K8 Hesitation/Stalling Issue

[TheNelson]

1993 MX3 with K8:
http://www.tigerjapanese.com/index.php? ... &Itemid=26" onclick="window.open(this.href);return false;

After the engine swap these are the parts that were used from the original motor:

VAF
TPS
IAC
Throttle Body
Disty
Crank Sensor
"Valves" on back of intake manifold
EGR solenoids
Fuel regulator solenoid

I have tested or replaced the following items knowing now or believing they are in operational condition:
TPS
Neutral Safety Switch
EGR
Both O2 Sensors replaced

The timing is good, the quality of the fuel should be good.

The car starts right up and idles nicely but, regardless if it is warm or cold (more so when warm though) the car will hesitate then stall out. If I take my foot off the gas pedal and let it "cruise" or idle the engine will run fine.

When this is happening and I give it ANY gas the engine stalls, in the same moment when I let off the gas pedal the engine sounds normal again.
Kind of like it's acting backwards - gas pedal depressed: nothing, gas pedal let out: normal idle/cruise rpm

Often this problem causes the car to stall. It is 100% bound to happen every time I drive the car, regardless if I drive it 2 blocks or 10 miles.

**Also: When coming to a stop sometimes the car will stall.

I'm considering getting a used VAF from another MX3 to test with but I am unsure if that will help.

[Daninski]

Kinda sounds like a vacuum leak.

[mikeinaus]

my car did similar things when i first got it. i never replaced anything and it just randomly fixed itself one day. im betting its something to do with your vaf.

but it could also be caused by a massive vacuum leak...

[TheNelson]

Thanks for the advice guys.

With the car at idle I tried misting some carb cleaner over different parts of the engine that may be prone to leaks and nothing happened there.

Because the car didn't come with a fuel pressure regulator solenoid originally I tried bypassing the solenoid with straight vacuum hose and that didn't help anything.

Also, when it stalls I can not start it back up immediately. Sometimes I have to wait up to 10 seconds or so and it fires right up strong, as if it's "waiting" for something to change or reset in the computer... I don't know.

I'll be replacing the fuel filter tomorrow or the next day so that should narrow down one more possibility.

[TheNelson]

Also, the problem seems to be getting worse. I think I will wait to try again until the fuel filter gets replaced.

The car sat for 2 years before I swapped the engine.

[K_I_R_K_S]

Sounds like air intake pipe might be torn or broken....
Also plug leads can do this...

[TheNelson]

Today I swapped out the fuel filter and not a whole lot changed.

Now I can at least drive the car, but the stalling out problem is still there. If I attempt to push the gas pedal more than 1/10th of its travel the motor dies.

If I "feather" the gas I can get around, but when I try to floor it I lose combustion.

[mikeinaus]

its probably your vaf...
http://s27494.gridserver.com/phpBB3/vie ... 56&start=0" onclick="window.open(this.href);return false;

take your vaf off your intake, turn the ignition to on (dont start the car) and play around with your volt meter on your vaf wires. i dont know what wire is which but there should be a ground wire, a power wire and a signal wire and maybe one other. you want the signal and ground wires. im not sure of what voltages your looking for but there should be a base for when the vaf is closed(idle) and fully open(WOT). pushing the valve on the vaf open should make a linear voltage increase until it reaches the voltage at fully open. judging by your symptoms im guessing your vaf is completely fucked and is giving totally inaccurate readings. if you play with the valve a few times it should give you the same voltage for the same % open every time. if the readings are not consistant or within spec (whatever that is) your car will flood itself.

edit: looks like the readings should be fully closed .5V and fully open 4.5V

found this for what wire is which if it helps at all..

alldata spesifies term a & b .
thats the two on the throttle body side or the out put of the maf.
d&e are for the iat sensor
& c is ground

abcde
big end small end

[TheNelson]

Just did a fuel pressure test and it reads 32psi at idle.

Is that normal?

Also tested both 2-wire coolant sensors on the passenger side of the engine. They both read right around 25K ohms. My information says that is way too high. Can anyone confirm?

[TheNelson]

its probably your vaf...
http://s27494.gridserver.com/phpBB3/vie ... 56&start=0" onclick="window.open(this.href);return false;

take your vaf off your intake, turn the ignition to on (dont start the car) and play around with your volt meter on your vaf wires. i dont know what wire is which but there should be a ground wire, a power wire and a signal wire and maybe one other. you want the signal and ground wires. im not sure of what voltages your looking for but there should be a base for when the vaf is closed(idle) and fully open(WOT). pushing the valve on the vaf open should make a linear voltage increase until it reaches the voltage at fully open. judging by your symptoms im guessing your vaf is completely fucked and is giving totally inaccurate readings. if you play with the valve a few times it should give you the same voltage for the same % open every time. if the readings are not consistant or within spec (whatever that is) your car will flood itself.

edit: looks like the readings should be fully closed .5V and fully open 4.5V

found this for what wire is which if it helps at all..

alldata spesifies term a & b .
thats the two on the throttle body side or the out put of the maf.
d&e are for the iat sensor
& c is ground

abcde
big end small end

Thanks for this. I tested the VDC at the D & E pins and I get a linear sweep in voltage from 1.2vdc up to 4.8vdc.

This does not seem to be the issue unless it is the wrong VAF for the car. It is the one that came on the car, but should I be using a different one now that I have the K8 in the car?

[TheNelson]

Pulled the spark plugs out a minute ago to check gap on them. Gap was set at around 34 and I regapped them to 44.

This is what they looked like though:



I reset the timing and got it spot on at 10 degrees. The car starts and idles great. No high idle and no surging.

Still have the same drivability problem.

[TheNelson]

I'm going to do a compression test on it today then start unhooking sensors.

[mikeinaus]

i dont know man. thats exactly what mine was doing. my car had sat for a year and a half before i got it. at the time i figured it was because of crap in the gas tank clogging the fuel lines. i put in a few bottles of injector cleaner/octane booster + high octane fuel and burned threw a few tanks and it seemed to fix itself. just keep burning gas and hopefully youll get lucky like i did. you could try replacing the fuel filter sleeve thats on the fuel pump in the gas tank and have a look for any debris while your in there.

[TheNelson]

Compression numbers.



What should the K8 compression numbers be?
Will the J-spec engine have the same as US-Spec?

[Ryan]

Thats not bad compression. A little low, but fairly even, which is the most important part.

From factory it was 193. rebuild is 140.

K8ZE will be the same as USDM K8