90 L98 - Stalling, running rough when cold/damp
Thread Starter
Le Mans Master
Joined: Apr 2002
Posts: 5,726
Likes: 46
From: Waukesha WI
St. Jude Donor '15
90 L98 - Stalling, running rough when cold/damp
The 90 apparently wants to be a PITA. Lately, the morning temps have been in the 60s and quite damp. When the car first starts up, it idles very rough and occasionally stalls. When underway, it bucks and hesitates for a few miles until it warms up. It's done this when it wasn't very damp but it is much worse when wet out. It eventually smooths out but I can still feel the rough idle thru the shifter. When coasting in neutral, the idle will "hunt" and vary about 500rpm or so.
So far I have checked:
Plugs and wires: All wires show very low resistance and no opens when twisting. Plugs are about 10k old NGK V-Power. Wires are about the same age.
Injectors: All injectors are at 12.4ohm cold. They are LS1 take-offs (from SLP) and have about 20k on them.
Fuel pressure: 44psi engine off, key on. 35psi idle and smoothly follows the throttle. The pressure did not drop off when the car tried to stall.
Vacuum: Very steady 19-20inHG at idle.
Distributer: Cap/rotor/coil all have about 20k on them. I've looked at the cap and it does not appear to be too crudded up inside but I am not sure what kind of real diagnostic test I can do.
I have access to DataMaster if anyone thinks that some datalogs might be helpful. I'm kinda lost. Any suggestions?
Thanks!
So far I have checked:
Plugs and wires: All wires show very low resistance and no opens when twisting. Plugs are about 10k old NGK V-Power. Wires are about the same age.
Injectors: All injectors are at 12.4ohm cold. They are LS1 take-offs (from SLP) and have about 20k on them.
Fuel pressure: 44psi engine off, key on. 35psi idle and smoothly follows the throttle. The pressure did not drop off when the car tried to stall.
Vacuum: Very steady 19-20inHG at idle.
Distributer: Cap/rotor/coil all have about 20k on them. I've looked at the cap and it does not appear to be too crudded up inside but I am not sure what kind of real diagnostic test I can do.
I have access to DataMaster if anyone thinks that some datalogs might be helpful. I'm kinda lost. Any suggestions?
Thanks!
Instructor
Joined: Oct 2006
Posts: 141
Likes: 7
From: Deltona Florida
hunting issue
I know for a fact that the hunting idle is the MAF. When i had that problem it was on the highway off ramp the idle would surge and ebb.
after replacing the MAF the problem went away. take the MAF off and look to see if the filament is still intact, should look like a light bulb filament. If your car dosent have a MAF then maybe you need one.
after replacing the MAF the problem went away. take the MAF off and look to see if the filament is still intact, should look like a light bulb filament. If your car dosent have a MAF then maybe you need one.
Le Mans Master
Joined: Aug 2005
Posts: 5,002
Likes: 5
From: No Opti Here Tn
St. Jude Donor '06
I know for a fact that the hunting idle is the MAF. When i had that problem it was on the highway off ramp the idle would surge and ebb.
after replacing the MAF the problem went away. take the MAF off and look to see if the filament is still intact, should look like a light bulb filament. If your car dosent have a MAF then maybe you need one.
after replacing the MAF the problem went away. take the MAF off and look to see if the filament is still intact, should look like a light bulb filament. If your car dosent have a MAF then maybe you need one.
Could even be just the MAF relays
Thread Starter
Le Mans Master
Joined: Apr 2002
Posts: 5,726
Likes: 46
From: Waukesha WI
St. Jude Donor '15
I cleaned the TB about a year ago. I pulled it off and cleaned out the passages again. The IAC pintle was a little sooty but not bad at all. There was a decent amount of oil from the PCV system in there, tho.
I pulled out all the plugs and didn't see anything unusual. They all look clean - no buildup on the electrodes. The gap was still at 0.035. None of them were loose or messed up as far as I could tell.
A ran a log while moving the car in the driveway. I can't see anything amiss. The CTS and IAT seem normal. The hesitation can be seen when I blipped the throttle - there is a significant delay before the engine revs up. It wasn't very cold/damp when I ran this so there may not be enough to go on. The log is a CSV exported from Datamaster. If you need some other values shown, I can re-export it.
Log
I pulled out all the plugs and didn't see anything unusual. They all look clean - no buildup on the electrodes. The gap was still at 0.035. None of them were loose or messed up as far as I could tell.
