sputtering and jerky idle

[mranderson]

Hey guys, i think this is my first post, i have been here for a while but just as an onlooker. You guys are very good at helping out!! so here we go

Just about every time i run my car now, not long after a get going it starts sputtering a little. It is only noticible on low rpms. When i let it come to an idle it begins to jerk quite bad. Like the whole car shakes from the jerky idle. then once i give it gas again it continues on into a sputter. I dont know a whole lot about cars and such but i really need to get this fixed. I recently replaced the spark pulgs to see if that had something to do with it, but runs the same. Could it be the fuel filter or maybe the oxygen sensor?

Thanks very much for your help.

hmm same problem for me

started after i changed sparks

happens sometimes due to bad quality petrol... but it was not my case

u can try unplugging the injectors 1 by 1 and see if any gives different result.. i.e. if u unplug an injector and car acts better then with others u ll know thats the faulty cyllinder and u try to find whats wrong there

most likely its whole petrol system which is faulty (my case)

strill have not figured out what it is exactly....

when did it start to happen? what have u done?

if we find similar things which dont look good we can narrow our search i guess...

the other guy here with similar problem said that it turned to be fuel pump and pressure regulator... dont think it is my case as i had bad iddle for 3 months, and pump still pumping up ... so something else ...

outa curiosity, are ur vacuum hoses new? is PCV good? hose from PCV back to intake, is it good?

Sergi

[immortal_suby]

Weird - my wifes car is doing the same thing. It happens each time on a cold start it runs fine and then after driving for about a mile she comes to a stop and it sputters. It feels like it is missing on one cylinder. I tested it and got the same. I put it in neutral and it still shook and sputtered. I shut it off and restarted it and it was still sputtering. Then once you get going it goes away and doesn't return.

If she lets it warm up to operating temp each morning by idleing in the driveway before she leaves it does not have the problem.

Maybe you're both visiting the same bad gas station in greenville?

Could this be a faulty temp sensor?
Have not had a check engine light yet.

[mranderson]

ok, it just started randomly about 3-4 weeks ago. It does fine if i let it sit and warm up for a "long" while. So could it not be the oxygen sensor or the fuel filter (as i know thes have not been changed in a while). I will try the injectors and see what happens.

seems like we have come across another seemingly common problem of some sort.

[Motorsport-SVX]

did the same thing last Spring for about 6 weeks....
then just went away....didnt change a thing.

(even posted something about it last yr)

then 3 months later, came back for a few weeks
and then went away again....
still, only thing that was changed was fill ups at the
gas pump...

checked the plug that goes into the MAF sensor
to make sure it was in all the way....
its still running fine....If I dont get a check engine lite
Im not going to try to fix it anymore and just deal with it
for the minute or so it happens.

It also happened to mine awhile back. I guessed on it possibly being bad gas or moisture getting in there from the wet conditions we've been having. Not to difficult to do with the tank opening being positioned the way it is. I added a bottle of dry gas to clean out any water. It did the trick.

ok how it does for me:
it works fine for first couple of minutes then starts to miss. Like on the traffic light, on iddle it works fine for couple of seconds, then misses the combustion (maybe all 6 cyllinders misses 1 cycle, i dunno) and then forks fine for another few seconds. Ie revs drop down to 400-500 for a half of second or soemthing. When i accelerate from stand still, it goes really bad in the beginning, like poor acceleration and it goes slower/faster. but once its on the second gear and revs are 2500 then it goes fast.

ok i ve noticed that with 98 petrol things are not that bad at all but with 91 it s just disaster. So it depends on petrol somehow.
Also if it jerks on iddle and i press accelerator so revs go up to 5000 or something, then its find for next 10-30 seconds. Injectors were cleaned twice in last 2 month...

well maybe it is the fuel pump...but still does not loook like it...

about themp sensor. there was a post not long time ago. Dude was explaining the simptoms of bad temp sensor...


cheers
Sergi

seems like i type faster then i think....

*works fine*

[Motorsport-SVX]

Originally posted by 6evil9
ok how it does for me:
it works fine for first couple of minutes then starts to miss. Like on the traffic light, on iddle it works fine for couple of seconds, then misses the combustion (maybe all 6 cyllinders misses 1 cycle, i dunno) and then forks fine for another few seconds. Ie revs drop down to 400-500 for a half of second or soemthing. When i accelerate from stand still, it goes really bad in the beginning, like poor acceleration and it goes slower/faster. but once its on the second gear and revs are 2500 then it goes fast.

ok i ve noticed that with 98 petrol things are not that bad at all but with 91 it s just disaster. So it depends on petrol somehow.
Also if it jerks on iddle and i press accelerator so revs go up to 5000 or something, then its find for next 10-30 seconds. Injectors were cleaned twice in last 2 month...

well maybe it is the fuel pump...but still does not loook like it...

about themp sensor. there was a post not long time ago. Dude was explaining the simptoms of bad temp sensor...


cheers
Sergi

It has nothing to due with Octane being 91 or less.
All we can get here in Az and Ca is 91 for super unleaded
(there are a few stations with 100 octane race fuel)
But Ill I use is 91 Unical 76 and mines still intermittent
Luckily for me its been gone for a few months.

