no acceleration, chugging, fuel injection, 80 spider

[thisismikehere]

Hi, i am troubleshooting my 1980 fiat spider with fuel injection. It was running well
except #2 earlier this year.
I have found one thing that perhaps is amiss so far, auxilliary air valve (AAV).
I removed it and it is closed when cool, can blow air though but no light. The info i have found indicates it should be open when cool. Could this cause the issues described?

Symptoms
1) recent problem, starts fine, if you keep it at 2-3000k rpm it can stay there,
but cannot increase above whatever RPM it was at start. Warming engine has no effect.
Sometimes idles a bit rough, but then can smooth out nicely much of the time.
Increasing the throttle causes a chuging. Speeds up, drops to almost stall,
speeds up, then drop, keeps repeating this cycle.

2) cooling - longer term issue, plan to fix #1 first
- brown greasy stuff inside rad cap, have cleaned it several times
- consumption of oil/coolant
- i only mention #2 at this time in case it somehow relates to #1 above.

• Diagnostics so far:
• • auxilliary air valve (AAV) Bosch 0 280 140 120
  • cold start system, bi metalic strip
  • this valve should be completely open when it is cold and completely closed when it is hot?
  • 12v on the connector when engine is running
  • 49 ohms disconnected
  • disconnecting it makes no difference
  • it is closed when cool, can blow air though but no light
• • coolant temperature sensor 0 280 130 023 - T junction front and center - ECU pin 13
  • stalls if unplugged, i recall this was always the case
  • when disconnected, cold reads 1900 ohms at sensor
  • i am cautious about removing ECU harness to measure from there per manual, unless necessary, maybe 1 screw holds harness attached?
• • throttle plate sensor (TPS) - Bosch 0 280 120 300
  • this is the thing which i have left disconnected for years
  • does not appear to be working at all, but maybe non-critical
  • removed it, do not see any effect of position on the resistance between pin 2 and 18
• • compression seems consistent between cylinders - but may recheck this again
• • AFM (air flow meter) - vane seems to move freely, checked contacts at harness
• • add 5L new gas in case there is bad gas - no effect

[azruss]

haven't experienced this with my FI car. nothing jumps out at me. here are some things I would check. remove the idle air screw on the throttle body and see what kind of shape the o-ring is in. look closely at the rubber plenum hose for leaks and cracks. At the same time check the hose T that goes to the cold start injector. Not sure the coolant temp sensor is reading right. Search for past threads on the resistance hot and cold. Have you looked at the dizzy to make sure the advance is working properly. While in there, look at the condition of the wires from the mag pickup. Also, I would look at the cam belt to make sure it didn't jump a tooth. This is not a time consuming list, and would get these possibilities off your plate.

[klweimer]

Mike,
Shoot me a PM with your email address and I'll send you the factory fuel injection troubleshoot manual. It's the best for this kind of work.
Kirk

[PhillySpider]

I'd start with the Bosch MAF...resistive tracks wear and the flap can stick. That was my problem with similar issues coupled with stalling.

[thisismikehere]

Thanks for the tips folks.
I'm working my way through the various ideas here and the Bosch manuals. Without a heap of experience in this it takes
me time to figure each thing out.
- Put a timing light on it and that seems right at 10 degrees.
- Flap in AFM moves freely, have not checked inside the control for track damage yet.
- placed the AAV in the freezer for an hour or two, a very small opening appeared i can see through, but very small
- I wanted to check the static timing to see the belt did not slip, but i have not been able to get the engine
rotated to the correct position. I use the starter and try to bump it bit by bit, but when it gets close, it jumps
ahead. It looks like you need a huge pipe wrench to manually turn the crank, which i dont have.
Thinking i might be able to put it in gear and push it bit by bit using the brake to get to the correct rotation.
Any better ideas?

[RRoller123]

The AAV should be pretty far open after a couple of hours in the refrigerator. It should appear that the opening is close to an equilateral triangle opening. It can be adjusted by loosening the small nut on the side and carefully moving the inner flap with a small flat screwdriver or similar tool, and retightening. The flap is delicate, so be careful. Open when cold, closed when warmed up is the right set point.

[thisismikehere]

Thanks for the tips folks. Lots to learn and check out here. Some of it i am still working on.

a) The symptoms i have are very similar to what is described here in sec 9.3 as "sawing".
https://oldtimer.tips/en/d-jetronic/aav
While this suggests AAV as a cause, see below, maybe not in my case?
AAV - i have cleaned the AAV and explored it. I tend now to think that it is ok. When frozen it opens the most and
there is a descent hole of a few mm visible. At room temp only a very small slit hole is visible. This seems in line with
what i have read in various documents and online.

