1G Misfire under boost

[Bluefire16]

Hey guys, posting in the newbie forum because i have been out of the DSM game for several years now and kind of stumped. Little bout the car, 92 awd laser, 2g maf, walbro 255, small fmic, 560s, aeromotive afpr, 14b.

Problem; it has a misfire under boost at about 10lbs.
New plugs gapped,
new wires,
newer coil pack,
and have checked couplers. (Getting my compressor this week for a BLT).

However, i suspect its electrical more than air leak. You can feel/hear the break up as it accelerates, without boost. Vac is at 15, and A/F is sitting at 14.5-15 at idle. Tried watching the A/F as it boosted and nothing jumped at me from being a fuel issue.

Previous owner said that he checked the coil pack and the voltage was off, and he replaced it with another and still bad, so im guessing the coil or PTU?

Thanks guys any help is appreciated. Looking for other possible suggestions.

 

[kchaazz]

What is being used to properly tune to compensate for the 560cc injectors? 2G maf will get it close, but you will still run pretty rich. What is the base fuel pressure with the vac line off the regulator? 37.5psi for a manual trans, 43psi for an auto is the correct base fuel pressure. What did you gap the plugs to?
.028- 30 for boost that low is good, but what plugs are on it? NGK BPR6ES is what should be on there, and if so, pull them and see what color the porcelin around the electrode is and come back.

 

[bcjjones]

I'd boost leak test it before throwing parts at it anymore. A boost leak can definitely feel like a misfire

 

[Bluefire16]

^^ Plugs are Bpr6es, gapped to .028, afpr is believe is set to 42 i believe, and mines a manual, however A/F seems fine, nothing to tune atm (have a maft translator, just havent installed yet)

So could it be running a little too rich actually?

It's actually set at 40 right now

 

[kchaazz]

Yeah, its going to be running very rich with those injectors and the extra fuel pressure. Dial the pressure back to 37- 38psi with the vac line off and do the boost leak test as mentioned above as those injectors, extra fuel pressure and boost leaks will really make it run rich under boost and the factory map is 9.3:1 at wide open throttle as is so you can imagine how rich itll be.

 

[Bluefire16]

3lbs is really going to bog it that bad?

 

[Dude McGee]

At this point id suspect the plugs are fouled out. Id replace them and reduce fuel pressure, then try another pull. BLT is always a good idea, even without these issues every oil change. Your probably hitting mid 8:1 afrs as she sits.

Have you done a plug reading for timing, knock and afr yet?

 

[Bluefire16]

^^ like i said i put brand new plugs in, only started 2 times since i put them in. I have a wideband so i have been monitoring as i have drove. I will be doing a blt first thing when i pick mine up

 

[Dude McGee]

Ah, I missed that keyword "new" up there. Still, sonetimes it only takes one rich pull to foul them.

 

[Bluefire16]

Update: Got my air compressor and did a BLT of course i found a couple leaks, however it didnt help at all. I checked my AFPR and set it like it states in the tutorial. Come to find out with the vac line off it was set to 46, so i turned it down to 37. However my A/F ratio is now close to a 15-16 rather than a 14-15 originally. I have noticed that the break up/misfire is happening at around 4000-4500rpm, it just cuts out and wont go any higher. Plugs are dirty but not terrible, im guessing it has to be a spark issue, either the coil pack or PTU.

Lastly when you watch the video you see that soon as I give it gas its going lean, how far should it be going? Should it be staying pretty close to 15-16 the whole time?

How do i test the Ohm of the coil pack? I have searched for hours and cant find a write up.

Couple pics and a vid of a/f at the bottom.

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http://s1290.photobucket.com/user/Gruss16/media/IMG_1768_zps8ed12a75.mp4.html

Lastly guys i think i may need to hook up my maft translator and 3" gm. I keep getting mixed answers from old posts. I have 550 injectors so do i set the Aux to 4 or 0? And what do i set my base at D?

 

[Mokkan]

The power transistor can cause cut out at that RPM. Its pretty easy to test if you have an analog voltmeter around (or get one from walmart for $10). See page 181 of the electrical manual for the procedure - you'll need a 1.5v battery as well.

 

[Dude McGee]

For the AFRs, your trims were correcting the previous richness. Im sure if you reset your ecu, they would get closer to what they should be.

 

[Bluefire16]

What I don't get is on the backside of my coil pack there is not a 3 prong like in the manual, just a 2?

