Hi all,
Don't post much but follow the thread and thought I'd give you all an update on my efforts to address the hesitation issues with my Edelbrock install.
My experience with the S/C began with the rotors seizing on the way back home from the authorized installer here in the Bay Area. Unit was found to be defective, and Edelbrock sent out a new unit which has worked. I have been plagued though by constant hesitation/stuttering problems on throttle tip in (like so many others). The hesitation/stuttering has ranged in severity from severe bucking in first gear, to subtle inconsistency in behavior of throttle tip in, to slightly rough idle, to random hanging of RPMs with clutch in. Never had any codes.
I'm happy to say that I think the issues are finally fixed, and the engine now runs more smoothly than stock. S/C went in at about 9k miles on the car, and I now have 62k. So it's definitely been a matter of persistence. There are many times I thought I had the hesitation licked, but it kept coming back. Hopefully it is now fixed for good.
Below is all I've been through to get to this point:
Vacuum leaks/Seals:
Many vacuum leak checks with a smoke machine
MAF O-ring found to have leak (pinched on original install), replaced with CSG O-ring
Edelbrock bypass actuator found to have leak and replaced
Replaced vacuum line going to bypass valve with smaller silicone tubing
Intake manifold gaskets replaced at the time bypass actuator was swapped
Hardware/Sensors:
Installed revised Edelbrock MAF air flow straightener
Cleaned MAF sensor and wiring harness contacts repeatedly
Replaced MAF sensor wiring harness housing (clip broken by installer)
Replaced MAP sensor with new Bosch part
Replaced throttle body in case it was the TPS sensor
Cleaned and re-oiled Edelbrock air filter
Installed radium dual catch cans with a check valve on the PCV side
Fixed exhaust leaks around the resonator joints on my Milltek exhaust
Tuning/Electrical:
Replaced alternator with high output unit
Installed Cusco ground kit
Edelbrock tunes (garbage)
Delicious tunes (now up to v25)
Delicious D-box
From the above list, the following interventions definitely led to a noticeable initial improvement in smoothness: replacing MAF O-ring, cleaning MAF, replacing bypass valve, installing grounding kit, upgrading alternator, refining Delicious tunes, D-box, and installing catch cans. Of these, the biggest deltas came from replacing the MAF O-ring, adding the catch cans (probably from addressing a subtle vacuum leak, although could be from effective increase in octane), and the Delicious tunes. All the other interventions listed made essentially no difference.
Any success has been transient, as the hesitation always crept back in, albeit subtle. All of the above brought me to about 50k, and I was resigned to accepting the subpar behavior.
In the last 10k miles though, on top of the hesitation, the idle started bouncing, running rough, and even stalling on cold starts. At first I thought the idle issue was random; it would sometimes go away after an ECU reset, or just go away on its own. But then it started persisting even after ECU resets. I found some exhaust leaks which I thought were responsible, and had them rewelded at a shop. This helped intially, but idle issues returned. After about 3 cycles, a pattern of a bouncing idle/stalling happening after long drives (several hours/hundred miles) finally emerged. Something was probably being incorporated into LTFT after the long drive.
A look at the logs showed a STFT of -29%, and MAF sensor readings of over 2 volts.
So I was forced to revisit all this since the car was now unreliable, and something was clearly out of whack. I was really pulling my hair out at this point. Bill suggested it may be a boost leak (loss of post MAF metered air leading to a rich condition), but I could find no S/C leaks.
Since the MAF was acting crazy, I formed a theory that perhaps I overoiled the Edelbrock air filter and fouled the sensor, since I cleaned the air filter at about 50k miles and the erratic idle started shortly after that.
So a few weeks ago I cleaned the MAF again. This led to a temporary reprieve from the hesitation and normal range MAF voltage of about 1.2V. So perhaps the MAF did need a clean. But the bouncing rough idle came back. Inspecting the MAF sensor, I noticed that the O-ring was once again damaged in several places even though I had replaced it with a CSG ring at 33k miles (ID 22mm, OD 26mm, 2mm section diameter, buna nitrile).
The MAF has always been really difficult to place in the Edelbrock intake housing. I was sure that with grease and gentle tapping in of the sensor with a wood block on top of it, I had gotten it to seat properly. Which I had. But inspection of the CSG O-ring at 60k revealed that despite these efforts, there was once again damage to the O-ring even when seated properly (see pics).
Could it once again be an MAF vacuum leak? I think that the Edelbrock intake housing tolerance is different from OEM; it is too small. Moreoever, the buna nitrile is pretty stiff, and I think wore out prematurely because of being overly compressed within the smaller housing diameter.
So I went in search of a more elastic/forgiving O ring that would fit better in the Edelbrock intake housing, and decided to go with silicone since it also has a high temp tolerance (not high anyway in the intake). The disadvantage of silicone is that it has poorer wear characteristics than buna nitrile. But this is not a seal exposed to repeated cycles, so thought I'd try it anyway. Ended up ordering a silicone O-ring from eBay, also at ID 22mm and probably about a 1.9mm section diameter. It definitely felt softer than the OEM/CSG) ring, and appears to have a slightly smaller section diameter.
Greased up the ring nicely, and on install the MAF sensor popped right in with gentle effort. On moving around the sensor it was nice and squishy within the housing, and seemed to have a nice seal.
On startup without ECU reset, the idle was solid. After ECU reset the idle was solid.
Drove a bit. And bouncing idle returned.
Back to researching on the web. Desperate at this point. Symptoms seemed possibly consistent with a bad PCV valve. Doubted this is the culprit. But may as well try since it's cheap. Picked up a new one at the dealer for $25. Old PCV came out easily with a U-joint even though under the supercharger assembly. Old PCV
maybe passed the rattle test, but not with a nicely clangy sound. Little bit of oil on inlet so a bit dirty. New one went in easily (teflon tape around threads). Whole thing takes about 3 minutes.
Result? Car now runs
really nicely: Idle is solid. Throttle tip in is very, very smooth. Power increased. Curve much more linear. Exhaust quieter. Fuel economy increased. No more hanging RPMs with clutch in. A pleasure to drive.
So, I know enough at this point to not get my hopes up, and that it will take a few thousand miles to know for sure if this is a real fix. Will update here with longer term results. But I recount my experience so you can see what what worked for me and what didn't, and what you may want to try.
TL;DR:
I've thrown a lot of money and effort at trying to solve my Edelbrock hesitation problem. Multiple checks by shops were never able to pinpoint a problem. Did not have CELs. In retrospect it may be a bunch of small issues in aggregate leading to the overall behavior. I think with Edelbrock MAF housing being too small, the O-ring issue is real and likely the case with many cars out there. The fix with a softer silicone ring makes sense, and replacing that costs just a few dollars, as does the PCV. Could it be as simple as these small, cheap fixes? Maybe. I would recommend replacing both of these before digging deeper. Give it a shot and report back. And obviously keep refining your tune.