Shakes/stalls when coasting up a hill to a red light/intersection

Hey all! Been lurking on these forums for a while now and finally wanted to post a question! So a few months ago I replaced the spark plugs, intake manifold o ring, brake pads and rotors and last week I also replaced the P/S and A/C belts in the car along with the crank shaft pulley. The biggest problem I've run into since getting the car is that when it idles there's a bit of shaking (not sure if it's an old car and that's how it's going to be for the rest of its life, or something else), and whenever I cruise up a hill or sometimes even on flat ground it will have a high chance of shuddering and stalling, even though I have an automatic car.

 

Previously it almost always happened at least once a day. After changing the belts the car runs a lot smoother, but the stalling is still almost guaranteed to happen if there's an intersection on top of a hill.

 

I was wondering if this might be a problem due to low RPMs, because if I abruptly brake, or "pump" the gas pedal to keep the RPMs up the car doesn't stall or shake, but if I simply let the car coast up to a red light it will shake and quite possibly stall. If it's due to a low RPM problem, can I simply up the Idle RPM on my Cobb AccessPort?

 

Here's a picture of how to car idles at a stop "normally". Just from eyeballing it it seems to be idling at around 400-500 rpms?

 

http://i.imgur.com/UYGwPhQ.jpg

 

Thank you so, so much everyone!

I believe you can increase the idle with AP.

 

You may want to contact http://www.tuningalliance.com Mike can send you better MAP.

 

First off, have you cleaned the MAF sensor and made sure there are no vacuum leaks ?

Sure there are no vacuum leaks?

Hey all, thanks for the replies. I cleaned the MAF a month-ish ago, but I could definitely re-clean it just to rule it out, plenty of cleaner left haha!

 

For the AP, I don't actually know how to use it hahaha, it was sold to me with the car and all I know is that the car is tuned for 91. If I put in a new map do I have to take it to a tuning shop? I did find the "Idle RPM" thing just by clicking through the AP earlier today but I didn't know what RPM to set it to, was thinking 900 seems pretty safe.

 

For vacuum leaks, I'm thinking this might be the biggest suspect. I only changed the intake o-ring, but I haven't inspected all the vacuum lines closely. Could be cracked or something. Are any lines like "hidden", for example the one under the TMIC? The ones I can see without taking anything out just with by eyeballing them and feeling them look good and feel pretty normal, but been too lazy to take TMIC off

 

Thanks again!

900rpm might be a bit high for a 5eat...?

 

You can do a vacuum leak test if you have a air compressor. I use a pint size paint can to plug the hose off the air filter box. Then pull the small hose off the blow off valve. Give that hose a short blast of air and put your thumb over the hose. listen for air leaks.

 

The tmic can be pita to get back on if the TB hose falls off. the clocking is important.

 

I think Cobb's site or youtube will have video's about AP.

Front O2 sensor is bad

Would I be able to get the O2 sensor (I assume upstream) from RockAuto: https://www.rockauto.com/en/catalog/subaru,2005,legacy,2.5l+h4+turbocharged,1430733,emission,oxygen+(o2)+sensor,5132

 

Googled some guides, looks like a pretty manageable fix to me, but anyone know roughly how much a shop would charge to do it? Doing valve cover gaskets at a shop along with KillerB in the near future if it's cheap might as well get them to install it?

 

Thank you!

http://legacygt.com/forums/showthread.php/idea-web-links-saved-various-parts-219238p5.html

 

The recommended O2 sensor will be in there.It should be easy for the shop to replace.

Wow, that's an amazing thread, thank you so much. Found the Denso and Bosch ones on RockAuto, will probably grab the Denso one after a quick Googling to compare the two.

 

Thank you so much everyone again, will first check vacuum lines and if that looks ok I'll grab the o2 sensor. Still feel iffy about changing stuff on the AP hahaha

Only use the denso one. Changing the stuff on the ap is perfectly safe. Good way to tell if you have a vacuum/boost leak is by looking at the A/F ratio on the monitor tab to see if its running rich or lean.

