Intermittent engine cutting out.. ???

[92snowmachine]

your car should run with the maf disconnected as long as you unplug it before you turn the key on. if it doesn't then you may have a fault with one of the sensors that the ecm uses to calculate airflow when it can't be measured through the maf. since it changes when you change the throttle position i would check your tps for glitches first.

[James Scott]

WELL.. . I replaced the TPS several years ago.. maybe 6 to 8 ??

If I hold the TPS in one position with gas pedal.. shouldn't it be a stable spot that the ECU can use to do that "temp" airflow determination. I mean.. if the TPS is faulty.. wouldn't it be at a certain position (no contact, change in resistance) .. or a very few positions. So, I should be able to get a stable RPM if I hold the TPS position constant.. at least at some positions.. right?

Thanks, Jim

[James Scott]

I was able to get the idle stabilized (with the MAF disconnected) after 30+ seconds holding the RPM above 2000! Every time I turned the AC (CC) OFF or ON .. It would take 30 to 60 seconds to stabilize again at the approximate normal idle speed values (600 to 800).

I will check the intermittent engine cutout tonight on the way home from work (MAF or not?) with the MAF disconnected. It'll be good to get that info!

Thanks, Jim

[James Scott]

YIKES!.. This CAR!.. You guys better start encouraging me again.. to resurrect this MONEY PIT.. yada.. Yada.. YADA!

Ok.. I drove home with the MAF disconnected.. It was searching for a stable RPM sometimes.. BUT, generally worked.. WITHOUT THE ENGINE SUDDEN DEATH SYNDROME! BUT, it would die at idle [oscillating between 500-900 RPM slowly.. then speeding oscillation.. until engine stopped (parked or stopped at long light)].

The bad news is.. I soldered the MAF.. reinstalled.. but now the RPM would sometimes jerk (die .. revive) quickly (rough running) especially at lower speeds.. during acceleration. [Didn't do like before?? No sudden death, but other dysfunction??] Worked good at 65 mph or higher.. drove a couple times at 80 to 90 mph.. very smoothly. BUT, at lower speeds .. even up to 60 mph sometimes.. a very jerky clunking (rough) or surging on/off would occur! Ironically, with the MAF in.. it would not die at idle now! Stable at idle!?

SO... I dont know what all this means??? ANY IDEAS?

Please lemme know if .. and how I can check TPS function.. and/or MAF function [anyone got an extra good one I could try .. for say $50 (+shipping to and fro).. ???]

Thanks, Jim

P.S. Wish I had a definitive defective part.. ?? SubaruParts.com has FREE S/H today! .. [$360 MAF? (Yikes!).. $235 TPS?.. Hmmm?]
P.P.S. Vacuum leak.. ?? Hmmm?

[92snowmachine]

if you have a voltmeter then you can easily check the tps. if not buy a cheap one and it will help you in the future. an analog one works best for sweeping a tps. backprobe the signal wire for the tps (go to fabric store and buy hat pins, they look like a T shaped needle) and slide it next to the wire into the connector. then attach your meter between it and ground. very slowly sweep the throttle open and closed several times. look for any glitches, sudden movements, or drops to zero. if all checks ok then your tps is fine. set it to spec with the throttle closed and move on to another possibility. one thing that can quickly check for a bad maf is to tap it with a flashlight (any object with some weight but won't hurt it) while the car is running and see if the rpm drops. doesn't always work but is easy to do.

[James Scott]

The crazy thing is.. that, now that I put back the re-soldered MAF, it idles very stable!!! [But, runs bumpy on slower acceleration???] .. With the connector (MAF) off.. it wud always die at idle after about one minute! I seem to have "traded" dysfunctions.. ??

Is there any way to swap MAF's with someone .. for money .. like I suggested? .. temporarily.. ??

I feel it's the MAF, but since it dint run great disconnected (surge/fade/rough sometimes, wunt idle right) must be sumpin else too .. RiGhT?

In short ..

Thanks, Jim

[92snowmachine]

go to the junkyard and grab one off a legacy. it won't work great but will work for testing purposes and probably cost less than shipping another maf.

another thought: run with the maf unplugged and the o2 unplugged, then maf unplugged and o2 plugged in with tps unplugged, next maf unplugged and ect unplugged. testing with all of the different options could help tell you something. that would basically give you some information but probably not make the care driveable.

[James Scott]

OK.. REALLY! How cud the resoldered MAF NOT do the sudden death syndrome now.. BUT the car now accelerates very jerky, especially at low speeds.. ???

It would seem to be a TPS problem.. since it's apparently a low position section on the TPS slide..

