Running issues

[sam3007]

I am still having some problems with my 86 that I am struggling to get to the bottom of!

It starts and runs ok, however it seems to be running very rich and when cold is idling around 1100rpm, but when up to temperature it is idling 1500 or more.
It will rev ok with no load. But I took it for a short drive and when you use more than around 25% throttle it is hesitating and misfiring

So far I have installed new earth straps to the chassis and engine, cleaned connections to the ignition coil, checked spark plugs and leads(it has iridium plugs fitted), cleaned sitributor points.
I have tried measuring the resistance of the throttle position sensor and I think that is OK. I have also bridged the diagnostic connector but it seems to display no codes. I have tried to set the ignition timing but I am struggling because even with the pins bridged in the diagnostic port it is still idling too high.

Any help or ideas appreciated, I am running out of ideas!

[Ivan141]

Perhaps try a different ECU.. at this age it would be strange if components started going bad (electrolytic capacitors have a limited lifespan).

[Dave W]

Sounds like a fuel pump is on its way out. First check the hose to the vacuum pressure regulator, and then verify fuel pressure. Should be around 38 psi. Anything below 35psi will cause your hesitation problem.

[sam3007]

It is not very easy or cheap to pick up spare parts is a lot of the problem, otherwise I would try swapping our various sensors and ecu etc

(06-20-2022 01:54 PM)Dave W Wrote:  Sounds like a fuel pump is on its way out. First check the hose to the vacuum pressure regulator, and then verify fuel pressure. Should be around 38 psi. Anything below 35psi will cause your hesitation problem.

I forgot to mention I have dropped the fuel tank and the inside of tank, pump, sock filter etc all look very good condition.
What is the best way to check fuel pressure?

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[Dave W]

To verify fuel pressure, use a jumper wire and bridge +B to Fp. Just attach a pressure gauge on the end of any hose connector and dead head into the gauge. [min of 38-40 psi] a new pump was 50+ psi. With my EFI system, I encounter lower fuel pressure the longer I drove and changing the fuel filter did not improve it. A new fuel pump worked like

[sam3007]

(06-21-2022 01:54 PM)Dave W Wrote:  To verify fuel pressure, use a jumper wire and bridge +B to Fp. Just attach a pressure gauge on the end of any hose connector and dead head into the gauge. [min of 38-40 psi] a new pump was 50+ psi. With my EFI system, I encounter lower fuel pressure the longer I drove and changing the fuel filter did not improve it. A new fuel pump worked like

What is the purpose of the jumper wire for checking pressure? My car is an early model with the 2 pin diagnostic port, so I don't have the labelled pins. But I assume it would work the same

Is what you are saying pump pressure then? I can measure that easy enough off a fuel line like you say.
But not sure how to measure fuel pressure at the rail as it doesn't have a valve/port to connect to.

I will see if I can find a suitable gauge at work to borrow!


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[Dave W]

The 38 to 40 psi is if you "T" into the fuel line, which regulated fuel pressure. If you dead head you will see the higher fuel pressure. Any pressure gauge will would, even an air pressure gauge, with a 50-60 psi range, and a barb fitting attached to it to fit the hose end.