Emissions – N/A running rich

[JAB89]

Working on my son's 89 N/A 5-speed (bone stock). Here’s the situation:
Plugs, Wires, Cap, Rotor and Air Filter are new. TB cleaned and Timing at 10 degrees. EGR valve is new and working as per TSRM (old one was completely clogged with carbon). O2 Sensor is new (Bosch) and checks out when bench testing with propane. I have now swapped out the AFM, TPS, ISC and FPR form a wrecked 90 N/A. Temperature Sensor resistance is OK hot and cold.
There are no error codes and the car runs great although it does burn a lot of oil (with blue smoke out the tailpipe).

Fuel pressure is at the high end, 44 psi (TSRM says 38 to 44 for N/A). It holds to well above 21 psi 5 minutes after engine is shut off. Pressure is still the same after swapping out the FPR.

I connected an A/F Ratio gauge to the O2 in diagnostic block for testing.
I know it’s a light show but it does respond well to cross counting.
It indicates a rich mixture most of the time except at idle.

When trying to check out the O2 Sensor per TSRM (running at 2500 RPM in diagnostic mode) the gauge shows solid rich with a Vf1 reading of 4.96 volts.

I did notice that it will cross count at about 1700 RPM. But anything above 1800 and it goes solid rich.

With the PCV hose disconnected, it will cross count as high as 2200 RPM, but not above.

The plugs although new are black with carbon as is the exhaust system.
I figure it needs a new Cat too but want to get the rich mixture cleared up first. I have done the ECU voltage checks and cable resistance checks as best I could. I would have swapped out the ECU from the wreck but did not since it is an automatic. Oh, the test results posted below are from the re-test after all this stuff was done.

Could injectors cause it to go rich? I would have thought lean maybe and it does runs well. But then I have zero experience messing with fuel injection.

So, what am I missing? Am I down to a bad ECU?
Help! Any advice will be greatly appreciated at this point.

Test results (click on the attachment and you can see it):

 

[jetjock]

First, my compliments on your methodical approach to the problem and posting the details. I wish everyone would do this rather than simply write "help, car broken"

However a few things need clarification:

>There are no error codes and the car runs great although it does burn a lot of oil (with blue smoke out the tailpipe).<

Regardless of fixing the loop if you're burning oil it will fail emissions for high HC. And if the loop is stuck rich you should be getting a code 26. However, since you seem to be getting cross counts some of the time a code 26 may not happen because that code uses a multi-trip detection scheme.

>I connected an A/F Ratio gauge to the O2 in diagnostic block for testing.<

Where did you connect it? To the O2 or Vf terminal? If to the O2 terminal, does a voltmeter connected to Vf with the diag block shorted and the engine at 2500 rpm also show cross counting?

>When trying to check out the O2 Sensor per TSRM (running at 2500 RPM in diagnostic mode) the gauge shows solid rich with a Vf1 reading of 4.96 volts.<

You can't check Vf with the block shorted. O2 sensor cross counting is checked using Vf with the block shorted. Are you saying Vf is 5 volts with the block shorted at 2500rpm? That would be true if the loop was driven full rich but you're not looking at fuel trim with the block shorted. What is Vf with the block open? If rich it should be opposite, 0 volts.

>I did notice that it will cross count at about 1700 RPM. But anything above 1800 and it goes solid rich. With the PCV hose disconnected, it will cross count as high as 2200 RPM, but not above.<

That does indicate a rich mixture as adding more air causes cross counting rpm to increase. What does Vf show when the O2 sensor is cross counting below 1700 with the diag block open?

>The plugs although new are black with carbon as is the exhaust system.<

Are they carboned or oil fouled? It does sound as if you're running rich but we need to clear up my confusion about whether you're measuring the O2 signal or fuel trim signal at the Vf pin since both are available there depending on whether T and E1 are shorted. Since you're using an A/F gage you must be hooked to the raw O2 pin but knowing what the ecu processed O2 signal is doing on the Vf pin using a voltmeter would be helpful. And this could all be moot if it's burning oil.

Also I'm unable to view the emissions report. Oddly, I can see the attachment when not logged in but it disappears when I do log in. What are the numbers?

 

[NATAN666]

if its burning oil, just for the test through in some lucas opil stabilizer or somethign simillar. i believe it basically makes the oil thicker and unable to seep through small leaks. if youre burning oil due to something major, it might not stop it. but for diagnostic purposes it would be good to try and eliminate that factor. it shouldnt be expensive and its advertised to stop oil burning so give it a shot, maybe put in some octane booster or whatever it is that you put in your gas to try and pass emissions, then try... i mean i know thats the ghetto work around method but it'll at least get the oil burning factor out of the way temporarily.

 

[Nick M]

If you have blue smoke out the pipe, you are buring oil. As you thought.

 

[JAB89]

Thank you all for the fast response.

JetJock: I have to go out of town today but will run it again when I return and post some exact Vf readings in both modes and different RPMs. will also write a clarification of my test hook up as you requested. Thanks again.

