Supercharger / fuel related question ->
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My car has not been quite right for a month now. Its almost there(those who've seen my posts over the last month know what I am talking about.) Right now, my car idles fine and generally drives alright on my commute to work. However if I go at it hard, I have like a hicup(hesitation\surge--don't know what to call it) around ~3600-3700 rpms and another one at ~4300 rpms. This only happens at WOT(or real close to WOT). After 4350 rpms the car cruises all the way up to 6500 rpms with a problem.
Is this considered a ping? knock(there is not a knocking sound)? To me, this seems like the car is not getting enough fuel at that point(?).
Also, note a compression/leak down test was performed and the car checked out alright. I have been running 94 octane gas and new NGK spark plugs 2 heat ranges colder than stock. I do not currently have any check engine lights.
(short version)
This all happened when part of the Evap system went bad a month ago (code 0316). Dealer fixed part, but screwed up supercharger hoses. IMPO re-did hoses.
What would help me diagnose/fix this?(haynes manual came in today) Would buying one of those Apex SFC's help?
thanks,
Matt P
Is this considered a ping? knock(there is not a knocking sound)? To me, this seems like the car is not getting enough fuel at that point(?).
Also, note a compression/leak down test was performed and the car checked out alright. I have been running 94 octane gas and new NGK spark plugs 2 heat ranges colder than stock. I do not currently have any check engine lights.
(short version)
This all happened when part of the Evap system went bad a month ago (code 0316). Dealer fixed part, but screwed up supercharger hoses. IMPO re-did hoses.
What would help me diagnose/fix this?(haynes manual came in today) Would buying one of those Apex SFC's help?
thanks,
Matt P
Senior Member
Joined: Aug 2000
Posts: 311
From: Algonquin, IL
you might want to try
running the Lorens fuel pressure mod. Just disconnect the vacuum line going to the hobs switch at the 'T' connector (near your secondary fuel pump) and place a vacuum cap over it. I don't know if this will cure your problem but its worth a try as it only takes 2 minutes to do this.
Your secondary fuel pump will run at all time with this mod.
Your secondary fuel pump will run at all time with this mod.
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Re: you might want to try
Originally posted by SteveChicagoSC
running the Lorens fuel pressure mod. Just disconnect the vacuum line going to the hobs switch at the 'T' connector (near your secondary fuel pump) and place a vacuum cap over it. I don't know if this will cure your problem but its worth a try as it only takes 2 minutes to do this.
Your secondary fuel pump will run at all time with this mod.
running the Lorens fuel pressure mod. Just disconnect the vacuum line going to the hobs switch at the 'T' connector (near your secondary fuel pump) and place a vacuum cap over it. I don't know if this will cure your problem but its worth a try as it only takes 2 minutes to do this.
Your secondary fuel pump will run at all time with this mod.
Matt P.
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Re: Re: you might want to try
Current condition of thing--->
Symptoms: Two “Hesitation”\buckle\jolt type thingies(ping? no knock sound though). But no ECU error codes(check engine light) are displayed. The first occurs around ~3700 rpms and the second at ~4300 rpms. (Idle seems fine, power is there, and car drives alright during at other rpms)
When: Car has to be warmed up. I think the ECU does not use lean/rich information from the front O2 sensor until it reaches (600 degrees F). This seems to only occur at ~75% throttle or greater. Problem seems to be slightly worse when gas tank is low.
What was done so far: obvious -> changed spark plugs, fuel filter. I even went to the larger 300 zx fuel filter -- seemed to help some but not get rid of the problem Compression leak down test performed(car checked out okay). Also, I always use premium gas. I have tried injector cleaner, but that did not seem to help.
Symptoms: Two “Hesitation”\buckle\jolt type thingies(ping? no knock sound though). But no ECU error codes(check engine light) are displayed. The first occurs around ~3700 rpms and the second at ~4300 rpms. (Idle seems fine, power is there, and car drives alright during at other rpms)
When: Car has to be warmed up. I think the ECU does not use lean/rich information from the front O2 sensor until it reaches (600 degrees F). This seems to only occur at ~75% throttle or greater. Problem seems to be slightly worse when gas tank is low.
What was done so far: obvious -> changed spark plugs, fuel filter. I even went to the larger 300 zx fuel filter -- seemed to help some but not get rid of the problem Compression leak down test performed(car checked out okay). Also, I always use premium gas. I have tried injector cleaner, but that did not seem to help.
