any ideas? idle/stalls but drives fine

[Big Ds mp5]

So im stuck and dont know what else to do. Ive read all throughout this forum and have tried everything i think. I checked my plugs and all are normal looking they are ngk and wires as well only two months old. I changed the coils, cleaned the egr valve. Checked battery and wires, looked at all vacuum lines and all look good. I also have a cai on it. Sometimes it runs fine. I have no light or codes on either. The first start up its fine but after i shut it off and start again its rough and idle goes up and down untill it either stalls out or almost stalls then idle shoots up to about 2k-2.5k then slowly back down and dose it all over. If i try to give it gas it kinda pops and has lil response and thats just taping the pedal as if i were reving it. If i hold it down a lil i can keep it goeing at about 2k rpm. Once im driving it runs just like it always did. When i come to a stop i have to feather the gas. I had an alarm installed on dec 23 and im wondering if that could have somthing to do with it? It started a few days after. Im lost now and need some help. Thanks guys.

 

[lowlevel]

I think your EGR is sticking open despite your efforts to clean it... the code takes about 20 to 40 minutes of driving before it shows up after the battery has been removed... it could possibly just be an air leak in your intake somewhere... these things are getting pretty old/brittle.

 

[Big Ds mp5]

When i pulled the egr it looked new like the previous owner replaced it. It just had slight carbon in it but not gunked up with chucks comming out. It opened and closed pretty smoothly also. And ive been driving it because i have no choice but still no light or codes on. I dont get it

 

[ap123]

next time it does that try un plugging the mass airflow sensor, it will start to run really rich since itll go into crawl mode but if its stops the idle from going crazy, it has to be a vac leak. Or maybe the sensor it self which is rare to go bad.

 

[kms1990]

maf senser is a good idea checking the fuel pressure regulator was going to be my next suggestion

 

[Big Ds mp5]

Ok i just unpluged the maf sensor it stopped the erratic idle. It was higher than it should be but def idle way better but as soon as i plug it back in it gets all wonky again. So you guys think its a vac leak?

 

[ap123]

yes most likely is a vac leak, what you're experiencing is exactly what cars with mass airflow sensor do when unmeasured air is entering the engine. The computer get stuck in this loop.

 

[Big Ds mp5]

After doing some research on the maf sensor im positive thats what it is. But sucks because its around $170-250

 

[kms1990]

could be a rip in the intake boot its common on these cars check that first

 

[Big Ds mp5]

It has a cold air intake on it, so thats not it. I did think it was fuel related early on but now im leaning more to the MAF now

 

[ap123]

a broken or loose coupler could still be a cause.

take a propane torch (dont light it LOL) and stick it around intake manifold, vac lines, anything pre MAF and see if the engine note changes.
Before you decide to buy the MAF, ive seen lots of people buy MAF sensor and it ends up being hose like the breather or something that was over looked.

 

[Big Ds mp5]

I dont have a propane torch but i have a map gas torch i use for plumbing it just burns way hotter then propain. Will that work? I dont want some spark to blow up my car even though thats not a bad idea at this point lol

 

[ap123]

I dunno if that would be such a good idea map gas is suppose to be more volatile i think. If you don't feel comfortable don't do it.

Propane is the safest thing to use.

 

[hornsfan10609]

You can try MAF cleaner spray to clean the element inside the sensor, it may just be dirty.

 

[Big Ds mp5]

Yeah i tried that too. I have maf cleaner because i always clean it at oil changes. Unpluged its good just a lil higher idle. Pluged in its rough and either stalls or wants to.

 

[kms1990]

yeah that signals to me the maf is failing, maybe swing by a junkyard and pick up a cheap junk one to test before buying a new one, as i wouldnt recommend a used one for long term use

 

[hornsfan10609]

The sensors are actually pretty good, they don't fail very often. The 1.8 NB Miata has the same MAF sensor as the FSDE proteges.

 

[kms1990]

yeah they are but they can still fail its a part on a car it gets exposed to hot, cold, dirt, water, soap, grease, oil ect so it can fail

 

[Big Ds mp5]

Well guys it was the MAF sensor!�� i just picked up a new one and BAM! Runs good again. It still has a slight low idle but i think its still relearning everything as i reset my ecu. But yeah thanks for all the info and help.

 

[kms1990]

glad to help