RC 550cc Injectors = Bad Idle?

[Mist3r Spool]

I can't fix my idle issue. It has that mmmmmmBLURPmmmmmmmmmmBLURP tone. I've come across some info from Hahn Racecraft stating that RC 550cc injectors will cause a poor idle and low-end driveability so they offer 650cc/660cc Injectors to remedy the issue . I haven't upgraded my fuel pump yet (still waiting for UPS) and thought that may help smooth things out. Any takes?

 

[Jafro]

My car does this. I'm convinced it's spark. It did it before DSMlink, it did it afterwards, too. I have cams, so I didn't notice it at first, but it's become more apparent and happens even while cruising. It feels like the timing is randomly going 20° out when I'm cruising, but comes on like a misfire. No CEL's or MIL's for it. It's been doing this through 2 sets of Magnecores, AN fuel line upgrades, stock ECU or DSMlink, 9 sets of plugs, 5 different kinds of gas, stock boost or higher... doesn't matter. I notice that it does it LESS with a SMALLER gap on the plugs, so I think it's my coil pack. I never put more than 5000 miles on a set of BPR7ES-11's, and the gap usually spreads about .010" in that time. It gets worse as they get closer to 5000 miles. I run stock boost but it doesn't really matter. It creeps to 22 PSI by 6000 RPMs anyway... so what's the point in turning it up?

Maybe I'll pony up the cash for a new coil pack or a MSD DIS-2 and put that thought behind me... but until I get my Colt running, my car will have to die before I'll replace it. I'll let you know how it goes if that day comes sooner than later.

FYI: New videos of the Colt project here for the curious:
http://homepage.mac.com/jafro/iMovieTheater47.html
http://homepage.mac.com/jafro/iMovieTheater50.html
... haven't rebuilt the donor motor yet. More to come.

 

[Mist3r Spool]

My car does this. I'm convinced it's spark. It did it before DSMlink, it did it afterwards, too. I have cams, so I didn't notice it at first, but it's become more apparent and happens even while cruising. It feels like the timing is randomly going 20° out when I'm cruising, but comes on like a misfire. No CEL's or MIL's for it. It's been doing this through 2 sets of Magnecores, AN fuel line upgrades, stock ECU or DSMlink, 9 sets of plugs, 5 different kinds of gas, stock boost or higher... doesn't matter. I notice that it does it LESS with a SMALLER gap on the plugs, so I think it's my coil pack. I never put more than 5000 miles on a set of BPR7ES-11's, and the gap usually spreads about .010" in that time. It gets worse as they get closer to 5000 miles. I run stock boost but it doesn't really matter. It creeps to 22 PSI by 6000 RPMs anyway... so what's the point in turning it up?

Maybe I'll pony up the cash for a new coil pack or a MSD DIS-2 and put that thought behind me... but until I get my Colt running, my car will have to die before I'll replace it. I'll let you know how it goes if that day comes sooner than later.

FYI: New videos of the Colt project here for the curious:
http://homepage.mac.com/jafro/iMovieTheater47.html
http://homepage.mac.com/jafro/iMovieTheater50.html
... haven't rebuilt the donor motor yet. More to come.

I've been having that issue for as long as I can remember. It seems like sometimes it just doesn't want to go anywhere, whether it's cruising or really getting on the throttle and then I'll let go of the gas and and hit it again (again, cruising or getting on it) and it pulls fine. I was always thinking it's the coil pack, but I was under the impression that they either work or they don't...it's 150K+ miles old so I should probably change it anyway.

 

[MyBeatGSX]

Mine is now back to doing what it was doing at the end of the summer (and had since randomly stopped). After sitting for around 20-40mins (no more, no less) the hot start idle is HORRIBLE (it starts perfectly though). When I say horrible I mean I expect it to just die at any time, like 12in/hg and fluctuating 3-4in/hg in either direction type horrible.

One interesting thing I noted, was that the air flow was exceptionally high considering it was idling at 400-600rpm. Normally at idle, its exactly 33-34hz. When it was running like crap I was seeing between 40-55hz. So I'm doubting that this is caused by a vacuum leak, because the MAF is seeing more air, its not leaking in. The question is, why more air?

What I really can't understand is, why so bad after a hot start? And what significance does the fact that it needs to be between 20-40mins for it to do it. Less time and its not bad, more time and its not bad. It still idles like crap all the time, but not this bad.

 

[Red97GST]

could it be that the MAF is seeing more air because it is pulling extra air to compensate for the vacuum leaks

 

[MyBeatGSX]

Vacuum leak = lean condition... so lets give it more air to make it leaner.... I'm not following your logic. My point was that it should be pulling like 20hz at 400rpm, and instead its pulling well over what it pulls at 800rpm. The ECU doesn't trick itself by changing its own MAF signal.

