# Stutter on acceleration



## turbinepowered (Mar 19, 2007)

1982 Quantum, CIS Basic 1.6L. 
I have an odd stuttering problem on acceleration. With the engine hot, the car will occasionally shudder and stutter hard enough to jerk the entire car around while under acceleration.
Happen at highway speeds (during passing or accelerating to a new limit), manifesting as a short-lived heavy stutter that's felt through the body, then it smooths out and accelerates.
More commonly it happens while accelerating from a stop. Super gentle acceleration lessens the affect, but even moderate acceleration makes it shudder and jerk enough that it looks like I don't know how to drive a stick. Opening the throttle further makes it worse, but I have yet to actually stall the car; a few seconds of hard shuddering are all that it takes before it smooths. Tends to be fine in the rest of the gears at city speeds, but will occasionally give me a little shudder.
My initial knee jerk reaction is that I have a vacuum problem somewhere, but I'll submit to the wisdom of the CIS board to see what other options people come up with.
No electronics to oxygen sensor to it at all, and leaving the cold start injector unplugged causes no change. Issue doesn't occur while the engine is cold, or at least has not occurred while cold to date.


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## ny_fam (Apr 3, 2004)

*Re: Stutter on acceleration (turbinepowered)*

How is the timing -
Also check for Air leaks.
Have a high idle ?


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## Tom A (Oct 20, 2004)

*Re: Stutter on acceleration (ny_fam)*

You mean CIS Lamda, right? It isn't basic if it has an O2 sensor.
Did this start happening suddenly, or has it been gradually getting worse?
There should be a switch on the throttle body that is triggered when it gets to full throttle. Make sure it is works, and is in adjustment.


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## turbinepowered (Mar 19, 2007)

*Re: Stutter on acceleration (ny_fam)*

Idle sits at right around 800 RPM, and is rock solid ever since I finally fixed the o-ring in the idle bypass screw.
_No_ oxygen sensor to it, sorry about the confusion.
Problem was sudden in nature, it started this past Monday and has steadily become more frequent. Still not a common occurrence, but it's happening more often.
Not sure about the timing, but I don't have the tools to check it here; they're twelve hours away while I'm here in Chicago. 
Air and vacuum leaks, sounds like I'm hunting up.


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## Tom A (Oct 20, 2004)

*Re: Stutter on acceleration (turbinepowered)*

On CIS basic cars, full throttle enrichment comes from a vacuum connection on the WUR, but your problem being intermittent would be a very strange failure mode for a WUR. 
Anyone you can borrow a timing light from?
On Edit: Just curious, did you get gas last Monday? How old is your fuel filter?


_Modified by Tom A at 12:04 AM 5-11-2009_


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## turbinepowered (Mar 19, 2007)

Distributor is still firmly clamped down, even trying to twist it manually is only scratching up my fingers instead of budging the distributor. No guarantee that the timing is still spot on, but that's a good sign at least.
I'm at home now, I'll shoot it with the light when I get the chance.
The twelve hour drive home Monday went off with only an unrelated hitch; had water in my gas, so I sputtered and nearly-died at 6AM on I294. Scary thing that left me pissed off until some ISO-Heet and fresh gas fixed it. The oil leak isn't helping, either.








Only stuttered once on the drive home, and I was pulling anywhere from 65-75mph the entire time. Smooth power delivery throughout the throttle range, and my one stutter came about during a fifth-gear passing situation. One second of shuddering, then she lit out like a scalded cat.
Well, as much as a sub-90hp engine in a 2k+ pound car can light out like a scalded cat.








And no, I didn't get gas last Monday, I had about half a tank. Filled up just before I left on Wednesday night. Prior to that, my last gas purchase had been the previous Wednesday. I get good enough economy that I only really need to fill up once every week, maybe week and a half if I'm only commuting to and from work.

_Modified by turbinepowered at 9:34 PM 5-11-2009_


_Modified by turbinepowered at 1:40 PM 5-12-2009_


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## Longitudinal (Nov 13, 2004)

*Re: (turbinepowered)*

The car is supposed to be CIS-Lambda, but the PO (my PO, not turbinepowered's) converted to Basic because the Lambda FD had locked up from sitting. 
Kurt, I wonder if this has anything to do with the E40 you have put through it.


