Dyno Pic Inside! Help find the problem and I will paypal you $40!
10-21-2007, 11:42 AM
#1
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Dyno Pic Inside! Help find the problem and I will paypal you $40!
Just took the Dyno hoping to give me a clue what my problem is, but doesn't help.
Before I describe it: If anyone here tells me what the problem could be and gives me a reason why ( no wild guesses) I will do it and if it works I will paypall him $40. It's not a lot : ) but it's worth a post.
Two months ago my car suddenly started hesitating while I was passing another car the CEL light popped right out. It was EGR flow malfunction. I took the EGR valve out, cleaned it, cleaned the TB as well, put new gaskets and silicon and put it back. Started the car and in a couple of minutes the CEL disappeared by itself. But THE HESITATION DID NOT. Now every time the car is with half to full throttle it will start missing firing when it reaches 3500 RPM. After 5k RPM missing disappears. You can se that perfectly on the Dyno runs.
I took the Dyno runs to check the AFR. I wanted to exclude vacuum leaks or fuel delivery problems. The AFR seems to be damn near perfect though! Also my car has a very nice idle right @ 700 RPM so no vacuum leaks, I think.
Thats why I think it's some kind of ignition problem now. Took it to 2 mechanics already and they didn't find nothing wrong, but they are fukin noobs. I want to try .org before I stick my head out @ the dealer.
The problem is not present under no load or very light load. Gas mileage is great as always.
What happens in midrange RPM that can cause that? Is it worth buying a new EGR valve and replacing it? Can the exhaust gassed do that? EGR has no correlation with ignition, but this problem appeared at once when I got the EGR malfunction code.
I started randomly checking and changing sensors since then. Changed the MAF, both oxygen sonsors, knock sensor and tested the TPS and nothing changed. I am desperate. It's getting cold and I need to fix this ASAP. Help a brother out!
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Before I describe it: If anyone here tells me what the problem could be and gives me a reason why ( no wild guesses) I will do it and if it works I will paypall him $40. It's not a lot : ) but it's worth a post.
Two months ago my car suddenly started hesitating while I was passing another car the CEL light popped right out. It was EGR flow malfunction. I took the EGR valve out, cleaned it, cleaned the TB as well, put new gaskets and silicon and put it back. Started the car and in a couple of minutes the CEL disappeared by itself. But THE HESITATION DID NOT. Now every time the car is with half to full throttle it will start missing firing when it reaches 3500 RPM. After 5k RPM missing disappears. You can se that perfectly on the Dyno runs.
I took the Dyno runs to check the AFR. I wanted to exclude vacuum leaks or fuel delivery problems. The AFR seems to be damn near perfect though! Also my car has a very nice idle right @ 700 RPM so no vacuum leaks, I think.
Thats why I think it's some kind of ignition problem now. Took it to 2 mechanics already and they didn't find nothing wrong, but they are fukin noobs. I want to try .org before I stick my head out @ the dealer.
The problem is not present under no load or very light load. Gas mileage is great as always.
What happens in midrange RPM that can cause that? Is it worth buying a new EGR valve and replacing it? Can the exhaust gassed do that? EGR has no correlation with ignition, but this problem appeared at once when I got the EGR malfunction code.
I started randomly checking and changing sensors since then. Changed the MAF, both oxygen sonsors, knock sensor and tested the TPS and nothing changed. I am desperate. It's getting cold and I need to fix this ASAP. Help a brother out!
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10-21-2007, 12:03 PM
#5
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No forced induction. 97GXE 5sp, hi flow air filter and exhaust, thats all.
No, I was thinking about the coils, but why would they run bad only in midrange?
Fuel filter changed 6mo ago, + AFR is almost 14.7 flat across the whole RPM range
No, I was thinking about the coils, but why would they run bad only in midrange?
