Occasional backfire on interstate, one stall..

[ZoomZoomZoom]

I've got a weird, very intermittent problem with my new build. The car is mostly stock: stock IC, stock BOV, K&N intake, 3" full exhaust, .57 trim DM turbo, 7m-gte rebuilt top and bottom. Twice in its first 3,000 miles, I faintly heard a backfire. Both have been at high speeds on the interstate coming after I let my foot off the gas. Yesterday was the second time it did it. Afterwards, when I was rolling back home through the neighborhood, I was coasting over some speed bumps and the car died. Check engine light came on. That was the first time it has ever stalled. Pulled code 31 which said it could be related to the AFM.

My husband heard the backfire yesterday and said it could be part of the break-in, although we both felt the stall was a little troubling. The car always starts right up and runs very strong. It did so again right after the stall. Prior to the rebuilt, this Supra NEVER backfired. My Supra before this one never backfired. I washed the car yesterday and did not find any oil on the bumper over the exhaust.

I need to do more clean up on the engine bay, and I was going to pull and clean the K&N and check all the hoses. I will check those spark plugs too.

Any other thoughts or suggestions?

 

[tlo86]

have you tried a known working afm just for giggles? wonder what a/f ratio you are running

 

[hvyman]

http://www.cygnusx1.net/supra/TechTips/engine_error_codes.aspx

Sounds like bad afm or wiring.

 

[ZoomZoomZoom]

http://www.cygnusx1.net/supra/TechTips/engine_error_codes.aspx

Sounds like bad afm or wiring.

Yea, thats the Cygnus reference I was using.

The car tried to stall again the next day, but just that morning. That afternoon it ran great. I went ahead and parked it. The AFM may be shot. I have a K&N, and some say those oiled filters can mess up the AFM. The AFM is old. I've never replaced it.

Got new IC, new pipes, new Apexi dry filter on the way. Will check all the vacuum hoses first. I will try all this first (it needed it anyways) and I will also hunt down an AFM along the way just in case.

thanks!!

 

[hvyman]

Ya k&n filters are no good. esp for the afm.

 

[ZoomZoomZoom]

Ya k&n filters are no good. esp for the afm.

A few years back everyone said that k&n's were great, they were the way to go, blah blah blah. So are they not good for any car? or is it just the sensitivity of the AFM in the sups?

 

[suprarx7nut]

A few years back everyone said that k&n's were great, they were the way to go, blah blah blah. So are they not good for any car? or is it just the sensitivity of the AFM in the sups?

The oil used in the K&N means it's not a good filter for any car using an air meter with any element that is sensitive to coatings. The 7MGTE is certainly sensitive and a K&N is a bad match for it. If you want an aftermarket filter I'd suggest AEM Dryflow or Apexi Power Intake. The will probably filter better than the K&N and will leave your AFM cleaner without any oil residue.

7MGTE AFM is optical-based and uses a light sensor and mirror to detect flow. Clever design, but it must be kept VERY clean. Even AFM cleaners will damage it.

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=FI&P=96

Sounds like it might be time for a new AFM and a new filter.

 

[jetjock]

^ Great post.

K&N works so well they sell a sock "prefilter" to put over it when the air is dirty...

 

[ZoomZoomZoom]

I purchased the Apexi kit from Driftmotion along with DM's silicone hose to replace the accordian hose on the intake. I also checked all hoses along the way. So far, with this setup, no stalls. Haven't had it on the freeway yet to see if it still backfires, but this is promising..

Should I even attempt to clean the AFM, or just leave well enough alone?

 

[hvyman]

Leave it.

 

[ZoomZoomZoom]

Leave it.

Well, I posted too quick or I forgot to knock on wood or something, but the car stalled again. Pattern is, it stalls when temps get up to 85 degrees. Ran it like crazy in the morning, but after lunch the temps went up and I was barely able to get it in the garage. Pulled code 31. Luckily, Allen came over with his spare AFM and we compared them and swapped them. My afm cable doesn't "click" in anymore, so Allen installed the zip-tie mod. That evening the car ran great, but the temps had fallen. Now a cold front rolled through today and I will have to wait a few days to test it in hot weather. Hopefully I will know by the end of the week.

 

[Nick M]

Twice in its first 3,000 miles, I faintly heard a backfire. Both have been at high speeds on the interstate coming after I let my foot off the gas.

Muffler explosions, as Toyota calls it, only happen for one reason. I will give you a hint. It isn't because there is no fuel in it.

Afterwards, when I was rolling back home through the neighborhood, I was coasting over some speed bumps and the car died. Check engine light came on. That was the first time it has ever stalled. Pulled code 31 which said it could be related to the AFM.

31 is the AFM circuit. As already mentioned in this thread.

 

[ZoomZoomZoom]

Just a quick update:

Replacing the AFM resolved issues with stalling and backfire

K&N setup currently for sale!