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#$*&@# EFI!!!! what have I missed?

544 Views 16 Replies 8 Participants Last post by  yesheadlou
OK - weather's a bit moist down her e in GA. the past couple days and ol' 78 is messing with me again. Dropped me like a bad habit on the side of the road 3 times on the way home yesterday - full on rich and won't start. Limped it home after creating a fairly large vacuum leak to compensate for the extra fuel ( I know - not good - but it beats a $100 tow bill). Here's what I did when I got home.

All contacts were cleaned with a tiny deburring bit for a Dremel tool until all corrosion was gone and clean metal was visible.

1) Pull AFM connector and clean all contacts inside plug. Spray clean with DeOxIt. AFM is reman/new as of two weeks ago. No time for corrosion on the blades - cleaned them too anyways.

2) Pull TPS plug - clean blades and contacts inside plug - DeOxIt'ed them.

3) Remove AAR and block off "L" elbows coming off AFM boot and off intake post AFM. (This probably doesn't matter, but I've read in prior posts it's not needed - so I'm just taking more things out of the equation.)

4) Pull ECU - clean and DeOxIt all blades and connections inside plug. It was completely dry and showed absolutely no corrosion anyways. Cleaned them for sanity's sake

5) Unplug cold start valve.

6) Unplug thermotime switch harness and removed.

7) Cleaned H2O temp sensor plug and DeOxIt'ed it. Brand new H2O temp sensor.

8) Pulled bullet connectors from H2O temp sensor and cleaned with sandpaper and deburring bit. Crimped the female portion of bullet connector down just slightly for better/more solid contact. DeOxIt'ed them and put in a little dielectric grease.

Car ran fine last night with all the procedures performed above.

I did not drive the car today because it is still moist outside. I know the moisture in the air must be causing some of these already failing connections to get even worse. Didn't want to deal with the BS today of getting in to work.

Is there anything else you guys can think of that I may have missed that would affect the EFI? This problem is totally intermittent, ranging from just dying while crusing, to not restarting after shutting off. I am at my wits end with this car and am about to get a can of gas and a match...... I do love her dearly though...
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It seems to me you are checking all the right places. It almost sounds like a loose wire or connection somewhere. Did you have this problem befor you replaced the water temp sensor? have you checked the vac line to the fuel pressure reg?
Looks like you covered all the standard stuff! I am impressed

Bad ground in EFI or power harness?

Leaking CSV?

Cold solder joint in ECU that rattles loose then back to good every now and then? (hit it next time it fails)

Problem could be ignition too. Check for spark as soon as it dies.
If no spark then you found the problem
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Oh no - it's definitely fuel. I can smell raw gas when it happens. New MSD box and Jacobs coil provide plenty 'o' fire. That was the first thing I checked when it started happening. **** - that spark jumps nearly and inch an a half to make contact with the nearest piece of metal! Problem was occurring prior to replacing the H2O temp sensor and AFM. I had taken Blue's advice and gone through his laundry list one piece at a time until yesterday when I redid the whole shootin' match.

Have checked vac line to FPR - no problems there. New FPR as of last year too.

Cold start valve has been unplugged for a while now. Didn't think it could fire without a little electronic help. I also doubt that one small injector like that can dump enough fuel in to totally kill my car while I'm driving at 2500RPM/45-50mph. Might richen the mix a bit, but not enough to totally shut it down.

Now the bad ground could be a potential candidate.

"Cold solder joint in ECU that rattles loose then back to good every now and then?"
Not familiar with that .... tell me more....
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Well the ECU is just a couple of circuit boards and some cables between them.

Many times, vibration from driving will take it's toll on a circuit board and cause a poorly soldered connection to fail.

Sometimes the failure is mechanically intermitent. Vibration may make or break the connection or thermal expansion/contraction can make or break it.

I have come across a few in my years in electronics. Usually resoldering resolves the problem but you have to have a keen eye and experience to spot the problem.

Here are 4 solder joints. The ones on the left are the bad ones (the top one has a circle crack and is probably intermittent and the bottom does not have enough solder and has pulled through) :

Here is another bad joint

This one is asking for trouble!

vibration for 30 years of driving can cause these to crack
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One thijng stands out for me...

#5: By "unplug" do you mean only electrically?

A leaking cold start valve will continually drip or spray fuel into the intake manifold wether there is an electrical signal to it or not! I always take a vice grips and clamp off the cold start soft line to make SURE it's not adding any fuel. They have been known to fail on occasion.

Also, have you done a physical resistance check per FSM procedures from the ECU pins to the injector and back to ground (loop check)?
While the connectors have been cleaned, I have a nice photo of green stuff that was residing up above the connector, making the wires useless. Shiny clean connections, but the last 1/4" of wire was so green with corrosion IT was the problem. Then it's pigtail time...

You may want to check your fuel pressure to make sure a blackage has not reared it's head in the return line, too...

