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Misfire from fuel injector?

 

I am tracing down a misfire. ?Occurs only at idle. ?Opening the throttle and it goes away.

Last season I was chasing the same issue. ?New plugs. ?Tested and cleaned plug wires.

As I understand it, the injectors have a screen in them that can get clogged. ?So, at idle, the standard fuel pressure is not enough to cause it to fire

But when the throttle is opened, there is enough pressure to overcome the blockage in the filter and allow it to fire.

Anyone had this happen to them?
 

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If 1980-95 take out the injectors and rake them to witch hunter to be tested.

Normally it will be an ignition issue rather than a single injector. But it never hurts to have them tested and eliminated as the issue.

Cheers
Colin J
604-807-4523?


-------- Original message --------
From: "Peter S s/v Dawa II via groups.io" <scottpeterd@...>
Date: 2024-06-13 9:18?a.m. (GMT-08:00)
Subject: [PacNW928] Misfire from fuel injector?

I am tracing down a misfire. ?Occurs only at idle. ?Opening the throttle and it goes away.

Last season I was chasing the same issue. ?New plugs. ?Tested and cleaned plug wires.

As I understand it, the injectors have a screen in them that can get clogged. ?So, at idle, the standard fuel pressure is not enough to cause it to fire

But when the throttle is opened, there is enough pressure to overcome the blockage in the filter and allow it to fire.

Anyone had this happen to them?

 

I think his is a 79 so CIS.? Can't remember if the individual injectors have screens, but there is one at the inlet to the fuel distributor that can be cleaned.?
I've had success identifying marginal injector by tapping at the base of the injector to see if the stumble clears up.?
You can also just pull and replace them (I think Roger 928srus sells them) as an option, but that gets expensive.

Did the driving not clear it up?
 

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If it is the CIS, you can just pull the injectors, put them in bottles and press on the throttle plate and see the spray patterns of each injector to see if they are all spraying correctly.?

There are screens in the dizzy and in each injector.?

If 1 injector isn't spraying just get a new set from Roger. They are not expensive and it's better to have them all new if 1 isn't spraying at idle.?

Cheers
Colin J
604-807-4523?


-------- Original message --------
From: "amidlman via groups.io" <midlman@...>
Date: 2024-06-13 10:14?a.m. (GMT-08:00)
Subject: Re: [PacNW928] Misfire from fuel injector?

I think his is a 79 so CIS.? Can't remember if the individual injectors have screens, but there is one at the inlet to the fuel distributor that can be cleaned.?
I've had success identifying marginal injector by tapping at the base of the injector to see if the stumble clears up.?
You can also just pull and replace them (I think Roger 928srus sells them) as an option, but that gets expensive.

Did the driving not clear it up?

 

Being inherently lazy, I was wondering if I could just take an IR temp gun and shoot each exhaust port to look for one that was cooler.

I replaced all of them about 5,000 miles ago.

But the car has been sitting for 8 months.
 

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The IR temp gun works best on long tube headers. Cast manifolds tend to heat up evenly. Unless its cyl 1 or 5

Cheers
Colin J
604-807-4523?


-------- Original message --------
From: "Peter S s/v Dawa II via groups.io" <scottpeterd@...>
Date: 2024-06-14 6:11?a.m. (GMT-08:00)
Subject: Re: [PacNW928] Misfire from fuel injector?

Being inherently lazy, I was wondering if I could just take an IR temp gun and shoot each exhaust port to look for one that was cooler.

I replaced all of them about 5,000 miles ago.

But the car has been sitting for 8 months.

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