b) TPS - throttle position sensor - this has been disconnected for years (electric plug pulled off). I was advised
it could run disconnected without trouble. I tested it and the readout on the pins is as follows, looks to me
like pin 2 is not correct, but then since it has been disconnected, wonder if this is actually relevant?
Anyone else comment on the idea of just leaving this disconnected?
2-18 seems 0 ohms at all times
3-18 varies as you turn it from 0 to infinite as expected

c) Idle speed adjust screw - i took this out and found the rubber washer left inside. I got it out now.
How to reposition this when putting it back?
My guess is that to is put on the adjust screw at its neck, above the threads, then install the screw with washer
on it. Is this correct?

d) Bosch fuel injection guide - I removed the ECU and did a bunch of electrical
tests suggested - seems to be within specs. I suspect that since the AFM portion seems ok perhaps it is working ok,
i had previously confirmed the flap was moving freely.

e) I attempted to check the timing belt position, appears to be close, but i have not found a way to rotate the engine to
line up so i can check all 4 pullies are algined correctly. I was using the starter moter and just trying to turn engine
a bit at a time, but each time it got close to the timing mark, it would zoom on by it. Any tips on how to rotate the
engine to correct position? I might try something like push starting the car to see if i can get it that way. Engine
is in the car, and dont expect i can put a wrench on the main shaft.

[RRoller123]

You need to hook up that TPS and measure the Zero ohms versus Infiniti Ohms back at the CPU under the glove box. The FI Manual gives the exact pins. It will shut off the injectors when you decelerate so that there is no backfiring/popping from overly rich mixture in the exhaust (It seems like it may have been disconnected because the wiring has a break?, thus test it back at the CPU.)

It should make an audible, easily heard "click" sound (when engine not running) and make a step function change, not a smooth change from zero ohms, as far as I know. It should be adjusted so that it clicks just barely after the initial throttle is opened with the gas pedal. Adjust the other throttle items first, then this, as it can artificially hold the throttle plate open if incorrectly set.

[DUCeditor]

Dare I say it?

"Oh, blessed carburettor!"

-Don

[RRoller123]

don't......

The FI is excellent once you sort it, and it really isn't that hard to sort through. Just have to check each of the few components and then it runs incredibly reliably and with good power and torque.

[ORFORD2004]

If you remove your spark plugs, you will be able to turn the engine with a ratchet on the crank nut.

[thisismikehere]

- It turns out to be very temperature sensitive, and so is starting to show some signs of life now we have cool nights.
- cool morning, perhaps about (10C/55F), starts and runs pretty good, was able to drive it up a hill
- once the sun comes on it, not even very hot yet, back to the same problem, cannot even drive it a foot
- engine only running no more than a minute, so engine temperature/cooling should not yet be a factor
- so what things are temperature sensitive?:

- coolant temperature sensor - resistance reading seem perhaps not far out
When cold(10C/55F) it was 1840 ohm, as it warms now just over 2000 ohm. While not far out of range, it might be wrong.
As it warms it should reduce resistance, not increase.
So i tried connecting resistors in place of temp sensor 820, 3200, 5800 ohm, no help or strong difference

- auxilliary air valve (AAV) - this seemed perhaps likely culprit. Did some testing as above.
So what it does it allows a variable amount of air in. So i disconnect the outlet side and replace this
with my thumb and try manually varying the amount of air. There is some good suction. While this seems
to have a noticable effect, i could not find an amount of air that made it run right.

- while some have suggested the timing belt may have slipped, it was replaced 5 years ago and only has 6500km on it.
Also since it runs pretty well when cold, maybe this is not at fault.

- any clever ideas on other temperature related things that might be at fault?

[KevAndAndi]

You mentioned that the AFM flap moves freely, but do you mean that it moves when it's supposed to? And is it fully closed at rest?

When we bought our car, I found that while the flap moved freely when I pushed it with my finger, it was actually resting in a "beyond closed" position - i.e., too far in the outward direction - and did not move inward when the engine was running. Therefore, while air was flowing through the AFM, it was not being metered. Make sure your flap is not behaving like a saloon door, resting ajar.

[lglade]

.......................................................................................... but i have not found a way to rotate the engine to
line up so i can check all 4 pullies are algined correctly. I was using the starter moter and just trying to turn engine
a bit at a time, but each time it got close to the timing mark, it would zoom on by it. Any tips on how to rotate the
engine to correct position? I might try something like push starting the car to see if i can get it that way. Engine
is in the car, and dont expect i can put a wrench on the main shaft.

With the engine in 4th or 5th gear you can gently push the entire car a few inches and rotate the engine even with spark plugs installed. I used to gap my points this way (on a different car), by bumping the car until the distributor lobe opened the points to their maximum opening. I could then set the gap at whatever the spec called for.

[wizard124]

Suggestions:
With the engine warmed up, use locking pliers to squeeze the hose downstream of the AAV. If performance improves then AAV is part of your problem.

Could be a bad cold start valve not closing completely. With engine warmed up, squeeze the supply line shut and look for improvement.

Disconnect the plug at AFM. Look for recessed pins, corrosion.