performance result from wrong injectors

[bitsoknittles]

Hey all, I have an 88 NA w/163 xxx mi, I put in a rebuilt motor and found out (through Az emission testing) that the car is way over the allowable limits for emission output. in checking for possible causes, I found that the injectors only have 3.3 ohms and the book calls for 13.8 (approx). Do I have the correct injectors and is this the main reason I am burning through fuel and failed emissions (too rich)?

[cre]

Originally Posted by bitsoknittles

Hey all, I have an 88 NA w/163 xxx mi, I put in a rebuilt motor and found out (through Az emission testing) that the car is way over the allowable limits for emission output. in checking for possible causes, I found that the injectors only have 3.3 ohms and the book calls for 13.8 (approx). Do I have the correct injectors and is this the main reason I am burning through fuel and failed emissions (too rich)?

Not likely to be your problem. Later years of the MKIII had high impedance injectors. The 89+ injectors have a green top whereas the pre89 have a yellow top. The pre89 have a resistor pack (ribbed aluminum block) sitting on top of the left (driver's side) wheel well.

Have you checked for diagnostic codes? If you don't know how it's covered in the MKIII FAQ section.

Specifically what was high in the emissions test? (HC, NOx, CO) Post all of the readings.

[bitsoknittles]

all three were high; HC at 3.75 (allowable 1.60), CO 62.82 (allowable 15.00), and NOX 4.50 (allowable 2.50). I have a set of 13.8 ohms injectors; would it help to put them in the 88? I am thinking that the low impedence injectors are putting too much fuel into the motor causing it to run rich, thus increasing the idle speed (at 1k rpms, not 800) and the higher emission readings. If it is not the injectors, what should I be checking to get the idle correct and the vehicle to pass? I will be checking the EGR valve for cleaning/operation later today. Thank you again for your help! There was one diagnostic code for the knock sensor, but the knock sensor only turned on when the car was started and put under load (driving normally) initially. I turn off the car and restart it, the code does not show until another load, idling does not show the code.

[cre]

Putting high impedence injectors in a system built for lean injectors with a resistor pack in place is only guaranteed to run lean and burn valves or melt a pitson. If you remove the resistor pack and install high impedance injectors then you're in the same place as before and it's a moot point. Excessive fuel isn't going to increase NOx... NOx is a post combustion heat problem and running super rich generally pulls down exhaust temps in a big way. I'd start with checking both the mechanical and ignition timing, make sure the cat isn't clogged from debris, inspect plug wires, test the injector resistor pack.

With an '88 you need to refer to the TSRM for '86.5, '87 and '88. There were a lot of changes to the electrical system starting toward the end of the '88 model year. You can find scanned versions at the link below (I think you need the EFI PDF):

http://www.turboninjas.com/mk3supra/


EDIT: I just saw the mention of the knock censor code... That'll screw ya. It causes the ECU to literally dump in a ton more fuel and reduce ignition timing heavily. It's an absolute way to fail emissions although the high NOx still seems off. Fix the code 52, if that triggers at any point when they're testing it your stats are going to soar and even if it only happens for a moment you've already failed.. They don't average your emissions results, you have to pass for the whole duration of the test.

[bitsoknittles]

checked the resistor pack and its ok. Found and cleaned one VSV for the egr and set the throttle position sensor as it says in the book, but the car is still idling high (900 rpms). If the throttle body or plate were to be stuck open due to carbon (haven't cleaned it yet) could that be the reason I can't get the car to idle at 750 to 800 rpms and have vacuum at the R and P ports on the throttle body (when there should be no vacuum unless at other than idle)? By cleaning them, should I be able to get the car to idle properly? Also, how do I fix the code 52 for the knock sensor? replace the wire; replace the knock sensor, etc?Thanks for the info!

[cre]

You need to fix the code 52 BEFORE anything else. It changes the way the ECU handle a lot of things in a MAJOR way. Look in the MKIII FAQ section for a thread about code 52 and knock sensor rewire. Often the wiring just needs to be replace with better wiring and a new connector is recommended. The knock sensors are very pricey so try the rewire first.

Make sure the TPS is for the right year. There was a change mid '89 and the interface tabs are clocked 90? different from earlier years. This will hold the throttle plate open, but I think it hold it open to a much greater degree than you're seeing.

[bitsoknittles]

Thanks CRE. that will be my next section of the motor to work on. I am presently removing the whole intake (from the throttle body to the block) and using carb cleaner to clean all the sludge/gum from the bad gas that had been sitting in it. I do have a question on the N/A; if air were forced into the intake/throttle body, what would happen to the performance? would it increase the power (using cooler air from the front of the vehicle, not the warmer, under-the-hood air) or just the gas consumption? If it would increase the performance, I have an idea....

[cre]

The factory intake is a cold air intake. It's not restrictive either as long as you use a GOOD filter element in it. Removing the passenger side footlights and making sure all of the under covers may increase air pressure when already driving at speed but even with an elaborate duct you're not going to see any massive increases in power. Keep the helmhotlz resonator and don't increase pipe diameter as it reduces air velocity which is more important on a non-turbo. I've written a lot about all of this on here before.... might be in the. FAQ thread about cold air intakes.

[bitsoknittles]

Thanks for the previous info on the emissions CRE; I recently did a retest and the NOX passed (barely, 2.23 of 2.5), but the CO and the HC still didn't. HC was at 3.96 of allowable 1.6 and the CO was 117.31 of allowable 15.0. The idle is still a little high, but it seems to be running rich. Any ideas? The timing is at 10@ BTDC, and I have checked and set the TPS, checked the ISC and the air flow sensor settings, etc, according to the factory recommended settings/values. Any help would be appreciated as to where to look/ what to fix/reset/replace. Thanks!