reactor2

I just replaced:

1) Coils (AC Delco)
2) Plugs (NGK Iridium, gapped at .038")
3) Rocker arms (Yella Terra ultra light)
4) Pushrods (CC 7.475" hi tech)

This is the first time I've taken the vehicle out this year (it drove fine when I put it away last year). When I first got on the highway and the converter locked it was running quite rough (very noticeable when I gave it throttle). I mildly gunned it a few times and it went away and drove nice and smooth for about 20 miles, where I stopped at target for about 15 min.

When I started the car it sounded "off". I revved it a little and it was a little rough and slow revving. When I started driving it, it was really noticeable. It feels like its dragging 1 or more cylinders (feels like a mild version of limp mode). For the remainder of my trip (about 3 miles) the wideband 02 was showing an afr of 15-16 (when its usually, of course, around 14).
Also, the exhaust note sounds similar to when I drive when its pouring rain (I have a SC so the exposed air filter sucks a lot of moisture). Its much louder than normal but it only sounds that way when its pouring rain out.....it was 77 and sunny today).

Codes:
PCM p0410 - (secondary air system malfunction).
LDCM u1064 - Loss of communication with left DCM (door control module)
RDCM u1064 - Loss of communication with right DCM
SCM u1255

None of those codes seem to be helpful at all.

Initially I thought the coils seem to be the most likely candidate. But I would think if a coil wasn't firing then I would see a rich condition, not lean (as indicated by wide band O2).

Maybe one (or more) of the injectors are failing? There's probably less than 3k miles on them.

Are the coils possibly junk Chinese knock offs? It does seem to be heat related, but it seems weird that for 20 miles on the highway at 60-70 it was running smooth.

Is it possible a cracked one (or more) of the plugs, would that cause the described symptoms?

Mods:

A&A P1SC SC (6.5-7psi)
60# injectors
LPE fuel pump
Dart Pro1 205
Yella Terra Ultra-Lights
228/232 .571/.573 112
CC hi-tech pushrods (7.475" for .045" preload)
CC OEM Lifters
Fast intake
LS2 TB
BBK Headers
NGK iridium plugs (gapped at .038")
GNPP wires
160 thermostat
Yank ss3600
3.42 rear
Self tuned w/ HP Tuners


Any help would be greatly appreciated!! Thanks!

reactor2

I haven't had a chance to investigate further yet but based on the symptoms discussed above I'm leaning towards an issue with the injector(s) and not the coil(s).

My reasoning is that the AFR on driver's side bank is lean (15-16) cruising. The motor is rough/stumbling under under acceleration. If an injector fails (plugged or otherwise), the computer is going to compensate by adding fuel to the injectors. However, it isn't going to add enough to bring the whole bank back to stoich, which is why I see 15-16 as opposed to 14ish.

Anybody agree/disagree with this cubicle diagnosis?

What worries me is the lack of codes. I would think if the computer couldn't bring the afr back to stoich I would see "lean bank" code.

martysauto

Did you tune out any of the codes? Where is the wideband sensor? Have you checked fuel pressure? If you have a dead miss that bank will show lean because there is lots of oxegyn flowing threw that cylinder. It only gets consumed if the cylinder fires.

reactor2

Thanks for the response!

1)No, I did not tune out any of the codes.
2)The wideband sensor is on the driver side pipe, top center, about 4" (if I recall correctly) from the shorty header collector (probably somewhat biased for the #7 cylinder).
3)Fuel pressure 59-60 (I have a gauge).

Question: Am I correct that if, for example, one injector fails, the computer will adjust (up to some maximum) the fuel for all the injectors in that bank in and attempt to bring it to stoich (computer assuming all injectors are functioning normal). The result is 3 cylinders run real rich. So, for example, if the computer did nothing the AFR would be 20, but because it attempts to bring the bank back to stoich it gets it to 16ish.

It happened again on the way home. Drove the car about 20 miles. It ran smooth. However, it really doesn't feel as strong as it should (seems like much more of an effort to rev and accelerate). AFR cruising 14.6ish.

I stopped about 2 miles from home for about 15 mins. When I started it, it was rough. It runs like its in limp mode, just not quite as severe. Its an auto and at stop light it chugs like a Harley (not the lope of the cam). Under acceleration (especially when converter is locked) it is real rough and has to work hard (motor shutters/shakes pretty bad). AFR 15.5 - 16.8 cruising. Don't know whats going on in the passenger side bank as I don't have a wide band sensor over there.

Codes:
*PCM p0410 cleared (DIC tells me: PCM No Codes)
LDCM u1064
RDCM u1064
SCM u1255

WTF is going on? What's the best way to diagnose this? This car is running like absolute crap. Would a bad coil(s) produce these symptoms? Doesn't seem like it.

How is the computer not throwing any codes, the motor is running like absolute garbage?

Thanks for the help!

reactor2

Just started it in the garage (probably 20 mins since I shut it down, so its still plenty hot).

Put the car in drive.

1)Chugs like a Harley (just not as severe).
2)AFR 15.5-16.8 (at idle 800 rpm or so)
3)Fuel pressure 63ish psi
4)Revs slow and rough
5)No codes
6)Oil pressure: 40psi
7)Coolant < 200

Not exactly sure how to diagnose this. No codes is just bizarre the way this thing is running.
Could it be that the new AC Delco coils I bought off of flee bay are junk Chinese knock offs?

reactor2

bump for the tractor parked in my garage

martysauto

Sounds like you need to get a scanner on it or your laptop with tuning software. Check all ECM inputs. Check fuel trim lt and st both banks. Check misfire monitors, current and history.
You might have a crank sensor crapping out. Possibly even an ignition switch. Both can cause bizarre problems.

reactor2

At the same time I did this work I installed an msd starter. Is it possible I damaged the CPS at this time?