Quick update, went to a shop highly recommended (edit: by friends/peers) to do KillerB and fix valve cover leak as well as do an alignment, and asked them to do some diagnostics. No vacuum leak, transmission isn't leaking (in case it was low transmission fluid), O2 sensor seems fine, and they scanned a faulty speed sensor and said it might be that. They cleared it and told me to drive it around for a bit and monitor it.

 

Could this be the source of the problem? I'm not sure if it's this speed sensor, which is $511 Canadian, or the ABS wheel speed sensor and I forgot the ask. http://www.rockauto.com/en/moreinfo.php?pk=4713483&cc=1430733&jsn=10395

 

Really hoping it's not the $500 part...

 

Once again, it seems to happen when the car is coming to a complete stop if I don't use the brakes (i.e coast to a light or parking spot), or when I lift off the brakes and let the car move forwards without me giving it gas (i.e. in rush hour traffic when I let off the gas and let the car coast forward a bit).

 

Since getting the car done required removing battery, etc so ECU was reset, would the speed sensor fault be "fixed" after the car relearns everything?

Shop highly recommended Killer B? Killer B what? Killer B line their pockets because it will be somewhat of a major project to replace ANY of the parts with Killer B? I would be quite wary of their so called diagnostic skills.

 

Front O2 sensor can be bad without throwing any kind of a code. It messes with your STFT and also LTFT and causes the engine to "hunt" during idle conditions. It will also allow you to go way down in rpm at idle-down to about 250 which is a stall anyway.

 

Find someone you know that has a good working unit and swap it and see if it clears up the issue. I've found in many cases the O2 is the culprit without ever throwing a code and once changed, everything evens up and runs fine again.

Oh oops sorry about that! It's a shop recommended by friends/peers, and I was there to fix a valve cover gasket leak and install the KillerB oil pick up and OEM oil pan (to fit the PU because I have the older 131 pan). While there I told them to see if they can figure out what's going on, and they checked for vacuum leaks, etc and the car threw a faulty speed sensor code.

 

Sounds good, I'll give the O2 sensor a go. I really hope it clears up the issue, nothing like stalling at a red light like when you first learn to drive stick. If I buy the part off RockAuto would I have to buy a pair of upstreams?

 

Should I be worried about the speed sensor code? No check engine lights so far.

 

Thanks again!

Cleaning the maf does not mean it's okay afterwards. It will typically throw a code but you never know. What's your maf reading? Another trick is to have the car idlng and lightly tap on the maf with the end of the screwdriver and see if the idle changes. I wouldn't normally recommend doing it, but I've found a few as the culprit by doing it that way.

Just checked MAF, not sure if I know how to use the AP properly and didn't get to go WOT, but reading 1.4 when cruising with foot off the gas, idles at 1.3 both in "Drive" and "Park", and when I give it gas max it read was 3.4.

It should fluctuate just as quick as you tap the gas. It's hard to say what the specs should be because it typically depends on where you live.

https://www.amazon.com/gp/product/B000CF5YGI/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1 5eat front sensor.

 

when mine went, had no codes but it played goofy games. cruise fluctuations, hard start condition

Yes, I do believe that the MAF readings fluctuate (increase) quite immediately when I give it gas. Sounds good, looks like O2 sensor will be the thing I replace as soon as possible. There are two upstream sensors right/I should replace both?

 

Forgive my ignorance, really don't know much if anything about cars, but the car is still good to daily to work right? I also might be making a ~300-350km total trip next week as well.

 

Finally, and sorry for so many questions, but could this be a fuel pump or torque converter problem? Also, should I be worried about the faulty speed sensor the shop scanned?

 

Thank you so, so much everyone!

Only one front O2 sensor. It's behind the right front wheel behind a plastic panel. With the panel removed you can see the sensor in the manifold.

 

Read here for the front O2 sensor. Post # 172 or post # 48

 

http://legacygt.com/forums/showthread.php/idea-web-links-saved-various-parts-219238.html

Great, thanks again just ordered the Denso one. Hoping the Canada Post strike doesn't affect things, and hopefully this solves everything! Also I might be grasping at straws right now trying to find the problem, but I think this stalling problem happened after I changed my winters over to summers. I don't think the car has ever shuddered or stalled before then, but it's happened after I changed out the wheels. Pretty sure this is just correlation and not causation but just in case that little bit of info is any use.