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Low RPM Sputter


radman3120

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The other day i replaced my Lower Intake Manifold and Fuel Pressure Regulator and I got rid of the coolant leak and the car starts right away now but now i have a sputter below like 3000. I have a 93 Z34 with the manual tranny. The sputer is most noticeable in first gear but can be felt in second too. When it sputters it acts like my bike when i am running out of gas or if its not warmed up yet in the morning. When i take off it will sputter for about two seconds before it winds up. Once the rpms get above about 3500 it will run smooth again but im not sure if it has all the power it should. I am wondering what i should check first. Since i did disconnect the fuel lines and pull the fuel rail i am wondering

1) could i have gotten dirt or something in the fuel lines?

2) could one of the lines not be connected correctly?

3) could i have gotten an injector messed up or reinstalled incorrectly in the process?

4) would a vacum leak cause such behavior?

 

Thats what i could come up with. Where do you guys think i should start or is there something else i should look at? The fuel filter is pretty new, same with the iac, and i just installed the 60v6 chip.

 

EDIT: The other day it gave a big puff of smoke at startup for the first time ever...hasnt really done it since though

 

 

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i did have problems with the car running rich in the past. I was pretty sure it was because the timing was off (fixed) and i had a bad O2 sensor (replaced) but every once in a while i wonder if there is a little something more to it. It doesn't smell anything like it did before and i cant honestly recall how it ran before in comparison to now. What would be the first things to check out?

 

Edit: Come to think of it i think the sputter is worse shortly after i start it up. The puff of smoke that it spat out the other day was a grayish color so being extra rich would explain that. Do fuel pressure regulators have any sort of self adjustment or learning time on them or anything?

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Yesterday, on the drive to school the sputter was very predictable and consistent. For example, in fourth gear it would sputter somewhere between 2000 and 2500 every time i hit the gas. The other gears did the same thing at slightly different engine speeds for each gear. If the car was just running rich/lean at a certain spot would the sputter be so easily reproducable? I'm starting to wonder if the problem is somewhere in the ignition. What do you guys think?

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New fuel pump and fuel pressure regulator so the fuel pressure should be good. Plugs are AC Rapidfires from like last year, wires are Taylor Spirro Pro from like 2 years ago. Probably original coils and module.

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Well, im going to go home this weekend so i will swap the chip back to the original to drive it home then i will check out everything once im home. Thanks for the input i will let you know what i come up with

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It only happens when the 60* chip is installed? I'd get hold of Ben ASAP.

 

I'm not sure........I installed the chip and then only a few days later did the top end work. I didnt really drive it much because i was riding my motorcycle everywhere but when i did i cant say i really noticed a difference either good or bad. Thats why i am going to take the chip out on my way home this weekend. Then if it is the chip i can send it back to Ben and if still sputters without it I can investigate further.

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Well this is my second problem with a Very Stupid Fix, but hey I didnt have to spend any money.

 

After the car still sputtered after the removal of the chip we decided to check out the spark.......One of the wires was loose! Ig uess we somehow pulled it loose when we did the top end work, i dunno, but it runs fine now.

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ok unless the wire came loose again i lied about it being fixed.......it sputter exactly the same on my way to and from work the last two days.

 

we did check the spark and the center coil had a little big of orange at the end of the spark but wasnt very noticeable. it stayed like that no matter how much i moved the gap on the tester. the other two coils were totally clean. is this enough of a difference to cause my problem?

 

also, we only tested the front bank of wires because each coil is connected to both banks and the rear ones are a pain to get to (plus it was starting to rain). is it likely for one pin on a coil to be bad and the other ok?

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Could be enough. I'd pick up an extra coil pack and swap it, just to see if it runs any better. You can usually find them at the JY's, but be sure to grab a few just incase the one you grab is bad.

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they are only like 20 bucks from advance...it seems like it would be worth it to not have to do it twice (looks fun to get in there)

 

Hopefully you are not grabbing Accel or MSD ones. Those are known to be junk on these GM ignitions. The AC Delco's(or equivilent) are good up to 500 hp, and possibly even farther.

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gp sorenson? thats their normally stocked stuff

 

Edit: why are the Accel and MSD junk?

 

Not sure why they don't work well, but hopefully someone can chime in. Everyone that has purchases Accel or MSD coils for these FWD GM vehicles has experience poor running conditions(even after we tell them to get rid of that crap, some keep them on and they still complain), and they don't last near as long. Something to do with how the waste-spark ignition system works. Again, hopefully someone will chime in.

 

GP Sorenson, I'm assuming is what they call for replacement OEM style, correct? If so, that should be fine.

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Quote from: radman3120 on Today at 09:52:33 PM

gp sorenson? thats their normally stocked stuff

 

Edit: why are the Accel and MSD junk?

 

Not sure why they don't work well, but hopefully someone can chime in. Everyone that has purchases Accel or MSD coils for these FWD GM vehicles has experience poor running conditions(even after we tell them to get rid of that crap, some keep them on and they still complain), and they don't last near as long. Something to do with how the waste-spark ignition system works. Again, hopefully someone will chime in.

 

GP Sorenson, I'm assuming is what they call for replacement OEM style, correct? If so, that should be fine.

 

Yea GP is the OEM stuff

 

It'd be interesting to know if anyone knows any specifics on the Accel/MSD thing

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