Technical Tips > Post 84

1986 C4 MAF Sensor replacement?

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Vettech:
Finnaly back onto Forum.

How did all this go on your C4 Peter's.

peterw:

--- Quote from: sirfixalot on July 09, 2020, 07:00:37 PM ---Checked the voltages on the 2 coils in IAC had 9.13V on  green pair & 0.9V on blue pair with ignition on, engine not running.Also thru tested wiring direct from computer to check for continuity, coils on IAC both test at about 56 ohms. Removed vacuum pipes from  rear of manifold & connected to vacuum pump both held good vacuum so no vacuum leaks in hoses & valves,Fuel regulator. Starting to run out of ideas.

--- End quote ---

My research tells me the MAF, IAC and TPS are what controls the engine at low revs.

I was wondering if you tried cleaning the MAF.  For the cost of a can of MAF cleaner it could be worth a shot.

TPS is very easy to test as well, mine varied from 1V to 4.2V which is what the youtube gurus said it should.

I was lucky in having a friend with an 86 and could do a MAF swap to test it.  It's very easy to take out so if your 87 has the same MAF as mine you are welcome to do a swap with mine and test yours.  I am at Peakhurst so not far away.

Pete

Vettech:
I know your reply is for Sirfixalot but.

When mine played up some time ago, I think I had carby cleaner, thus it was cleaned.

But touching that hot wire did not appeal.

But I had varying codes, as stated early, new (correct) relays, new connectors, new wires.

Was running great until the coolant decided to depart recently.

The thing wrong with this, is I don't have the smoking gun but a mass of probables.

This bit is for you MY081  :banana: :nutkick:

Vettech:
I'll send some more tomorow, I just typed for an hour only to loose it all.

But we need some more details about how the ECM operates - esp after looking at 8A-20 - 0.

Geoff - if your getting a constant voltage on one coil all the time, I think this is in-correct

There are three possible scenerios.
1. The IAC is only operated when SOC is reached (SOC - Standard Operation Conditions)
2. The cct is only energized when at idle and adjustment required.
3. Adjustments like  Drive engaged, A/C applied etc.
4. Alternatively it may give constant pulsing voltages to either Hi or Low coil.

But for a constant voltage on one coil, means the ECM is trying to Drive Hi or Low constantly.
Note that 8A-20-0 may not be correct,  I would imagine the "A" coil (blue wires) should be marked Hi and the other coil both wires Low.

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