Sr20det Sr Gods Help!

[sidewayzcraze]

Hey guys,

I would like to start out and say I have been trying to fix this problem for a while and I am at MY whitts end.

So I got my sr running finally! However, it still is not ideling. I fixed all vacuum leaks and made sure plugs and coils are good. CHECK. So I unplug the maf and vuela the car runs great. I know this is a dead giveaway that the maf is bad but here is where it gets interesting. I have purchased a maf and another but still same problem. Right when I plug the maf in the car sputters and dies. Could all the mafs I tried be bad or is there another problem I may be over looking that have similar results. Took maf wiring all the way back to the ecu and it is fine. Plug A has 12 v. Plug B is ground. And signal is fine. Someone please help.

Zilvia love.

Christian

[Kaifd3s]

I would double check the ground. Its either the MAF's your using, the wiring for the MAF, or the ECU (highly doubt).

[sidewayzcraze]

Thanks for the reply kaifd3s.

Just read an article about re grounding the maf. Would this semi groud caust this issue? I checked voltage of maf on ground and it reads 0.3 v is that normal?

[sidewayzcraze]

If the wire is semi grounded

[Kaifd3s]

A semi-ground could cause the issue, or hide the problem, just reground it and clean the mating surface.

From what I remember for the MAF wiring it should be

12V for power
1.5V - 2.0V with a max 5V for signal

[Kingtal0n]

also check the ecu for a chip. and what color is your injectors.

do a boost leak check, fill the plumbing with air pressure. you might have missed a coupler.

[sidewayzcraze]

U will check the ecu asap. They are the purple injectors pretty certain they are stock. I know yellow are the 555 or 700

[zurud]

. check your wiring again.

[s13mikesr20]

Check the 02 I had similar problem I tried about 3 mafs
And it happened to be a 02 sensor being all fucked up

[sidewayzcraze]

Wiring is fine even ran a jumper ground to make sure the maf was grounded propelrly and still no dice. It does show a code 11 and 12. Bad cas and maf. But I'm sure the cas is fine. S13mikesr20 is it normal for the o2 to work when the maf is unplugged and not when the maf is plugged in? Are they in conjunction? I have never heard of that before......

[s13mikesr20]

They do go off each other
As far as I know I fried a 02 and my maf went out then vice versa I had the mike moused wiring harness it was cherry after I fixed it from the goof ball that ha it before me try a 02 from a donor sr and go from there

[ultimateirving]

When you unplug the maf it ignores the o2 sensor Input and idles off of base maps.

[badATcustomerservice]

check grounds

[Kingtal0n]

Originally Posted by ultimateirving

When you unplug the maf it ignores the o2 sensor Input and idles off of base maps.

Im not being mean or rude. But think about what you are saying. the base map is there for the maf vs RPM. If the maf is gone... It can no longer use the base map.

And now, think about the oxygen sensor. When you first start the car, or when the car is sitting idle for long periods, the O2 sensor stops working because the exhaust temperature drops too low for it to be functional. The oxygen sensor is only useful while driving at steady speeds, to make corrections to the base map, small % adjustments that the computer remembers for the long-term to help get the air fuel ratio closer to ideal, while compromising for emissions. If the fuel map is swinging around, if RPM is changing wildly, that is, if the rate of change of RPM or grams/minute of airflow is high, the O2 sensor does nothing.

When the O2 sensor goes bad, and the ecu still tries to use it, thats when the engine either runs [poor rich] or [poor lean]. To verify the bad O2 sensor at that point you unplug it and watch the engine run fine again. Any body diagnosing a suddenly appearing issue with air fuel ratio should immedialy unplug their O2 sensor before going any further. They should also perform a boost leak check right away, by filling the plumbing with pressure.

[sidewayzcraze]

Thanks Kingtal0n

I was thrown for a loop when I heard that. I didn't think it would cause the car to run so horrible either. Almost went out and bought one right now. I am leaning towards the maf being ruined. Just trying to find a donor or a good maf seems to be very difficult, who woulda thunk it. Im in socal (951) if anyone has a donor or one to be sold I would greatly appreciate it. Its just a simple little sr right? lol

[Kingtal0n]

Originally Posted by sidewayzcraze

Thanks Kingtal0n

I was thrown for a loop when I heard that. I didn't think it would cause the car to run so horrible either. Almost went out and bought one right now. I am leaning towards the maf being ruined. Just trying to find a donor or a good maf seems to be very difficult, who woulda thunk it. Im in socal (951) if anyone has a donor or one to be sold I would greatly appreciate it. Its just a simple little sr right? lol

Do you have a redtop?

If so, a SOHC KA24E maf will work. they should be easy to find, practically free.

2. Its probably not the maf. everyone loves to blame the maf, but tell me, be honest, have you performed a boost leak check ? FILLED the plumbing with pressure to 15-20psi?