Fuel filter changed 6mo ago, + AFR is almost 14.7 flat across the whole RPM range
10-21-2007, 12:27 PM
#6
Coils. I have had a misfire and the car bogged until like 5k and pulled like normal...made runs like this at the track. it didnt always happen...very intermittent. I ended up replacing all 6 for about $350 out of frusteration but you could probably buy one or two and swap them out "one by one" until it goes away
10-21-2007, 01:14 PM
#8
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Coils would be easy to do myself, right? Checking prices on ebay now..
Damn, there are sets for like 240. I don't want cheap **** though. Are there some reliable brands/ manifacturers that you can recommend guys? Dealer-mealer is out of question : )
Last edited by truculent; 10-21-2007 at 01:25 PM.
10-21-2007, 03:00 PM
#10
13.5 A/F Is a good point to start at. 14.7 is pretty lean to be running. Definately should be running 91octane at a minimum.
Well first of all id check the plugs, if you clean the TB and intake manifold, all that crap could dirty up the plugs. check those if there filthy either replace them or clean them. know when my plugs were on there way out under normal driving it was fine but once you got on it it would miss like a ***** lol..
So in this order id check the following:
Spark plugs
Coil packs
Also vacuum leaks can pretty much be exlcuded if the car idles alright. Vacuum leaks seem to mostly affect idle, but the car runs fine once its moving. When my egr gasket fell off lol long story, the car barely idled, but if you were driving it was fine.
Also the dyno does show top end loss a bit, but remember the USIM is notorious for loosing power after 5500RPM, so its not that far off normal assuming you are auto with the USIM or functioning MEVI.
Id check the plugs, its easy and if you read the plug it can tell you a lot about how your engine is running. good luck!!
Well first of all id check the plugs, if you clean the TB and intake manifold, all that crap could dirty up the plugs. check those if there filthy either replace them or clean them. know when my plugs were on there way out under normal driving it was fine but once you got on it it would miss like a ***** lol..
So in this order id check the following:
Spark plugs
Coil packs
Also vacuum leaks can pretty much be exlcuded if the car idles alright. Vacuum leaks seem to mostly affect idle, but the car runs fine once its moving. When my egr gasket fell off lol long story, the car barely idled, but if you were driving it was fine.
Also the dyno does show top end loss a bit, but remember the USIM is notorious for loosing power after 5500RPM, so its not that far off normal assuming you are auto with the USIM or functioning MEVI.
Id check the plugs, its easy and if you read the plug it can tell you a lot about how your engine is running. good luck!!
10-21-2007, 03:31 PM
#11
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I put NGK iridium 15k miles ago. I overgapped them too. I know they say you shouldn't overgap spark plugs but the car ran great for 1 year exactly with them. I will pull a few plugs out when I check the coils.
But now I am concerned about the AFR. If sparks/coils doesn't help will have to go to dealer.. Can I do something myself to troubleshoot the lean AFR?
Also, the stock coilpack has 97k miles. If I buy new coilpack and change them and it turns out that wasnt the problem do you think that was a waste or they we due for change anyway?
But now I am concerned about the AFR. If sparks/coils doesn't help will have to go to dealer.. Can I do something myself to troubleshoot the lean AFR?
Also, the stock coilpack has 97k miles. If I buy new coilpack and change them and it turns out that wasnt the problem do you think that was a waste or they we due for change anyway?
10-21-2007, 03:40 PM
#12
the AFR you will not be able to adjust unless you have an AFC(SAFC/VAFC/NEO) or some sort of piggyback ecu or jwt/ts ecu.
I would check the plugs. Now ive read that the maximas are picky with spark plugs, and NGK platinums should be run (PFR5G-11 going off by memory of over a year ago). They are pricey but do last awhile so its kinda a trade off. Alternatively you could try some ngk copper plugs BKR5EGP/BKR5E-11 which are ALOT cheaper then the platinums but dont last aslong. Quick way to rule out plugs. The coils you may as well check as you will have them out. refer to the FSM for proper resistance and testing procedure. Good luck!