 

[Tiki2777]

Go with the easy thing to rule out first. Try BPR7s and gap them closer. Should definitely help nonetheless.

 

[Bluefire16]

I am just clueless on the electrical of this car, and under the steering column it is a hack job, im not sure what the kid was even attempting to do.

So plain and simple what should I check and what should my psi for my AFPR be set to for my 550s?

Well no difference between 37 or 43 psi (SIM suggested I run 43psi) a friend in the DSM world came over and helped me diagnosis, fuel seems ok on pulls when watching afr. But like clockwork I keep getting a break up at 4-4500rpm. Think the coil pack is bad so I am waiting on my new one to arrive.

I am also hooking up my maft translator to see if that helps. However I feel the ptu could be a reason. I keep throwing a Tps cel, this couldn't have any affect could it? Car drives fine when low rpm but breaks up at that 4k rpm range. Thoughts?

 

[Bluefire16]

Think i just fixed the problem, took out the 2g maf and replaced it with 3" gm and maf-t. Started up and reved just fine, didnt have time to take out for a drive though. Will no in a day or so.

 

[Bluefire16]

Well its now reving past 4500rpm, however afr is reading rich when accelerating. I turned the fuel pressure back to 37 psi. Found a boost leak on the throttle body so I need to pull and replace the seals inside.

Now would a bad TPS and a bad coolant sensor be a reason it could also be missing? Still not running 100% under boost, still getting some shuddering when WOT.

 

[norcalboostin707]

Ok so.im having the same issue.... A few of my tuner friends have said that with the spark breaking up it could be the cam angle sensor/ crank angle sensor that is causing it... Due to the fact that the cas registers when your spark shoild be hitting... Not to sure about this so i was seeimg if anyone else thinks the same... Even after replacing coil pack plugs wires tps... Idk if i should spend the 449$ at autozone for a new cas or if anyone else has had this identical issue and fixed?

 

[Bluefire16]

^^ why not just pick up a used one off the classified? Only 40-50$. I have 2 codes that need to be dealt with first, my coolant temp and tps which could be causing my symptoms. IF that doesn't fix it ill prob try a case.

Also almost positive I have a 1.3 maft, tried to set aux=0 and base=D and car ran like crap. Friend may have a old set of 450ccs so I may be putting those in for the moment to get it running correctly. Anythings worth a shot at the moment.

 

[WES_393]

Now would a bad TPS and a bad coolant sensor be a reason it could also be missing? Still not running 100% under boost, still getting some shuddering when WOT.

Yes. Those two things could very easily cause the problems your describing.

As for your AFR question, you should be fluctuating around 14.7 at idle and in the 10's at full boost.

 

[Bluefire16]

Alright, well I finally have a half day at work (get out in 20 mins) then am going home to tinker with the car and install my new sensors. Funny that 90% of time I am on tuners I am at work

 

[norcalboostin707]

Have you fixed this issue yet bro?

 

[Bluefire16]

Replaced plugs with a COP, and new TPS sensor, set fuel pressure back to stock and care seems good so far. Car has been parked for over a week though, as i was fixing this issue my new struts n shocks came in so I have been putting those on as well as new brakes and rotors. Then at the same time gutting and removing my interior and other things like 4-point harness.

For the couple small pulls i did car seemed to be running correctly, however my clutch is messed so i need to fix and adjust it before i drive it more.

 

[clipto]

This is not goin in the right direction . I suggest you go back over the upgrade path and read how to properly. Here is a few articles.
http://www.dsmtuners.com/forums/ecmlink-tuning-log-file-advice/443297-please-read-before-you-ask-ecmlink-dsmlink-log-advice.html

http://www.dsmtuners.com/forums/frequently-answered-dsm-questions/55418-what-should-my-first-mods.html

http://www.dsmtuners.com/forums/tuning-engine-management/357356-bigger-injectors-ok-without-tuning.html

I highly recommend to ditch the gm maft and maf translater. Biggest waste of money I wont get into that it's just my opinion and my 2 cents. Just want to you to do it right and not waste money. Better safe then sorry I dont wanna see a blow up my car thread what happend. Good luck hope all comes out good for you. Theres tons of good guide lines for keeping your car tip top shape. Read up and take in the insight.

 

[Bluefire16]

^^Alright pal calm down, this isnt my first DSM, and this car was a hack job before I even took over. I no what im doing, as far as upgrade path, I no exactly what im doing and how i plan to do it. I am in the process of getting link from a friend. At the same time, the car came with all this stuff that was WRONG and i am correcting it.