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Matt
Matt, Mechanical Engineer
Category: Mazda
Satisfied Customers: 22247
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have a 1992 MX5 that has just begun stalling on

Customer Question

I have a 1992 MX5 that has just begun stalling on acceleration and ranging wildly when idling. My mechanic has run diagnostics but come up with nothing. Any ideas?
Submitted: 2 months ago.
Category: Mazda
Expert:  indy-tech replied 2 months ago.

Hi, I'm Greg (Indy-Tech).
Welcome to JustAnswer. I'm reviewing your question now, and will post back with your reply ASAP.
Rgds Greg.

Expert:  indy-tech replied 2 months ago.

Hi what did your Mechanic test don't want to double shoot whats been done .

Greg

Customer: replied 2 months ago.
Can't tell you. He didn't specify, and I wouldn't understand his answer anyway. But he said he did consult an MX5 mechanic that he has worked with in the past, and between the two sets of diagnostics, they found nothing.
Customer: replied 2 months ago.
When will you reply?
Expert:  Matt replied 1 month ago.

Hello

another expert here

This could be an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and can lean the engine out and can also allow the engine to rev up when not desired causing rough running.

As its a mechanical fault it tends not to turn on the fault light and you can sometimes hear a 'hissing' noise with the engine running.

Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.

The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propane around each joint in turn. If the engine rev's up you've found your leak.

Now you might think that spraying lighter gas around a hot engine isn’t wise, however the flash /ignition point of gas is about 400°C so you need a naked flame or spark to set it off and I’ve used this method for many years without incident.

Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.

air / vacuum leaks can be very temperature dependent as things in the engine bay will expand as they warm up so you can have leak that come and go with different temperatures

It’s also worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a poorly pump will all result in insufficient fuel being delivered to the engine

Might also be worth cleaning out the idle speed control motor / valve as these get clogged up with carbon and some brake cleaner washed through helps free things off.

Might also be worth checking the wiring and connector to the airflow meter for any signs of corrosion or damage. you can do a quick fault find if you unplug the meter and run the engine without it.

if the engine condition is the same then chances are the meter or the connection to it is faulty

It’s also worth cleaning the MAF sensor wires, as they can get coated with dirt over time which then offsets the reading

Use some contact cleaner or brake cleaner to spray onto the wires to remove the dirt – on no account touch the wires with anything as they are very fragile

Customer: replied 1 month ago.
Thanks! I'll take this to my mechanic.
Expert:  Matt replied 1 month ago.

no problem

just get back to me on this post