Humboldtgrin

If there's a local college in your area that has an automotive shop and a Dino you might be able to talk to the instructor into putting your car on the Dino for a load test and you could check out the fuel pressure. Or get a hose with the correct fittings on the ends, run it up to the windshield wipers and connect the fuel gauge there for a quick one time test run. but I would seriously replace your ignition wires first. You may just have an awesome light show going on under your hood.

moalaska

Yeah I got a set on order just waiting. I know the corrosion on that one is bad and obviously way worse then the rest. May have one cylinder not getting good spark at certain rpm because of that wire. Have also looked into getting electronic fuel pressure sender with guage in car that would be handy to have.

Dave W.

Here's a quick test for the fuel system. Get a hand pump with a 50psi gauge, attach it to the fuel pressure regulator line, add a jumper line to the fuel pump so it's running with the car off, then slowly add pressure to the afpr and watch both fuel pressure gauge and the air pump gauge. Make sure they both rise at the same rate. If the fuel pump is getting weak it might not handle higher pressure, the fuel pressure might start to drop off as boost pressure goes up. A good fuel pump should be able to produce 63psi, which is enough for 43 psi (3 BAR) base pressure plus 20psi of boost.

I have a feeling your old plug wires were bad. Your symptoms point to spark blowout. I personally don't like Magnecore wires on this car. I tried a set since they worked very well on my other car, but the problem is the boots on the plugs are weak and difficult to remove. After a few remove/install sessions the boots ripped and the wires separated from the crimp terminals. I'm using NGK wires now and they're been great.

Also, make sure your plugs are gapped to .026" to .032" Anything bigger might misfire under boost.

moalaska

I just replaced fuel pump last week to rule out weak pump. New plugs and gapped, and wasnt hitting enough boost to really musfire under boost but yes thinking im having weak spark due to bad original wires. I had already peeled all the heat shielding off of them as it was cracked badly.

Dave W.

If it still cuts/ misfires, could you watch the wideband AFR to see how rich it gets right before the misfire? I'm interested in the richest AFR you see. The gauge might move quickly, so watch carefully.

Humboldtgrin

It's probably just the spark plug wires that are bad because if you have a miss fire in the combustion chamber you'll have unburned fuel and oxygen that go into the exhaust showing your air fuel ratio meter that it's running lean because of the oxygen content in the exhaust, does that make sense. Just replace your wires you're gonna fix your problem most likely. you should probably replace your spark plugs, cap and rotor as well. I had to fix this post at a rest stop, driving and typing doesn't work well. And talking into the phone really doesn't work that well sometimes.

Tom M'Guinn

Agreed. Based on your description of the wires, I'd change them even if they weren't the cause of this issue. And, there's a reasonable chance they are the issue... Back in the old days, we'd open the hood in a dark (well ventilated) garage and look for arcing from the wires with the motor reving. Spark plug wires weren't as good in 60-70s, so it wasn't uncommon to see a little firework show. They have to be seriously bad to see arcing these days, but no harm taking a look.

moalaska

Cylinder 4
cylinder 2, very likely grounding with each other
Cylinder1
Ok so I cleaned my old plug wires yesterday and wrap them with splice tape. Made a coil wire out of some super heavy guage amplifier wire and the old crimp fittings boots from original. Well not original the boots were but had some coil wound replacement wire. Drove around and same symptoms.

Got a noid light and here are results
1 and 4 no light pulses
2 and 3 light pulses but inconsistent

I tore into my injector harness and here are the results

Cylinder 2 Was the only one obviously grounding out but the others were bad as well.

moalaska

After putting some electrical tape on the exposed sections i now get a steady 3 pulses from each cylinder per revolution. Pretty confident that's what is causing my car to stumble go lean. Time to get some replacement connectors and fix my harness up a little.

Tom M'Guinn

Glad you found that. It's unfortunately all too common. I'd fix the spark plug wires too of course Some to your findings are hard to explain (3 pulses per rev?) but clearly you need to fix the harness regardless. The link below has info about the connectors. I wonder if the rpm-based change you were feeling was related to when the Vitesse system shifts from semi-batch to full batch --i.e., the effects of the bad harness gets worse in single batch mode -- though that's an academic question at this point I suppose...

https://rennlist.com/forums/944-turb...onnectors.html

moalaska

Yeah i wonder how many pulses each injector is supposed to get. There is a kit for 149 that has all the injector connectors plus tps speed sensor temperature sensor etc. I think ill just get that and gom through all my connectors. The wires seem fine except where they join the connectors and factory heat shrink is hard.

Tom M'Guinn

Yeah, that's a design flaw. That sealant/glue/potting material inside the connectors just cuts the wire insulation over time. Probably worth doing the speed/ref connectors while you're at it, since they suffer from the same problem...

Humboldtgrin

Two pulses I believe. That's how batch fire works from what I remember in class.

moalaska

Maybe John changed the fueling/ pulse lengths etc for the bigger injectors i know he modifies the fueling for his software along with allot of other things.

ealoken

Do yor engine loom from DME to injectors have any resistors?
I just tok my kit out of the car since im going standalone, and my kit has Resistors in it.