A ran a log while moving the car in the driveway. I can't see anything amiss. The CTS and IAT seem normal. The hesitation can be seen when I blipped the throttle - there is a significant delay before the engine revs up. It wasn't very cold/damp when I ran this so there may not be enough to go on. The log is a CSV exported from Datamaster. If you need some other values shown, I can re-export it.
Log
Thread Starter
Le Mans Master
Joined: Apr 2002
Posts: 5,726
Likes: 46
From: Waukesha WI
St. Jude Donor '15
Sunday morning the stalling was very bad. It bucked and hesitated for a few miles and then levelled out enough to drive but it was still there a little.
Any more ideas?
Any more ideas?
Le Mans Master
Joined: Feb 2005
Posts: 5,146
Likes: 3
From: The Motor City
The log I see doesn't show me enough info, and appears to be a snap shot of running from 70-80mph? If you have a datamaster log, with idle etc. at warm-up and in closed loop may help.
Last edited by mseven; Oct 15, 2007 at 10:16 AM.
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Thread Starter
Le Mans Master
Joined: Apr 2002
Posts: 5,726
Likes: 46
From: Waukesha WI
St. Jude Donor '15
Is the car stock ? Comparing datalogs with ones from a higher ambient temp. may shed some light on things, if everything was good at higher temps. it could be a number of things, I would start by looking at CTS numbers, MAT sensor (controls temp change), blm, etc.etc.
The log I see doesn't show me enough info, and appears to be a snap shot of running from 70-80mph? If you have a datamaster log, with idle etc. at warm-up and in closed loop may help.
The log I see doesn't show me enough info, and appears to be a snap shot of running from 70-80mph? If you have a datamaster log, with idle etc. at warm-up and in closed loop may help.
The last column in that log is speed... 0-5mph or so.
Datamaster log in the driveway: Here This log shows me moving back and forth in the driveway. The car almost stalled a few times but it recovered.
Datamaster log running around the neighborhood: Here The end of this one shows the engine jerking and changing speed with no change in TPS. This has some open and closed loop data.
I may be able to get a better log during the stalling/hesitating episodes in the morning if it would be helpful - I won't like getting up extra early tho
. I have a feeling the logs will be inconclusive. This seems to be a "mechanical" problem to me - something is crapping out that has nothing to do w/ the ECM directly. I could be wrong.Thanks for the help!
Le Mans Master
Joined: Feb 2005
Posts: 5,146
Likes: 3
From: The Motor City
is the hesitating coming in at around 850 rpm going into 1100-2200 rpm (around 8-10 mph)?
At certain places of idle I see the timing dropping as low as 8* (near end of log when at 195 OT), should be at approx. 20*(closed throttle setting in chip). This could keep the BLM rich off idle, as I am seeing in your logs (OT)
My experience on MAP cars, is when the fueling changes as dramatic as what I see in your logs, it usually causes it to have a strange reaction/s. Going from a low BLM of 108 ish at 800 and then climbing into to power band (starting at 1k rpm -3K+ from 50-80ish kpa.)it goes way lean (150+), way fast. (feeling like a miss, stuttering etc. when that much fuel is being removed). As your OT increases, at idle your BLM is dropping and is out of range (109) for the ecm to comp.
The rich idle should be addressed, as well as adding fuel in the 1100 -4000rpm in the 50-80 kpa areas, spark knock and pulling timing approx. 4* should be addressed as well (adding fuel would probably fix that area). The de-cell through 30-25 kpa is going a bit lean as well.
Because I have never seen a "before" log, and if we are to assume it was right to begin with, there may be a fueling problem which would be a reason for it going so lean under load. ???
Is this a stock tune ?
At certain places of idle I see the timing dropping as low as 8* (near end of log when at 195 OT), should be at approx. 20*(closed throttle setting in chip). This could keep the BLM rich off idle, as I am seeing in your logs (OT)
My experience on MAP cars, is when the fueling changes as dramatic as what I see in your logs, it usually causes it to have a strange reaction/s. Going from a low BLM of 108 ish at 800 and then climbing into to power band (starting at 1k rpm -3K+ from 50-80ish kpa.)it goes way lean (150+), way fast. (feeling like a miss, stuttering etc. when that much fuel is being removed). As your OT increases, at idle your BLM is dropping and is out of range (109) for the ecm to comp.
The rich idle should be addressed, as well as adding fuel in the 1100 -4000rpm in the 50-80 kpa areas, spark knock and pulling timing approx. 4* should be addressed as well (adding fuel would probably fix that area). The de-cell through 30-25 kpa is going a bit lean as well.
