I have this behavior on a fuel-injected ZZ430 motor w/S&P ramport setup and it's driving me nuts. Under load the engine bucks and jerks at every throttle-lift, i.e. between shifts and coasting. In open-loop it often backfires while it's stumbling. In closed-loop my O2 values drop to double-digits and the ECM struggles to compensate. It only happens below about 1500rpm and only when throttle is under 15%. I've seen in searches that some others have had this problem too. Has anyone found a solution? Thanks, Dave

Sounds like either a vacuum leak or you need to do some tuning. How do the data logs look?

RBob.

I'm pretty sure there aren't any vacuum leaks, the cam is pulling about 14" of vacuum and there is no audible evidence of a leak.

I have a detailed datamaster log you can view.

http://zz430fiero.com/datalogs

It's available in both uncompressed UNI format and ZIP.

Thanks,
Dave

Can you cut and paste your timing, and VE table?.
Manual or auto?.

Never tried it before, can I get those from Datamaster or do I need a different app?

It's a 5-speed manual.

Dave

If you would like various folks to look at your logs, it needs to be made easy. A CSV file can be viewed by darn near anyone. . .

RBob.

That's all I needed to know! I've posted a CSV file at the same location.

Dave

The page opened for like 3 msec., and then I got page not found.

It might be overloaded with traffic, try a page refresh.

After reviewing the data log I'd say that there are some serious issues with this calibration. Are you setup to do PROM burning?

RBob.

I'm not set up for PROM burning yet, I'm working with Alvin at pcmforless.com. That was the log from the calibration that he sent me based on how the engine is configured, but without any feedback from the ECM in the calibration yet. The engine ran a lot worse with that burn than it did with the original one from S&P. In addition to magnifying the bucking/jerking problem, it was also way down on power, and backfired frequently. I will record a log of the original S&P calibration for review too.

Is there any reason an LT4 hot cam can't be calibrated to work properly in a MAP system?

Thanks,
Dave

Why not have Alvin just make good on his work?.
He's charging you money for alledegly doing work for you. Or contact Alvin and get your money back since he doesn't know enough to be selling his work to begin with.

The name of the board it DIY PROM, not Trouble Shooting for the Commercial Guys, that don't know what they're doing.

Sounds like you should be writting the BBB instead of the list.

Yes, you touched a nerve. And is exactly why I don't try and do too much for helping folks with really getting things correct, other then the ones I've meet face to face.

For the money you've wasted, you could have been doing your own, and for the time invested at least doing as good as job as what you've paid for.

When you start doing your own, lemme know, I might be willing to help out some.

I'm just stuck in the middle here with a car that doesn't run right. The guy who built the car has abandoned me, lecturing me about how it's not possible to run the hot cam with MAP. S&P isn't any help, they want me to fax a sheet with a snapshot of static values taken at 2000, 3000 and 4000rpm, which I've already been through twice with them and it just got worse each time. It's especially pointless because the major problems exist well below 2000rpm.

Alvin hasn't asked me to solicit anyone's help, I'm here because I'm trying to educate myself on this - but I want the car to run right now, not run poorly until I can get a Ph.D in electronic engine management. I've already put up with this for almost two years trying to figure out what to do about it, troubleshooting it from the mechanical angle - replacing sensors, setting timing, checking plugs, etc.

Dave

CrazyD:

Grumpy HAS a Phd. in electronic engine management.
He can help better/faster and more accurately than most.
There ARE a lot of others here that know much more than I.
However, I have a Masters in electronic engine management.

I know what it's like to be at everyones mercy trying to get something done.
That' probably why I know 99.9% of the things I have learned in life, because about 99.9% of the experts...aren't.

Email me those logs and I'll take a look at them. May can make some reccomendation.

Send me this info also: (or post it here for all)

1) ECM Number/Type
2) Injector Size in lbs./hr
3) Fuel Pressure

**I'm not set up for PROM burning yet,**

Those are your words.
What good is it to tell you anything?.

PhD?
Just in a dose of reality, you haven't even signed in yet. Until you get to where you can burn a chip, this is all an exercise is writting skills, since you can't even do anything other then possibly relay the info to Alvin. Which I find completely in opposition to the purpose of this board, it's The DIY PROM Board.

So now your going to help Alvin?.
CrazyD can't burn a chip.

All you're doing is forcing him into being at the mercy of those willing to disassociate money from him. Is that your intent?.

I don't see where that helps anyone but Alvin, who's one of the causes of his problem. If it wasn't for folks willing to lighten his wallet he'd have been forced into learning what to do years ago.

Hey Grumpy,

Didn't mean to step on anyones toes or anything.

I don't think any of the folks he's associated with can help him and that's why he's asking for help here.

If 'Alvin' or whoever COULD fix it they probably WOULD have before now instead of telling him it's 'this' or 'that' which PROVES they don't have a clue what the problem is.

We all K-N-O-W this tuning stuff can't be done very well via long distance.
You've said it a million times and that's one of the reasons I got into do it.
Doesn't take much common sense to read where someone burned 400 chips before they got satisfied with a tune to know it can't be done in two or three trys by some self proclaimed wizard of chip burning/engine builder like 'Alvin'.

I certainly WOULD NOT UNDER ANY CIRCUMSTANCE burn him a chip.
That would make me be responsible for his engine if it burned/blew up.

But I WOULD reccomend he buy his chip burning equipment and learn to do it himself.
If I could determine what parms. he needs to adjust to get it to run 'closer' I'd do that.
It would be totally up to him to get the chip burned,etc.

I believe in teaching someone to fish. All I have EVER wanted is for someone to tell me something I don't know.
That's the most valuable thing anyone can give me...knowledge.

Anyway, I'm out on this subject cause you guys help me way too much and too many times for me to tee anybody or anyone off.

Jimbus, out.

You dont need to get a PhD in engine managment, you dont even have to know anything about electronics or ecms. You do, however, need time to pick up on some engine theory as well as a couple of bucks for some extra hardware like a burner. The computer will keep on fighting you untill you start tuning it. I suspect that even small changes for starters will produce big results that are in the right direction.

No reason whatsoever! I haven't been there yet, but I know of several people on this board that have more radical cam's than the HOT cam. Mine with a carb on it still idles fairly decent, especially when to cam's specs are taken into consideration.

One year, I will have EFI on that car and may be able to offer up some advice, until then, get the stuff and start playing with your own chip!