Has anyone fixed the low-rpm bucking/jerkiness problem?
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Car: 1988 Fiero GT
Engine: ZZ430 Ram-Port
Transmission: 5-speed M282, SPEC Stage III clutch
Has anyone fixed the low-rpm bucking/jerkiness problem?
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
Thanks,
Dave
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Re: Has anyone fixed the low-rpm bucking/jerkiness problem?
Originally posted by crazyd
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
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
RBob.
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Car: 1988 Fiero GT
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Re: Re: Has anyone fixed the low-rpm bucking/jerkiness problem?
Originally posted by RBob
Sounds like either a vacuum leak or you need to do some tuning. How do the data logs look?
RBob.
Sounds like either a vacuum leak or you need to do some tuning. How do the data logs look?
RBob.
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
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Re: Has anyone fixed the low-rpm bucking/jerkiness problem?
Originally posted by crazyd
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.
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.
Manual or auto?.
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Re: Re: Has anyone fixed the low-rpm bucking/jerkiness problem?
Originally posted by Grumpy
Can you cut and paste your timing, and VE table?.
Manual or auto?.
Can you cut and paste your timing, and VE table?.
Manual or auto?.
It's a 5-speed manual.
Dave
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Re: Re: Re: Has anyone fixed the low-rpm bucking/jerkiness problem?
Originally posted by crazyd
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
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
RBob.
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That's all I needed to know! I've posted a CSV file at the same location.
Dave
Dave
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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.
RBob.
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Car: 1988 Fiero GT
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Originally posted by RBob
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.
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.
Is there any reason an LT4 hot cam can't be calibrated to work properly in a MAP system?
Thanks,
Dave
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Originally posted by crazyd
I'm not set up for PROM burning yet, I'm working with Alvin at pcmforless.com.
I'm not set up for PROM burning yet, I'm working with Alvin at pcmforless.com.
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.
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Car: 1988 Fiero GT
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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
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
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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
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
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Originally posted by crazyd
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
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
**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.
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Originally posted by VetNutJim
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)
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)
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.
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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.
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.
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Originally posted by crazyd
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
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
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Originally posted by crazyd
Is there any reason an LT4 hot cam can't be calibrated to work properly in a MAP system?
Is there any reason an LT4 hot cam can't be calibrated to work properly in a MAP system?
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!
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