WTF?!?! Misfire, Bucking, and almost a backfire at high RPM's?

[gsturbo91]

OK, My car is acting real weird when it is cold. I have a 1991 Eclipse GS Turbo and when the temp. is below 40 deg. outside it will skip and studder and buck all over the place above 5000rpm. I have replaced the plugs, wires, and cleaned my K&N. Please give me ay suggestions on what it can be. I have searched the forums, but none of the skipping problems sound like mine. Please help, this is making me .

Thanks Guys,
Justin (GSTurbo91)

 

[GetEvryGear]

My car just did that this morning (27 degress outside), it only did it in first gear though when I went above 4k RPM. So I thought man that was funny never did that before, so I gunned it in 2nd and it was fine. Does it do it all the time or does it quit when the car warms up?

 

[Boosted19]

did any of you guys mess with you MAF meter recently? i know that can mess alot of stuff up. or mabye what it could be, MOST cars the boost spikes up when its cold out, it might spike up to much and the car will get knock, and cut the fuel.

 

[gsturbo91]

It does it even when the car is warmed up in all gears as long as out side temp. is below 40deg. or so. Only thing I've done with the MAF is remove the silencer, and that was a while back. As far as the boost spike, I thought that too, so I turned the boost down and it did the same thing at 10psi as it did at 15psi. I've been reading up on this a little more and I saw the Coil comming up a lot. Could it be that? I would think that if it was the coil, it would do it at any temp. though. Plus, I dont want to dump $150 that I don't have for something I don't need. Please help guys!!!

Thanks,
Justin (GSTurbo91)

 

[DSM90AWD]

Have you changed your fuel filter recently?

 

[gsturbo91]

I changed the fuel filter about 6000-7000 miles ago. What else guys, help !!!

 

[92 AWD ECLIPSE]

yah man, my car does the exact same thing ( 92 GSX). I ve replaced everything for the ignition components, still no luck. However my next step is the vaccumm lines. On my previous car(95 GST) it would do that, but it threw a MIL(check engine light) which was for the malfunction of the EGR valve. Once I replaced that it was fine. Check your vac lines going to and from the Egr valve with a Stethoscope to hear if they are hissing or if there is a leak.

 

[DSM90AWD]

I see that you still hav the stock 1G MAS?

Mine used to fuelcut even at low (12-15psi) boost levels until I removed the lower HC and backed out the calibration screw.

 

[gsturbo91]

Ok thats an idea, what are you talking about when you say caliberation screw? I'm scared to try and pull out the lower honeycomb as it might break the MAF. Whats the easiest way to do it? Also would this make it do it only when it is cold out and I'm at 4500+rpm? Also when I did turn down the boost to 10psi, it still did it.

Thanks,
Justin (GSTurbo91)

 

[cbellsondsm]

youll see the calibration screw, its head is covered with glue, scrape the glue out and back the screw out, til yousee straight trough the maf with no obstructions and i removed the lover honeycomb by bending the forks that hold it in with a scredriver, that way youcan still put it back in

 

[DSM90AWD]

..what he said

The cold air makes fuel cut onset much more reachable even at low boost settings as it is factored in the ECUs computation of total air volume.

The two "mods" I list allows a bit more unmetered air in so less is measured.. less likely to hit fuel cut.

Warning.. please take into consideration that this will make your car run a little leaner which necessetates use of an A-F Meter, EGT or Datalogger to monitor Knock Sum.

The 1Gs run rich from the factory.. and have lower comp (than 2Gs) so there is a safety level for these mods.

 

[Spidey]

What kind of plugs are you running and what are they gapped at? If they're not the right kind, they may not handle the increase in power from the cold weather well.

 

[DSM90AWD]

Originally posted by Spidey
What kind of plugs are you running and what are they gapped at? If they're not the right kind, they may not handle the increase in power from the cold weather well.

Good point. Though he says he has "new" plugs.. doesn't mention type or gap. FYI.. I tried Douch Platinums once... they fouled up very quickly and ran pretty crapily at higher RPMs / Boost.

NGKs are the only plugs I'll ever use (.028 gap).
BTW... It's recommended go one heat range colder for every ~100HP over stock.. though since you're nearly stock... stick with the BPR6ES.

 

[gsturbo91]

Ok guys, I'll try the MAF hacking stuff monday, and as far as the plugs go, I run nothing but NGK's gapped at what my shop manual tells me (don't remember off the top of my head). So Monday, I will check the gap on them too, just to be sure. Aren't NGK BPR7ES what OE calls for? If so, I think thats what I'm running. Do I need to go with 6's? Could that be causing it? Sorry I'm asking so many questions, I just want it fixed so I don't have to shift at 5 grand every time I'm on it.

Thanks all,
Justin (GSTurbo91)

 

[DSM90AWD]

The -6ES are the OEM plug.. -7ES is a heat range colder. Running a colder plug could have an impact as see in Extreme Motorsports Sparkplug FAQ

The reason we cannot use a colder plug from the outset is fear of never getting the plug warm enough. A spark plug must reach what is called its "self-cleaning temperature" (or region) which generally occurs at about 500 degrees C depending on the A/F ratio. This is normally reached during high engine or vehicle speeds. This "self-cleaning temperature" allows the plug to burn off carbon deposits accumulated at lower speed and idle conditions. If this temperature is not consistently reached, you will have definite fouling problems

Let us know how you make out

 

[gsturbo91]

Ok for some reason I do believe that the plugs are 7's. If so are they hurting anything, and what should I have them gapped at? I'm pretty sure they are at .032". Could the extra power from the colder air be "blowing out the spark"? If so what is a safe gap to be sure that isn't happening with my mods?

Thanks again,
Justin (GSTurbo91)

 

[DSM90AWD]

At your level of mods / boost there is no way you'd be blowing out the spark. More likely that the plugs are not operating at the correct heat range so crud is building up on the electrode from incomplete burning.

.032 is the correct gap. If you were running an MSD ignition could go wider (more current).. or if running alot of boost on the Stock Ignition a smaller gap (so to prevent blow out).

Spark plugs are pretty cheap and having an extra set around for MCCC cleanings is a good thing ..so IMO go ahead and grab a set of -6ESs gapped to .032 and see how it runs. In the summer (when warmer) swap the -7ESs back in.

If this doesn't fix it do the suggested MAS mod

 

[gsturbo91]

Ok guys,
I have done the MAF hacking and put new BPR6ES's gapped at .032". It hasen't gotten really cold the past few nights, but last night it was about 38 deg. and it didn't do that what so ever. But, now I have another problem. My car is idleing kind of funny, ever since I hacked the MAF. I tried adjusting the Idle Set Screw, but it only helped a little. I don't know what it could be since I did nothing else but the MAF mod. What could be causing this?

Thanks again,
Justin (GSTurbo91)

 

[DSM90AWD]

You just removed the screen right? I consider "hacking" to be the actual opening up of the MAS air-bypass tunnel allowing in even more unmetered air. If you did that you'd have Idle Probs.

If this is not the case.. make sure all intake couplers are tight and no leaks.

 

[gsturbo91]

I did remove the honey comb, but I also ran that glue covered screw out a little also, I screwed it back in most of the way and the idle straightened up a lot but not all the way, so I'll run it in the rest of the way when I get a chance. Thanks for all the help! And if there is anyone in the Atlanta area wanting some exhaust work done, or any kind of fabrication at all done, let me know. I know a great shop that just fabricated a 2.75"-2.5" O2 Eliminator Downpipe (w/flex) and welded in a 2.5" hi-flow cat I had for $200 for me.


Thanks again,
Justin (GSTurbo91)