Natan: Thanks for the Lucas Oil Stabilizer idea. I thinks it's a good one and is worth a try at this point. If it removes some of the oil from the combustion process it would help the diagnosis as well as the emission test. And if it really helps oil consumption, all the better.

Nick: Thanks for your response on the blue smoke. It's always nice to have your thoughts confirmed when you are scratching your head on a problem like this.

 

[JAB89]

OK, Re-ran more tests today to collect some more exact data. First a little clarification on my test hook up which remains the same throughout all testing:

A/F Ratio gauge is connected to the O2 terminal on the diagnostic block thereby monitoring raw O2 Sensor data via light show. Digital voltmeter is connected between the Vf terminal and ground.
Note: It was warmer here in GA this afternoon (65 F) so cold RPM was much lower.

These tests performed with Te1 = open (not shorted to E1):
1) Warming up: Temp Gauge = Cold, Idle at 800 RPM, A/F gauge shows steady STOICH, Vf = 2.20 volts, Exhaust = clear.
2) 10 minutes later: Temp gauge = Normal, Idle at 700 RPM, A/F gauge = steady STOICH, Vf = 0 volts, Exhaust = clear.
3) Increase to 1700 RPM: A/F gauge = cross counting, Vf = 0 volts.
4) Above 1800 RPM: A/F gauge = solid Rich, Vf = 0 volts.
5) Decrease to 1700 RPM again: A/F gauge = cross counting, Vf = 0 volts.
6) Decrease to 1500 RPM: A/F gauge = solid Rich, Vf = 0 volts. Note: not a smooth transition from 1600 to 1500. It sort of stumbles and wants to drop @ 400 RPM but then I could ease it back up to 1500.
7) Decrease to 1000 RPM: A/F gauge = solid Rich, Vf = 0 volts.
8) Below 1000 RPM: A/F gauge = solid Lean, Vf = 1.06 volts.

These tests performed with Te1 connected to E1:
9) At Idle: A/F gauge = solid Lean, Vf = 4.95 volts.
10) 1000 to 1500 RPM: A/F gauge = solid Rich, Vf = 4.95 volts.
11) 1700 RPM: A/F gauge = cross counting, Vf = cycling between 0 and 4.95 volts.
12) Above 1800 RPM: A/F gauge = solid Rich, Vf = 4.95 volts.

I take back what I said about the car running great all the time. At WOT it runs great. However I noticed today that at a steady 3000 RPM or above, it seams to stumble a lot or act like what I think is being fed a ton of fuel.

Emission Test Results (if you can&#8217;t see the attachment):
HC ppm: 140 allowed, actual was 710 - Fail
CO%: 0.89 allowed, actual was 10.41 - Fail
NOx ppm: 984 allowed, actual was 98 &#8211; Pass
RPM: 3000 max allowed, actual was 1996 &#8211; operator controlled
CO+CO2%: 6.0 min allowed, actual was 18.0

Here is a plug I pulled after testing today (click on it for a better view):

 

[3p141592654]

Please test the TPS and let us know if its okay. Also check that VTA-E1 resistance varies smoothly with throttle angle. I am wondering if the TPS is giving the ECU a WOT signal when it is not.

http://www.cygnusx1.net/supra/library/TSRM/fi/FI_101.html

 

[JAB89]

Please test the TPS and let us know if its okay. Also check that VTA-E1 resistance varies smoothly with throttle angle. I am wondering if the TPS is giving the ECU a WOT signal when it is not.

http://www.cygnusx1.net/supra/library/TSRM/fi/FI_101.html

Thanks for the response 3P. What your saying makes a lot of sense.
However, I have to confess that in my first post I listed the TPS as a part that had been swaped out. In reality I destroyed my spare TPS trying to open it up to see if I could clean the wiper, haha. So I ended up installing a new one.

But just for kicks I just now went out and checked the VTA resistance again and yes, it does vary smothly from open to close with both limits well within specs. It was a good thought though. Thanks again.

 

[3p141592654]

Sheesh, I need to read more carefully. Okay, how about the cold start injector. Not likely to be the problem given that you are holding fuel pressure, but if it comes on you will have a severely rich condition. I would also check the cam timing to make sure you haven't skipped a tooth on the belt although I don't think your symptoms really match up with that scenario either.

 

[JAB89]

3P: Today I totally eliminated the cold start injector by disconnecting it's supply line from the fuel rail and plugging the rail with a bolt and crush washer....no effect. Also checked cam timing and it's right on. Thanks for the suggestions.

Now then, Anyone: Where I? any other ideas? Is it time for another ECU?

 

[3p141592654]

Running out of ideas here. Has the car ever run properly since you got it? Maybe it has turbo injectors (440cc) instead of the NA injectors. Otherwise, looks like time to find an NA ECU. Have you tried disconnecting the battery for 30 minutes to reset the ECU?

 

[JAB89]

The final resolution: Picked up an ECU on eBay which fixed the problem.

This thread is old now but I have only worked on this in my spare time.

By the way, this thread was originally posted in the N/A section which is where it should be. I myself own a Turbo but this car is my son's N/A. Thanks.

 

[supraman7mgte]

Dam,that was the best explanation of a problem i've ever read!