Idles Fine but Rich Misfiring revving

[congers87@hotmail.com]

Hi guys,

It has been a while since I've been here. The beastie is so close to complete after 2 and a bit years. Now comes the part of getting this thing to run as sweet as it did before.

The car idles good. On start up around 1200rpm with an occasional burp. Fueling doesn't make your eyes water. Currently there is only a dump and exhaust to just under the sump. However the minute I flick the throttle, the idle drops (800-900rpm), and becomes rough with a misfire. Accelerating the car misfires worse and the mixture is rich as fark. Eye watering.

I have adjusted the idle mixture screw to 3 turns out. As suggested by Damo in an old post. It was at 1/3rd of a turn out, why I don't know. I will try and list things I have done and checked.

- Standard intake setup to the T25G turbo. (only the elbow and a longer straight piece of silicon changed)

- VL TB, I fricked around with the stop screw when I was a younger (dickhead) but I have returned it to a middle position and adjusted the TPS accordingly.

- 450 wide front mount ( I have triple checked all hose clamps)

- I cleaned the injectors back flushing them with carby cleaner and a momentary switch. New pintle caps and baskets ( I regret doing this as I am suspect the injectors are now fucked) The resistance of the injectors checks out though and they still click open with a momentary switch and 12v.

- I have tried a spare computer. No change (standard ecu still)

- The AFM passed all the checks in the workshop manual

- I cleaned the dissy contacts and checked timing

- I have double checked the leads are on in the correct order

- I have checked the fuel regulator hoses are on in the right order. The regulator is orientated sideways but I couldn't imagine this is an issue.

- The spark plugs all foul after say 5min of running. I have cleaned them.

- I have checked for vacuum leaks. Only chance of a leak could be an
injector grommet or the intake manifold gaskets. However those gaskets have been replaced. The brake booster is not leaking, fuel reg hose not leaking, idle hose not leaking, wastegate hose not leaking, no BOV.

- I have jiggled the ecu plugs

- I have jiggled the AFM connector and other various connectors


I am at the end of my tether with this thing. I have sifted through old posts and the manual but I am hoping for a pearl of wisdom to sought this shit out asap.


Any help appreciated

Cheers,
Chris

[tassuperkart]

Check coolant temp sensor and wiring back to ECU.
Any issues here will cause excessive overfuelling.

Oracle

[Damo]

First things first, make sure the engine meets tuneup specs. Correct timing, correct tps switch point blah blah.
I was going to suggest as Evan did, but somehow I dont think this will be the issue, as a fubar temp sensor should make the engine stall after startup timeout. Also make sure you check the correct one, the one you want is the 2pin one with the injector style harness, not the single wire job for the temp gauge. With the engine running and at operating temp, if you unplug the ecu temp sensor the engine 'should' stall.
Have you checked the plumbing of the FPR? If done wrong it can cause excess fuel pressure and dramas.
But I would be having a good hard look at your afm spring, sounds like a loose spring.

Damo

[congers87@hotmail.com]

I had probed the temp sensor wiring at the ECU connector and across the terminals of the sensor which I repeated today. Approximating the sensor was probably around 20 degrees it hit the specified resistance from the manual (maybe a full heating test is necessary?). No change in running.

I had checked out my AFM and it had past all the multimeter tests. However I had 3 other AFMs which I simply swapped one by one. They all had dramatically varying idle screw positions so I tried them all at 3 turns out. One AFM saw a noticeable improvement. It now only backfires and sounds like turd when backing off the throttle from say 3-4000rpm. Not sure if this is simply because I have fuck all exhaust. Only to the sump, which may enhance any noises. FPR is connected up correctly. Bottom barb returns to tank and side barb to fuel rail. Vacuum line leads to junction that the brake booster feeds vacuum from. TPS set, Idle bang on 15deg, valve clearances checked. I also removed each spark plug to find they did not have that powdery build up of carbon. More a grey appearance.

Idle is bang on around 700-800 rpm and sounds good. Much less missfire on free reving.

I think it is time to get an exhaust and drive it under load.

What should I expect for vacuum at idle and 3000 - 4000 rpm (no load). It is still running a standard cam and a T25g. Does vacuum increase or drop when free revving? Sorry for the rookie question.

Thanks for the quick responses.

Cheers,
Chris