89 NA6 cranks but won't run - fault codes 1, 8, 10 and 34

twr7cx · Postby **twr7cx** » Tue Aug 23, 2022 4:13 pm

89 NA6 won’t run – cranks and tries to run but stalls after a few puffs…
Diagnostic test is showing:
01 / Ignition pulse / No signal. Check Ignition system – igniter, coils and wiring.
08 / Airflow meter / Open or Short circuit
10 / Intake air thermistor in airflow meter / Open or Short circuit
34 / Idle speed control valve / Open or Short circuit
[Format: Code / Sensor or Subsystem / Diagnosis]
Is there a relay, fuse and/or wiring connector that these systems have in common? Particuarlly one I may have knocked about while doing the timing belt? Otherwise I’m guessing the problem may lie with the ECU and/or connection/wiring to it.

Recent history:
The vehicle hasn’t run since January 2022. It died while driving and was flat bedded home. Initially though it was a CAS issue (tried replacement CAS and checked connection between CAS and ECU) but turned out to be snapped timing belt. Timing belt has been replaced along with new spark plugs, ignition leads and oxygen sensor. On reassembly it cranks and tries to run but stalls after a few puffs.

StanTheMan · Postby **StanTheMan** » Tue Aug 23, 2022 6:40 pm

what happened to good old fashioned deduction?

is there spark?
is there petrol?
most likely you have air.... unless you have the timing wrong?

all this sh*t is so confusing

bruce · Postby **bruce** » Tue Aug 23, 2022 8:03 pm

So many error codes ( u have to use a weird process to get those?).
Tried a new battery?

twr7cx · Postby **twr7cx** » Tue Aug 23, 2022 8:41 pm

StanTheMan wrote:what happened to good old fashioned deduction?

In this case, I’ve run out of ideas on where to look next…

StanTheMan wrote:is there spark?

Yes, as it fires up and runs very roughly for a few seconds before stalling.

StanTheMan wrote:is there petrol?

Yes, as it fires up and runs very roughly for a few seconds before stalling.
I’ve test the fuel pump by jumping the diagnostic connector pins to run it.
I’ve replaced the fuel filter today (intended to just as part of general servicing). With the fuel line disconnected I ran the fuel pump to check fuel flow output.

StanTheMan wrote:most likely you have air.... unless you have the timing wrong?

Yes, as it fires up and runs very roughly for a few seconds before stalling.
Have cleaned the air filter as part of routine general servicing.
Timing has been double checked - the crankshaft and camshaft sprockets all line up on their timing marks and correct number of belt teeth between the two camshaft sprocket timing marks.

twr7cx · Postby **twr7cx** » Tue Aug 23, 2022 8:45 pm

bruce wrote:So many error codes ( u have to use a weird process to get those?).

Yes. It’s a fair few error codes which is why I suspect a common connector, wiring loom or ECU fault perhaps as that could be a single cause for all of them.
Codes 01, 08 and 10 cleared with the BTN fuse pulled. Code 34 remained and code 01 returned on the next starting attempt.

If you deem fitting a jumper wire between two terminals, an LED into another two and turning on the ignition to be wired, then I guess so…

bruce wrote:Tried a new battery?

I have not. The one fitted is not very old. Has been maintained on a Ctek charger during the downtime and is testing fine.
Issue continues even when a 12v supply is added on.

twr7cx · Postby **twr7cx** » Wed Aug 24, 2022 4:57 pm

Engine compression:
4 - 195psi
3 - 200psi
2 - 182psi
1 - 200psi
Specifications:
Minimum 132 psi
Maximum variation between cylinders 28psi

Red_Bullet · Postby **Red_Bullet** » Wed Aug 24, 2022 6:01 pm

Can you beg or borrow another ECU to try? After that it might be time for an oscilloscope to actually look at Cam angle sensor signal for a starter. Check for voltage on coil and injectors, check that ECU is switching the switch side low.

The risk with trying another ECU is that slight chance that an electrical fault has destroyed your ECU and may destroy the next ECU. Time for an auto electrician?

twr7cx · Postby **twr7cx** » Thu Aug 25, 2022 6:08 pm

Update:
The ignition coil for Cylinders 2 and 3 would seem to be faulty/intermittent.
Now to narrow down if it’s a faulty coil, wiring or ignition module.
The coil has a three pin connector - I haven’t got wiring diagrams with me at the moment, but assume that one wire is the main power and the other two wires are triggers for which coil is to fire. I imagine no earth is required as it’s earthed through the spark plug to the engine to create the spark. It’s possible therefore that the trigger for the cylinder 2 and 3 coil is faulty - damaged wiring, faulty ignition module, or the coil is receiving it but is faulty itself… I need to work out how to test these.

twr7cx · Postby **twr7cx** » Mon Aug 29, 2022 9:57 am

After confirming continuity of the ignition module to coil wiring I fitted a new NGK coil pack that I was able to source. No change. The coil was quickly available and the primary resistance on my previous coil was above spec so worth the try changing it out as it needed to be done anyway.
I've now confirmed continuity of the ignition module to ECU ignitor signal wires (brown and brown/yellow on pins 2 and 7 of the ignition module).
As such it's only a faulty ignition module or ECU that can be the cause. I've sourced a replacement ignition module that will hopefully arrive today...