Coil packs are freakin expensive from the dealer, i just replaced a set of 6 on a 99 at my work and it was like 700$ for a set, there was only 2 bad, but the people insisted on having all 6 replaced, so i scored 4 good ones haha.
check the for sale forum, often people are selling sets of 6 good coil packs, make sure there tested and within spec for ~100
I would check the plugs. Now ive read that the maximas are picky with spark plugs, and NGK platinums should be run (PFR5G-11 going off by memory of over a year ago). They are pricey but do last awhile so its kinda a trade off. Alternatively you could try some ngk copper plugs BKR5EGP/BKR5E-11 which are ALOT cheaper then the platinums but dont last aslong. Quick way to rule out plugs. The coils you may as well check as you will have them out. refer to the FSM for proper resistance and testing procedure. Good luck!
Coil packs are freakin expensive from the dealer, i just replaced a set of 6 on a 99 at my work and it was like 700$ for a set, there was only 2 bad, but the people insisted on having all 6 replaced, so i scored 4 good ones haha.
check the for sale forum, often people are selling sets of 6 good coil packs, make sure there tested and within spec for ~100
Last edited by 96blkonblkse; 10-21-2007 at 03:43 PM.
10-21-2007, 04:00 PM
#13
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[QUOTE=truculent;6019099]I put NGK iridium 15k miles ago. I overgapped them too. I know they say you shouldn't overgap spark plugs but the car ran great for 1 year exactly with them. I will pull a few plugs out when I check the coils.QUOTE]
There is a reason why you shouldn't overgap your plugs. As they get worn out and used, the gap increases, which I guess could make a coil pack "work harder" and cause premature failure. It's always best to go within spec.
There is a reason why you shouldn't overgap your plugs. As they get worn out and used, the gap increases, which I guess could make a coil pack "work harder" and cause premature failure. It's always best to go within spec.
10-21-2007, 04:22 PM
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You said you checked the TPS.
I assume you checked the full range from closed to fully open. Did you check it at the ecm terminals or just at the sensor?
Do you have an AFC of some sort?
The reason I ask is that if you don't, your afr curve looks like the ecm is staying in closed loop (trying to maintain afr at stoich)
I assume you checked the full range from closed to fully open. Did you check it at the ecm terminals or just at the sensor?
Do you have an AFC of some sort?
The reason I ask is that if you don't, your afr curve looks like the ecm is staying in closed loop (trying to maintain afr at stoich)
10-21-2007, 04:41 PM
#16
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I checked the TPS at the sensor. I only checked it at closed throttle (was 600 ohm) and full throttle (4000 ohm). I read that the specs are 500 and 4000 so I though mine was acceptable.
What can cause the ECU to stay in closed in closed loop even in WOT?
Also, on the coilpack again, does it have some normal life expectancy? Is it ok if I change it at 97k anyway?
What can cause the ECU to stay in closed in closed loop even in WOT?
Also, on the coilpack again, does it have some normal life expectancy? Is it ok if I change it at 97k anyway?
10-21-2007, 04:52 PM
#17
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Coolant temp, throttle position and engine rpm are the three main things controlling the shift from closed to open loop operation. Most OBD-II scanners will tell you in realtime what mode the control system is in.
I wouldn't bother with coilpacks if your engine runs smoothly throughout the rpm range at lower throttle positions.
I wouldn't bother with coilpacks if your engine runs smoothly throughout the rpm range at lower throttle positions.
10-21-2007, 06:08 PM
#18
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I'm going to get $40 dollars...............
It's one of 3 things. First thing is first, check the short 1.5" vacuum line on the bottom of the egr valve, it likes to corrode and crack and tear and what not. It also likes to plug itself up. If the line is good, then on a whim replace the egr-selenoid valve, it's the green colored one near the intake manifold in the vacuum galley area. If that still doesn't resolve it, replace the entire EGRC-BPT, while doing so make sure to label every vacuum hose and check them for obstructions. Normally I am against tossing parts at a problem, but in this case It's almost easier to just pay $20-40 at the junkyard and call it a day. IMHO anyways. Of course you could always run some of the checks in the fsm, It starts on page 222 section EC, but waste of time imho, and I didn't feel like re-typing all of that info, not to mention replacing everything will give you a great opurtunity to also check the vacuum lines for obstructions without having to trace them 1 by 1.
