Interpret these results please

I am learning to use my new to me innova 5610 scanner and am using it to fix my rough idle and p0303 code. I have installed new injectors, iac valve, fixed horrible exhaust leak with new manifold and gaskets at motor and both sides of converter. New plugs and cleaned throttle body. Please help me interpret these values. 1996 2.4 5 lug auto

 

I dont know why cat is lit up in red it brand new and completely clean.

 

Something is way off, you have -40% fuel trim.
What is you MAF reading at idle?

The ones in red are monitors that have not ran, they don't mean that part is bad just that the OBD monitor hasn't been completed for that part.

 

I am assuming you unplugged your battery or cleared your previous codes? The cat, egr, and heated o2 are all part of your emissions 'checks' which reset everytime you do either of the previously mentinoed and will just take time to re-populate back to green if they are in fact good to go... egr being the last of all of them to do so.

I am not sure on the trims, but wonder if they also reset as well and haven't been ran long enough to get back 'normal'.

 

Here is the info you asked about

 

Fuel trims are no bueno. Neg 40 means that it's pulling fuel. Have you checked your plugs to confirm? I believe anything over 25+/- will trigger the CEL.

 

Your MAF is reading high, that's more than likely why your fuel trim is -40%
Have you tried cleaning it?

 

I have cleaned it several times with maf spray and air dried it. -40 on fuel trim means it's cutting back on fuel right, it leaning it not riching it.

 

I know it is working because if i unplug it the engine immediately dies. Of course i checked it this way before i got the scan tool.

 

It's pulling back because it's rich. If it was lean it would be positive.

 

Well something is going on with it, at a hot idle MAF in Grams/Second (g/s) should be very close to engine displacement in Liters. You have a 2.4L engine so you should see about 2.4 g/s or 0.32 lb/min, your reading 0.67 lb/min (5.1 g/s) which is about 72% higher. The PCM is seeing the higher airflow and adding more base fuel causing a rich condition, the AFR sensors are reporting the rich condition back to the PCM so the PCM compensates by subtracting fuel to bring the Air/Fuel Ratio back to stoichiometric.

Correct it's compensating for a rich condition using feedback from the AFR sensors, -40% is likely the limit of what it will go so your likely not in "fuel control" as we call it.

 

I changed #2 and 3 plugs and wires expecting for misfire to change cylinder, but it did not. It runs good cruising down the road the misfire on shows up when idling at a stop light. I replaced all the lines from vapor canister to purge valve and tested it. The valve never opened for 20 minutes of idling. It is getting voltage and it is between 30 tp 50 ohms according to haynes manual. I am currently looking for a replacement. I rechecked long term fuel trims and are -29 instead of -40.

 

Purge valve isn't gona affect fuel trims unless it's stuck open.

But what is your short term trim?
Total trim is long term + short term trim.

The engine is going to misfire and run poorly if it's not in fuel control.
Have you addressed the MAF issue?

 

The maf is working as far as live data, i just dont know what values are good or bad, i just know it works. I just hate to throw parts at it ya know. But if you think changing it will help i will give it a try.

 

Dm is trying to tell you the MAF values are not normal, it's way too high. The high maf reading will trick the pcm into adding way too much fuel. The extra fuel won't get noticed until the oxygen sensors see it, and then they'll tell the pcm to pull back on fuel. Hence the negative trims

Garbage in, garbage out.

When cruising it's able to gulp down the extra fuel so it seems to run OK. But at idle its suffocating on the extra fuel, so it hiccups and misfires.

Disconnecting the MAF and watching the engine stall doesn't tell you anything of value in this situation

 

x3 on MAF reading too high. Should be around 2.5g/s, you're at 5. Fuel is leaning out to -50% and still too rich because it thinks you're ingesting double the air you are.

 

You won't know how rich or lean the mixture really is unless you actually read the O2 results. (Standalone AFR sensor or techstream monitoring the actual signal from the stock O2). It could be running hella lean and that's why it runs like crap.

The 96 doesn't use an AFR sensor like 2000.5+ trucks do in the first sensor position, it's an older O2 sensor style.

I agree with above though, you gotta figure out why the MAF reading is so high. I assume it's 100% stock as far as engine\ECU wiring goes?

 

That's actually exactly what the trims are for. If it was running lean the trims would be positive

 

I know, I guess I didn't phrase it the best. All I'm saying is you don't really know the AFR unless you measure it properly. The ECU *could* be getting false data and trimming inappropriately...we know something is wrong, and can't assume even the trimming is correct by the ECU.

 

I know what you're trying to say. In addition to telling you if it's rich or lean, AFR sensors can tell you how far out of stoich it is.

But for the mixture to be lean and report negative trims an oxygen sensor (or all of them) would have to be way out of spec. We can't see those readings on the screen.. but that maf reading is obviously wrong