My 1990 V6 Sei is finally back on the road

[dcz1643]

My V6 engine has decided to intermittently, do silly things. I took it for a drive today and it stalled as I backed off my drive. It then drove fine for a couple of miles and then at a roundabout, it hiccuped, the engine light came on and then it was fine again. When I got hope I turned it off and restarted it, no engine light. I put the blink tester on it and there are no codes stored.
Later in the day, I had the engine idling and it surged again. I decided to change the fuel filter, as I ordered one and it was on my list of things to do. Unfortunately they didn’t sort the engine but at least it’s done now. Looking at the one I took out, there is a chance it has never been changed! I will find this stupid engine problem eventually. Here are some pics of the old fuel filter.

[Dieselman]

For intermittent engine running issues I would check the crank sensor and connector and in particular, the fuel injection relays on the front of the ECU box.
The relay connector are well known for having poor connection, caused by splayed female spade contacts in the sockets.
Also check the throttle potentiometer is sound and the engine loom connector under the Lhm reservoir, which are known to have poor connections.

It's odd that there are no codes if the engine warning lamp illuminated, as that should have stored one. If power is cut for 10 minutes any codes will reset.

[dcz1643]

Hi, thanks for the check list. I have done everything except the crank sensor and I still need to put my multimeter on the throttle potentiometer but I have given it a good go with Servisol and worked the pot. Things seemed to have improved but again, when I tried to accelerate hard, it hiccuped again, warning light came on but then it was ok again. I drove home, turned the engine off, started it again, no engine light. I rev’d the engine and it took too long for the revs to go back to idle. Onwards and upwards, do you know where the crank sensor is on the V6 auto? Cheers

[Dieselman]

On the bell-housing under the throttle body. The connector is the brown one mounted next to the throttle body.
I doubt it's the crank sensor, otherwise the engine wouldn't run at all.

Lubricate the throttle flap mechanism, check the output of the throttle position sensor, perform a smoke test on the intake and fuel pressure test and check the MAP sensor pipe is neither blocked, or leaking.
Check all vacuum take off ports into the throttle body and intake manifold are clear.
The TPS setting and operation is crucial to acceleration performance, as it momentarily overrides the Lambda sensor to increase fuelling for acceleration.
Check the output is ~0.5v at throttle closed and greater then 4.5v at WOT. The TPS sets base mixture strength.

I doubt it is this, but check the spark output and the distributor rotor a for corrosion.

The throttle and idle compensator should directly control engine revs, so if they are working smoothly, the revs holding up has to be an air leak.

Given the engine management lamp illuminates there should be stored codes.