If you have doubts that it is indeed related to the egr, here's a quote for you...........
"if too much EGR flow exists due to an EGRC-BPT valve malfuntion, off idle engine roughness will increase."
Paypal is Kevgoods@hotmail.com
It's one of 3 things. First thing is first, check the short 1.5" vacuum line on the bottom of the egr valve, it likes to corrode and crack and tear and what not. It also likes to plug itself up. If the line is good, then on a whim replace the egr-selenoid valve, it's the green colored one near the intake manifold in the vacuum galley area. If that still doesn't resolve it, replace the entire EGRC-BPT, while doing so make sure to label every vacuum hose and check them for obstructions. Normally I am against tossing parts at a problem, but in this case It's almost easier to just pay $20-40 at the junkyard and call it a day. IMHO anyways. Of course you could always run some of the checks in the fsm, It starts on page 222 section EC, but waste of time imho, and I didn't feel like re-typing all of that info, not to mention replacing everything will give you a great opurtunity to also check the vacuum lines for obstructions without having to trace them 1 by 1.
If you have doubts that it is indeed related to the egr, here's a quote for you...........
"if too much EGR flow exists due to an EGRC-BPT valve malfuntion, off idle engine roughness will increase."
Paypal is Kevgoods@hotmail.com
Last edited by KRRZ350; 10-21-2007 at 06:16 PM.
10-21-2007, 06:14 PM
#19
in my personal experience I never noticed any drivability problems with the egr stuff disconnected. I think at one time I even took the EGR off and put a block off plate and never noticed any difference.
When I had a misfiring issue with teh coilpacks it was the most intermittent thing. If it was hot outside it was doing it alot more often..and studdering slightly at idle SOMETIMES...when I floored it, it would be normal and bog like 2k to 5k and then pick back up and pull normally as if a misfire never occured.
When I had a misfiring issue with teh coilpacks it was the most intermittent thing. If it was hot outside it was doing it alot more often..and studdering slightly at idle SOMETIMES...when I floored it, it would be normal and bog like 2k to 5k and then pick back up and pull normally as if a misfire never occured.
10-21-2007, 06:24 PM
#20
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That's because in both of those examples the EGR was fully closed all the time, I had identical symptoms on a customers car combined with occasional egr flow codes. But who knows, I'm not saying anything is definite, but if it's related to the EGRC-BPT than I win 
10-21-2007, 07:33 PM
#23
The EGR hypothesis doesn't explain the perpetual closed loop condition, though.
10-21-2007, 07:40 PM
#24
As for the bucking in the midrange, that's where volumetric efficiency is at its highest with the USIM. I say the jaggies are from knock and the subsequent timing retard. The real problem is the inappropriate closed loop condition (as eng92 mentioned). 
10-21-2007, 08:09 PM
#26
And to answer the question, I'm not really sure. Never really heard of this happening before. I'll try to dig up what I can, though.
10-21-2007, 08:15 PM
#27
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Wow, great advice! I will take a day off this week and change alot of things.
I appreciate all of the advice. I promise I will send 40 buck to someone. If nothing works and I take it to dealer and it's something noone said I will donate the $40 to the site. But I think you got everything possible covered : )
I have a OBDII scanner, the car has no codes. I checked it after I cleaned the EGR valve but it had no codes -- it cleared itself.
About the solenoid, it took alot of abuse when I was changing the knock sensor -- might change it anyway.
I don't know if the car is in perpetual closed loop, but the 14.7 AFR suggests that. I will tell you what, tomorrow I will disconnect one of the oxygen sensors from the harness. I think I should get the CEL and the ECU should go in open loop, right? Or do I have to disconnect both of them?
I appreciate all of the advice. I promise I will send 40 buck to someone. If nothing works and I take it to dealer and it's something noone said I will donate the $40 to the site. But I think you got everything possible covered : )
I have a OBDII scanner, the car has no codes. I checked it after I cleaned the EGR valve but it had no codes -- it cleared itself.