Seriously GM, the car runs like an effin tractor and the computer doesn't recognize any issues?

RonSSNova

Have you double checked the plug wire connections ?
Pulled the plugs?
Had a peek under the valve covers?

If it ran fine before all the parts you replaced, it's good to suspect the recent work.

I would assume you have your old coils. I don't think coil failures are very common.

Scanning as Marty mentioned is a great idea. The PCM is only ok at finding faults.

dankhts

had a similar problem when I took my car out of storage this spring and the computer on mine showed no issues as well!... last thing I did last fall was plugs and Vara Ram filter, ran great at the time.... put it on the dyno with my tuner guy at the controls to see if we could nail it down but it just showed and confirmed we were getting a misfire - it would misfire and act up intermittantly then clear up and the power was back, pulled and checked the new plugs and replaced them again and messed with the MAF wiring, now all is good and running fine, not sure what the problem was....but I figure mine was electrical caused by an imtermittant loose wire or bad ground... hope you solve your problem ....

heavymetals

You might try putting the stock pushrods back in and see how it runs.

The "ran well for 20 minutes" might be because the lifters were still pumping up and equalizing.

reactor2

Yeah it seems far to coincidental for this issue to not be related to the work I recently performed.

I do have the old coils, and I'm going to replace them as soon as I get home from work.

I haven't pulled the plugs yet as I the heads (dart) require the type with the crush gaskets and I would have to replace the plugs if I pull them (unless I can but those crush gaskets separately). Its possible, however unlikely, that I cracked a plug putting them in.

I haven't pulled the valve covers. I would think if I already broke a rocker it would never run correct, not just when the car gets hot (and sits and then I restart it). But I suppose it wouldn't be a bad idea to pull them just to see if something is going on under the covers.

I did check all the connections and everything seems to be good.

This is the first time, with all the mods I've made, that I've had any issues so its really frustrating....especially since it runs like a total POS and no codes are thrown.

Sigforty

Are you sure the rocker arms and pushrods are the correct combo? Could have the pushrod size off and holding open some valves a little bit, or have too much lash. I would also double check all the plugs and wires to make sure they are seated. One might not be connected, but I would almost suspect a rich condition if a plug is not firing. I would really lean to the pushrods and rockers causing the issue.

reactor2

Interesting. I hadn't thought of that.
I can't, however, put in the previous pushrods since they are too short for the shimmed yella terras. The previous pushrods gave me around .080" preload. I'm running the CC 850 lifters and from my research (including several phone conversations with CC) is that .40"ish is what you want with those lifters. So I calculated that with a 7.475" pushrod on the shimmed Yella Terras I would have .045"ish preload.

reactor2

I spent a good amount of time determining that the 7.475" pushrods with the shimmed Yella Terra's would give me the correct preload (.045").
If I was running too much preload (i.e. .100") I would agree that the valves could be held open a little. I'll pull the covers to see if anything interesting is going on.

I agree that if a plug isn't firing I would see a rich condition. My driver side wide band tells me that I'm a little lean while cruising (once the issue starts manifesting itself), which is why I initially suspected the injectors (which I haven't ruled out yet).

When the issue manifests itself, it definitely feels like its dragging a cylinder (maybe a couple). Its not a random misfire...it chugs just like Harley sitting at the stoplight. Its a less severe form of limp mode.

How likely is it for an injector to fail? And whats the best way to determine if an injector has failed or is failing?

heavymetals

The only thing i can suggest is putting back the old rockers and pushrods then.

if it runs fine, then you know where your problem is.

IMO you have to much pre load.

check your oil pressure @ idle with the setup you have now when warm.

I usually see under 38lbs max normal around 35, over 40 indicates (to me) to much preload.

reactor2

I did have to disconnect the MAF so I could get at the crank to rotate the engine by hand. Its definitely plugged in but maybe it didn't seat right. I'll check it when I get home.

reactor2

I fairly certain my preload is good (.045"ish). I have a pushrod length checker and I spend a lot of time verifying the preload. I used the same method with the last set of pushrods to determine a .080" preload and I definitely have less preload now (I can tell by the amount of "play" I have when the cylinder is at TDC).

If I had too much preload wouldn't I have the same symptoms immediately, not just when the motor was hot?

reactor2

If a single injector failed (computer says fire but the injector doesn't) would I have the symptoms I've described?

1) Chug like a harley (especially at stop light)
2) Engine shutter under acceleration (especially significant when converter locked.
3) AFR lean at 2000 rpm cruising (15.5-16.8)
4) No codes

On a carburated V8 I wouldn't expect one cylinder to have such a noticeable impact but with a computer controlled fuel injected vehicle I would expect a failed injector to perhaps cause the symptoms. All the computer knows is that left bank is lean and applies extra fuel to all injectors trying to bring the bank back to 14.6. Result is 3 rich cylinders and the one failed cylinder.

Does that make sense or am I smoking crack? I would expect a "bank lean" code in this scenario however.

heavymetals

The lifters need to pump up and equalize.

Welcome to hydraulics 101.

The usual range of compression for a lifter is about 0.125".

What is your oil pressure @ idle after warm?

If you start it cold and it is in the mid - high 40's, i would suspect too much preload.

I went through a similar dilemma when i switched to MOREL lifters.

They were the happiest with preload that just got the cup off the retainer or about 0.008"-0.012" of preload.