Car runs rough with MAF plugged in (a known good MAF)

[CAFIFTY]

I just purchased a 92 VR4. Car would barely run with the MAF plugged in. Thinking it was just a MAF I brought a know good MAF from a 93 TSI talon and swapped it but it didn't change anything. Car runs okay with it not plugged in but obviously not the greatest. I am thinking it's a intake leak. I am going to run a boost check on it but wanted to see if anyone had any additional insight.

Also, I should note that the car had a ECU swapped in it before i purchases it (the old ones caps went bad). But the ECU swapped into it was from a Talon. Should that matter? Found some post that says the galant's MAF is different then the talon's and the ECU would be different

I also noticed the boost solenoid is bypass (plugged in but no vacuum lines going to it) and so is another solenoid attached to the air filter (assuming purge). Did some searching but it sounds like that shouldn't matter

Thanks in advance!

 

[James]

I don't know about a difference in MAFs but it doesn't matter because you put in a dsm ECU and a dsm MAF.

My money would be on air leaks. Bad gaskets, bad TB shaft seals, ect.

 

[jnava]

My car runs like crap without the maf. So if your car is running better without the maf, you have some serious leaks. Check the vacuum lines, hoses and anything in between to find cracked or split lines. BTW, you haven't mentioned whether your car is stock or has some modifications. Is your car's bov vented to atmosphere or recirculated. Let us know.

 

[CAFIFTY]

Just got in from the garage. Car didn't seem to have any major leaks did repair some minor ones but nothing huge (now i can get to 20psi on a boost check *but it leaks down pretty fast*). Car will idle and kinda run with MAF plugged in now. It is unresponsive and surgey when trying to drive in non-wot conditions. Wot conditions seem sine

Notice that at idle the car runs the same whether the idle switch sensor is plugged in or not. The wire and connector look questionable, wondering if that could be the problem.

I also have a TB from a 1Gb talon in the garage. Going to try to swap that in. Not 100% sure if they are compatible but i will search around. Also will probably do the emissions delete while i am at it.

Thanks!

 

[5OF2k]

Sounds like you definitely still have some leaks, it should hold 20psi no problem. Find the leaks, fix it, and enjoy the car.

-Jake

 

[citymunky]

This weird guy video might help you. https://www.youtube.com/watch?v=zMok2y05jNE

 

[CAFIFTY]

Jake,

I am going to replace the BOV seal and turbo outlet seal because they seem to be leaking slightly. I can get to 20psi but it leaks down over time. I am about 99% sure this isn't the issue, the amount of non-metered air that could be leaking past them under vacuum (part throttle-where i am having the issue) would be minimal and learned out in close loop. Car now idles around 700rpm. If i had a significant intake leak this wouldn't be the case.

Anyways, i swapped throttle bodies and rewired the idle switch but no improvement. The old throttle body's ISC motor read 35 ohms everywhere so that wasn't the problem. I think it would be pretty unlikely that the FIAV is bad in both throttle bodies. Couldn't be the TPS because the car run good when the MAF is unplugged. Wonder is the BISS is set really wrong? I know the owner said that he messed with it. Also wondering if my knock sensor could be bad but i think that would be unlikely also.

About to make one of these to try to aid me in trouble shooting it. But not 100% sure it will work with TMOs data logging software. Would be nice to be able to see fuel trim values, knock count, etc.


So here is what i think:
BISS set wrong
Bad knock sensor
or the previous own put some whack ECU in there (will check part numbers). Is there an easy way to tell if a ECM has been chipped?

 

What mods are done to the car that would help use help you.

 

[jnava]

Asked him a while back, no answer. Biss can be a major factor. When I was dialing it in with link, it was way off and caused some issues. That was based on link wiki to dial in base tune.

 

[CAFIFTY]

Sorry. No mods. Car is 100% stock beside that ecu was swapped in it when the original blew.

