Not so smooth Idle

[robbz28]

My car runs pretty good and it idles down low where it should, but its ever so faint, you can hear a miss every now and again. It idles a tad bit erratic, not that its major, but enough to make me want to figure out what it is. It also has a slight hesitation from idle to when I give it some gas. If it's idled up it don't have this hesitation. It's almost like theres not enough gas available. I am going to start going through the ignition system bit by bit. First I will change the plugs, if it persists, test coil packs and wires. I got this car about 1000k miles ago and not sure when this stuff was changed last (if ever). It has 70k miles on the whole car, but the engine had about 35k on it when LPE did its thing to it, but that did not include altering the ignition system. Any tips, anything else I should check out?

[Kevin]

a "slight miss" being felt is a major miss being absorbed by the DM flywheel if you still have it. injectors, plugs are a good place to start. pull the plugs and see how they look

[ZZZZZR1]

Details help

When work was done and what was done in the past

Likely the typical:

Fuel injectors
Coil packs
Spark plugs and wires

Check with daniel in Louisiana (he has done these changes a few times)

:cheers:

David

[robbz28]

a "slight miss" being felt is a major miss being absorbed by the DM flywheel if you still have it. injectors, plugs are a good place to start. pull the plugs and see how they look

I can't say that I actually "feel" the miss. I just can hear it, I suppose I can feel it when I rev it up to about 2k and hold it.

And as for the work, 35k miles ago LPE tore it down and ported the heads, intake, bored it to a 368, put new rods ans 12:1 pistons in it. "Chipped" it to match the new setup. No cam change, no headers.
I have been trying to get it to run like it should since I got it, and it runs awesome right now, but this little miss needs attention.

[XfireZ51]

Did this start when LPE did their "thing"? What mods did LPE do?

[robbz28]

Oh I listed the mods earlier in the post. This was done years ago. Its been like this sinfe ive had it.

[PhillipsLT5]

Have you contacted LPE about mods
Try
http://www.linkedin.com/pub/dir/Graham/Behan

[XfireZ51]

Oh I listed the mods earlier in the post. This was done years ago. Its been like this sinfe ive had it.

You could also send me the memcal and I'd read it.

[scottfab]

When was the last time injector cleaner was run though?
Cheap and easy to do compared to coils etc.
I run the Techron stuff through once a year on 1/4 tank
before bed time in winter.

[robbz28]

You could also send me the memcal and I'd read it.

The mem-what?

[robbz28]

I think the hesitation has something to do with my secondaries. I have them tied open and i bet the computer is not calibrated to run the secondary injectors at all times. Of course when my foot hits the floor they kick in but theres that moment when its a "dry hole" with both runners open but only one injector pumping...of.course over 2k its a non issue because i am guessing the secondaries are engaged by then.

[scottfab]

I think the hesitation has something to do with my secondaries. I have them tied open and i bet the computer is not calibrated to run the secondary injectors at all times. Of course when my foot hits the floor they kick in but theres that moment when its a "dry hole" with both runners open but only one injector pumping...of.course over 2k its a non issue because i am guessing the secondaries are engaged by then.

Yes, I think you're onto it.

[XfireZ51]

I think the hesitation has something to do with my secondaries. I have them tied open and i bet the computer is not calibrated to run the secondary injectors at all times. Of course when my foot hits the floor they kick in but theres that moment when its a "dry hole" with both runners e open but only one injector pumping...of.course over 2k its a non issue because i am guessing the secondaries are engaged by then.

The stock calibration has a .2sec delay for secondary injectors to come on. Probably to give throttle plates time to open. That is changed when secondaries are eliminated.

[robbz28]

.2 seconds huh? Sounds about right...its just over an eyeblink of hesitation...

[Paul Workman]

In my experience, I recall what a difference injectors (Accels) made, far as idle goes. At the same time my plugs were new and my coils were only a couple years old, as were the plug wires.

Back to the injectors: They were NOS at the time I bought the car, and only a couple years old. I didn't realize they were NOS at that time, and the tell-tale resistance readings didn't show up until the eve that Marc was about to dyno tune the thing.

Marc was adding fuel at WOT and the AF mix remained leaner than he wanted. He asked me about the injectors, and I told him they were only a couple years old. He told me they were stock (really news to me at the time!) and recommended 16 Accel replacements.

Once the new injectors were in place, the AF numbers responded immediately to fueling table change inputs, the car ended up with 432 RWHP (stock cams), and the idle was as smooth as a sewing machine (and remains so to this day, two years later!).

