1984 porsche 944 explosions
#1
1984 porsche 944 explosions
Any help would be appreciated...car turns on fine in the first turn of the key.. it idles fine but then once you press the gas it stutters and then does an explosion in the intake j boot... everything involving the fuel is new(fuel pump, filter, injectors, fuel, fuel pressure regulator ).. also anything involving the spark is new too (coil, rotor, distributor, plugs). My speed and reference sensors are new too...check every line and fixed for a vacuum leak and made sure all lines are routed correctly...
Hers a video of what's happing
This is what is coming out the exhaust
Hers a video of what's happing
#2
Rainman
Rennlist Member
Rennlist Member
that is classic backfiring typically caused by running lean.
if it idles ok then the idle switch is probably good, so since it happens when you touch the throttle i suspect your AFM may be screwy.
also, your timing/balance belts are WAY too tight based on the sound in the video.
if it idles ok then the idle switch is probably good, so since it happens when you touch the throttle i suspect your AFM may be screwy.
also, your timing/balance belts are WAY too tight based on the sound in the video.
#4
#5
that is classic backfiring typically caused by running lean.
if it idles ok then the idle switch is probably good, so since it happens when you touch the throttle i suspect your AFM may be screwy.
also, your timing/balance belts are WAY too tight based on the sound in the video.
if it idles ok then the idle switch is probably good, so since it happens when you touch the throttle i suspect your AFM may be screwy.
also, your timing/balance belts are WAY too tight based on the sound in the video.
that's what I though too, so I bought another AFM used, and the same thing, but what I just notice is that it has different part number.... My original is :0280202028
The "new" one is 0280202064
I don't know if the one I bought is actually from a newer Porsche and that's why its not working right either...
I also thought that some belts sound to tight, turns out the old owner took it to someone to get them done but I doubt that they have that 700$ tool to set the tensions right... I feel like doing it my self but I don't want to spend 700$ on one tool...im wondering if the tool 920Xv6 by ArnnWorx Specialty Tools is a good replacement? 165$ isn't that painful to spend on 1 tool that I will only use it for one car.
#6
Race Car
that's what I though too, so I bought another AFM used, and the same thing, but what I just notice is that it has different part number.... My original is :0280202028
The "new" one is 0280202064
I don't know if the one I bought is actually from a newer Porsche and that's why its not working right either...
I also thought that some belts sound to tight, turns out the old owner took it to someone to get them done but I doubt that they have that 700$ tool to set the tensions right... I feel like doing it my self but I don't want to spend 700$ on one tool...im wondering if the tool 920Xv6 by ArnnWorx Specialty Tools is a good replacement? 165$ isn't that painful to spend on 1 tool that I will only use it for one car.
The "new" one is 0280202064
I don't know if the one I bought is actually from a newer Porsche and that's why its not working right either...
I also thought that some belts sound to tight, turns out the old owner took it to someone to get them done but I doubt that they have that 700$ tool to set the tensions right... I feel like doing it my self but I don't want to spend 700$ on one tool...im wondering if the tool 920Xv6 by ArnnWorx Specialty Tools is a good replacement? 165$ isn't that painful to spend on 1 tool that I will only use it for one car.
Get a volt meter set on 12v dc, find which wire responds to movement of the door. Key in run/engine off. Red lead on AFM sensor voltage (out to DME), black lead on any ground (one of the afm wires is bound to be a ground source) Record closed voltage and wide open voltage. With door at closed, slowly move door and make sure voltage increase is incrementally smooth and not eratic.
Report back after you run this test with both part numbers.
T
#7
Race Car
Yes, SO your output sensor voltage on an early car would be 0-12v and a late sensor would output ,5v (?) at idle and 4.5-5.0V at WOT, door open fully due to -0- resistance to 5V input.
At idle, strangely enough, both voltages could theoretically be close enough for DME interpretation to have decent mixture.
