scoobyste1

Need some help here peoples. Funny misfire and cold running issues. I'll start by listing the mods first then the issues.

1996 impreza sti. 70,000mls.
Walbro pump,
FSE valve(no guage).
Full blitz cat back.
De-cat.
Simtek ECU. Mapped at 1.2 Bar. Map 1 Optimax. Map 2 optimax + NF.
Supersonic dump valve.

Car was always running fine apart from cold start issues after Simtek etc fitted. Won't start on first turn of the key. Turns over but doesn't sound like its gonna start properly but if it does it splutters and dies. Next key turn starts first time as it should. Pump always primed and still primes. Cold start gradually getting worse with now problems with starting after imeadiately stopping when hot. When its eventually started from cold when you quickly depress the throttle it sort of cuts fuel, misfires, splutters then gradually gains revs if you release the throttle a bit then depress throttle slowly but still misfires till its above 2000 rpm misfire disapears. This problem is there until the engine temp reaches just less than halfway. Up until this point when it has the misfire it sounds like at low rpm (1300 ish)it has slight engine knock but the ECU isn't telling me i have knock.
Next issue got me proper frustrated. Occasionally when accelerating in any gear slowly and aggressively when boost comes on full (approx 3800-4000rpm) the car dies/jerks back for a sec then picks up as it should and occasionally backfires. When the car comes on boost normally it hits you like a kick in the ****. But occasionally when your anticipating the **** kick its like someones punched you in the back throwing you forward instead. Had it to the place where i've taken the car since i bought it (John Pye motors in Bishop Auckland) and these guys are well renowned with Subarus in the area and rally imprezas themselves. Just serviced as always every 4000mls, plugs were changed, fuel and air filter changed, oil etc. They advised that they increased the charge on 1 of the coil packs which incidently were renewed 4 yrs ago with new ones at Scoobyclinic. Also that the throttle position sensor was out. Adjusted. Problem seemed be fixed when i picked the car up but literally 2 mins up the road well louding it on the way home, cut then Boom! almightly backfire. Help. Don't want it to go bang.

Turbotits

iTrader: (2)

Who mapped it? That should really be your first port of call. It sounds like its to rich when its in the cold start phase

Baker

Not that I can help but would be interested in what solves your problems, keep us updated.

Mikej857

Does sound like a fueling problem to me

vulnax999

iTrader: (7)

Definitely some set up issue, if nothing wrong with hardware must be the mapping ...

How do you increase charge to just ONE coil pack? In the ECU ??


Sounds like timing and / or fuel mapping is well out.

Have you changed other parts reently like fuel injectors, pump, ? Having no fuel pressure gauge on the regulator doesn't help, maybe it's jut the fuel pressure that has changed and caused rich mixture?

Can you still get Shell optimax up there, VPower was the norm ages ago!!

Pramas

could be a variey of things, 1st call is look at map, the coilpacks need a change it its around 20 yr old or so

alcazar

iTrader: (2)

Change the dumpvalve for a recirculating type. that would be my first port of call.

scoobyste1

VPower up here.
Problem is there on both maps so doesn't sound like the maps or it would only do it on one i think. Also the ecu has been on 3 yrs.

scoobyste1

Coilpacks are 4 yr old. Genuine Subaru. Could 1 coilpack breaking down give these issues? When the car isn't having the jerk at 4000 rpm it runs as normal. **** of a shovel !!! Been out today and didn't do it once but as always won't start when cold well and misfire till 2000rpm until warm.

KAOS_JNR

iTrader: (2)

I have this issue now when I spoke to my specialist he has advised this could be a coil pack breaking down or plugs what plugs have you got fitted I run 7's at 6.5mm but mine when cold starts runs really lumpy till warm then bit spluttery on boost initially once car is up to temp runs fine

vulnax999

iTrader: (7)

You are not too far from Harvey (HarveySmith) up in Darlington, he can help diagnose the car by taking a look at it.

scoobyste1

Was running 8's but now on iridium 7's. Changed to these at service as i thought plug could be on the way out. But nope. Just the same. The jerking back seems the strangest problem as it only happens at 4000 rpm every time. Done about 20 mls today and did it twice. both times at 4000 rpm.

Could it be the the Walbro? fiitted 20,000mls/3 yr ago.
Coil pack? New fitted 4 yrs ago.
Crap in the boost soleniod i've read previously on threads?
Sticky actuator?

scoobyste1

Who is this guy Harvey? Does he have experience with Simtek ECu's if this is the prob?
Its going back to the garage in Bishop Auckland tomorrow so i'll see what they come up with a second time. I haven't got loads of money to chuck at the car at the moment but you know what its like when your cars got niggly little problems. You just want them sorted asap. Had no issues since i bought it 7 yr ago with only 34,000 on the clock. Is it time to let it go and upgrade to a Hawkeye with PPP. My brother in law just got a Spec D with PPP etc with 22,000 on the clock for £11350. What a steal! Made me think about giving the classic up. When fixed of course. Hmmm. Pondering begins.

Pramas

Harvey
https://www.scoobynet.com/member.php?u=5340

drop him a message, he maybe able to point you in right direction

scoobyste1

thanks for the address. Harvey responded today with some good info. Obviously not giving too much away as he is in the game of fixing said cars for a living and not a hobby. Anyway, i dropped the car back to the garage i normally use as they have the access codes for the ECU etc to give them 1
more shot. Failing that i will ask for the access code and go to Harveys as he has Bob Rawle doing mapping early September.

Cheers

Pramas

Just to add to that, when you have Bob + Harvey mapping your car, if he knows it has some kind of problem before hand, he normally has Darren on standby who is an excellent mechanic and even though hes some 40 mile from me, thats who i'll be getting to do any work on my car

alcazar

iTrader: (2)

Don't agree fully with this, Harvey will tell you what he knows, he won't hold back to make money from you, trust me, the guy is 100% honest.

EngineMapper @ Group B Motorsport

That sounds 100% a mapping issue, although very hard to diagnose over the internet, so could be a number or issues, although last one sounds like boost cut. I urge you to consider who you might see next if John Pye cannot sort it. You'll need to have it re-mapped completely if you go to someone else as the system does not allow another dealer to access the previous dealer's map.

You're welcome to contact me regarding advice on the Simtek and any help I can give FOC you are more than welcome to.

Hope this helps,

Graham

Micheru

Has the issue been resolved? I've had similar recently, on start up it's choppy and nearly cuts out (did once) though usually picks up straight away and idles at 1.2-1.3k revs until warm. Runs fine while cold though of course I never get in boost revs until warm.

Standard ecu and fuel pump, decat system recently fitted. I had an almighty backfire today that's got me a bit worried, was pulling out to over take a stopped bin lorry in first gear and lost power and there was a bang at abut 3k revs. Seems to be running fine otherwise.

I realise a new ecu and remap is in order, but might be another month before I can afford it all. Looking at a simtek/apexi power fc. In the meantime is there anything to worry about or should I prioritise the ecu and remap to be done asap?

scoobyste1

Don't know if this helps but here goes. Back to garage. Coil packs 1 and 4 said to be breaking down on full boost (4000 rpm) which showed up on Simtek software. Advised to renew all coil packs but only replacing 1 and 4 at the moment. Also cold start issue with mis till warmed up attributed to low battery voltage (11.2 V) according to software. See how it all goes when i get it back. Keep you updated and thanks to Harvey in Darlo for all his info and contact regarding my issues.