Because I have never seen a "before" log, and if we are to assume it was right to begin with, there may be a fueling problem which would be a reason for it going so lean under load. ???
Is this a stock tune ?
Last edited by mseven; Oct 15, 2007 at 12:31 PM.
Thread Starter
Le Mans Master
Joined: Apr 2002
Posts: 5,726
Likes: 46
From: Waukesha WI
St. Jude Donor '15
is the hesitating coming in at around 850 rpm going into 1100-2200 rpm (around 8-10 mph)?
At certain places of idle I see the timing dropping as low as 8* (near end of log when at 195 OT), should be at approx. 20*(closed throttle setting in chip). This could keep the BLM rich off idle, as I am seeing in your logs (OT)
My experience on MAP cars, is when the fueling changes as dramatic as what I see in your logs, it usually causes it to have a strange reaction/s. Going from a low BLM of 108 ish at 800 and then climbing into to power band (starting at 1k rpm -3K+ from 50-80ish kpa.)it goes way lean (150+), way fast. (feeling like a miss, stuttering etc. when that much fuel is being removed). As your OT increases, at idle your BLM is dropping and is out of range (109) for the ecm to comp.
The rich idle should be addressed, as well as adding fuel in the 1100 -4000rpm in the 50-80 kpa areas, spark knock and pulling timing approx. 4* should be addressed as well (adding fuel would probably fix that area). The de-cell through 30-25 kpa is going a bit lean as well.
Because I have never seen a "before" log, and if we are to assume it was right to begin with, there may be a fueling problem which would be a reason for it going so lean under load. ???
Is this a stock tune ?
At certain places of idle I see the timing dropping as low as 8* (near end of log when at 195 OT), should be at approx. 20*(closed throttle setting in chip). This could keep the BLM rich off idle, as I am seeing in your logs (OT)
My experience on MAP cars, is when the fueling changes as dramatic as what I see in your logs, it usually causes it to have a strange reaction/s. Going from a low BLM of 108 ish at 800 and then climbing into to power band (starting at 1k rpm -3K+ from 50-80ish kpa.)it goes way lean (150+), way fast. (feeling like a miss, stuttering etc. when that much fuel is being removed). As your OT increases, at idle your BLM is dropping and is out of range (109) for the ecm to comp.
The rich idle should be addressed, as well as adding fuel in the 1100 -4000rpm in the 50-80 kpa areas, spark knock and pulling timing approx. 4* should be addressed as well (adding fuel would probably fix that area). The de-cell through 30-25 kpa is going a bit lean as well.
Because I have never seen a "before" log, and if we are to assume it was right to begin with, there may be a fueling problem which would be a reason for it going so lean under load. ???
Is this a stock tune ?
This problem did not appear until later, tho. I think I have a copy of the original bin on an old laptop. I can put it back on and give this another try.
Thread Starter
Le Mans Master
Joined: Apr 2002
Posts: 5,726
Likes: 46
From: Waukesha WI
St. Jude Donor '15
I returned the chip back to stock except for the injector constant (24lbs), rev limit and fan temp. After taking it out for a drive, the problem appears to be almost gone. There is still a little hesitation at slow speed and low RPM but it is barely noticeable. It was cold this morning but not as damp as before, however.
I find it odd that the tune would have fixed this even tho the problem only appeared a short time ago - long after the changes were made.
New DM log: Here.
If I am reading this right, the BLM is still 108 most of the time. I suppose I should really take some time to tune this thing. Odd that the stock tune would be so far off.
Thanks for the help! Hopefully it is really fixed.
I find it odd that the tune would have fixed this even tho the problem only appeared a short time ago - long after the changes were made.
New DM log: Here.
If I am reading this right, the BLM is still 108 most of the time. I suppose I should really take some time to tune this thing. Odd that the stock tune would be so far off.
Thanks for the help! Hopefully it is really fixed.
Thread Starter
Le Mans Master
Joined: Apr 2002
Posts: 5,726
Likes: 46
From: Waukesha WI
St. Jude Donor '15
I noticed yesterday that the idle still acts funny. When coasting at speed with either the clutch engaged or in neutral the idle likes to "bounce" - it'll jump about 3-400rpm then drop back and repeat. As soon as the speed gets less than about 7-10mph, it returns to a normal, steady 750rpm.
Team Owner
Joined: Jul 2004
Posts: 28,475
Likes: 3,291
From: Hartford WI
When it's up to temp, the IAC count is at about 20 +/-2 at 725-750RPM and 15* advance.
