Re: 505 SW8: "Bucking" on the highway

Alan Samet (aas0918@mail.ecu.edu)
Tue, 05 Jan 1999 21:51:25 -0500

If the answer is found, I would like to know. My turbo does this also, so
bad that it nearly turned sideways today while I was in second and got me
pulled for careless/reckless last week because it lays serious MXV4 when it
happens sometimes. I thought it was related to the rising richness of the
fuel mixture and the O2 sensor, but apparently from your postings and the
fact that it happens at WOT indicates that it's not. I tend to lean against
it being an overboost switch on mine because it only bucks a couple times
before stopping.

-Alan

Karl Wolf wrote:

> Just one more piece of data (can't guarantee this, though):
> I mentioned previously that the mechanic had run the air intake hose
> back to the engine block (in search of warmer air). I removed this
> modification and put the original hose back (draws air right in front of
> the radiator). The bucking is instantly worse (at least in cold
> weather...I am waiting for it to warm up).
>
> George Nunez had suggested that the air temp contact on the air flow
> sensor may not be functioning.
>
> Karl
>
> A few post scripts to my previous email:
> 1. Initially, the bucking is under load only (the steeper the
> incline, the worse it gets). As time goes on, bucking happens at other
> times as well.
> 2. Pumping the pedal gets rid of the bucking.
> 3. I tried dry gas and fuel injection cleaner...with no noticeable
> improvement.
>
> Does this get us any closer to a conclusion?
>
> Karl
>
> -----Original Message-----
> From: Steve Coleman [mailto:scoleman@ca.newbridge.com]
> Sent: Monday, January 04, 1999 4:20 AM
> To: Karl Wolf
> Subject: Re: 505 SW8: "Bucking" on the highway
>
> >On a recent trip from NYC to Western PA, our 92 505 SW8 suffered some
> >"bucking". Here are the conditions:
> >
> >Bucking did not start right away...after about 3 hours of driving.
> >Temperatures were fairly warm (35 F) when starting the trip, but
> started
> >to drop with nightfall.
> >Once bucking started, seemed to get worse with travel.
> >Happens whether tank is full, partial, or near empty.
> >On the return trip, bucking was much less...I kept it at about 65 mph.
> >
> >Before you reply, let me "disarm" some red herrings:
>
> >3. Scavenge pump in the tank seems an unlikely suspect: If it were
> >at fault, I would have problems only when below a quarter tank of gas.
> >
>
> Karl,
>
> Last summer I experienced bucking on my 86 505 STI. This only happened
> when
> accelerating (not at continuous moderate to low revs) and was like the
> ingnition being toggled off/on. Like you, I dismissed the in-tank
> scavenger
> pump because I thought with more than half a tank it made no difference.
> However, that is what turned out to be the culprit. I got a replacement
> unit for a Jetta ($79 CDN); but be advised that the polarity is reversed
> on
> the Jetta pump.
>
> Steve Coleman
> Vancouver
>
> _____________________________________________________
> To unsubscribe, send email to PEUGEOT-REQUEST@PADUI.ORG with the word
> UNSUBSCRIBE in the message body. Leave the subject line blank.
> _____________________________________________________