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ECMlink Stuttering/hesitation-ahhh!

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Vegas Smith

20+ Year Contributor
5,190
3,106
Dec 2, 2002
Houston, Texas
1). Any boost, vac, or exhaust leaks?
No
Boost leak tested 5psi above your max boost with no leaks?
Yes

2). Verified mechanical timing?
Yes

3). Verified base timing?
Yes

4). Ignition system
COP or Stock Coil: Stock
Wire brand and Age: NGK
Spark Plug brand, type and Gap: NGK-BR7ES/.028



5). Motor health (Compression Test)
Cylinder 1: 160
Cylinder 2: 160
Cylinder 3: 160
Cylinder 4: 160

6). Performed basic throttle body adjustments?
Idle Switch: Yes
Throttle Cable: Yes
TPS: Yes
BISS: Yes

7). Compression ratio
8.5:1

8). Any known bad sensors or brittle wiring?
No

9). Any DTC/CEL codes?
No

10). Electrical system
Car off (not running): 12.4 volts
Car running: 13.9 volts

11). Base fuel pressure and injector values
Base Fuel Pressure: 43.5
Injector Size (cc/min): FIC hiz-1650

12). Properly calibrated and configured wideband sensor
Sensor Brand: LC2
Calibration Date: 11/30/2018

13). Type of fuel
Type: 93 Octane
Percent of Ethanol: 8%

14). Watched ECMlink how-to videos?
Yes

Hello all, A couple months ago I completely rebuilt my car and ever since then I've had this severe stuttering/hesitation. As you can see from the logs the car sputters and you see a jagged TPS, wideband and MAP. I have no idea why this is. Kevin Jewer thinks it has something to do with the TPS but I can't find anything wrong with any of the wiring. I've tried all new sensors and jiggling of wires near tps and ecu with no difference. The TPS is not improperly grounded either. No idea what this could be. I've looked for shorts everywhere and have checked and re-checked mechanical timing and other sensors as well. Thanks
 

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  • log.2018.12.04-01.elg
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It hesitates at all loads. I cant even go WOT on the car with this issue. I've tried different PTUs, CAS, TPS, Coil, plugs, wires, o2 sensor, wideband sensor (happen to have all this stuff laying around). Injectors have been cleaned. Fuel pressure is good. Ecu was in for repairs last year and I can't find any obvious damage on the board. New gasoline.
 
What are you using specifically to show crank and / or cam signal to PCM?
Rebuild, hesitation at all loads, circuits checking out. I’d question the validity of the timing of the electrical signal to the pcm.
I haven’t gotten TOO in depth with these cars yet. But look and see if your electronic values for your timing are lining up with the actual timing.
Example, if there’s a way to identify crank signal is sensing 10* BTDC #1 cylinder at rest —> verify that cylinder is where the sensor says it is. Same with cam.
If I ever get to a computer I’d like to look at the log.
Will be keeping tabs on this...

Edit: Give an example, I’ve seen first hand on a Ford where the trigger wheel for crank sensor on harmonic balancer (which is pressed on btw) somehow f***ing moved, placing everything out of time electrically. Fricken wild... The Ford was so out of time it wouldn’t start, but if yours is only little out, maybe? It could cause that?
What are fuel trims doing?
 
Did u rececently replace cams or did any timing work? My car had a stumble/lack of power after I swapped cams back to stock. Turns out one of the rockers was not seating right on cylinder 1 causing this.

New gsc s2 cams (gets yelled at by bastarddsm for too big a cam ), new CB 2g head, new fidanza cam gears. I'll check rockers again but I'm pretty sure they're good.

Try another ecu.
Yes sir, will do.
What are you using specifically to show crank and / or cam signal to PCM?
Rebuild, hesitation at all loads, circuits checking out. I’d question the validity of the timing of the electrical signal to the pcm.
I haven’t gotten TOO in depth with these cars yet. But look and see if your electronic values for your timing are lining up with the actual timing.
Example, if there’s a way to identify crank signal is sensing 10* BTDC #1 cylinder at rest —> verify that cylinder is where the sensor says it is. Same with cam.
If I ever get to a computer I’d like to look at the log.
Will be keeping tabs on this...

Edit: Give an example, I’ve seen first hand on a Ford where the trigger wheel for crank sensor on harmonic balancer (which is pressed on btw) somehow f***ing moved, placing everything out of time electrically. Fricken wild... The Ford was so out of time it wouldn’t start, but if yours is only little out, maybe? It could cause that?
What are fuel trims doing?

Fuel trims are OK. A little too inconsistent. I'll check on the timing verification.
 
Your likely backfiring through the intake which is bouncing your throttle plate, causing your tps signal to spike all over the place and your map signal to spike all over the place and your fueling issue is causing your wideband to also be all over the place. Sounds like you have a fueling issue, too much or too little or ignition timing is out, also are you sure that your cas is not installed 180 degrees out?
 
The ecu normally never uses tps for load.
It uses airflow/rpm
On MAF, I think he’s Speed Density.