I noticed yesterday that the idle still acts funny. When coasting at speed with either the clutch engaged or in neutral the idle likes to "bounce" - it'll jump about 3-400rpm then drop back and repeat. As soon as the speed gets less than about 7-10mph, it returns to a normal, steady 750rpm.
I noticed yesterday that the idle still acts funny. When coasting at speed with either the clutch engaged or in neutral the idle likes to "bounce" - it'll jump about 3-400rpm then drop back and repeat. As soon as the speed gets less than about 7-10mph, it returns to a normal, steady 750rpm.
Le Mans Master
Joined: Feb 2005
Posts: 5,146
Likes: 3
From: The Motor City
I find it odd that the tune would have fixed this even tho the problem only appeared a short time ago - long after the changes were made.
If I am reading this right, the BLM is still 108 most of the time. I suppose I should really take some time to tune this thing. Odd that the stock tune would be so far off..
If I am reading this right, the BLM is still 108 most of the time. I suppose I should really take some time to tune this thing. Odd that the stock tune would be so far off..
As I have added various little changes after the initial build, I have had to tweak ve tables, PW decay, IAC cts. in drive, dead band, closed throttle pos.timing, AE, values, etc. etc. etc.
As to the neutral at MPH, this can tweaked in a number of ways. Slope gain, iac follower decay, pulse width decay etc. and would really depend on what you are seeing on the scans at the time of the event.
Before doing any of the aforementioned it is best to begin w/blm's being under controll, and all other tweaks when motor is at OT, then work backwords for cold settings.
Last edited by mseven; Oct 22, 2007 at 09:20 AM.
Thread Starter
Le Mans Master
Joined: Apr 2002
Posts: 5,726
Likes: 46
From: Waukesha WI
St. Jude Donor '15
I'm assuming that your TPS is either set right no not adjustable and your timing is set correct. Your plugs are all firing at the right time and all that, right? How about seeing if your plugs are firing correctly? Do you have an inductive timing light where you can check RPM? All should have the same RPM when you go from wire to wire.
The idle is steady with no apparent miss and all the plugs look great so I would guess the ignition system is running fine. Under load the engine is reasonably smooth now that I have the stock tune back. I can use 6th gear at 50mph again w/o the engine bogging (much).
Team Owner
Joined: Jul 2004
Posts: 28,475
Likes: 3,291
From: Hartford WI
The TPS is technically non-adjustable but I did get it set to .57v. The base timing was set to 6* last time I had the intake off. I should probably recheck it to make sure nothing wandered, I suppose. I do have an inductive-pickup timing light but it does not have an RPM readout - its a cheapy. Not a bad idea for tracking possible ignition problems, tho.
The idle is steady with no apparent miss and all the plugs look great so I would guess the ignition system is running fine. Under load the engine is reasonably smooth now that I have the stock tune back. I can use 6th gear at 50mph again w/o the engine bogging (much).
The idle is steady with no apparent miss and all the plugs look great so I would guess the ignition system is running fine. Under load the engine is reasonably smooth now that I have the stock tune back. I can use 6th gear at 50mph again w/o the engine bogging (much).
Thread Starter
Le Mans Master
Joined: Apr 2002
Posts: 5,726
Likes: 46
From: Waukesha WI
St. Jude Donor '15
Not really odd, on a stock tune you would be lucky if you are +,or -10 in the blm's. ANY changes on these SD cars (weather via mods to the set-up or the tune) seem to have dramatic effects across the board.
As I have added various little changes after the initial build, I have had to tweak ve tables, PW decay, IAC cts. in drive, dead band, closed throttle pos.timing, AE, values, etc. etc. etc.
As to the neutral at MPH, this can tweaked in a number of ways. Slope gain, iac follower decay, pulse width decay etc. and would really depend on what you are seeing on the scans at the time of the event.
Before doing any of the aforementioned it is best to begin w/blm's being under controll, and all other tweaks when motor is at OT, then work backwords for cold settings.
As I have added various little changes after the initial build, I have had to tweak ve tables, PW decay, IAC cts. in drive, dead band, closed throttle pos.timing, AE, values, etc. etc. etc.
As to the neutral at MPH, this can tweaked in a number of ways. Slope gain, iac follower decay, pulse width decay etc. and would really depend on what you are seeing on the scans at the time of the event.
Before doing any of the aforementioned it is best to begin w/blm's being under controll, and all other tweaks when motor is at OT, then work backwords for cold settings.