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## turbinepowered (Mar 19, 2007)

*Re: (Longitudinal)*

Possible, maybe kinda, but it's had several tanks of straight gas between the E40 tank and now. 
It's still happening, though I only get it after the car has either been run hard on a hot day (Was late for work the first time it happened) or some other circumstance has come up to make it toasty. My non-dash gauge says I'm not overheating, but I am running up around 215-220F post highway run.
Residual effects? I hope not, as that was part of why I was stoked about having the Basic fuel distributor, steel and ethanol mix, I could build a Premium/E85 flex fuel.


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## brandon0808 (Mar 19, 2009)

wait i think my car does the same thing sometimes. 
around right corners if i get on it it feels like either fuel or spark? gets cut. 
and sometimes if i accelerate from a dead stop hard it does it. the best way to explain it is how turbinepowered did. like you dont know how to drive stick. 
the weird thing is its hard to pinpoint/make it happen. it likes to do it around right corners or from a dead stop if i get on it at all. not every time. not even half of the time.it doesnt make sense..
my fuel pump thats in that black box under the car is noisy maybe thats it. i drive a 88 jetta gli 16v


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## lawtond (May 28, 2009)

*Re: Stutter on acceleration (turbinepowered)*

Wanted to revitalize this thread as I am currently having the same issues.
For me it happens very spuratically (spelling?). It is entirely NOT REPRODUCABLE on demand, which makes you look like a jack ass when u ask someone for help and cant show them whats wrong :S:S:S:S
For me it most often happens after I have exited the highway, lets say after a duration of 30km at 120km/h. I take the off-ramp, and can pull away from the stop light at the end of the off ramp but then about 1km up the road it will start to stutter. You can generally feel it in the pedal about 30secs prior to all kinds of embarassing hell breaks loose. The initial feeling is like a hesitation in the gas pedal, like it instantaneously becomes 'softer' then returns to normal firmness. When it does finally start "happening", in the truest sense, it is a VIOLENT jerking motion (hahah did not mean to write "violent jerking" but im keeping it cause i think its funny). It really seems like someone that doesnt know how to drive stick is trying to and having a really bad time at it! This happens even when the clutch in fully engaged! When I clutch out, I can maintain revs at any level but as soon as the clutch is re-engaged and a load is put on the engine... BAMN stuttering.
When it happens to me I generally try to limp to the closest parking lot, wait about 5 mins (smoke length) and it is good to go (for a while, the length of time it is 'good to go' is as mysterious as its origins). This leads me to believe that waiting and allowing the engine to cool might be what allows it to run properly...until it happens again(which may be product of engine heating back up). One should note, however, that is has happened in the winter but that was on the highway so the heat buildup could outweigh the heat loss to surroundings.
The shear magnitude of the stuttering/jerking/shuddering really makes you want to think its something mechanical but I can almost 99.9% rule that out. 
So far I have gone through all the bently ignition diagnostics and everything checks out. Changed plugs, wires, rotor, cap, ignition module, fuel pump relay and alternator. Also cleaned all ignition related terminals (i.e. coil terminals, battery terminals, etc...)
I have also taken the fuel pump out and it runs fine but that does not rule out the fuel system at all, still lots to check. I put a voltmeter inline with the fuel pump to monitor its level during the trouble but it does not seem to be the culprit, atleast power getting to the pump does not seem to be it. 
Next step for me is to hook up fuel pressure gauge to monitor the amount of fuel making its way to the engine. My current hypothesis is that it is caused by some sort of fuel pump cavitation. Reasoning: It happens when the engine is hot and the frequency of stuttering could be related to the pulses of cavitation. I also have some small exhaust leaks which could maybe be releasing heat onto the fuel lines thereby increasing the vapour pressure of the gassoline which promotes cavitation. All just a theory though...
One last note, inclines may have something to do with it, i.e. driving up a hill. But I cannot say that it does or does not affect it as it has happened on level ground as well. The fact that it happens on inclines may just be coincidence as the offramp I take daily is inclined. 
This is a huge shpeal but it sounds like Im not the only one with this problem!!
Any help or suggestions are GREATLY appreciated.
Davey,
1987 vw fox wagon


