RE: [DML] Re: Idle gradually increased to 1700 RPM during warm up

[<rob@xxxxxxxxxxx>]

Dennis,

 

That extra info helps a lot! How old is your distributor cap, rotor,
wire-set, and spark plugs and, equally important, what brands are they? You
have defective, incorrect, old, or improperly installed tune-up parts to be
sure (Or that was one hell of a monsoon you drove through!). Bad wires are
the most common problem and usually get better after drying out for a while.
If water fills a spark plug well, or the distributor cap is cracked, the
problem will not usually go away on its own. As Tom noted you may also have
a vacuum leak and yes a lean condition could cause the header to glow. It
seems like your problems have at least two contributing factors involved.
Has anyone worked on the motor recently as most PVR vacuum leaks are created
by improper repairs as opposed to natural causes such as gasket or O-ring
failure? My guess is someone was in there recently? Check for a loose
fitting idle air regulator brass vacuum pipe as the possible sudden high
idle condition. Again I still suggest that you double check the fuel tank
for problems there unless you are certain that everything is in good shape.
I haven't come across an original fuel pump support or cover boot that is
still in good condition in many years. The newer fuel blends are only
compounding the problems for these marginally engineered parts. EVERY
DELOREAN OWNER NEEDS TO KNOW WHETHER THEIR FUEL TANK IS IN PROPER SHAPE OR
TRUST THAT THEIR MECHANIC KNOWS!

 

Rob Grady,

 

P.J.Grady Inc.

 

  _____  

From: dmcnews@xxxxxxxxxxxxxxx [mailto:dmcnews@xxxxxxxxxxxxxxx] On Behalf Of
dmc_5180
Sent: Monday, May 18, 2009 7:06 PM
To: dmcnews@xxxxxxxxxxxxxxx
Subject: [DML] Re: Idle gradually increased to 1700 RPM during warm up

 






Thanks Rob and everyone else for the suggestions. 

Unfortunately I won't be able to work on it for 2 weeks. 

The fuel system Is clean. With 2 tanks of Spring gas and I put 350 miles on
it 3 weeks ago. I will mention this The last 150 miles was in on and off
heavy rain. So much so, That the last hour driving on the Interstate was
rather nerve racking. The high humidity and water got to the ignition and
the engine would start missing and stumbling If I tried to accelerate. It
was all I could do to just maintain speed. I figured once things dried off
again it would be fine. When I got home I shut it off and figured It would
be fine in the morning when it had the chance to dry out. The next day I had
to drive the car back to my storage building 18 miles away the car ran just
fine nothing out of the ordinary. When I started it up yesrtday was the
first time since then. Because of this uneventful drive I did not think to
mention it before.

Do you think the Drive home with a not so perfect running engine could have
cause Ignition system damage thus possibly causing the CAT to load up with
fuel, thus possibly doing internal damage IE; plugging it? 

The car ran sooth when I started it and showed no signs of missing or
stumbling. In fact, At the time during the 1700 rpm running the engine
seemed as smooth and evn sounded like the EVEN-FIRE engine.

Dennis

--- In dmcnews@yahoogroups <mailto:dmcnews%40yahoogroups.com> .com,
<rob@...> wrote:
>
> Dennis,
> 
> 
> 
> If the fuel in your tank happens to be old, or new fuel recently mixed
with
> old stale fuel, then the fuel injection circuit would be the primary
> suspect. Substantially unequal volume delivery by either the fuel
> distributor or faulty injectors could easily cause your symptoms. The
> increased idle would tend to reinforce this diagnosis.
> 
> A second but less likely possibility due to the increased idle speed would
> be an ignition problem such as an arcing spark plug, ignition wire or a
> cracked distributor cap.
> 
> My first suspect would be the fuel system or some other combination of
> issues and it couldn't hurt to take a peak into the fuel tank to check for
> sour fuel or damaged fuel supply components. Let us know what you find
out?
> 
> 
> 
> Rob Grady,
> 
> 
> 
> P.J.Grady Inc.
> 
> 
> 
> _____ 
> 
> From: dmcnews@yahoogroups <mailto:dmcnews%40yahoogroups.com> .com
[mailto:dmcnews@yahoogroups <mailto:dmcnews%40yahoogroups.com> .com] On
Behalf Of
> dmc_5180
> Sent: Sunday, May 17, 2009 9:52 PM
> To: dmcnews@yahoogroups <mailto:dmcnews%40yahoogroups.com> .com
> Subject: [DML] Idle gradually increased to 1700 RPM during warm up
> 
> 
> 
> 
> 
> 
> 
> 
> This is a never before seen problem on my car during my 16 years of
> ownership. I went to start the car this afternoon , it had not not been
> driven since the DMCMW open house weekend 3 weeks ago. The car fired right
> up as usual Idle was stable at 775 +/- 25 with a very subtle hunt but
> virtually stable. I walk away from the car after 20-30 seconds I'm letting
> it warm up. I was getting a few things from the trunk of my other car to
put
> in the D. While I had my head in the trunk of the other car The RPM starts
> to gradually increase on the D. I did not think too much about it Figuring
> that the Idle Micro switch might not be tripped. I walk back over the D
get
> in driver seat to see the IDLE is at a steady 1700 RPM . I tap the Pedal a
> few times NO change. OK, I Go back to engine bay to make sure the Micro
> switch is depressed. It IS. Then I happen to Look down at the Left EXHAUST
> HEADER. This Is a JET-HOT coated system. The header starts GLOWING and IS
> increasing rapidly. I do a quick check of the Right Header which appears
to
> NOT be turning colors at this point. FYI I was in a rather dark building
at
> the time so it was fairly easy to see the heat GLOW. Well I've never had
> this happen before. and As the header starts turning very RED rather
quickly
> , I Shut it down immediately. While the engine was shutting, down I hear a
> woooof sound in the exhaust, almost like I flame igniting. The exhaust
> header quickly turns back to normal color. I wait about a minute then
start
> the engine again. Idle is steady at 1700. The scary part for me was the
Left
> exhaust appearing to be much hotter than the right. Again I did not notice
> the Right side turning color as the left did. This is a STAGE I exhaust.
> both sides are independent each with a CAT. I thought about the
possibility
> of maybe a plugged CAT but I'm not so sure about that. Any thoughts of
what
> may have caused my idle to increase like that?
> 
> Dennis


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