nmuir

Hi. I am posting this to see if any more knowledgeable contributors can help with some diagnostics – confirm or counter some of the points.

First, the background. I put my 84’ 3.2 Carrera back on the road after many years. First there was no start (no spark). I ran through the standard steps of DME relay, the DME itself (no cracked solder joints), then onto the sensor tests. Courtesy of a great youtube video I found the rpm / speed sensor was bad. Replaced it started straight up. I figured I was gold.

Now past the 1st month of driving, it stumbled a few times coming back from work. It might have been when under load (or coincidental) and so easiest place to start was to replace the spark plugs.

Back out on a few test drives things got worse. The symptoms were:
• After 3-4 minutes of driving - not immediately.
• Typically stumbles intermittently and once bad enough it stalled. (I restarted right away and drove gingerly home).
• Sometimes I can see the tach needle bounce down - even when not noticing a miss. With a noticeable miss, the tach bounces to zero.
• There is no alternator light or anything else when it misses.

Then the most recent and longer test run had different / worse symptoms that may narrow things down.
• After some intermittent missing (as above) I turned to head home. A few minutes later I thought the car was going to die altogether, but it was a narrow road with nowhere to stop. The engine kept running (barely) at *very* low power and I limped 100 yards along slowly to a pull-off. When pulled over the engine kept running, but what sounded like only a few cylinders and at a few hundred rpm. It stayed running like that until I turned it off.
• Once turned it off, I waited a few minutes, then fired it up fine and we drove home.

So some thoughts I am interested in others more experienced commenting on:
• I don’t think it is the ignition switch as no alternator light etc, plus I don’t think that would result in the weird running on a few cylinders.
• I checked the TDS sensor the first time round and it was fine. I also don’t know if a sensor would cause intermittent issues like this. Do they cause intermittent issues?
• Same with the DME relay.

Any ideas and/or thoughts?

Thanks in advance!

dwight45

I have to ask the obvious. Did you have new gas? oil change before starting? Sorry to hear about that problem. Very scary when you not close to home, did you have cell service if needed? I'm sure that other folks on this forum can come up with some thing to check.

nmuir

Tx for the comments. Some quick answers:
* yes fresh gas - have been driving it for a month to work and gone through a few tanks fulls (and in Canada that costs $ )
* yes oil change, tranny oil change, etc

theiceman

if it only does it when warmed up elliminate your CHT sensor .. jumper it out with a paper clip once the car is warmed up. if issues diminish it is a bad sensor. it is one of the white connectors on he left when you look in the back , not sure which as i cant remember , just make sure you are jumpering out the input. unplug sensor and shove a paperclip in the harness.

Amber Gramps

Ice may be right (again). Vacuum leaks can also be temp sensitive. A bad coil usually just dies so I don't think it is that. Same with alternator. Any chance you are in SoCal?

theiceman

Doug i cant remember which connector it is , could you guide him ?

Amber Gramps

My manual is out in the shed. I will post it in a couple hours tops.

theiceman

i think my tactic was all wrong .. i should have just said " its the top one " coz when you get something wong on the inernet it usually takes people about 1 second to correct you

nmuir

Thanks Guys.

Wll try to check the CHT sensor tonight but might slide to the weekend. Some separate searches showed CHT symptoms and how to test it - so that might be the issue! I'll post an update.

Amber Lamps - I am in Vancouver (Canada). No nice weather for me at the moment......

nmuir

Dang.

Jumpered the CHT with a 330 ohm resistor as per http://forums.pelicanparts.com/porsc...-cuts-out.html and still have the same symptoms - once warm, intermittent cutting out. Initially triggered when gunning it a bit hard, then after a few more minutes it occurs with more sensible driving. After once when it totally stalled, it started right up with no waiting (ie I didn't have to let it cool).

I have a spare sensor and so may swap the TDC sensor on the weekend 'just in case'.

Any other suggestions?

nmuir

Next update, still with no positive result.

Changed the TDS sensor as I had one - just in case - with no change.

I thought to go back to the DME computer and DME relay. No cracked solder joints I could see on the DME computer. The relay *might* have has some so I reflowed the solder whilst I was there.

Still no better, and it does seem to be getting worse with missing and lurching within a few minutes of start-up.

Any suggestions from the forum on next steps?

budge96

Maybe I missed this in OP post but I would suggest a cap ,rotor and even wires depending on how long car has sat...Bert
And a fuel filter never hurt...

theiceman

ive never heard of that "resistor" but it may make sense.. just use a damned paperclip once it starts lurching.

gerry100

Did you eliminate the DME relay? If not your symptoms sound just like mine ('86 3.2) when the relay went bad.

Simple easy fix with replacement of a $50 part. Many on this board carry a spare.

CHT symptom were intermittent no start when cold and especially when wet ( washing car or rain). Slight PITA to replace but I did it on the floor of my garage.

Andrewspencer

I fought a similar problem for years, although mine progressed to where it would not run if the temperature was below 65deg.

I would bypass the DME relay, (just to be sure)
http://www.clarks-garage.com/pdf-manual/fuel-05.pdf

But I know 99% of all driveability issues come from the crank position and reference sensors.

After you replace the sensors (autozone has the best price and a lifetime warrenty) and make sure they are properly gapped (info in the Haynes manual, not Bently)

And it is still intermittent problem, get the car running and fiddle with the connectors for the sensors. I suspect you will find one that is loose / goofy and is causing your problems.

Good luck! keep us posted!