_Modified by lawtond at 11:15 AM 6-16-2009_


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## tomacGTi (May 28, 1999)

*Re: Stutter on acceleration (lawtond)*

Check your intake boot between the FD and TB for cracks. They're tough but they're 10+ years old now and made of rubber.
When accelerating, the boot is fixed at the FD and flexes with the motor via the TB and will open any cracks letting unmetered air into the engine. Depending on how hard you get on the throttle will dictate the severity of the bucking.
Remove the boot entirely and flex it in every direction you can find. Either replace it if you find one or you can clean it off with brake clean and reseal the hole with shoe goo.
I had run into the same problem a number of years ago and did the same thing: went over everything. It wasn't until a friend suggest this that I checked the boot. The clutch cable had worn a hole on the underside causing the bucking.
-Randy


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## lawtond (May 28, 2009)

*Re: Stutter on acceleration (tomacGTi)*

Checked the intake boot - it's clean, no holes or even hints of wear; it's probably fairly new by the looks of it. I also checked the fuel pressure from the pump to distributer, with a gauge and installed it in the dash as to monitor the pressure during bucking or stuttering. The fuel pressure maintained 50psi, the idle value. I have changed the battery even though it was fairly new, with a new one. I re-cleaned battery terminals, ground strap bolts/nuts/washers/body mount corrosion, I also replaced the ground strap entirely. I'm kinda running outta ideas here and its driving me nuts! Any more things you recommend me to check?


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## Southcross (Jul 2, 2004)

*FV-QR*

only 50 psi? I'd have to check, but that sounds crazy low


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## lawtond (May 28, 2009)

*Re: FV-QR (Southcross)*

Fingers crossed.... I THINK ITS FIXED!!!
Hot-wired around the ignition switch and everything seems much better, I'm even getting about 0.5-1.0 volts more than before everywhere I measure and the dash lights seem to be brighter! So going to order a new ignition switch since these toggle switches scream "steal my car, please! "
Thanks to everyone for their help! Learned a whole lot in the process!!


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## lawtond (May 28, 2009)

*Re: FV-QR (lawtond)*

Not fixed, improved but not fixed... I'm going to keep this thread alive in the fox forum as it seems somewhat more relavent there since it may not be due to CIS...
http://forums.vwvortex.com/zer...37629


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## Southcross (Jul 2, 2004)

*FV-QR*


_Quote, originally posted by *Southcross* »_only 50 psi? I'd have to check, but that sounds crazy low

I post because I have nothing better to do


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## turbinepowered (Mar 19, 2007)

For what it's worth, my car hasn't done the stutter thing since I got back from Chicago in mid-May.


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## VWFOX407 (May 10, 2007)

*Re: (turbinepowered)*

Perhaps it was the weather or like longitudinal said, E40. I wonder if 10% Ethanol in the gas nowadays is killing our old engines one day at a time>>?


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## turbinepowered (Mar 19, 2007)

*Re: (VWFOX407)*


_Quote, originally posted by *VWFOX407* »_Perhaps it was the weather or like longitudinal said, E40. I wonder if 10% Ethanol in the gas nowadays is killing our old engines one day at a time>>?

I'm doubting the E40, as I kept on using it. My blend varies from 40-50% tank to tank due to the splash blending in the tank and my guesses as to how much my total fill is going to be, but the stutter has not returned.
I'm keeping an eye on my hoses for leaks, but the CIS-basic pulls quite nicely. I need some extra compression to get the power back, but I'm hardly a slowpoke even without it.


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## prom king (Aug 14, 2004)

*Re: (turbinepowered)*

Im having the same problem bump.


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## tylernt (Dec 24, 2005)

*Re: (prom king)*

I had the bucking when one or both of my fuel pumps was on it's last legs. The transfer pump for sure was going out (the debris screen was long gone and the impeller was seizing up) which starved the main pump for fuel.
Very, very gentle acceleration got me home. Replaced both pumps and works fine now.


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