About the solenoid, it took alot of abuse when I was changing the knock sensor -- might change it anyway.
I don't know if the car is in perpetual closed loop, but the 14.7 AFR suggests that. I will tell you what, tomorrow I will disconnect one of the oxygen sensors from the harness. I think I should get the CEL and the ECU should go in open loop, right? Or do I have to disconnect both of them?
Last edited by truculent; 10-21-2007 at 08:17 PM.
10-22-2007, 06:18 AM
#31
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Disconnected the bank 1 sensor 1 oxygen sensor this morning. I had recently replaced it with a Bosch direct replacement from Autozone ($79.99). After 15 mins the CEL came on.
1. No diffference as far as my problem. The misfire comes right after 3k RPM and disapeares after 5k. And I have to tell you, it sounds like misfire because the sound from the exhaust becomes interrupted and discontinuous. It's not like the car just loses power in that range. The engine just doesn't run continuously.
But 2.! Not to stir anything up with the guys who hate the 'but dyno', but the car definately pulls stronger now! That Bosch sensor looked absolutely used although I bought it from Autozone. It was brown and yellow and looked burned with torch. Also, the mechanic that I took my car to, who couldn't find any problem actually mentioned that the Bosch sensor has quite different reading with the other sensor (I think he said 400 mv vs 260mv, but not 100% sure). I am sorry, but this is enough for me and the Bosch sensor goes away tomorrow. Just my 2 cents.
But like I said, that made no difference on my midrange misfiring..
1. No diffference as far as my problem. The misfire comes right after 3k RPM and disapeares after 5k. And I have to tell you, it sounds like misfire because the sound from the exhaust becomes interrupted and discontinuous. It's not like the car just loses power in that range. The engine just doesn't run continuously.
But 2.! Not to stir anything up with the guys who hate the 'but dyno', but the car definately pulls stronger now! That Bosch sensor looked absolutely used although I bought it from Autozone. It was brown and yellow and looked burned with torch. Also, the mechanic that I took my car to, who couldn't find any problem actually mentioned that the Bosch sensor has quite different reading with the other sensor (I think he said 400 mv vs 260mv, but not 100% sure). I am sorry, but this is enough for me and the Bosch sensor goes away tomorrow. Just my 2 cents.
But like I said, that made no difference on my midrange misfiring..
10-22-2007, 06:37 AM
#32
Sounds exactly how my car was when my coilpack(s) was bad. It felt horrible under WOT in that same rpm range.
As far as the 02 sensor...more horsepower? I better go unplug mine!! Jk. But that burnt look might just be due to how they treat the metal...I think my brand new ones looked like that as well. You could ask to see another one at autozone and compare it...but I still think the problem is the coils or one/ a few of them at least. My 95 had like 130k on it when mine started acting up...maybe less.
As far as the 02 sensor...more horsepower? I better go unplug mine!! Jk. But that burnt look might just be due to how they treat the metal...I think my brand new ones looked like that as well. You could ask to see another one at autozone and compare it...but I still think the problem is the coils or one/ a few of them at least. My 95 had like 130k on it when mine started acting up...maybe less.
Disconnected the bank 1 sensor 1 oxygen sensor this morning. I had recently replaced it with a Bosch direct replacement from Autozone ($79.99). After 15 mins the CEL came on.
1. No diffference as far as my problem. The misfire comes right after 3k RPM and disapeares after 5k. And I have to tell you, it sounds like misfire because the sound from the exhaust becomes interrupted and discontinuous. It's not like the car just loses power in that range. The engine just doesn't run continuously.
But 2.! Not to stir anything up with the guys who hate the 'but dyno', but the car definately pulls stronger now! That Bosch sensor looked absolutely used although I bought it from Autozone. It was brown and yellow and looked burned with torch. Also, the mechanic that I took my car to, who couldn't find any problem actually mentioned that the Bosch sensor has quite different reading with the other sensor (I think he said 400 mv vs 260mv, but not 100% sure). I am sorry, but this is enough for me and the Bosch sensor goes away tomorrow. Just my 2 cents.
