mx5cartalk.com

Car: NB8B with Rotrex Supercharger and supporting mods

I just got back from a 3 month jaunt around Europe, the car has not been started for 4 months. I checked all the fluids (done just before I left) and they were okay, circulated the oil by cranking with fuel injector fuse pulled. I have filled the tank with fresh fuel.

The car ran fine before going away but now I have the following problems:

Slow to start.

Idle is okay but tickling the throttle to pull away gently causes it to stall, a larger throttle opening will make it stumble a bit but it will pick up and run fine. It runs fine over 2000RPM with normal temperatures and pressures and it still performs fine at full throttle / high RPM.

Sudden closing of the throttle causes it to stumble below 2000-ish RPM or stall as does doing something that causes an idle dip such as turning on AC, lights, using brakes etc.

Part throttle cruising is not good...It is impossible to maintain something like 50kmh, the revs creep and backing off the throttle slightly causes an instant drop in revs. It is like the throttle is either on or off at that speed. It is fine at 100kmh+

Biggest worry is that on the cold start I get a heap of White-ish / Blue-ish smoke out of the exhaust, increasing RPM just increases the smoke but it does seem to clear and all but vanishes once it is at full temperature. Cold start has a lot of moisture coming out of the exhaust to.

So what is wrong?

Sticking or gummed injectors? I need to deal with the same problems for an Astina that has sat around for a year. I'm sort of encouraged that you have the clouds of smoke too, it makes it more likely that it's a sitting problem rather than a terminal piston ring problem.

Do the easy things first, check the spark plugs look ok and aren't fouled. They shouldn't have from sitting, but it's a simple check.

Then I'd go and give it a tank of fuel, if the fuel in the tank went stale you'll want to dilute it as much as you can with fresh stuff. 98ron from BP/CAltex is a good bet since from memory they're got all sorts of detergents in them that may help loosen any crap in there.
If not, buy a bottle of injector cleaner. I recommend the one made by STP, purely because it comes with a free T Shirt.

Other than that, I can't think of anything else that's likely to have changed while sitting


edit:
Just noted, supercharger.
Petrol tends to lose octane as it ages from memory, and boosted engines tend to want more octane to prevent knocking/pinging (depending on tune)
I'd try new fuel and se how that goes before I went and spent any money on parts.

Hmmm sticky fuel injector sounds like a plausible cause.

I assume that injector cleaner needs to be run through with a full tank? Might be hard as I rarely take the car on the road...is there a way of verifying injector operation first?

i would drop some new fuel in it and allow it to idle for 15+ minutes. then drive it like you stole it.

Agree with the comment from project r . Same thing happened to my old mans car. Took it out for a good thrashing. Worked a treat.

I think I remember unleaded fuel is hydroscopic, so you may have enough water content to be causing problems. How much fuel left in your tank? If very little, maybe fill up with new 98 or 100 to dilute the water?

There was under a quarter tank of fuel and I lobbed 20L in, I will brim it and chuck a bottle of injector cleaner stuff in then take it for an Italian tune up and see if that makes a difference.

deviant wrote:There was under a quarter tank of fuel and I lobbed 20L in, I will brim it and chuck a bottle of injector cleaner stuff in then take it for an Italian tune up and see if that makes a difference.

Love the "Italian tune up". Take care and remember which side of the road we drive on.

Yeah. It sounds like bad fuel.
having spoken to bp once about it because of similar issue, they recommend
putting a good quality octane booster in. They say it re-invigorates the igniters in the fuel to 'workable' condition. It does work.. have dkne it many times. Plus yes the ITALIAN tune up works a treat.
I would recommend the nulon pro strength octane boost. Really good stuff.
part number is PSO.

So I went to Repco and got a bottle of STP injector cleaner additive stuff...got my free t-shirt to and it was reduced from the $22 sale price to $10! T-shirt doesn't fit though.

Cold start today seemed to be slightly improved from last time, a bit of smoke but not as much and cleared almost straight away. Chucked the additive in and went and brimmed the tank with another 20L.

Not many chances to get Italian with it but I managed a few pulls through the gears and drove around for an hour including about 15km on the freeway.

The idle seems to be better and although it still stumbles a little bit it does not stall as easily. It is more willing to let me tickle the throttle.

The exhaust still stinks of fuel so I dont think we are quite there yet!

check you r throttle body and air bypass valve arent jammed opem/closed

Cheers mate, will have a look tomorrow. I picked up a can of upper head cleaner stuff...not sure how much difference it will make but I will feel better doing it maybe