misfire/breaking up under boost

[baby6]

OK, so I posted this awhile back and still cant figure it out.

Multiple misfire/breaking up under boost, gets noticable over 3800 and really bad over 4200. Almost intermittent, it will sputter and breakup and then catch itself and then start again. Fuel pressure bounces as misfire happens, boost does as well. FP rises fine until miss starts to happen.

Things I have tried/changed - FPR, Fuel pump, spark plugs, new hotwire, wires, coil pack, ignition module, MAF

When I pull the plugs out after this happens, it indicates a lean condition. Plugs are a scary white (lean/detonation condition)


Need help, driving me NUTS!! Car is no fun and do NOT want to blow it up. Thanks.

 

[87_we4]

Do you have any scan master numbers?

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[87_we4]

Need help, driving me NUTS!! Car is no fun and do NOT want to blow it up. Thanks.[/quote]

Also I would recommend not driving the car and boosting it at all until you get it figured out. You will soon be rebuilding the motor if it keeps up

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[baby6]

Trust me, I know. I am not flooring the car at all, I let the boost build and bring it up into the rpms, that is the only time the problem happens. I just unplugged the cam sensor to see if that would make a difference, it doesnt. Also, boost fluxuates heavily.

Scanmaster numbers arent really helping me, but here are some.

At idle right off hand

AF 6-7
BLM- 121-125
TPS- -.40
IAC- 20
02s- bounce around in open loop (700-850, mostly hanging around the 830 area)
I have noticed my BLMS are lower than usual, hanging around the 118-122 area while cruising. 02s seem to drop off to near nothing every time I let off the throttle (050-200 area) and then they pick back up after I start giving it some throttle again. 02s under boost are around 700-800, never lower, never higher. MAF rises to 255 under heavy load. I have a translator with an LT1 MAF.

 

[87_we4]

Set tips to .42.. what spark plugs you running and at what gap? Are you running fresh 93 octane? What chip are you running?
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[baby6]

Plugs are r43ts gapped at .030, I have also tried different gaps as well, no difference.
TPS I have set anywhere from .38 to .46 doesn't make a difference

 

[1fastcobra]

I had sort of the same issues. My blm
Were real low. 110 ldle. 116 under load
Unplugged the cam sensor.running. No change.
So I reset the cam sensor now sits on 128 idle. 128 under load. Tps 42. Iac 26
Fuel 43.
Ur5 set at 30 gap

May help !!!

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[earlbrown]

are the wastegate hoses brand new?

 

[87_we4]

How much boost are you running?

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[baby6]

I noticed when I unplugged the cam sensor, my blms went from 121 at idle to 132. Wastegate hoses are new, no cracks in the rubber/dryrotted. I currently have it setup as hose coming from compressor housing to rjc boost controller- then back to wastegate. is this how it is supposed to be setup? Also, I need honest opinions on this question. Can VALVE SPRINGS cause boost to freak out under high rpms, and cause a breakup?

 

[john keskes]

Check the Voltage. what is the SM saying for voltage? should be at least 12.5. Does you volt light come on right before you crank the motor ? I had the same thing happen me.. Perhaps a bad ground ? My voltage was all over the place 9.5 - 11.5.. KR jumped to 12.5 ( i think this was false though ) i didn't damage anything thank God.. i limped home.

 

[baby6]

Interesting. My voltage appears to be great, I have 13.5 to the pump in back, battery and alternator both show 13.9. Scanmaster has always bounced around,12.5 to 14.0. I have never been able to get a good reading from it but I've heard it's no biggie as long as the ign block in the fuse box is showing 13.3 (which it does) 87 we4 when I was running the wg tuner style (no boost controller) it would go to about 16lbs
I noticed that sometimes it would only pump out to about 13 other times...now that I have the p.o.s rjc back on there for troubleshooting this problem only, it shoots to around 15 at barely half throttle. I hate that thing! But I just put it on to see if it would make a difference with the break up, and nothing.

 

[john keskes]

ok. just throwing ideas out there

 

[87_we4]

You have a flat tappet cam? Could have a flat cam

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[broke]

Did ya change the fuel filter when ya did the pump? Just throwin out another idear.

 

[baby6]

Filter has been changed. I hope it's not a wiped cam, I guess there I that possibility too. I am halfway done doing valve springs to it, we'll see what happens

 

[GNONYX]

What is the mileage on original stock 86' motor, besides bolt ons?

 

[termn8rgn]

I've had this problem twice.Once was coil pack.Other time plug wire.

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[baby6]

I have tried like 3 different coils, different wires, 2 modules, 3 sets of plugs. I just finished valve springs, same thing. The problem is definitely more distinct now, it is a backfire through the intake at high rpms, fuel pressure and boost both bounce like crazy when it happens, i need more opinions please. Note- it does not seem to do it under no boost at high rpms in first gear.

 

[1fastcobra]

Did u blow out the fuel lines?
You may have a bad pump.
Intall the fuel filter back wards !!
Sounds like fuel. == Back fire intake
Back fire exhaust.== Timming.
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