[urq] Stumbling

[DGraber460 at aol.com]

In a message dated 11/24/2004 7:16:32 PM Mountain Standard Time,  
IRautenberg at comcast.net writes:

> My  problem lingers, though I haven't been aggressively trying to fix
>  it.  But I noticed a couple more things that make me wonder if  it's
> not an electronic problem.
>
> First, when the  problem happens, the revs drop, but I can hear the
> engine still  firing.  But, the tach drops to zero and then bounces
> back up  again right away.  It will do it when I'm off the throttle
>  (coasting) too.
>
> Second, which sensor is it that can cause the  fuel pump to cut out?
> The MAP sensor in the  ECU?



I think a critical diagnostic here is that the tach drops to zero.  Fuel pump 
cut out (or fuel supply issues) don't do that. The usual suspect is  the Air 
Temp sensor.
 
There is another intermitant gremlin that I have recently encountered  in 
spades! Over the 3-4 years I have had my car (83 URQ- fuse panel under  the hood) 
it has 2-3 times a year cut out going down the highway at  speed. The tach 
drops to zero, and it acts like you dropped anchor and pops out  the exhaust. 
Unburned fuel ignited by the hot turbo & exhaust  backfires. Until last week, 
pulling off the road, shutting the car down and  restarting (rebooting the 
computer) was the only way to remedy the problem, and  until last week always did.
Last week I fired it up and a block from the house it did it again- only  
this time (for the first time) it was cold, and would not restart. After sitting  
for a few hours, I replaced the ignition module (above the glovebox), and it  
fired right up and has not recurred.
Due to it's extremely intermitant nature, I have no idea if it's  permanantly 
"cured", but it is for now.
When I last posted about this problem in September, the _wonderfully  
helpful_ list responded with 2 possible culprits.
1) Flywheel TDC sensor
2) Ignition module
After I encountered the problem coming home from UPG in Park City Utah, I  
replaced the TDC sensor, and last week did the IM.
If it happens again- hell I have no idea!!
Sorry for rambling and all the too numerous ( ).
HTH 
 
Dennis
Denver