I need to get to a computer so I can view your logs. Lol. Suspense is killing me.
I’ve seen on IDS on Fords w/ EGR the pulses will def foul sh*t up. Supporting what motomatt said.
if that helps at all...
 
Gotchya. Def got more reading to do.
Clearly misinterpreted some info I think. What I’ve deduced is while the throttle plate may dictate load (airflow), the throttle position signal does not. That sound about right?
Thank you. :)
 
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Did you get a check engine light? Is your ecu a factory eeprom, or a converted one?

I didn't even bother driving the car because it was falling on it's face just revving it with my hand, therefore, I'm not sure if it pulled a code. I'm also uncertain about the ecu as I don't know a whole lot of about our ecus. Haha, I probably knew this answer 15 years ago, though. I can look into all this tonight after work. Thanks.

Your likely backfiring through the intake which is bouncing your throttle plate, causing your tps signal to spike all over the place and your map signal to spike all over the place and your fueling issue is causing your wideband to also be all over the place. Sounds like you have a fueling issue, too much or too little or ignition timing is out, also are you sure that your cas is not installed 180 degrees out?

I've always felt like this is the case. I think the tps/map/wideband are symptoms of some other problem. I'm pretty sure the cas isn't 180 out because you can really tell when it is. The car has a bigger lope with the S2s than the bc272s that they replaced but I wouldn't call it abnormal. I don't think the timing and ve tables are far out balance so I don't suspect a tuning issue either. I've even tried disconnecting my arc-2 and that doesn't help either.
 
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Standardized durations of:
BC0101 —> 208/212 @ 0.050”
BC0104 —> 220/220 @ 0.050”
GSC S2’s —> 230/230 @ 0.0394”

So uhh, I’d have to look at the entire spec of the cams to determine LSA’s / overlap, but looking strictly at those durations —> if you tuned on BC0104 and jumped to GSC S2’s, that’s a pretty sizeable difference for airflow/VE (estimating maybe 226-228 @ 0.050” for the S2’s).
If you jumped from the BC0101’s, good god!
 
Standardized durations of:
BC0101 —> 208/212 @ 0.050”
BC0104 —> 220/220 @ 0.050”
GSC S2’s —> 230/230 @ 0.0394”

So uhh, I’d have to look at the entire spec of the cams to determine LSA’s / overlap, but looking strictly at those durations —> if you tuned on BC0104 and jumped to GSC S2’s, that’s a pretty sizeable difference for airflow/VE (estimating maybe 226-228 @ 0.050” for the S2’s).
If you jumped from the BC0101’s, good god!
I'm not making the argument that the car will run great on an old tune but I also don't buy the car would be almost undriveable just because of the new parts. I'd expect the car to be choppy but not backfiring/stuttering so badly.
 
I'm not making the argument that the car will run great on an old tune but I also don't buy the car would be almost undriveable just because of the new parts. I'd expect the car to be choppy but not backfiring/stuttering so badly.

It's tough to say on this. Everything affects everything, and weird shit happens. I cannot imagine a backfiring issue modulating the throttle plate and showing up on the datalog - but anything is possible. Generally I'd believe that a cam swap shouldn't make it underiveable, it might run poorly, but it shouldn't be that hard to fix up the VE map. I don't think it's that much of a cam swap here.

Does this car have a crank trigger? Are the plug wires on right? I've seen that happen, plug wire switched. It'll start and run sometimes, but not well.

Gotchya. Def got more reading to do.
Clearly misinterpreted some info I think. What I’ve deduced is while the throttle plate may dictate load (airflow), the throttle position signal does not. That sound about right?
Thank you. :)

We are getting OT here, but throttle angle is not a good indicator of engine load on a turbo car, so it is never used. You can have wildly varying manifold pressure at a constant throttle angle.
 
Does this car have a crank trigger? Are the plug wires on right? I've seen that happen, plug wire switched. It'll start and run sometimes, but not well.
It does not have a crank trigger. I've tried new plugs, a COP setup and a new CAS. Nothing has helped at all. Wires are on right and that's further evidenced by the problem also occurring with the COP setup. Tried a different PTU as well.

Also, I've tried different ve maps and have tried to tune the ve map myself as well as use the Sd Adjust tool. None of that has helped this problem at all.
 
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Are the plug wires on right? I've seen that happen, plug wire switched. It'll start and run sometimes, but not well.

+1 on checking this. My last engine build my friend hooked up the spark plug wires as if it were his Evo. So he was counting cylinder 1 as cylinder 4. The CAS was also 180 out if I remember correctly. Either way the car started and sounded like a normal cam idle. The motor would rev up decently well but didn't sound right. When I tried to set the timing with a light and could not get it right that gave away that something was wrong.
 
+1 on checking this. My last engine build my friend hooked up the spark plug wires as if it were his Evo. So he was counting cylinder 1 as cylinder 4. The CAS was also 180 out if I remember correctly. Either way the car started and sounded like a normal cam idle. The motor would rev up decently well but didn't sound right. When I tried to set the timing with a light and could not get it right that gave away that something was wrong.
My timing light worked fine when I set the timing. It's unlikely that the wires are the cause as I threw on my COP setup. Also, I'll double check the CAS.
 
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