[Motorsport-SVX]

I think it could be is the Mass Air Flow sensor itself
whether it be an electronic glitch, one constant we
all have though is it happens between start up
and the engine gets to operating temperature, then they
are fine for rest of the day for me.

[mranderson]

so it is or is not possible for it to be the oxygensensor or the fuel filter??

[Motorsport-SVX]

Originally posted by mranderson
so it is or is not possible for it to be the oxygensensor or the fuel filter??

if it was an 02 sensor it would usually throw a check engine lite AND doubt it would go away after a few minutes..

A dirty fuel filter would give you problems all the time too, it wouldnt just go away after it warmed up.
Couldnt hurt to change it though if its been over a few yrs.

[immortal_suby]

I'm thinking it is sensor related. The car runs fine for a little while from a cold start - probably while it is still running in default open loop mode. Once it has run long enough to go to closed loop (but not long enough to be warmed up fully) it starts the sputtering. Once it is warmed fully it runs fine again.

I agree - probably not fuel filter or O2 sensor. Neither would make it sputter/ misfire in these conditions without other symptoms.

I can swap MAF sensors between my wifes car and mine to try to diagnose.

[Motorsport-SVX]

Originally posted by immortal_suby
I'm thinking it is sensor related. The car runs fine for a little while from a cold start - probably while it is still running in default open loop mode. Once it has run long enough to go to closed loop (but not long enough to be warmed up fully) it starts the sputtering. Once it is warmed fully it runs fine again.

I agree - probably not fuel filter or O2 sensor. Neither would make it sputter/ misfire in these conditions without other symptoms.

I can swap MAF sensors between my wifes car and mine to try to diagnose.

I have an extra MAF sensor, but since my problem just went away outta the blue, I left it alone....
Let us know what you find out thanks

[James Scott]

Now your all admitting your dirty little secrets! I started a thread last November about MY intermittent problem. It was fairly consistent (with rough idle for a few minutes after startup [had to be sitting for hours first], and sometimes high-speed shuddering [the car shook at speeds of 60 to 80 mph - the Dealer tried to sell me a transmission {you guys said don't diagnose AT until engine running good - glad I heeded that advice}]). The high speed shuddering was later diagnosed by me as the same engine performance problem >> When the shuddering occured on the country roads near my job, I would stop briskly >> and lo and behold >> THE SAME ROUGH IDLE!

I never really diagnosed the problem. Beav suggested cleaning the TB and AIC. I did that, but no change. I removed the Tornado air fan gizmo I'd bought off the TV ad which swirls the air just past the MAF sensor. I checked and sprayed the MAF harness (and every harness I could find, including ECU harnesses and those in the engine near ignitor and harnesses to engine wiring on right side of rear of engine (to coil wires, injectors, and sensors). I ran many continuity, voltage and ground checks on many harness terminals according to OEM shop manual>> couldn't find the problem! But, in about May, almost suddenly, the problem diminished and has been very infrequent until just recently! This must be related to some temperature thingy!! The first thing I replaced (after spark plugs and fuel filter - no change), because I thought it was temperature related, was a temperature sensor (no change), the second was oxygen sensors (on a whim! - no change). Needless to say, this has been frustrating!!! Especially, now that it is returning more often (gettting colder now here!). This is the first time I've heard that several of you have a similar problem. On the one hand, it's encouraging to be with kindred spirits. On the other hand, none of us have collectively been able to get a handle on this - How depressing! We must band together and look up!

Recently, a mechanic friend from work had an intermittent problem like this and it turned out to be a fuel pump! I got a gauge like he used, but it's hard to hook up while driving. The one time I hooked it up at home, the pressures were good >> 26 to 30 psi with the regulator functioning and 34 to 38 psi with the vacuum hose off the regulator. I need to rig the gauge so I can see the gauge thru the windshield while driving. The real test is checking this pressure while the rough idle (or shuddering) is taking place!

One time, I was able to pop off different injector connectors during this temporary (2 to 5 minutes for me) rough idle to find that one cylinder (driver rear) made no difference. AHA! I thought! But I replaced both the coil pack wire AND the injector without a change! That took a lot of the life out of me! I really thought I had it!! Then later, I popped off the injector connectors to find that ANOTHER (different - middle passenger side) didn't make a difference when removed (?).

It's dangerous to not be able to count on a good response from our SVX's when starting out in the morning (or eve). Mine also responded during this intermittent "cold" period often with a very unresponsive throttle (the car kept going, but no response for a few seconds up to a minute) even if the idle was not rough (?). I cleaned the TPS with electrical solvent as instructed here (no change), but couldn't quite bring myself to buy a TPS (or fuel pump, or MAF, or ECU for that matter)!

PLEASE DON"T GIVE UP GUYS! I THINK WE'RE CLOSE!