[jcahill761]

I have a 2003 Tiburon GT with just over 100k miles. Completely stock besides a cold air intake.

The problem I have started a few weeks ago and gradually got worse. It's to the point where I cant confidently take it out anywhere. I've searched the forum and haven't found a thread that discusses the issue i'm having. This is my first post.

The car starts perfectly... every time. Even when I've let it sit in the cold for long periods of time it has never had an issue starting. While in park, the idle is low (below 1k) and jumps around. As soon as I put it into gear, the RPMs go even lower to the point that I fear the car will die (it hasn't yet). It gets a bit better when I am moving. When i drive it around the neighborhood to test things out it seems to run ok. However, when i pull up to a stop sign the idle drops below 1k and the car sort of shakes and acts like it may stall out. I've noticed there is also now a smell of unburnt fuel. Recently I've noticed there is a backfire coming from the intake area during acceleration (this did not happen before).

I took it to a shop for diagnosis and they told me it threw a MAF code and a misfire code for cylinder 3. They told me they would start by replacing the MAF and the spark plugs/wires. I did both those things and the car is still running like crap. Seems like the problem got worse rather than better.

There is no CEL and the shop told me the MAF and misfire codes were the only ones that came about during the diagnostic test. I ordered an ignition coil pack and i'm going to install tomorrow. Wondering if anyone has had a similar issue? Or if anyone sees something obvious that i'm missing?

 

[Acura_Kal]

Have you checked and cleaned/replaced the IACV?

Have you checked for arcing on the spark plugs?

Could also be worth checking the TPS too.

 

[dmdicks]

First thing I would check is the condition of the crank shaft position sensor. Those get cooked with high miles and will cause most of the problems your having. Replace ONLY with OEM sensors.

 

[jcahill761]

Thanks for the input. I’m currently at work but I’m going to start working on it when I get off. DefinItely going to take a look at the TPS, crankshaft position sensor & IACV. I’ll update this thread later on today.

 

[aveenav]

Was the MAF an OEM part made by Siemens or aftermarket? As dmdicks suggested, only use OEM sensors.

 

[jcahill761]

The MAF is an aftermarket one. Not OEM. However I have been running an aftermarket MAF for the past two years with no issues so I’m pretty sure that’s not the root of my problems. I’ve been pretty busy so I haven’t been able to install the ignition coils yet. I cleaned the IACV last night and found a hairline crack on the plastic casing. I sealed it with JB weld and put it back in to see if that would make a difference but nothing noticeable happened. I ordered a new crank position sensor and I’m hopefully gonna get the coils in tonight. If that doesn’t help I’m going to order an OEM Maf to see if that helps at all. I appreciate the help and will keep this thread updated.

 

[h8isgr8]

The MAF is an aftermarket one. Not OEM. However I have been running an aftermarket MAF for the past two years with no issues so I’m pretty sure that’s not the root of my problems.

OK, but you said the MAF was replaced, so I assume that means it's a different aftermarket MAF than the one you used for 2 years?

Nearly all aftermarket MAFs cause problems on the tib. There is a small exception, like a Beck-Arnley MAF I had, but even that one only lasted less than 2 years.

If the MAF looks like this, chuck it in the trash...

If it looks like this (this was the Beck-Arnley), then it might work, but it could still be the cause of the problem...

 

[jcahill761]

I installed the new coil pack and it did next to nothing. I also pulled off the Maf to check and it looked just like the one you said was junk... it’s now in the trash. I looked at the aftermarket one that I had in before and it looked more like the bottom photo so I’m assuming that’s why it lasted for a while. I went to an auto parts store and picked up an OEM one and installed it.

The idle is still messed up (low and shaky in park & even lower and shakier in drive). I could tell something changed though. It seemed like the computer was trying to figure out what was going on or something. I wanted to take it out and drive it around to see if it would correct itself but it’s -4 degrees here in Omaha and the roads near my house are iced over. I don’t want to get stranded if it were to die on me. I’m going to take it out tomorrow when it’s a bit nicer.

