Lump in Idle; 01 PT Cruiser

My beloved PT Cruiser with about 90,000 miles works to perfection; almost.
With the air running I experience a serious lump in the idle, perhaps once
per sec, or so. With the air off, and the car in or out of gear the lump is
mostly gone, at least not noticeable. Yes, it has new plugs and wires, and
the filters are new and the throttle body has been cleaned.

Recently I had to have the air conditioning recharged; twice. First charge
lasted just 3 days. It is now holding a charge and cooling more than
adequately, for about a week. Don't know if this was related.

Any suggestions?

Richard.

"Richard" > wrote in message
...
> My beloved PT Cruiser with about 90,000 miles works to perfection; almost.
> With the air running I experience a serious lump in the idle, perhaps once
> per sec, or so. With the air off, and the car in or out of gear the lump
is
> mostly gone, at least not noticeable. Yes, it has new plugs and wires, and
> the filters are new and the throttle body has been cleaned.
>
> Recently I had to have the air conditioning recharged; twice. First charge
> lasted just 3 days. It is now holding a charge and cooling more than
> adequately, for about a week. Don't know if this was related.
>
> Any suggestions?
>
> Richard.
>
>

Does your radiator fan come on as soon as you turn the A/C on?


Glenn Beasley
Chrysler Tech

"maxpower" > wrote in message
news
>
> "Richard" > wrote in message
> ...
>> My beloved PT Cruiser with about 90,000 miles works to perfection;
>> almost.
>> With the air running I experience a serious lump in the idle, perhaps
>> once
>> per sec, or so. With the air off, and the car in or out of gear the lump
> is
>> mostly gone, at least not noticeable. Yes, it has new plugs and wires,
>> and
>> the filters are new and the throttle body has been cleaned.
>>
>> Recently I had to have the air conditioning recharged; twice. First
>> charge
>> lasted just 3 days. It is now holding a charge and cooling more than
>> adequately, for about a week. Don't know if this was related.
>>
>> Any suggestions?
>>
>> Richard.
>>
>>
>
> Does your radiator fan come on as soon as you turn the A/C on?
>
>
> Glenn Beasley
> Chrysler Tech

Perhaps not. What does this tell us?

Richard
>
>

"Richard" > wrote in message
...
>
> "maxpower" > wrote in message
> news
> >
> > "Richard" > wrote in message
> > ...
> >> My beloved PT Cruiser with about 90,000 miles works to perfection;
> >> almost.
> >> With the air running I experience a serious lump in the idle, perhaps
> >> once
> >> per sec, or so. With the air off, and the car in or out of gear the
lump
> > is
> >> mostly gone, at least not noticeable. Yes, it has new plugs and wires,
> >> and
> >> the filters are new and the throttle body has been cleaned.
> >>
> >> Recently I had to have the air conditioning recharged; twice. First
> >> charge
> >> lasted just 3 days. It is now holding a charge and cooling more than
> >> adequately, for about a week. Don't know if this was related.
> >>
> >> Any suggestions?
> >>
> >> Richard.
> >>
> >>
> >
> > Does your radiator fan come on as soon as you turn the A/C on?
> >
> >
> > Glenn Beasley
> > Chrysler Tech
>
> Perhaps not. What does this tell us?
>
> Richard
> >
> >
>
>
You say perhaps not? it either is or isn't.

Glenn

maxpower wrote:
> "Richard" > wrote in message
> ...
>> "maxpower" > wrote in message
>> news
>>> "Richard" > wrote in message
>>> ...
>>>> My beloved PT Cruiser with about 90,000 miles works to perfection;
>>>> almost.
>>>> With the air running I experience a serious lump in the idle, perhaps
>>>> once
>>>> per sec, or so. With the air off, and the car in or out of gear the
> lump
>>> is
>>>> mostly gone, at least not noticeable. Yes, it has new plugs and wires,
>>>> and
>>>> the filters are new and the throttle body has been cleaned.
>>>>
>>>> Recently I had to have the air conditioning recharged; twice. First
>>>> charge
>>>> lasted just 3 days. It is now holding a charge and cooling more than
>>>> adequately, for about a week. Don't know if this was related.
>>>>
>>>> Any suggestions?
>>>>
>>>> Richard.
>>>>
>>>>
>>> Does your radiator fan come on as soon as you turn the A/C on?
>>>
>>>
>>> Glenn Beasley
>>> Chrysler Tech
>> Perhaps not. What does this tell us?
>>
>> Richard
>>>
>>
> You say perhaps not? it either is or isn't.
>
> Glenn

Hi...

Absolutely not trying to hijack the thread, but just because I'm
intensely interested throwing in what mine does for what it may be
worth...

(94 lhs, in every respect just like brand new

And if "lump in idle" is the word, mine has it too... very noticeable
idling at a drive thru; quite noticable driving very slowly.

"lump in idle" in this case would be the engine rpm's dropping at least
100 rpm (first time you'd bet it would be going to stall), the tach
dropping, and surprisingly the interior fan slowing a lot. All for just
a second, then all comes back to normal, only to repeat a couple of
minutes later. I can live with it

However, the fans don't come on immediately. Sequence at idle and
hood open is the compressor engages. 10 seconds later the fans start.
Fans run only 3 or 4 seconds, then quit. This repeats at about two or
three minute intervals.

The owner's manual says the AC has a sight glass - like in the olden
days - but I sure can't find it. Anyone know where it might be?

