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ECMlink Random lean condition, delayed throttle response, no luck

BrandonGST

Proven Member
53
8
Aug 24, 2016
Columbia, Missouri
So I will elaborate on the title a little. I was on a trip home from a car meet, highway cruising had no issues for 80 miles. All of a sudden I noticed the car bucking every so often, then out of nowhere started losing power, afr very lean around 17-20. Came to a stop and the car died. Tried to start it and when hitting the throttle, there's a second to two second delay before the car actually revs and shortly after starting it dies out even full throttle. Towed the car home an began diagnosis.
Quick rundown of the car:
Wiesco 8.5:1 pistons
Eagle rods
Eagle crank
manly valves
GSC everything else valvetrain
GSC S3 cams
Walbro 450
ID1000's
Speed density
DSMLink v3
Aeromotive FPR
The list continues but for sake of time reading I'll leave it at some of the most important items. Now things I've done to try and solve the issue. First I checked for spark, pulled the wires and plugs all plugs had spark. Flashlight in the cylinders #2 was dry the other 3 cylinders were wet. All plugs are looking the same nothing odd. So I assumed a clogged injector, removed the injectors cleaned all of them with my little setup and they all sprayed fantastic. Ohmed them out as well and got 12.3 on the 20 setting on my volt meter for ohms on all 4 injectors. Reinstalled the injectors, same problem car would start up and about 5 seconds later it would start lagging on throttle input, running lean and dying. Double checked fuel pressure and its right where it needs to be(I have fuel pressure set to be logged in the logs below). disconnected the feed line to make sure there's fuel at the rail and there is tons. I then checked compression, 152 across the board(100 miles on fresh motor), boost leak tested for the 100th time and found no leaks, checked the intercooler, every inch on piping, TB, biss, ISC, Turbo, Exhaust, everything and no leaks anywhere. I have had issues with my transistor plug coming loose so I checked that and no go. I also bought a second power transistor to test and make sure that wasn't the issue, same issue. Noticed my brake fluid cap was leaking onto my coil packs a little, I decided that the car is on the original coil packs, lets replace that. Ordered a brand new Mitsu coil pack off Extremepsi and got that in, no change. Changed spark plugs out for new ones just because, replaced the fuel filter, checked all wiring, checked mechanical timing, still in time. I decided this could be an ecu issue, so I sent the ecu to ECMTuning. I got a response to day and they said they don't see anything wrong with the ecu itself. They were thinking something in the settings not being compatible could be the cause, but on further inspection they said that the tune settings that myt car was running on when the problem occurred agree with the chip and should cause no problems. I'm kind of at a loss as to what this could be. I'm hoping someone else has experienced a similar issue and might be able to give me a little insight to what this could be. I will attach 2 logs. Log 2021.04.24-03 is the night the car started acting weird on the highway and quit running randomly, I started it and logged this while waiting for a tow. Log 2021.04.23-02 is from the day before logging for my tuner to dial in the car, no changes were made to the tune from the day before and I drove the car about 80 miles that day before this randomly happened. Any help is appreciated and if any more info is needed please just let me know!
 

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  • log.2021.04.24-03.elg
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BrandonGST

Proven Member
53
8
Aug 24, 2016
Columbia, Missouri
Hmm I hadn't thought of the map sensor, I just switched to speed density within the last year, I did check the connections to every sensor just to make sure nothing came loose. Is there a way to test the map besides replacing it that you know of?
 

Vegas Smith

Proven Member
4,625
2,404
Dec 2, 2002
Houston, Texas
I don't see any issues with the map sensor (only looked at 2nd log). I do see a ridiculously high idle around 1400 that needs to be fixed. I'm also suspecting an alternator issue because the car goes lean and the alt voltage drops to 12.4ish. Not sure if that's the cause or effect of the issue. Our cars don't like to be run at 12.4v. I 'm not seeing anything else causing the lean condition.

edit: the more I look at the log the more I think it's an alternator charging issue that causing the front o2 to read poorly/malfunction.
 