All that said, I stand by my position that my scanner was the best $$ I ever spent, far as sorting out over 41 different "goings on" in this, my second C4. And, most importantly, the O2 sensors (which I can tell ya from experience) can also roughen up the idle a little, and the scanner will put a finger on those rascals PDQ. (If you don't have a scanner, take it to AutoZone - or the like - and get a print-out of how everything is working. Being able to see what all is going on is soooooo much better than checking this and checking that, tho I too suspect that plugs, wires, or injectors to be the propblem)

One last thought tho... If you are running sans secondaries, at idle the primary injectors only are running, and the dwell time is "stock". Only after you go to above 1% throttle tip in does the secondary injectors come on, and the dwell time is adjusted to provide proper AFR for two injectors.

P.

[WARP TEN]

Nice to see you have been back on line and hopefully feeling better. I was thinkng about your signature (below) and thought that to commemorate your recent experience you really should add an extra line ahead of the FBI one:

"Personal top end ported & relieved" :-) --Bob

Paul's current sig:
90 #1202
"FBI" top end ported & relieved
Cam timing by "Pete the Greek"
Sans secondaries
Chip & dyno tuning by Haibeck Automotive
SW headers, X-pipe, MF muffs

East Central Region Director

[robbz28]

In my experience, I recall what a difference injectors (Accels) made, far as idle goes. At the same time my plugs were new and my coils were only a couple years old, as were the plug wires.

Back to the injectors: They were NOS at the time I bought the car, and only a couple years old. I didn't realize they were NOS at that time, and the tell-tale resistance readings didn't show up until the eve that Marc was about to dyno tune the thing.

Marc was adding fuel at WOT and the AF mix remained leaner than he wanted. He asked me about the injectors, and I told him they were only a couple years old. He told me they were stock (really news to me at the time!) and recommended 16 Accel replacements.

Once the new injectors were in place, the AF numbers responded immediately to fueling table change inputs, the car ended up with 432 RWHP (stock cams), and the idle was as smooth as a sewing machine (and remains so to this day, two years later!).

All that said, I stand by my position that my scanner was the best $$ I ever spent, far as sorting out over 41 different "goings on" in this, my second C4. And, most importantly, the O2 sensors (which I can tell ya from experience) can also roughen up the idle a little, and the scanner will put a finger on those rascals PDQ. (If you don't have a scanner, take it to AutoZone - or the like - and get a print-out of how everything is working. Being able to see what all is going on is soooooo much better than checking this and checking that, tho I too suspect that plugs, wires, or injectors to be the propblem)

One last thought tho... If you are running sans secondaries, at idle the primary injectors only are running, and the dwell time is "stock". Only after you go to above 1% throttle tip in does the secondary injectors come on, and the dwell time is adjusted to provide proper AFR for two injectors.

P.

A scanner is something i would really like...any recommendations? My bro would probably ahare in that expense with me...

[Paul Workman]

A scanner is something i would really like...any recommendations? My bro would probably ahare in that expense with me...

Mine happens to be an AUTOXRAY. Rides nice in the storage box behind the passenger seat. However, a "Netbook" with the proper sofware & connectors might be even better.

The scanner allows for recording data in a stack of registers until an "event" occuures and a button is pushed. Then the previous 10 registers freeze and the next 10 or so are recorded for a post-event comparison/analysys.

This combo of always being there goes a long way toward troubleshooting.

P.

[chriskinzel]

Where would one find 'the proper software and connections' for a net book?

[scottfab]

Where would one find 'the proper software and connections' for a net book?

That was a minor typo. I think he meant "notebook" with software based scanner. That's what I have.

[vilant]

That was a minor typo. I think he meant "notebook" with software based scanner. That's what I have.
Do you think the software on a Notebook is better than the scanner ( as far as performance and features)?

[scottfab]

Do you think the software on a Notebook is better than the scanner ( as far as performance and features)?

I have two data logger/scanners that run from a notebook.
I have a stand alone scanner named INOVA.

The scanner is less capable than the scanner/data logger.
The scanner gets the error codes from the car and
can reset them. The scanner/Datalogger gets the codes and
can "log" various data points live as you drive the car
or idle. You can actually see problems in O2 sensors etc.
My scanner/data logger is a Dyno Scan.
I also have an older scanner/data logger called "Diacom" but it
only runs on an older PC circa 90s. I don't know if they are available
anymore.

[QB93Z]

Does your car still have the emmissions reducing air injection system connected to the headers?

My LPE 368 had a "ticking" noise that could be heard at idle. Thanks to Marc Haibeck help, we determined that the noise was coming from one of the AIR system check valves on the right side of the engine. I removed the air system and used pipe caps to seal the exhaust header connections and the noise went away.

Good luck,

Jim