Help and Advice Please - Misfire

[BIG_MVS]

After 3 failed pumps, fuel spilled in hair, arms and eyes , I think I've cracked it!

Replaced the front fuel pump again and all seems well after a few days...touching wood, cloth and everything!

You can definately hear it prime and is on all the time whilst driving.

What a nightmare this has been, only taken almost 12 months to fix, and now the dreaded MOT awaits....

Do you feel like a walking fireball about to flare up?
Well done!

BIG_MVS how's your car running now? Still okay? Mine seems to have developed a similar fault.

The other day it cut out on me a couple of times whilst sat idling in traffic and at a junction. Back home checking leads, wires, etc I noticed the fuel pipes were leaking again (well more like one was jetting petrol into the engine bay rather than into the engine! ) So I renewed them with new hose and clips, gave it a run - no petrol leaks and no cutting out - problem solved I thought, thinking the fuel leak might have been the cause of the cutting out on idle, because not much looked like it was going into the engine!

So, thinking the car's running perfect I took it for a nice long run into Wales and back yesterday to enjoy it on some proper roads for a change. Heading home it starts misfiring in fourth - just wont rev at all. Dropping to third seems to fix it - revs like mad, back into forth - misfire! Trying some sustained acceleration in forth and the damn thing wont rev, just misfires, then it starts doing it in fifth, then it does it in second off a roundabout, misfiring like mad, then it suddenly clears and it accelerates and drives perfectly for miles, no problem. It would one minute accelerate away from lights revving through all the gears, running perfect, then a few miles down the road it would misfire for a few seconds then be perfect again! It all comes to a head literally two miles from home in the outside lane on the Runcorn expressway, sandwiched amongst HGVs it starts misfiring and slowing chronically. I start changing down the gears in desperation, hoping into burst back to life, it's stopped properly this time! I manage to avoid death by HGV and manage to limp onto hard shoulder. Giving it a cursory check at the roadside I can't see anything wrong. All the leads are on and the petrol pipes are still okay - no leaks. I try starting it and it starts, but when I try to rev it, it misfires and dies. So I wait another minute or two and try again. This time it starts and runs, so I set off down the hard shoulder but it misfires and dies again. I wait 3 or 4 more minutes. This time it starts and runs fine and I drive the last couple of miles home without a single splutter!


So, I'm thinking it's a fuelling problem of some sort? I plan to give it a service anyway - change oil, filters, plugs, but reading the previous posts I'm also going to change the fuel filters.

I'll check to see if I can hear the front fuel pump working too. I can hear the rear pump working, so I'm thinking that's probably okay. Would it be worth changing the fuel pressure regulator too (bearing in mind the recurring leaking fuel pipes problem, I'm thinking this might be somehow related)?

I'm thinking (hoping) renewing the fuel filters will cure it, because it seemed to cure a similar problem 2 or 3 years ago and they haven't been changed again since.

Appreciate any advice/suggestions!

Cheers!

Juzz.

Check your Ht Leads.

I had water around the top of a plug in the head and that caused a spasmodic misfire, but no stalling.

One thing everybody should do on GTAs, renew/sort/check the wiring to the rear fuel pump, and bin the suppressor mounted onto it...

The rear fuel pump is very critical on voltage, it will only flow properly if it has proper voltage. If the wiring or connector is bad/corroded, the voltage drops and the flow drops right down, and with voltage drop the current goes up, and puts even more strain on the wiring/pump.

I had a car in the other day, with 12v before the connector, 11v after, and 8v after the suppressor! Pump was wirring, but not how it should. The best thing is to renew all the wiring from the fuel pump relay - if you can't do that, cutout the plastic connector and resolder and heatshrink the wiring back together, and bin the suppressor, or replace with a new one. Earth the pump better if you can too. All that wiring and connector back there has been subject to nearly 20 years in the elements, and is never really checked, even though its the source of ALL power and torque to your engine!

Is the fuel pump relay one of the ones under the ECU, so I guess at least it should be a pretty short wire run?

Is the fuel pump relay one of the ones under the ECU, so I guess at least it should be a pretty short wire run?

Yep, should be the one on the left.

Thanks for the replies. I'm pretty sure the HT leads are okay. I changed these last time.
When I had my head gaskets and turbo recon done (over 18 months ago now) the car wouldn't start when the garage finished the work and went to do its MOT. They traced it to the wiring to the rear fuel pump. I think it was broken or corroded or something, can't quite remember. They rewired it into a new block connector and ditched the suppressor. I've never looked at exactly what they did myself, so I'll check this too, thanks David.

[BIG_MVS]

Does your rear pump whine or seem to struggle when the car misfires?

It sounds different to my problem as my misfire happened after a certain time and in hotter conditions at it's worse. Worth checking the front pump is running though.

In my experience its always spark, not fuel..3 times now and its always been plugs or leads! Not connected properly or plugs sitting in water or fuel....the bastards!!!

Had the rear wheel and fuel pump cover off today. The suppressor was still there but it was unplugged and the wiring had been bypassed and connected directly to the pump. The pump wasn't whining and didn't seem excessively noisy and i got a reading of over 10 volts when I put a voltmeter to the pump terminals.

Anyway, I thought I'd undo the wiring to the terminals and clean them up because they seemed quite dirty and corroded. The first one I attempt to undo and the little nut holding the wire on is so tight and corroded it shears off! Now I've got no way of holding the wire on the terminal and need a new pump. Oh well, might as well change that too as well as the filter while I'm at it! At least it'll be one more thing eliminated.

So I didn't get round to checking the front pump too. What's the best way of accessing this and the front filter, does it have to be got at from underneath? Also, none of the local motor factors list a filter for the front. Where's the best place to source one of these? Are they dealer only?

Juzz, I find I can get good access under the car when it is up on ramps. I have to use two 3 foot scaffold boards to make a very shallow incline up the ramp, otherwise the bumper hits the ramps before the tyres. I think you will need to remove the under tray. The other way to get access is to remove the wheel, but is seems very limited and dark in there.

Good luck, When I removed my bumper, 3 bolts sheered after the nuts had done about 2 turns. Next time I will be more cautious and ease the nuts off with turns off and on to clean the threads gently as they come off.

Cheers Simon. I was hoping the reply wouldn't be 'remove the undertray'! I think I'll try removing the wheel first. I haven't got very fond memories of removing the front bumper last summer when I had to remove the radiator. It was a nighmare I hoped never to have to repeat!

I know what you mean about ramps. I find the usual metal ones most places sell are too steep for the GTA. I use two solid wood old railway sleepers with one end of each cut to a slope gentle enough for the GTA. Works great!

You may just get away without removing the bumper.
Just the rear undertray, or undoing the fasteners from the bumpers undertray and fold it down. After you have had the wheel off, you will know what is next.