Re: Heat and My ur-q don't mix

[Jeff & Staci Hemmerlin <hemmsta@sc.llu.edu>]

At 02:00 PM 5/11/98 -0400, you wrote:
>   We recently had a warm spell here in Southern Cal.  The temp probably got
>   up to about 90-95.  I was returning from the Drive up Angeles Crest
Highway
>   with the local chapter of the Q-Club.  I his traffic and was moving at 5
>   mph for about 45 min.  After being in traffic for a little while the car
>   would not idle on its own.  I had heel and toe just to keep it running.  I
>   have since installed a manual switch for the injector cooling fan and
>   insulated the fuel lines running to and from the control pressure
>   regulator.  The problem still occurs even if I run the injector cooling
fan
>   anytime I am below 20 mph.  The A/C was on until the car started running
>
>Running the AC will actually help cool the engine (forces the rad fan to
>Hurricane Force setting).
>
>   rough.  When I turned it off it did not help.  The temp gauge was not
>
>What do you have for a temp guage, and where is it connected?
The temp gauge is installed in the dash next to the fuel gauge.  It
replaced the boost gauge.  It is a stock 4000Q gauge using the 4000Q sender
screwed into the back of the head.
>
>   reading hot.  When the traffic cleared I had NO power.  The 0-60 time was
>   about 2 min.  I could barely keep it at 60.  After driving in the slow
lane
>   for about 15 min hoping that I would not have to be towed.  The engine
>
>Would it rev readily in neutral, or was it sluggish irrespective of
>applied load? Could you tell if it was "obviously" running rich or lean?

It would not rev readily in neutral and was sluggish all the time.  Under
full throttle it bogged heavily.  At this point the temp gauge began going
above the 3/4 mark.  I backed off and It cooled back down.  At the time I
thought that I had a clogged cat.

I could not tell if it was running lean or rich.  I am planning on setting
up my two multimeters.  One to monitor the duty cycle and the other to
monitor the O2 sensor.

>   suddenly surged a few times and then all 160 hp was returned like nothing
>   was wrong.  
>
>   Any suggestions?
>
>Wow, that's one even mine hasn't come up with (Quiet! you'll give it
>ideas...)
>
>   Would reduced voltage do something like that to the computer?
>
>I should think that highly unlikely -- the ECU will most likely just
>completely fu, er, ah, fail...
>
>   Am I experiencing vapor lock. (where)
>
>Doesn't really sound like it, especially if it took 15 (!) minutes of
>driving to restore the system (vapor lock should just take a few seconds
>to blow it (vapor) out of the injectors (assuming that's where the
>vapor-lock occured).
>
>Aside -- I've never seen any use for the injector cooling fan, hot
>LA/SJ-valley summers, 100+, hot engine, it would never come on by
>itself; installing a manual switch to force it on never seemed to make
>any difference in restarting the engine either. I finally just pulled
>the whole damn thing out. Makes it a lot easier to get to the plugs...
>
>   Does the control pressure reg (fuel boiler) need to be attached to the
>   block or can it be located in a cooler environment?
>
>It needs the (lower block, away from the exhaust manifold) block to heat
>it up properly (to set proper "warm engine" fuel backpressure) for proper
>overall mixture.
>
>Dunno quite what to say, other than some quasi-random speculations.
>
>First, irrespective of this problem, I'd install a lower-temp thermostat
>and rad fan switch (I'm running the 180F setup). But I really don't
>think that's your problem here.

BTDT  At the end of last summer I flushed the cooling system and changed
thermostat and thermoswitch to the lower temp ones.  Now the slow speed fan
comes on very often.

>The "idle" problem almost sounds like air leak, but I don't see how
>an air leak would affect performance across the board...
>
>Maybe fuel pressure? Fuel pump?
Could be?  Fuel pressure has been checked recently when the car was
operating well.  I will need to check it when it is running poorly.  I just
need to wait for more warm weather.  Not that I am looking forward to it.
I work out in the sun all day.

>
>It really doesn't sound electrical in nature...in my experience...I
>think I'd concentrate on fuel delivery -- mount a pressure gauge to
>monitor overall system pressure, and pressure to the injectors.
>Monitor the Frequency Valve output (duty cycle) from the ECU to see
>what the ECU is trying to do with the system (that'll tell you if
>the mixture is going rich or lean; reading the O2 sensor directly
>will tell you which way the ECU *should* be pushing the mixture),
>that can tell you a lot, very easily. (Have you bought yourself a
>SunPro 7678 yet? Do they even still make it? The duty-cycle readout
>is invaluable for maintaining the UrQ (mid-80's) cars.)
>
>I wish you luck, those beasts can be a real challenge!
>
>					-RDH
>
Thanks for you suggestions,

Jeff Hemmerlin