But like I said, that made no difference on my midrange misfiring..
1. No diffference as far as my problem. The misfire comes right after 3k RPM and disapeares after 5k. And I have to tell you, it sounds like misfire because the sound from the exhaust becomes interrupted and discontinuous. It's not like the car just loses power in that range. The engine just doesn't run continuously.
But 2.! Not to stir anything up with the guys who hate the 'but dyno', but the car definately pulls stronger now! That Bosch sensor looked absolutely used although I bought it from Autozone. It was brown and yellow and looked burned with torch. Also, the mechanic that I took my car to, who couldn't find any problem actually mentioned that the Bosch sensor has quite different reading with the other sensor (I think he said 400 mv vs 260mv, but not 100% sure). I am sorry, but this is enough for me and the Bosch sensor goes away tomorrow. Just my 2 cents.
But like I said, that made no difference on my midrange misfiring..
Last edited by chillin014; 10-22-2007 at 07:01 AM.
10-22-2007, 08:07 AM
#33
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No, I just think my Bosch O2 sensor gives the ECU readings not up to factory specifications, that's all.
Anyway, if you have a OBDII scanner you can disconnect the harness and drive around for an hour in open loop just for the heck of it. Then just plug it back and trip the CEL. Takes 1 min to plug off an on : ) Mine felt stronger.
Alright, will test and swap a few coils this weekend, may be even this week.
Anyway, if you have a OBDII scanner you can disconnect the harness and drive around for an hour in open loop just for the heck of it. Then just plug it back and trip the CEL. Takes 1 min to plug off an on : ) Mine felt stronger.
Alright, will test and swap a few coils this weekend, may be even this week.
10-22-2007, 09:08 AM
#34
Good luck with this. I am having what appears to be the same exact problem and have changed all kinds of stuff. The only difference on mine is I don't have any CEL's. I even went as far as swapping a newer motor(thought timing was ***'d when did timing chain and still have the same problem) I'm to the point where I am going to have to look at the engine harness to make sure all connections are fine. Again good luck and hope something gets resolved soon. (For both of us)
10-22-2007, 03:29 PM
#36
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If i were you i would check your spark plugs, it might not be them, but it is worth a shot at it. I overtightened mine and the piston hit the end of a plug and bent it so it wasnt firing. Mine only misfired when going up a hill just cruisin but WOT it seemed fine. just pull them and check them, and make sure your gap is set just right.
10-22-2007, 04:06 PM
#37
MAFS, that'd be my guess, ecpecially due to the 'high flow filter' you installed, is it an oiled filter or paper? if its paper it would allow particles through that will toast your MAFS. Test that Mass air flow sensor and see what pops up.
10-22-2007, 04:07 PM
#38
Sounds exactly how my car was when my coilpack(s) was bad. It felt horrible under WOT in that same rpm range.
As far as the 02 sensor...more horsepower? I better go unplug mine!! Jk. But that burnt look might just be due to how they treat the metal...I think my brand new ones looked like that as well. You could ask to see another one at autozone and compare it...but I still think the problem is the coils or one/ a few of them at least. My 95 had like 130k on it when mine started acting up...maybe less.
As far as the 02 sensor...more horsepower? I better go unplug mine!! Jk. But that burnt look might just be due to how they treat the metal...I think my brand new ones looked like that as well. You could ask to see another one at autozone and compare it...but I still think the problem is the coils or one/ a few of them at least. My 95 had like 130k on it when mine started acting up...maybe less.
10-22-2007, 04:32 PM
#39
honestly, I dont know...because I couldnt test the problem since it was so intermittent. I ended up just replacing all of them...but kept the old ones. I sold the "new" ones before I swapped motors and put the old set back in. I got the misfire again and decided to try to just buy 2 extras to test with but I dont think I ever got rid of it even with the 2 extra junkyard coils to swap out.