But at say 50% throttle (door opening) the late sensor on an early car would report 2.25-2.5V to DME while the early sensor on an early car should be 6V (1/2 of 12V system voltage).
The late sensor on an early car would be very lean.
T
At idle, strangely enough, both voltages could theoretically be close enough for DME interpretation to have decent mixture.
But at say 50% throttle (door opening) the late sensor on an early car would report 2.25-2.5V to DME while the early sensor on an early car should be 6V (1/2 of 12V system voltage).
The late sensor on an early car would be very lean.
T
Trending Topics
#8
Don't have time to go look it up but I'm pretty certain early vs late AFMs report a different sensor voltage to the DME. Early works on 12v input to sensor and late has 5V input.
Get a volt meter set on 12v dc, find which wire responds to movement of the door. Key in run/engine off. Red lead on AFM sensor voltage (out to DME), black lead on any ground (one of the afm wires is bound to be a ground source) Record closed voltage and wide open voltage. With door at closed, slowly move door and make sure voltage increase is incrementally smooth and not eratic.
Report back after you run this test with both part numbers.
T
Get a volt meter set on 12v dc, find which wire responds to movement of the door. Key in run/engine off. Red lead on AFM sensor voltage (out to DME), black lead on any ground (one of the afm wires is bound to be a ground source) Record closed voltage and wide open voltage. With door at closed, slowly move door and make sure voltage increase is incrementally smooth and not eratic.
Report back after you run this test with both part numbers.
T
I just decided to got another used one but with the right part number the :0280202028 and it still did exactly the same...I did the test then and I got
Closed
Input: 10.56v
Output: 188.9mV
Full open
Input: 10.5v
Output: 8.98v
And at idle I get .540v
#9
Race Car
Is it possible somebody replaced the DME with a late version...?
EDIT -
Just had another though about this, have you done anything to rule out that the cat might be plugged....?
Passing just enough exhaust to allow smooth idle but restricting exhaust at all throttle openings.
What my friends in exhaust business do is drill two small holes for a rubber tipped pressure gauge to read, one before cat, one after, and compare readings to look for excessively high pressure before the cat compared to after. You can always just weld the holes closed if converter checks out ok.
T
EDIT -
Just had another though about this, have you done anything to rule out that the cat might be plugged....?
Passing just enough exhaust to allow smooth idle but restricting exhaust at all throttle openings.
What my friends in exhaust business do is drill two small holes for a rubber tipped pressure gauge to read, one before cat, one after, and compare readings to look for excessively high pressure before the cat compared to after. You can always just weld the holes closed if converter checks out ok.
T
Last edited by 951and944S; 06-16-2017 at 03:06 PM.
#10
Is it possible somebody replaced the DME with a late version...?
EDIT -
Just had another though about this, have you done anything to rule out that the cat might be plugged....?
Passing just enough exhaust to allow smooth idle but restricting exhaust at all throttle openings.
What my friends in exhaust business do is drill two small holes for a rubber tipped pressure gauge to read, one before cat, one after, and compare readings to look for excessively high pressure before the cat compared to after. You can always just weld the holes closed if converter checks out ok.
T
EDIT -
Just had another though about this, have you done anything to rule out that the cat might be plugged....?
Passing just enough exhaust to allow smooth idle but restricting exhaust at all throttle openings.
What my friends in exhaust business do is drill two small holes for a rubber tipped pressure gauge to read, one before cat, one after, and compare readings to look for excessively high pressure before the cat compared to after. You can always just weld the holes closed if converter checks out ok.
T
#11
Race Car
no I checked the dme and its for my early car, plus I also had a wrong afm for the newer one but still didn't change anything...so I bought another on for my early car but still same problem... I don't have a gauge so what I did is just disconnect the exhaust from the cat for free flow and no change same thing
T
#12
yes that's exactly where...I left the exhaust manifold on, and disconnected at the flanges...bolts were rusted on but I got it off..
#14