Last, I put dielectric on EVERYTHING to keep moisture out, if air and water can't get to the spades and pins, they can't corrode.

Good Luck in the search.
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Re: One thijng stands out for me...

Thanks guys - more stuff to check this weekend. So Blue.. I have to physically crack open the ECU and hunt for bad connections?

Tony D - I was hesitant to put dielectric grease on the connections, now that you have confirmed my suspicions, I will pull everything back apart and put it on all connections. I guess I should just slice open the rubber boots around the connections and check for corrosion there too. Do you have any other suggestions as to how to check in the pigtails?
And yes - #5 - physically just unplugging the CSV.

Will be removing CSV this weekend as well so that will take it out of the equation as well. I could see residual fuel pressure in the line dripping in and making the car not start after being shut off, but when I'm riding down the road at 50mph and 2500+rpm, I have a hard time believing that one injector can totally kill my car to the point where you hit the gas and there's nothing. Oh well - that won't be a problem after this weekend either. Any suggestions on how to block off the cold start valve? Fabricate a metal plate and gasket?

I will also get out the FSM this weekend and the multimeter and check resistance values too. Problem is, it is so intermittent, that it usually happens on the side of the road - and I usually don't take my tools to work along with a multimeter. The ol' gal runs fine in the garage! Go figure!

Thanks guys!

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thats the best thing to check, and dont always think that new parts will stay new for a year, or will even last for a year. Im sure plenty of us guys have bought something only to have it break in an hour to a week.
Most seem to just kick the ECU when driving to see if there are any vibration related problems.

I wouldn't go deeper that that unless you had experience with electronics.
Then a good whack is what she'll get!! Thanks man!
I know you mention fuel smell, but I did just go through some sudden stalling issues.

The car would be able to be restarted instantly..

I would drive along and not even realize it stalled. I did notice that when it did it, the tach dropped to zero instantly.

In the end it was the ign module on the side of the dizzy. Replaced and everything has been fine.

BTW it was my 82 280zx N/A


VG30ET Powered 280Z T3/T4 Hybrid, i/c, @ 15psi
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Found this pic of bad solder joint in Bosch Ljetronic part (same line as Z's EFI electronics)

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Pigtail Check...

the resistance check is done through the pins at the ECU.
If you know the resistance of the coils in the injectors through a component check, you will be able to simply do the subtraction and figure out if the harness (therefore the pigtails most likely) is the problem.
soldering doubtful...

been working 20+ years, I'd shy away from that route of diagnosis.
I had a Z I fought with a few weeks ago that was doing this. I checked and double checked everything I could think of. We had some spare parts around so I tossed another AFM/ECU etc and it still would go full rich intermitantly. I even directly wired the temp sensor direct to the ECU with new plug and sensor. Still went full rich on the second day driving it home as a test. Ended up just replacing the whole harness as I never could get the intermitant failure to occure while testing it. I think it's somewhere in the AFM wiring but it was easier for me to just throw away the harness.

It isn't as weird as the one that would die when you opened the drivers door. That turned out to be a cold solder joint in the ECU...
Can confound you...

There was a glitch in the early VW Type III in the ECU shielding. If driven within 100 feet of a 70's era Amana Radar Range the car would stall!

I had a customer that had an intermitten stall on a 69 VW Type 3 (Squareback) that would stall at only ONE corner in town, and ONLY when going to work in the morning!

Through a total LUCK fluke, accompanying the customer to work one morning (talk about service...) the car stalled, and by a FLUKE I was watching the corner house at the time. I saw the lady through a window stick something into a RadarRange. My friend's mother did promotions for Amana, and instructed people on how to cook with a microwave, so I knew they sometimes "leaked".... Knocked on the door to ask the lady if we could use her phone to call in the symptoms to the regional service manager, and she offered us coffee....

put 2 and 2 together and jumped to 12! Sure enough, the car stalled at idle everytime this lady started her RadarRange on "high"! Another quick call to my bud's mom about "leakage symptoms" and we were sure we had the problem isolated...

Some tinfoil later we confirmed it...

Then all that mattered was the lady being upset that the VW mechanic told her that her Microwave (Radar Range in those days...) was LEAKING RADIATION, and needed another seal...

The customer, with a foil-wrapped ECU (grounded to the chassis) was advised to "avoid that intersection" and the warranty claim on the used vehicle was closed....
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2eighTZ4me Did you fix your flooding problems. My 77 has been doing the exact same thing over the last month or so(floods - stalls as I drive). I have checked all the same things you did and finally disconnected my cold start valve. I have had no problems for 2 weeks, more then enough time for the problem to reoccur. Today I decided to clean up the CSV and reconnected it. On the test drive it stalled twice as I was driving and the fuel smell was evident. It took some time before it would start again. She is back to driving fine without the CSV connected. My thermotime seems to be working fine so I guess its the csv.
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