Will the computer auto-correct itself if the crappy Maf was the issue? Is there anything I should do besides rest the ECU to get it to adapt quicker?

Also thanks for the pics that really helped!

 

[h8isgr8]

I installed the new coil pack and it did next to nothing. I also pulled off the Maf to check and it looked just like the one you said was junk... it’s now in the trash. I looked at the aftermarket one that I had in before and it looked more like the bottom photo so I’m assuming that’s why it lasted for a while. I went to an auto parts store and picked up an OEM one and installed it.

The MAF in the first picture is using (exploiting) the temperature coefficient of resistors to do the sensing. Not an ideal solution, but they do this with aftermarket MAFs because resistors cost pennies.

The MAF in the second picture uses a platinum RTD (resistance temperature detector), which is also technically a resistor, but it's designed specifically for measuring temperature. These cost quite a bit more than a resistor.

The sensors in the OEM MAF are extremely sensitive (and fragile) and have a way faster response time than a resistor or RTD. I don't know if the tib ECU just doesn't like the slow response of the aftermarket MAFs or if it has something to do with the circuitry inside.

Is there anything I should do besides reset the ECU to get it to adapt quicker?

Unless you have access to an advanced OBD diagnostic tool to reset the adaptive values, disconnecting the battery or pulling the ECU fuses is really all you can do.

 

[jcahill761]

I disconnected the battery in order to reset the ECU and the car is not responding well today. It still starts fine but if I don’t give it a bit of gas it won’t idle at all. It dies about three seconds after it starts.

It is brutally cold where I live today with temperatures in the -10 to -15 degree range. I am wondering if this may have something to do with the poor performance? I don’t know why the car would be running worse with the new OEM Maf installed... any thoughts?

 

[aveenav]

I went to an auto parts store and picked up an OEM one and installed it.

You mean from the dealer? Coz no auto parts store sells OEM part.
Did you replace the crankshaft position sensor too?

Usually few mins of driving/idling or disconnecting the battery would reset the ecu.

 

[h8isgr8]

I disconnected the battery in order to reset the ECU and the car is not responding well today. It still starts fine but if I don’t give it a bit of gas it won’t idle at all. It dies about three seconds after it starts.

It is brutally cold where I live today with temperatures in the -10 to -15 degree range. I am wondering if this may have something to do with the poor performance? I don’t know why the car would be running worse with the new OEM Maf installed... any thoughts?

The main problem with the aftermarket MAFs is that they cause the fuel trims to go high and eventually peg. That's what happened with both of mine, even though it took a long time for the BA MAF to finally do it. That could have been why you smelled unburnt fuel.

Do you still smell unburnt fuel? Maybe the engine is running too lean now with the OEM MAF because there is another problem like an intake leak or bad IACV. I know you said you cleaned it, but did you check it to make sure it moved freely? The rotor inside should have some springiness too it and move smoothly. I had to replace mine around 90k; cleaning it did nothing and the rotor movement was sluggish. I also had to replaced my TPS shortly after that.

 

[h8isgr8]

You mean from the dealer? Coz no auto parts store sells OEM part.

I believe the only one that's a Siemens MAF is the VDO 5WK9643Z (Siemens owns VDO). It's an insane $242 from AutoZone and $152 at Advance.

Here's a genuine OEM at amazon for only $72.65 if someone wants to snag it fast...

https://www.amazon.com/dp/B00BJNTXPA

Amazon prices fluctuate all over the place and this is the cheapest I've seen one yet.

 

[jcahill761]

PROBLEM SOLVED:

Sorry if anyone was eager to hear a reply from the last few posts I’ve been horribly busy working and getting ready to go back to school.

Turns out the issue was being caused by a fuel injector. Replaced them and the car is running like new again.

Thank you to everyone who offered advice and input.

Cheers

 

[cmcribbs86]

Usually its the IAC Idle Air Control Valve that makes a vehicle idle up and down.