BUT!!! .. WHy wasn't it doing THIS before the apparent MAF problem..??(KISS - Keep It Simple Stupid - tells me .. very very VERY unlikely that a TPS wud go bad JUST when I resoldered/fixed the MAF!)

Have the laws of physics and common sense been suspended? .. OR IS THAT YOU .. ALAN FUNT..??? .. IS THIS CANDID CAMERA!!!???

Thanks, Jim

P.S. So, U2 think it's unlikely I'd have the TPS go bad right when the MAF started "working"? In other words, you think the MAF is still malfunctioning differently.. even tho after re-soldering, it doesn't do the temporary sudden death syndrome now?

MAYBE the MAF is WORKING POORLY AT LOW SPEEDS.. BUT works OK at higher speeds.. . MAKE SENSE.. ??? Even tho it was failing differently before.. ? .. OH WELL??? OOPS!.. except it now idles perfectly! Ha!

[icingdeath88]

Try cleaning the MAF using MAF cleaner (should be findable at most auto parts stores, I think). You were careful not to touch the element while you were handling it, right? Maybe one of the points that you soldered isn't making a good connection, or it isn't plugged in quite all the way or something. Is the ECU throwing any codes?

[THE NEW GUY]

sometimes a failure is a mix of many irregular condtions.
If the engine dies after one minute working wihtout the maf, and the TPS is ok, and the idle valve is ok, then you have a vacuum leak or bad auxiliary idle valve.
Did you try overriding the auxiliary idle valve with the long nose plier?

[James Scott]

I haven't had a chance to remove TPS and check resistance smoothness.

It just is crazy that this "apparent" TPS problem (?) of jerky acceleration at low speeds.. wud occur suddenly after MAF fix!

IT DINT DO THIS EVER BEFORE MAF FIX!!!

I'll do the TPS check soon.. just Bcuz.. . BUT, seems it must be MAF further malfunction.. ??

Thanks, Jim

P.S. Yes, I dint touch the MAF sensors.. and YES I did clean those sensors with MAF spray cleaner also..

P.P.S. I soldered all 8 points thoroughly.. Doubtful one is inadequate.. Possible solder heat damaged a component??

P.P.P.S. Ya know! I haven't checked for codes yet! Obviously my MAF disconnect will cause a CEL.. I saw it on THEN. Can I check the codes without a meter??

[James Scott]

Originally Posted by THE NEW GUY

sometimes a failure is a mix of many irregular condtions. YES, but these were NOT coexisting.. THAT wud explain this. BUT, only started crappy jerky acceleration AFTER MAF fix!
If the engine dies after one minute working wihtout the maf, and the TPS is ok, and the idle valve is ok, then you have a vacuum leak or bad auxiliary idle valve. Yes, it did die when disconnected, but WORKS FINE NOW..
Did you try overriding the auxiliary idle valve with the long nose plier? .. SO.. How cud aux idle valve figure in.. ??

Thanks, Jim

[92snowmachine]

if your car isn't obdII then you can check codes by jumping the connector in the driver kick panel. if i remember correctly, stick one of the blue wires into the socket on the black connector in the top row just left of center when you hold it with the notch side up. it does sound like you may have a combination of problems that is creating some weird symptoms. i just tossed out the tps as a possibility based on the fact it was dying when the maf was unplugged, and it's one of the easiest things to check. you don't really have to take it off the car. if the maf intermittently makes a bad connection then the ecu has to switch to speed density to calculate air flow on the fly but it could be many other things. when my maf went bad i did the resolder and it didn't help but changed the way it acted a little. i took it apart after getting the new one and the hot wire was bent up, i presume from all the k&n oil and dirt from the previous owner.

[James Scott]

Ya know.. I replaced the TPS years ago (2003??? - haven't checked receipts yet) when trying to fix another impossible situation.. Ha! Then, the car would run rough at startup.. rarely later at high speeds.. checked coils, injectors, TPS... eventually added multi-ground post on battery.. bought coil pack, which never improved function regardless of which cylinder location it was placed.. replaced TPS .. sorta slowly got better! .. YIKES! TPS checked OK as I remember.. but replaced outta frustration!

Anyway.. I was thinking the "NEW" TPS shudn't go bad.. BUT, if it was 2003 when I replaced the last one.. then it was 8 years old (1995 SVX).. Now it's 8 years from 2003.. SO, maybe it's reasonable.. for the built-in failure rate.. for the 2003 part to fail .. 8 yrs later in 2011! .. ??

Thanks, Jim

[THE NEW GUY]

Jim, now that you have reconnect the maf, how high are the rpm at idle?
if it is over 1000 rpm when the car is hot, then I would say you have a vacuum leak or the axiliary valve does not close properly.
Jose.