Technical Tips > Post 84

1986 C4 MAF Sensor replacement?

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Ausrs:
One thing with Vats removal is the ability to remove that start enable relay as even with vats removed from the memcal the key still has to talk to that relay for the car to start

Vettech:
The only issue I've had with keys - is the actual tweezer type contacts which fail to contact the chip on the key.
Replace or retension - no more issues - or read the chip resistance and hard wire an equivalent in parrallel with the contacts - this does defeat the purpose of the security function - I like the car to be where I left it, upon my return...

Now FYI .
The CS inj is near number 5 injector - but injects direct into the manifold.
The Thermo Time Switch is located under the Throttle body on the front of the engine, looks like a Temperature Sensor, in fact, to its right is a smaller sensor which is in fact Coolant Temp Sensor.

I'd check these out before ripping the dash apart.
Regards.

peterw:
Vettech

I just ran the test you gave me in post 5 and wasn't able to get a result because my car had been giving me code 33 beforehand.

I assume it works when you are getting code 34 (which mine originally did).

It will idle when warm but hunts around and still gives me code 33.

That page out of the manual said something about a rough idle test so I really need a shop manual.

What manual do you have?  It looks to be very informative.

The Official Chev manual is expensive at $240.  Haynes for $67.

I have looked at online/disk manuals and can't tell if they are any good.

Any recommendations from you guys?

Pete

Vettech:
I have the GM Service Manual ST-364-87 AND
the GM Electrical Diagnosis Service Manual Supplement ST-364-87 EDM.
They are a strange setup, the GMSM has basic electrical, all the Code stuff and Six fold out double sided six panel circuit diagrams - concise but a bitch to read and wire trace thru, with failing eye sight.
The GMEDM is in chapters covering each system, circuits,  pics, large diagrams, text on tests and usefull info for that system, also mine is coloured, but only because I went over the cct lines with coloured pencils. The cct lines have cct #'s and colour written on, but its easier when it is Coloured.

These are for '87. I also have Haynes for 87 & 78 somewhere - not a patch on the GM books, pics etc are dark and hard to read, waste of time but they came with the cars.

I bought the GM's from Ian at Chev Parts at Yennora, cant remember how much, but have been well worth while. I also bought when I first got the 78 a Builders Book, this is not avail for C4's, but shows exploded diagrams of just about everything and would be the Bible for anyone in NCRS, since it shows every detail for every nut, bolt and washer. This is great when your C3 has been butchered - sorry I mean converted, and nearly everything behind the dash has been ripped out and scrapped.

If you intend to keep the car and do your own work - the GM books are well worth while. I replaced a rear hub using the GMSM.
Regards.

Vettech:
If cct 998 goes O/C, then the ECM will see a high signal voltage and set a code 33, meaning it thinks the MAF air flow is too high.

On my 87 I got 33, 34 & 36, if not one then the other, the relays look the same BUT THEY ARE NOT.

Ensure correct relays, then I ripped out some wiring or cut & replaced connectors, all the connectors, wires etc were well & truely cooked, hardened and filled with greace and oil and other general crap. Eventually all went well.

Sorry if I'm a bit vague, with all this Corvid19 going on, its hard to concentrate.

Regards

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