Supporting Maxima.org Member
Joined: Aug 2000
Posts: 2,138
Re: Re: Re: you might want to try
Originally posted by Matt_P
Current condition of thing--->
Symptoms: Two “Hesitation”\buckle\jolt type thingies(ping? no knock sound though). But no ECU error codes(check engine light) are displayed. The first occurs around ~3700 rpms and the second at ~4300 rpms. (Idle seems fine, power is there, and car drives alright during at other rpms)
When: Car has to be warmed up. I think the ECU does not use lean/rich information from the front O2 sensor until it reaches (600 degrees F). This seems to only occur at ~75% throttle or greater. Problem seems to be slightly worse when gas tank is low.
What was done so far: obvious -> changed spark plugs, fuel filter. I even went to the larger 300 zx fuel filter -- seemed to help some but not get rid of the problem Compression leak down test performed(car checked out okay). Also, I always use premium gas. I have tried injector cleaner, but that did not seem to help.
Current condition of thing--->
Symptoms: Two “Hesitation”\buckle\jolt type thingies(ping? no knock sound though). But no ECU error codes(check engine light) are displayed. The first occurs around ~3700 rpms and the second at ~4300 rpms. (Idle seems fine, power is there, and car drives alright during at other rpms)
When: Car has to be warmed up. I think the ECU does not use lean/rich information from the front O2 sensor until it reaches (600 degrees F). This seems to only occur at ~75% throttle or greater. Problem seems to be slightly worse when gas tank is low.
What was done so far: obvious -> changed spark plugs, fuel filter. I even went to the larger 300 zx fuel filter -- seemed to help some but not get rid of the problem Compression leak down test performed(car checked out okay). Also, I always use premium gas. I have tried injector cleaner, but that did not seem to help.
Jim
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Re: Re: Re: you might want to try
I did Loren's fp mod back in March. It helped a lot when going into and out of boost. My problem has just come about last month. Do you know if there is an intake filter/screen? Is it possible that there is some type of sediment build up there?
Matt P.
Matt P.
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Update on situation ->
I went over to my mechanics(small shop) today and borrowed his snapper ODB-II scan tool thing. I noticed that the results I was getting from the TPS were not accurate with my actual amount I was pressing the throttle. The results were changing, but they were not linear at all. I have a Micrometer comming into monday. I will futher test the TPS(Ohms ..resistance etc). In addition, the os2 sensors were very slow in updating. (Ray-mechanic) said they should be quicker in updating the display after I nail the throttle.
Matt P.
[Edited by Matt_P on 10-06-2000 at 04:13 PM]
Matt P.
[Edited by Matt_P on 10-06-2000 at 04:13 PM]
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Here's just a thought, Matt-->
Originally posted by Matt_P
I went over to my mechanics(small shop) today and borrowed his snapper ODB-II scan tool thing. I noticed that the results I was getting from the TPS were not accurate with my actual amount I was pressing the throttle. The results were changing, but they were not linear at all. I have a Micrometer comming into monday. I will futher test the TPS(Ohms ..resistance etc). In addition, the os2 sensors were very slow in updating. (Ray-mechanic) said they should be quicker in updating the display after I nail the throttle.
Matt P.
[Edited by Matt_P on 10-06-2000 at 04:13 PM]
I went over to my mechanics(small shop) today and borrowed his snapper ODB-II scan tool thing. I noticed that the results I was getting from the TPS were not accurate with my actual amount I was pressing the throttle. The results were changing, but they were not linear at all. I have a Micrometer comming into monday. I will futher test the TPS(Ohms ..resistance etc). In addition, the os2 sensors were very slow in updating. (Ray-mechanic) said they should be quicker in updating the display after I nail the throttle.
Matt P.
[Edited by Matt_P on 10-06-2000 at 04:13 PM]
When I was a tech, I had worked on a couple cars with a problem similar to what you explained. (both were Mopars, but that's besides the point)
They had stumbles/misfires when under heavy throttle, and only at certain points. After monitoring the situation, they had a faulty ECU.
In your case, perhaps the pulley problem you had (that messed up your electrical system was the culprit.
Just for the hell of it, check your engine ground cables (don't remember where they are) Make sure they are firmly attached and intact.
Also, check your ECU and it's ground. If your sensors are showing slow update rates, the sensors could be bad, or perhaps the wiring harness to the sensors could have excessive resistance in them (possibly because of your past problem)
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