gerry100

Had the '86 out for our first morning workout in about 2 weeks( roads have been snowy and or wet)-

- stumbling and "miss" when warm seems to be getting worse. Power seems OK but engine runs rough when accelerating although intermittently.

- I first noticed this phenomena after a Techron treatment. this is the first tankfull after running out a tank with the Techron added.

- Temperatures have been fluctuating above and below freezing for a few weeks now so I suspect condensation may be collecting in my fuel system. Thids feels like my previous experiences, although the 911 system would have to be pretty sensitive to this.

Any problem with adding some gas line antifreeze(alcohol) ("dry gas") to the '86 3.2 fuel system?

More Techron? Could this problem be related to the crap loosened by the first batch?

I heard suggestions that it could be the DME relay but I'd like inputs on these chemical approaches first.

Thanks as always.

r22tek

Sorry, Gerry, but the DME relay is the most likely fix-keep adding chemicals to your fuel system and you may end up with a large repair bill. Have you priced a fuel line for your car yet? Let me help you out-ITS CLOSE TO $500.00 JUST FOR THE LINE AND IS A MAJOR PROJECT TO REPLACE!!! It's obvious to me, and I'm no expert, that the problem is not your injectors or clogged fuel lines, nor is it condensation in the tank- the Techron treatment would have taken care of that IMO. Did you know that the DME relay has a direct effect on fuel delivery? Maybe you ought to research it more so you know why evryone recommends replacing it. At Only $45.00 and about five minutes worth of work, even for an "all thumbs" kind of guy-why not just do it? Quit putting all that "draino" down the sink!

gerry100

I hear you on the DME?

How about the fuel filter?

gerry100

Oh yeah. Thanks for responding.

r22tek

Gerry- I just feel it is an electrical problem based on your description. the DME relay is a KNOWN problem and is the CHEAPEST fix to try first, and if it doesn't work-YOU NEED A SPARE ANYWAY FOR WHEN YOU GET STRANDED AND THE CAR WON'T START!!! What will probably end up happening is you replace the DME relay and notice a "great improvement in overall drivability" but still complain about poor idle when warm and a bouncing tach, ect. ect. Then you will have to look futher into the electrical system: plugs, wires, dist. o2 sensor, airflow meter, idle control valve, head temp. sensor and so forth. So my advice is to replace the DME relay ONLY! If that doesn't work either take it to the shop , or if you want to fix it yourself- get a Bentley's manual and start tracing the electrical problem with a good meter and some time.

gerry100

R22tek-

I'm going for the DME relay but I've got a basic question-

Since I don't know what one looks like I don't know which of those gizmos under the seat it replaces -

Is this just a pull out the old and plug in the new? I't kind of cramped under there
so I don't want disrupt anything.

any tips? thanks

r22tek

Tilt seat up in front and slide all the way back. You will see the DME computer(big box) and the DME relay (small black cube with plug on back) held in with one screw-remove screw, slide seat all the way forward and unplug and remove. Now plug in new relay, slide seat all the way back, re-install the screw- Your done. This is, of course, under the Driver's seat. I can't remember the size of the nut but I just used a crescent wrench since one was close by- once the screw is loose, you can use your hand to get it the rest of the way. Really, it's no big deal- rates about a 0.5 in difficulty on a scale of 1-5.

DTFASTBEAR

I'd also give a careful look at the head temperature sensor. I had an '86 with very similar symptoms. I chased the fuel system theory for a while because the symptoms first appeared, coincidentally, the first time I ran the tank VERY close to empty. I figured it was dirt/water in the tank.

After cleaning all the grounds and replacing the head temp sensor itself, my horrific intermittent miss went away and the car ran perfect.

Just a thought if the DME relay doesn't work (the shop tried this first on my car, too)

Good luck,

Dean

gerry100

R22tek you were dead on. Put in the new DME relay and power delivery better and smoother with almost all "stumbling" eliminated. ( there is a minor stumble around 3500-3800rpm, but I may be getting picky). Thanks for your help.

I did notice that the relay I removed "rattled " when shaken whereas the new unit was solid as a well "potted" and sealed circuit should be. could be that the potting breaks down and the circuitry becomes prone to the effects of vibration or corrosion.

Anyway this might be a useful"shadetree" check of the DME relay.

gerry100

R22tek you were dead on. Put in the new DME relay and power delivery better and smoother with almost all "stumbling" eliminated. ( there is a minor stumble around 3500-3800rpm, but I may be getting picky). Thanks for your help.

I did notice that the relay I removed "rattled " when shaken whereas the new unit was solid as a well "potted" and sealed circuit should be. could be that the potting breaks down and the circuitry becomes prone to the effects of vibration or corrosion.

Anyway this might be a useful"shadetree" check of the DME relay.

gerry100

Well I was bored and performed an autopsy on the DME relay-

Not a sealed circuit but two solenoids with spring loaded contacts mounted oin a circuit board.

No obvious broken cicuits, maybe the solenoids wear out and start to stick, the springs get tired
or the contacts corrode.

Anyway doesn't look fixable.

gerry100

DME replacement was a vast improvement but I've noticed that the 3200-3800 hesitation comes back after the first warm start, and overall engine feels a little rougher.

Temp will only reach the first hash mark in this weather and open road driving. I'm wondering if this will get worse in warmer seasons.

Seems to be engine temp related.

Where is the Head temp sensor and how hard is it to check?

Thanks as always