I've since talked to a few people that have the EXACT same problem (the hot start thing), no one seems to know what causes it and no one cares to find out because it doesn't effect much other than the first idle. Whatever is causing it is making the engine run stupid rich because the exhaust smells like straight fuel.

As for the neverending misfire...

I replaced my TB gasket to no avail. At the time I also noticed my power transistor was zip tied to the fuel feed line with only a very old and dead 22 gauge wire grounding it. I took it off, cleaned the contacts and rezip tied it now with an 8awg platinum/silver audio cable and 24k gold terminals.... also to no avail.

I ALSO tried the Sea Foam engine cleaner (same thing as the mopar stuff) and checked/replaced every vacuum line... again to obsolutely no avail.

I plan on ordering new coils tommorow.

Has anyone else had any progress or at least tried anything different? Don't the wisemen have an opinion on this?

 

[Sharkcus]

Vacuum leak = lean condition... so lets give it more air to make it leaner.... I'm not following your logic. My point was that it should be pulling like 20hz at 400rpm, and instead its pulling well over what it pulls at 800rpm. The ECU doesn't trick itself by changing its own MAF signal.

I've since talked to a few people that have the EXACT same problem (the hot start thing), no one seems to know what causes it and no one cares to find out because it doesn't effect much other than the first idle. Whatever is causing it is making the engine run stupid rich because the exhaust smells like straight fuel.

As for the neverending misfire...

I replaced my TB gasket to no avail. At the time I also noticed my power transistor was zip tied to the fuel feed line with only a very old and dead 22 gauge wire grounding it. I took it off, cleaned the contacts and rezip tied it now with an 8awg platinum/silver audio cable and 24k gold terminals.... also to no avail.

I ALSO tried the Sea Foam engine cleaner (same thing as the mopar stuff) and checked/replaced every vacuum line... again to obsolutely no avail.

I plan on ordering new coils tommorow.

Has anyone else had any progress or at least tried anything different? Don't the wisemen have an opinion on this?

I have you tried new plug wires? I'll let you know if it fixes mine as soon as i get my car back together. Let us know if the new coils fix yours, I am considering trying that if it helps you.

 

[Mist3r Spool]

You know, I was thinking that but I haven't changed them yet. I've been using some Taylor Thundervolt 10.4MM wires for about 2yrs and it may just be time, I'll go pickup a set of NGKs and post back.

 

[MyBeatGSX]

I never did get around to ordering the coils that day. I planned on doing it today but I just got called into work, so I might have to wait again.

The plug wires as well as the plugs are brand new NGK's (less than 6,000 miles). My old plug wires were terrible, replacing them helped the idle a lot, but that was long before the injector install. Its far worse now then it was back then.

 

[Mist3r Spool]

Well, my transmission blew last week so I'm pretty much screwed. I've been posting around trying to find a new tranny. I was cruising home from work and it started to spudder, at first I thought I was out of gas, then suddenly it went BOOM and and it felt like there was something dragging on the ground...then to make things worse, my tires locked up! I got out (on a busy street giving no regard to traffic since I was soo shocked) and there was fluid gushing out of my transmission (where it meets my 4G63). I guess the input shaft blew on top of other things. Hopefully, I'll get her up and running soon so I can finally put a end to the idle issue....I purchased a Sil-80 to keep me busy in the mean time.

 

[Red97GST]

you bought a 240sx that already has the silvia front end conversion?

 

[Mist3r Spool]

you bought a 240sx that already has the silvia front end conversion?

Maybe....

 

[Carter97GSX]

It sounds to me like the MAF is reading incoming air (the 55hz quoted above) thats not actually getting to the engine (the rich condition as evidenced by the smell of the exhaust). Could it be possible that you have a boost leak? I know that the car doesn't have any boost at idle, but even at idle the compressor is spinning and putting a bit of pressure on the throttle plate. I had an IC hose come off one time and the car would Idle but it would run like crap cause there was a bunch of air getting windmilled through the MAF that wasn't actually going into the engine and the MAF readings were really high. This is just a thought seems how nobody seems to know what's going on here. I hope this helps, or gives you an idea of somewhere to look or something.

 

[airmail96]

In your parts profile i didn't see a fuel pressure regulator, could that maybe be causing your idle problem also? Because i know when you run a 255 it should be accompanied by a AFPR, and i know the slowboy kit doesn't come with one that i know of.

 

[Mist3r Spool]

In your parts profile i didn't see a fuel pressure regulator, could that maybe be causing your idle problem also? Because i know when you run a 255 it should be accompanied by a AFPR, and i know the slowboy kit doesn't come with one that i know of.

Yeah, I purchased an Aeromotive FPR, but my tranny is gone, never got to check out if whether or not it would be the final fix to the issue...I suppose the fuel pump that is running the injectors pretty hard is definitely contributing to the issue...I guess, since my car still does turn on & rev I could give it a shot...nah, I'll wait for the new tranny.