[sidewayzcraze]

Yes sir there is no boost leaks whatsoever. But to my surprise I pulled apart the ecu and I noticed a burn mark. Looking directly down on the ecu with the plug facing you there is two little black boxes near a large gold resister that is fried is there a likely hood that this may be my issue. The ecu light goes off when the car starts and idles fine without the maf however I tested the maf and the voltage with the engine off is .8 v and when I blow through it I can get it to meter up to 2.2 to 3v. So I'm assuming the maf is fine. I'm lost. Wiring is correct and o2 looks new and wired apropriatley.......HELP! HAHAH

[sidewayzcraze]

This circled here is burnt on my ecu

[sidewayzcraze]

Your awesome zilvia also kingtal0n. Thank you so much for your replies

[Kingtal0n]

yeah, next step would be test a different ecu.

you can find a #62 for $50-$80. And re-sell it for just as much, so you dont lose a single penny.

[ultimateirving]

Originally Posted by Kingtal0n

Im not being mean or rude. But think about what you are saying. the base map is there for the maf vs RPM. If the maf is gone... It can no longer use the base map.

And now, think about the oxygen sensor. When you first start the car, or when the car is sitting idle for long periods, the O2 sensor stops working because the exhaust temperature drops too low for it to be functional. The oxygen sensor is only useful while driving at steady speeds, to make corrections to the base map, small % adjustments that the computer remembers for the long-term to help get the air fuel ratio closer to ideal, while compromising for emissions. If the fuel map is swinging around, if RPM is changing wildly, that is, if the rate of change of RPM or grams/minute of airflow is high, the O2 sensor does nothing.

When the O2 sensor goes bad, and the ecu still tries to use it, thats when the engine either runs [poor rich] or [poor lean]. To verify the bad O2 sensor at that point you unplug it and watch the engine run fine again. Any body diagnosing a suddenly appearing issue with air fuel ratio should immedialy unplug their O2 sensor before going any further. They should also perform a boost leak check right away, by filling the plumbing with pressure.

Is it not limp mode when it idles off the base maps? I figured incorrectly and I'll admit I was mistaken.

[Om1kron]

I can confirm everything on my engine is to oem spec, so much so in fact that it was thrown on a dyno and tuned to factory spec. everything is in-line and the harness has been checked in so many ways it would make you sick, and then also checked by someone else to double check my triple checks. I've used multiple ecu's and multiple mafs, tps's, and iacv's all individually tested as well. My car has NEVER idled under 1000rpm always 1200.

I think this is just super fucking common with sr20s' depending on the weather or conditions sometimes it will idle at 900rpm, at that point I think something is wrong with the car, but after a couple of sprints, right back up to 11-1200 steady.

coolant is all hooked up oem spec as well, no pass throughs.

If you want the car to idle like a kitten, buy an aftermarket engine management system, ditch the fucking maf and the iacv and have someone who knows how to tune set you straight. especially on whatever piss gas is available in your state.

Your engine will last a lot longer this way.

[sidewayzcraze]

Hopefully Picking up ecu tonight guys. I'll keep ya updated
Om1kron great info but not something realistic for me rightnow. Just trying to get the darn car to idle at all so I can drive it lol

[jakemkz]

Sidewayz:
The two devices that you have circled are transistors, I believe they should be labeled Q455 and Q456, they are positioned next to the gold cylindrical capacitor C654. Unfortunately I don't have an ECU on hand that I can use to identify the engine system these parts are associated with, but it is certainly possible that failure of these components could cause the issues you are experiencing. From the symptoms it is reasonable to suspect that they may be associated with MAF or O2 sensor signal processing or IACV control. On a positive note, if the transistor part number or specifications can be determined it is very likely that replacement parts could be found. The size and shape of the transistor (designated TO92) is perhaps the most common transistor package, which makes locating replacements easier.

ps. Many of the components near these two transistors are associated with the fuel injectors, but it is also near the output pin for the IACV (Pin 113).

[sidewayzcraze]

Thanks jakemkz,

I am assuming any circuitry failed could cause adverse effects elsewhere right?

I am just barely dipping into vehicle electronics and it seems like a monster in itself lol.

What does the average fix cost for something like that?

[jakemkz]

If it is just two blown transistors it could cost as little as a dollar or two for the parts, but of course replacing them requires a moderate level of soldering skills. The one concern that I have is that these transistors probably didn't let go out of the blue and their failure may have been caused by a wiring fault. Before plugging in your new ECU I would suggest going over the wiring to check for shorts. If you can trace the blown parts to an ECU pin it will narrow down the amount of wiring to be inspected immensely. Vehicle electronics is indeed an intimidating field, and it only gets more complicated with modern cars, the Bosch ECUs I work with have a 6000 page manual and well over 10000 variables.

[sidewayzcraze]

Good god. I hope you get paid well my friend!

[sidewayzcraze]

Update guys!

Repinned an j4 ecu for my harness (what it should have been all along) and the car still has all the same issues. Does idle much better in loop than it did before. For what thats worth. And I have hawk eyed the while sphagetti loom and all is well. Am I just getting bad mafs??

[Twiglet240]

Have you checked your timing? Also have you confirmed that your c.a.s. is stabbed correctly? If your c.a.s. is stabbed even a tooth off your car with run like shit and your idle will be off. I had this problem with my car when I first got it and it took me a long time to track down.