dutchcrunch

oh, not a violent buck but just a little hesitation till the system catches up. as a matter of fact on my way home this morning i tried it again and my toyota had this momentary pause and then caught on. maybe yours is worse than i am tryin to explain. as i am going down a steep hill and i let off the gas for lets say 5 seconds and coast, as soon as hit the gas it has that little pause, maybe for like a half second, you have to really pay attension or you will miss it. hope you get your car fixed. could you have a vacumm leak? there is a small elbow when i was working on mine that was cracked but you would not know till you removed it. i know the fuel pressure regulato has a vacumm line going to it and its also a small elbow and it too was cracked, i found this out when i took the whole induction system off.

the fuel regulator is buried in the middle of the engine. you should take a look into this. the part was cheap a couple bucks or so.

Heirsh

Yeah Dutch,

It is a new fuel pressure regulator, but when I changed it... The car runs different. I can't say exactly how, but it is different. Not bad or good, just something different. Did not affect this hesitation/mixture/whatever problem at all, though.

I am still looking at the afm as the culprit, but until I just pull the trigger on a new one, or find someone who's willing to loan me a known good part, I'll never know. I have adjusted my driving to the problem. Too bad cruise can't adjust itself.

/shrug

dutchcrunch

did you look at that rubber elbow that goes to the fuel regulator?? mine was cracked. i will go and look at my car in the next coulple of days and see whats what. how come you cannot take out the afm and put a analog ohm meter on it and move the flap and see if there is any fluxuation or does the needle swing smooth.

Heirsh

Dutch,

My elbow is fine. In fact it is new b/c when I checked it originally it was shot. I thought at the time I had found the problem, but no.

I have checked the afm with an ohmeter several times. It seems ok, but I have no way to check its calibration, only that it seems linear. That doesnt tell me if the linear relationship between angle and output voltage is correct. Originally I found it had grooves worn in the track so i bent the arm to run on fresh track hoping this was the problem. It didn't help, however. I keep wondering if that area of damaged track is causing a different resistance in that area thus throwing off the voltage output. It is an unknown I have not, as of yet, been able to rule out.

The only "fix" I have found so far is pulling the ox sensor. This, of course, is just ignoring the problem so I don't run like that.

dutchcrunch

there is another at the trottle body and there is a Y tube in the back of the throttle body too that was shot. it has a small rigid step down tube on it. when i say trottle body i am referrring to the unit that the trottle cable hooks to.

it suck when you have to shot gun thing and hope it fixes it, can get exspensive. but you mentioned that the afm tracks were worn and you repositioned the slider. seems like if it was worn you have been cycling that thing quit abit to wear like that. i wonder if that track has a given value like you said and even though you repositioned it the value of the track has changed and therfore repositioning has not benifit you. i can see that point you made. well how many miles on that afm.

what i could do is give you some static values if you give me the pins on yours in relation to mine and see if the numbers match.

i am not sur on porsches but i had a camaro,( here we go again) and i had to spice into the harness and it gave me an actual voultage at closed and wide open position, the car was not running just had the ignition on. is there a test that like that for porsche.????

i think the afm has seen its day. you know that electronic stuff is so sensitive and static test vs live and running are two differnt things.

let me know if i can give you some values off mine, i will do that for you.

warmfuzzies

not sure if htis has been covered, and it's not really ananswer, but more of a suggestion.

IIRC when in gear and coasting, the brake and clutch are sometimes monitored for position due to emissions regs, so in effect they cut fuelling, now I don't know if this is related or not, but checking any microswitches here maybe a long shot?

Kevin

Heirsh

I was recently loaned, by a fellow Rennlister, a known working AFM. I ran it for a couple weeks and my car was absolutely flawless. My car has always had good power, but the AFM not only cured this downhill power loss problem (more accurately a slight throttle power loss problem) it also improved the drievability at small throttle imputs.

I calibrated my afm to his, as best I could, and have helped my issue. I won't bore anyone with the actual test procedure, but I measured the flap opening and the voltage output of his and mine. (a more accurate way would have been to measure sfm, but I dont have the ability) I then moved my wiper to give the same readings as his. It helped mine quite a bit, but it hasn't cured it 100%. I will continue to tinker with it as a new afm is over 1g and a maf conversion is over 1.5g. Absolutely rediculous amounts.

I just wanted to put closure on this issue. It is my AFM that is causing this problem in my car. Even though I felt it was for sometime I wasnt willing to pop the amount it would take to test.

A big thanks to the person who helped me verify this. I would continue to bang my head on it if it wasn't for the loan of the AFM. I can't thank you enough.

dougn

finally some answers.

BTW i discovered that opening the bypass screw in the AFM greatly improved my low speed drivability and throttle response.

i don't think i had as bad a hesitation problem as some people decsribed here.

DarrylH

Well, at least I know if I get irritated enough to spend the ridiculous dough they want for an AFM that it'll likely fix the problem! Thanks for trying this. Some days, it drives me nuts. Other days, I shrug.

RichieRoo

Any further developments or verification on this would be good.

My '91 C2 Cab has exactly the same flaw described by Heirsh. On downhill sections or long,
throttle closed situations, gently reapplying the throttle results in a disconcerting loss of power.

The revs drop to idle for about 3 seconds, despite ever-increasing throttle input until close to WOT.
Engine then returns to normal operation.

Rich

boxsey911

I've had the hesitation problem when going down hill regularly in the past but hardly at all since I did the AFM wiring harness TSB fix.

http://www.ciborg.net/share/tsb%20wire%20harness.pdf

PaulW_964

Alright Richie fancy seeing you here!

I've notice the same issue with mine on two separate occasions. The first time I thought I was imagining it. I'll investigate Steve's AFM wiring harness TSB fix.

Cheers

Paul

RichieRoo

Hi Paul

Good to see you on Rennlist.

I did the wiring harness mod a good while back because of a different issue, so I don't think it's anthing to do with that unfortunatley.

I'm not going to get time to look into it this weekend. Keep me posted on any developments.
(Popping down to Porsche in the morning to pick up two cooling fan relays... but that's a different story).

Rich

92silver964

This happened to me this morning as I was ending a long decline (and with less than a 1/4 tank of gas). Fortunately, things recovered as the hill bottomed out and I needed to accelerate uphill. The other time it happened (same place) I thought maybe I had imagined it. But, since I stumbled across this thread at lunch today I now know it is a real issue. As I've read through the many posts, it still doesn't sound like anyone has a 100% positive answer though. At least I know I'm not imagining things!

garrett376

I think it's fairly clear it is an Air Flow Meter issue.