block and it "appears" that the flywheel is standing still or relatively still. You just line up the marks and the computer takes care of the rest.

Most computer controlled cars also have a knock sensor that the computer adjusts timing to the fuel that you use and so timing is normally automatic. However, you will get the best performance and mileage if you consistently run one type and grade of fuel. All of the fuel and spark adjustments happen over time, and fuel makes a considerable difference.

Still don't know what year or mileage your car is, but if you are over 100K miles and get less than 75-80% of the new car mileage, but the car runs decently and doesn't use a lot of oil- it is VERY likely that you need a new O2 sensor. It is the key to the entire fuel system.

 

thanks all!

 

My results the last time were
HC minimum 109 - 142 my car
CO minimum 0.84 - 0.52 my car

if i retard the timing, will it raise the CO or no?

 

I don't have enough experience to say if you will see any changes on the timing.

As I recall - as engine temp increases (lean), so does NOx, however, if mixture is either too rich or too lean, then the cat cannot do its job and you will see high NOx and high HC. HC is unburned fuel and CO is a product of not enough air. The presence of CO would seem to indicate that your engine is running too rich.

Another cause of high HC is an oil leak (like pushrod guides or rings).

All you can do it try the timing. I would still be suspicious of the O2 sensor. But, if the car has been running too rich for too long, the Cat could be shot as well.

 

thanks man. I just replaced both the cat and o2 sensors a week ago