And if it means anything, on a 90F day at start up the vents ouput
air at about 45 to 50 degrees idling.

Take care.

Ken

"Ken Weitzel" > wrote in message
news:ijJci.31322$1i1.25959@pd7urf3no...
> maxpower wrote:
> > "Richard" > wrote in message
> > ...
> >> "maxpower" > wrote in message
> >> news > >>> "Richard" > wrote in message
> >>> ...
> >>>> My beloved PT Cruiser with about 90,000 miles works to perfection;
> >>>> almost.
> >>>> With the air running I experience a serious lump in the idle, perhaps
> >>>> once
> >>>> per sec, or so. With the air off, and the car in or out of gear the
> > lump
> >>> is
> >>>> mostly gone, at least not noticeable. Yes, it has new plugs and
wires,
> >>>> and
> >>>> the filters are new and the throttle body has been cleaned.
> >>>>
> >>>> Recently I had to have the air conditioning recharged; twice. First
> >>>> charge
> >>>> lasted just 3 days. It is now holding a charge and cooling more than
> >>>> adequately, for about a week. Don't know if this was related.
> >>>>
> >>>> Any suggestions?
> >>>>
> >>>> Richard.
> >>>>
> >>>>
> >>> Does your radiator fan come on as soon as you turn the A/C on?
> >>>
> >>>
> >>> Glenn Beasley
> >>> Chrysler Tech
> >> Perhaps not. What does this tell us?
> >>
> >> Richard
> >>>
> >>
> > You say perhaps not? it either is or isn't.
> >
> > Glenn
>
> Hi...
>
> Absolutely not trying to hijack the thread, but just because I'm
> intensely interested throwing in what mine does for what it may be
> worth...
>
> (94 lhs, in every respect just like brand new
>
> And if "lump in idle" is the word, mine has it too... very noticeable
> idling at a drive thru; quite noticable driving very slowly.
>
> "lump in idle" in this case would be the engine rpm's dropping at least
> 100 rpm (first time you'd bet it would be going to stall), the tach
> dropping, and surprisingly the interior fan slowing a lot. All for just
> a second, then all comes back to normal, only to repeat a couple of
> minutes later. I can live with it
>
> However, the fans don't come on immediately. Sequence at idle and
> hood open is the compressor engages. 10 seconds later the fans start.
> Fans run only 3 or 4 seconds, then quit. This repeats at about two or
> three minute intervals.
>
> The owner's manual says the AC has a sight glass - like in the olden
> days - but I sure can't find it. Anyone know where it might be?
>
> And if it means anything, on a 90F day at start up the vents ouput
> air at about 45 to 50 degrees idling.
>
> Take care.
>
> Ken
>
The owners manual shouldn't have anything in the about a sight glass because
it doesn't have one!! your probably referring to a repair manual such as
Chilton or Motor manual. Junk Manuals!! The PT cruiser will do this is the
compressor kicks out due to extreme high pressures, (normally due to an inop
fan) and when the pressure drops to allow the compressor to kick back in it
puts a huge load on the 4cyl Engine and it is very noticeable. You have a 6
cyl and normally not that noticeable when the compressor kicks in and out.
It would be hard to say what you are feeling with the LH If you are loosing
a cam or crank sensor intermittently you may be feeling that.
sorry not much help

Glenn Beasley
Chrysler Tech

You say perhaps not? it either is or isn't.
>
> Glenn
>
>
It isn't! But it does come on after a while.
Are you on to something?

Richard

"Richard" > wrote in message
...
> You say perhaps not? it either is or isn't.
> >
> > Glenn
> >
> >
> It isn't! But it does come on after a while.
> Are you on to something?
>
> Richard
>
>

Replace the fan assemble. The motor for the a/c is not coming on when the
a/c is turned on. IT IS SUPPOSED TO!! At idle your a/c should not be blowing
cold and will cycle on and off with extreme temperatures/pressures. At
highway speeds the a/c will work and blow cold due to force air across the
condenser. When you say it comes on after awhile what you see coming on is
the coolant temp sensor requesting that the 2nd stage of the motor to turn
on. If that stage goes out you will have an overheat condition. You do not
want this engine to go into a severe overheat condition or engine damage
could occur.

Glenn

The motor for the a/c is not coming on when the a/c is turned on; this has
been confirmed. But when I bypass the high speed fan relay the high speed
function on the fan comes on. Since this relay is controlled by the computer
I don't see any choice but to bring it into a dealer to figure out the
problem. These are not the "good old days" were it was possible to figure
these things out on your own. Thanks for all the guidance.

Richard

On Jun 21, 9:24 am, "Richard" > wrote:
> The motor for the a/c is not coming on when the a/c is turned on; this has
> been confirmed. But when I bypass the high speed fan relay the high speed
> function on the fan comes on. Since this relay is controlled by the computer
> I don't see any choice but to bring it into a dealer to figure out the
> problem. These are not the "good old days" were it was possible to figure
> these things out on your own. Thanks for all the guidance.
>
> Richard

There should be TWO relays -- high and lo speed relays for the fans.
What Glenn suggested (and this sounds perfectly reasonable) that in
the fan assembly has the low speed circuit burnt out somehow.

You can test this assumption by "bypassing" (be careful how you do
that as not to burn out the computer, etc) the low speed "function".
My guess that the fans won't come on, which will confirm Glenn's
diagnosis of a bad fan assembly/wiring related to it.

Hope this helps,

Alex