haulsballs

so what resistance should the temp. sensor read, and at what temperatures? i would love for it to be something other than the welt chips, i miss 15 psi! the fuel pressure is fine. i had a gauge taped to my window while my friend watched it. it was well within spec, not even on the low side. i figured it was more of a timing deal because it would still ping with the welt chips in, and the shim out. thats enough fuel for 15 psi, but only giving the motor 9. and thats low because i had a vacumm leak, thus bleeding off pressure and making it even richer. it was so fat, that i had minimal throttle, and wot. the midrange was total crap. it would hesitate, buck, and more importantly, still detonate under wot. thanks for your help.

take care,
brian

Jaak Lepson

Brian ... see below. I had posted it over a month ago. Hope this helps.

Jaak Lepson

Folks ... I have the same problem with my stock 86 951. It turns out the temperature sensor in the AFM is shot as well as the meter has sporatic
voltage spikes when the throtle was opened. I have ordered a new one from the dealer. When the engine was cold a 3 cylinder Dihatsu would run circles around the car and when the revs where below 3500 RPM it lags a bit until boost came on.

I also checked the Lindsey site and they also confirmed that the "air temperature" sensor was vital for hot and cold running. Maybe others can also confirm/deny this. Anyway, this looks like what my broblem is and will report back once it has been fixed. I have replaced the engine temperature sensor, plugs, checked for vacuum/exhaust leaks e.t.c.

Shade Tree Mechanic Test Procedure

To test make a few jumpers to connect pins 3 and 4 from AFM to cable socket. Terminal 3 will be 5 VDC and 4 the negative. The air filter must be removed and use something plastic to open the valve. From terminal 2 to ground you should read 250 - 260 mVDC. Slowly open the air flow valve and
the voltage raise should be smooth (mine was erratic = faulty) and fully open should read close to 4.5 VDC. Also, any K&N type wet filter may leave oil deposits inside the AFM. Mine looked a bit wet ... may cause a problem; unsure as to how to clean it up.

The temperature sensor can be checked by placing an ohm meter on pins 1 and 4 on the AFM socket. The readings should be as follows:

0 degrees C = 4400 to 6800 OHMS

15 to 30 degrees C = 1400 to 3600 OHMS

40 degrees C = 1000 to 1300 OHMS

Hope this helps.

pk951

I know that my swiss had a set of welt. chips and on the dyno at 13.5 psi his af was 10.5 very rich,so had he been running 15psi his af would have been closer to 12 or12.8. with those chips he never experienced any detonation problems.

Jaak Lepson

PK951 ... I now own those chips! No problems with the car!

Jaak Lepson

pk951

MY SWISS car would pull to 260km no problem with those chips.

haulsballs

so is the air temp sensor available seperatly, or is it integrated into the air sensor?

take care,
brian

Jaak Lepson

Brian ... it's part of the AFM. If it is faulty you will have to replace the whole unit. I did and got great performance improvement.

Look around. You may find a good used one.

Hope all goes well,

Jaak Lepson