Grrr, this is my daughter's car about 1,600 miles away. It all started on 3/12 with P0243 & P0171 codes. Searched around a there were no clear answers but about 75% of the threads lead to a bad MAF. So I shipped her a MAF and after the MAF change, the car did NOT want to start. Start, run for a second, then die. So she pulled the MAF and the car starts and runs rough.

Thinking that used MAF may have been bad, I sent her one that I test on my turbo 850. Same thing, the car will not run with the MAF plugged in but will run rough with it unplugged.

So I had her reset the system by pulling the battery connectors and holding them together for several seconds. Then I had her unplug her ECU and plug it back in a few times while the battery was disconnected. Connected everything back up and has the same issue.

After driving the car a little, the only code now is the P0102 MAF code because she is driving with it disconnected.

Any suggestions before she takes it to a shop?

 

When it all started did it just set codes or did it run and die, run rough too ??

 

The P0102 is low circuit input or low air flow. Have you had her do a really good visual and tactile search of the tubing all the way up to the manifold, IAC too ??

 

I think it just set the code.

I told her to check for air leaks but I'm not sure she did a good job looking. I'll shoot her a little video in a few minutes.

 

The P0102 code if from starting it with the connector unplugged. The issue is with it not staying running when it starts with the MAF plugged in.

 

I told her to plug the MAF back in, clear the code, start the car and keep it running until it pops a code.

 

Well, she could not find anything loose or leaking. Not sure if she had help.

She hooked up the MAF, got it running and kept it running for about 5 minutes by keeping the motor rev'd up but it would NOT throw a code so she gave up.

She has an appointment to have it checked out Tuesday am. Any other suggestions are welcome till then.

 

First thing that came to mind was a idle control valve or the coolant temp sensor. Leaning on the coolant temp sensor.

 

The IAC is humming and she claims the hoses are connected good.

I'll have her scan it for temp reading.

 

boxpin, why would the coolant temp sensor be a potential answer? I am having some issues and think the coolant temp sensor may be a problem

 

I saw an S40 start drive fine then all of a sudden as it got warmed up just would not idle any more. It would stumble and die. Crank and crank and crank to get it started then you had to hold the throttle open to get it to stay running. Swapped the sensor, fixed.

 

I wonder if it had a code? Last time this one had a bad temp sensor it tossed a code and made the fan run a lot.

 

I dont recall a code, its been a couple years, sorry.

 

Fixed. Shop said it had an air leak that was quickly messing up the MAF. Not sure how that works unless it was sucking oil back into the air box.

 

What was happening there was it was sucking in air and the MAF didn't know about it. While its sucking in air from somewhere else the MAF gets even less and the computer tries to adjust for it. When you disconnected the MAF there was no reading to adjust so that was why the car seemed to run better. Would have been great if she would have been able to spray some carb cleaner to find the leak. I know the cars fixed now but figured I would explain what was happening.

 

Yea, I tried to tell her and hard headed boy friend. That's what you get when you let a Bengal work on your car. :/

This is what the mechanic wrote: "Vacuum & boost pressure leaks. Secured intercooler & reattach lower hose." The radiator was hanging down. I told them to look down there at the hose, even sent them a video.