Last edited:

BrandonGST

Proven Member
53
8
Aug 24, 2016
Columbia, Missouri
That’s really odd, I just replaced it due to having an issue before with voltage and was registering 14v+ while driving before. I also tested the alternator at the connections and got 14.9 up front and 14.7 at the battery(in the trunk) I was figuring voltage dropped because of the car not wanting to run and being low rpm. But I will look into the alternator again as well when I get the ecu back. When the problem first occurred voltage was steady on the highway in the high 13-low 14 range
 

BrandonGST

Proven Member
53
8
Aug 24, 2016
Columbia, Missouri
I don't see any issues with the map sensor (only looked at 2nd log). I do see a ridiculously high idle around 1400 that needs to be fixed. I'm also suspecting an alternator issue because the car goes lean and the alt voltage drops to 12.4ish. Not sure if that's the cause or effect of the issue. Our cars don't like to be run at 12.4v. I 'm not seeing anything else causing the lean condition.

edit: the more I look at the log the more I think it's an alternator charging issue that causing the front o2 to read poorly/malfunction.
Also on the idle issue it’s been a pain trying to get it to idle right. So with that, I have done everything, grounded in link to set base timing. Grounded in link to set base idle on the biss, replaced the isc, found a leak near the isc, fixed that. So when the car was running it would idle perfect, after a decent drive and a hard pull is when the idle would stick to 1400. If you let the car idle for about 10 minutes it goes back down to normal
 
Last edited:

BrandonGST

Proven Member
53
8
Aug 24, 2016
Columbia, Missouri
Waiting on the ecu to show back up, alternator on order to see if that fixes the issue. It is an oreilleys alternator thats on the car so it wouldn't surprise me if the regulator or something is going. I will update here as soon as I know if that's the issue. Thanks for the input guys!
 

Sniffbooger

Proven Member
228
75
Apr 12, 2020
Torrance, California
Wow looks really tricky diagnosing..I think that is why my DSM link is still sitting unused in my closet... I know nothing about tuning so I've been running my black box ECU since I got the car last year and it's been really dependable for commuting to work every day....there are a lot of different sensors on these engines...one day after revving third going onto the freeway my car just died...so I quickly pulled over to see what happened...checked under the hood carefully, and it turned out one of the clips was broken on my sensor and it popped loose from the high rev (the large clip right behind the fuel rail on top of the #3 intake runner)...I almost didn't see it at first cuz it was still sitting in the right place but not fastened securely....and that's why I always carry some zip ties in my tool bag LOL...got it secured and the car started right up! Sometimes we are looking for the complicated things, but don't overlook the simple things in the process...be sure to check all the sensor connectors and grounds, and maybe it is something simple! That would be worth having a cold beer! Cheers! And may the problem be found quickly!
 

BrandonGST

Proven Member
53
8
Aug 24, 2016
Columbia, Missouri
Update on this, replaced the alternator with a 90A Galant and no luck. Same issue. So I tried a couple other things the one yielding some sort of result being the map sensor. Its an omnipower 4 bar from the speed density kit. I unplugged the power from it and the car wouldn't start at all. Then plugged power back into it and removed the vacuum line from it, car started right up and idled on its own, normal throttle response. But after a few seconds the car runs funny of course because the vacuum leak/vac not right with the map. So my current guess is the map sensor is not reading right causing the issue. New map will be in tomorrow, fingers crossed that's the fix.
 

BrandonGST

Proven Member
53
8
Aug 24, 2016
Columbia, Missouri
It's about a year old, I actually considered that first because I previously had an issue with the harness pulling out of that connector. That has since been repaired, I double checked that its still solid wiring wise and the temp still rises as I mess with the car trying to start it
 

BrandonGST

Proven Member
53
8
Aug 24, 2016
Columbia, Missouri
So Update, It was indeed the map sensor. New one put in and the car runs like a champ. I'm wondering if this had anything to do with a random knock issue that was progressively getting worse. No matter how much fuel was added up top, or how much timing was pulled there were a couple counts of knock. Never consistent, very spastic. Guess we will see once I resume tuning over the next week or so. Thanks for all that contributed!
 
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