 

[CAFIFTY]

Adjusted the BISS. Still does it. Adjusted the idle switch. Still does it. Changed the wires. Still does it. Change the plugs. Still does it. ECU part number says its out of a 1990-1992 awd talon. Ugh, i forgot how fun owning a DSM is.

So part throttle NOTHING. But WOT it goes like its fine. Maybe my TPS is out of adjustment.

Knock sensor felt a little sticky when i checked.....

 

[CAFIFTY]

Just pulled the knock sensor off. Sticky, melted, can see the screw. So i am assuming this was the problem. Will post results once i try it out. If this isnt it i am running out of sensors to check!

 

[James]

If you need a sensor I have one for sale.

 

[CAFIFTY]

If you lived down the street i would be down but Florida is pretty far. Is there anything wrong with getting one from autozone/napa? I am assuming there some re manufactured crap but it is what it is.

 

[James]

Well I could ship it out ASAP tomorrow if you needed. I don't know what they charge for one at somewhere like napa or autozone. From what I hear they can be hit or miss though. Like their alternators haha.

 

[CAFIFTY]

Thanks for the offer but i think ill pass. Just hope this is it.

 

[5OF2k]

push for a Beck Arnley knock sensor, and you should be just fine. That's going to be a factory or as close to a factory part as you can get.

Good luck, sir!

-Jake

 

[mikus]

Knock sensor will either:
- put you in limp (retarded timing) if not grounded/connected, or
- produce false knock if failing.
... I don't think this has anything to do with your knock sensor. More likely, either you have a poor, gunked up connection on a MAF pin or a wire got broken/pinched/etc. Not uncommon on a car this old.

Disconnect your MAF, get a voltmeter and check your ground wire first. Jiggle the wiring when you do this. With car off, spray some electrical cleaner on, slide the connectors on/off a few times right after spraying. Let it dry out. Reconnect the lot and fire it up.

If that ground is questionable, you can run it from MAF to chassis instead, with a lower gauge wire. It's completely fine to do, and easier to produce a quality ground. Solder & use good connections!

Here's the MAF pinout.

1G MAF pinout:
ECU?? • 1G MAS Pin 1 • green w/ yellow str • idle position sw
ECU10 • 1G MAS Pin 2 • green w/ blue str • Airflow Hz
ECU102 • 1G MAS Pin 3 • red • +12V from MPI
ECU23 • 1G MAS Pin 4 • green w/ red str • +5 volts
XXXXX • 1G MAS Pin 5 • blank
ECU24 • 1G MAS Pin 6 • green w/ black str • Ground
ECU16 • 1G MAS Pin 7 •green w/ yellow str • Barometer
ECU08 • 1G MAS Pin 8 • green w/ orange str • IAT

 

[CAFIFTY]

Thanks Mikus. I thought knock sensor would be a reach also. Unless it was pull out crazy spark in part throttle conditions. I sprayed some electrical cleaner on it but didn't help. I will pin it out when i get home.

 

[desant78]

Quoting CAFIFTY:
Adjusted the BISS. Still does it. Adjusted the idle switch. Still does it. Changed the wires. Still does it. Change the plugs. Still does it. ECU part number says its out of a 1990-1992 awd talon. Ugh, i forgot how fun owning a DSM is.

So part throttle NOTHING. But WOT it goes like its fine. Maybe my TPS is out of adjustment.

Knock sensor felt a little sticky when i checked.....




If I had this problem, I would base-line all those adjustments first. Using Vfaq or a factory service manual, adjust base timing, BISS, idle switch, TPS. Make sure you are adding the proper grounds, or any adjustments will make things worse. This can be found on Vfaq. This is something you should do, and aids in troubling shooting. It will allow you to rule out a few things.

I would also make sure all my sensors are correctly plugged in, because my car gets all funky without the temp sensor to the ECU giving any signal. Do you have a logger? Sorry if this was answered already, but a logger would help and I honestly don't know how I would own my car without one.

Good luck!