8 cylinder front engine iconic vehicle
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By hessank
#164956
Just completed a 500 Mi trip. On the return home and about 1 hr from home car started stumbling and lunging. Eventually it shutdown on the Expressway. It would restart easily and idle (lumpy) but would NOT accept any throttle increase.
I pissed off a few drivers but eventually got it on a side street to investigate.

(1) Car started easily and idled (but badly), so I believe the CPS, FP ok
(2) FP output remained at 52 Psi(g) even 2 hours after shutdown. Does this indicate that my injectors are not leaking?
(3) With car idling and pulling the vacuum hoses to the Fuel Reg and 2 dampers did not leak raw fuel so I believe the diaphragms are still ok (fire ext was at the ready)
(4) Brings me to the Temp II. Pulling the connector off did not interfere with starting the engine.

(5) After sitting at the side of the road for 2 hours waiting for a tow truck (flatbed) I decided to start it BUT this time it allowed me to use the accelerator pedal. It felt normal and so I cancelled the tow and drove it home without incidence. It did, however, had flat spots

Today, trying to get at the low hanging fruit first I decided to test the Temp II as per Worf's page. Thanks Worf
Here are my results. Please note that this Temp II (Bosch 0 280 130 069) was bought and installed back in June 13, 2019.
This model did not have one long and one short pin. So I could not tell which was for the LH and which was for the EZK. I identified them as left and right.
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By worf
#164972
From memory those TEMP-II values look ok. *But* my guide directs you to test them at the ECU pins so as to rule out wiring issues.

But with an ‘89 you can also use either a Bosch Hammer, Theo’s tool, or Durametric.

As for your symptoms….

How many miles since the Mass-air Sensor was rebuilt?

Has the LH ECU been rebuilt?

What was the last service you performed and when time/miles.
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By hessank
#165000
I didn't undo the ECUs because when not flooding the car drives as normal suggesting that the wiring is ok.
Before starting the trouble shooting today I took it for a drive (with my wife driving behind me in another vehicle) and it drove ok, no bucking, no stalling.

Alpha N so no Maf. ECUs rebuilt by Louis Ott ,5 years ago.
Last service last year replacing the coolant, fresh plugs, rotors and caps. Ignition wires less that 5 years old.
However, my coils are about 10 years old (the black ones). Tomorrow I will remove, check their resistance and
waiting for my spark tester to arrive.
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By worf
#165016
hessank wrote: Mon Aug 08, 2022 8:14 pm Alpha N so no Maf.
ok. I have zero knowledge of failure modes associated with MAP sensors.

hessank wrote: Mon Aug 08, 2022 8:14 pm ECUs rebuilt by Louis Ott ,5 years ago.
Last service last year replacing the coolant, fresh plugs, rotors and caps. Ignition wires less that 5 years old.
However, my coils are about 10 years old (the black ones). Tomorrow I will remove, check their resistance and
waiting for my spark tester to arrive.
I would bet on the final stage coil amplifiers before “black” coils.

Also, wiring issues are usually intermittent initially. So, your theory that because it runs ok every once in a while doesn’t rule out wiring issues.

The fact that it runs best when cold points to a heat issue or wiring (grounds in particular.) The coil amps tend to display bad behavior initially when they’ve been operating for a while.

How many miles? Ever had any problems with the LH harness? Are the grounds at the back of the block clean and tight?
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By hessank
#165078
hessank wrote: Mon Aug 08, 2022 8:14 pm
I would bet on the final stage coil amplifiers before “black” coils.

Also, wiring issues are usually intermittent initially. So, your theory that because it runs ok every once in a while doesn’t rule out wiring issues.

The fact that it runs best when cold points to a heat issue or wiring (grounds in particular.) The coil amps tend to display bad behavior initially when they’ve been operating for a while.

How many miles? Ever had any problems with the LH harness? Are the grounds at the back of the block clean and tight?
I absolutely treasure your advise Worf. As I said initially, I was only plucking the lowest hanging fruit which is the Temp II sensor at the front of the engine JUST AFTER I got home from my trip. Yes, I was hoping that it was the problem, but now a more comprehensive troubleshooting will be done. Today I will remove the air intake filters to get at more stuff, the coils and the ECUs. I have already identified PIN #19 for the EZK and PIN # 13 for the LH to retake the temperature readings.

Car has about 60K miles. Never had a problem with the LH harness. Fuel Injection harness renewed 3 years ago incl all new 2 and 3 pin connectors. Alpha N re-tuned by Jim Corenman 2 years ago.
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By worf
#165172
hessank wrote: Tue Aug 09, 2022 9:35 am Fuel Injection harness renewed 3 years ago incl all new 2 and 3 pin connectors.
So, you mean that you replaced the 2 and 3 pin connectors on the LH harness?

How did you deal with the EMI shielding on the 3 pin connectors?

A poorly shielded CPS circuit will produce symptoms like you describe.

Your timing light should provide some data when you get to use it.
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By hessank
#165205
I used a 3 layer (metal braided, foil and outer skin plus heat shielding) shielded wires for the CPS (I think).

UPDATE:

(1) The LH readings taken at Pins #13 & 17 and EZK at Pins #19 & 18 were almost similar to the ones taken at the Temp II Sensor.
(2) I removed both Ignition coils and found this: Driver's side (Primary at 1.0 Ohms & Secondary at 6.93 K Ohms). Passenger had a Primary of 1.0 Ohms but a Secondary of 0 Ohms (did I read that right as being 0 and shorted)? Check photo.

Image
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By worf
#165250
hessank wrote: Tue Aug 09, 2022 6:44 pm ... but a Secondary of 0 Ohms (did I read that right as being 0 and shorted)? Check photo.
OL means Zero Load: Open Circuit.

So, check your measurement device first and in particular that it's making good connection to the contact in the well of the coil. If you are sure that OL is an accurate observation of the coil, then the coil's dead.
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By hessank
#165449
Thank you.
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