Maf showed up, but they sent the wrong one. tried a new MAP, ran Worse. it'll "powerbrake" to 2000 RPM without a miss, but Full throttle under load and it breaks up, won't rev past about 2000.

Try replacing the coil packs.

[This message has been edited by phonedawgz (edited 07-12-2017).]

Put some new copper spark plugs in. They cost way less than any sensor your trying. Miss under load is almost always spark related. Pull your spark plug wires and have a good look for burns or cracks. Check the plugs for carbon tracking down porcelain. Put some dielectric grease in the boots with the new plugs.

You can load it up in drive with foot on brake in the dark somewhere and have someone look around engine for arcing, or mist water around and see if it causes a miss.

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10.007 @ 135.54MPH. <-- Video
Best 60' 1.42
Best mph 138.82
Billet 6262 Precision turbo, PT1001 intercooler, ST1 cam, 140lb springs, comp pushrods, HV3, stock L32 bottom end and heads.

Old M90 XP Cam time -
11.425 @115.60
1.543 60'

LIke I said, " I Can "power brake" it to 2000 rpm with No Missing", that's as high as it will rev "in 1 spot in gear". so looking for sparks "power braking" is not going to do anything. it seems to be that when the throttle is opened quickly, the engine cannot get enough FUEL to keep up with the volume of air rushing in . going down the road, any "foot to the floor" brings nothing but backfires coughs and a big BOG. I get the feeling I could probly drive it 100 miles with no problem as long as I drive it like "Granny", but IF I need to get out of someone's way, I'd be dead ! will taking the car to a "SHOP with a sscanner" , will they be able to pin point the problem ?

OK, I'll Price the Coil packs.

quote Originally posted by Lou6t4gto: OK, I'll Price the Coil packs.

Rockauto has them like 5-7 bucks each

"Try replacing the coil packs." by that, do you mean all 3 coils, OR the coils AND the ign module ?

quote Originally posted by Lou6t4gto: "Try replacing the coil packs." by that, do you mean all 3 coils, OR the coils AND the ign module ?

Unless your getting a "random misfire" code, I'd guess ICM. However the one I bought new lasted less than a year..find a junkyard and salvage one?

Coilpacks themselves are a cheaper guess though.

Have you tried running it with MAF disconnected? I'm no 3.8 specialist but some vehicles will run without MAF connected by just going to default values or using just the MAP. I did not see you mention trying this. Does it backfire through the intake or exhaust?

Have not tried that yet. Backfires from intake, more like "Coughs"

So it's either lean or just a misfire. Try it with maf disconnected.

I'd swap all three coil packs. Not the ICM.

runs about the same with MAF disconnected.

while I'm waiting for the New Coils to arrive from Rock Auto, can anyone tell me IF it is "possible, or NOT" to be the "Listed sensors" below to be" causing" the problem listed in the 1st part of this thread ?

MAP-
MAF-
TPS- is brand new
Fuel pressure "Reg"- no fuel in the line- no vac leak
crank "sensor"-
Cam" sensor"-
ICM-
ICM" Harness"-
spark plug" wires"-
engine" Harness" broken or shorting-
loose wire somewhere-
looking for ANY possibilities to check, running out of places to look. Thanks

Waiting for 3 new COILS.

Phonedawgs, anything on that list it might be ??

When I did my first 3800 install, I had identical symptoms which you describe but I did change to the early LS1 MAF. A change to the right MAF table solved the problem. I would suspect that you have an incompatible MAF or a defective low end Chinese product.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

sounds likely to me, but, why did it run so fantastic for the first 30 or so miles ? MAF went bad from sitting ??

I doubt it can be fully tested. Maybe some basic resistance checks across some of the pins.

Best thing to check is what the computer is seeing for grams/second using a scan tool. Unless you know what the signal wire values should be at various rpm's then tap into the signal wire with a multi-meter.

Scan tools are pretty cheap for a basic OBD2 scanner and it will show most values needed for diagnostics.

Is the ICM the" same" for a 3800SC and a N/A 3800 ??? 3800 N/A are all over the place in the bone yards. (The ECM was programmed for 1998 Grand Prix)-- the MAF, Because of the "hole size" in the throttle body, I think I'm "Limited to" a 1998 MAF. much harder to find

bump

You really need to get a scanner on there and find out if its specific cylinders misfiring, or is it random.

next step, when I get my hands on $120 to have it scanned.

With the engine running check the voltage on the pink wire of the ICM. You will need to backprobe it. It should be battery voltage or close.

can I "Stab" the pink wire with a sharp probe ? the "connection" to the ICM is under the rear window and almost impossible to get to the connection without removing the coils.

If you retained the 8 pin main harness to ICM harness connector you could do it there. If you pierce the wire's insulation you should seal the hole created. Piercing the insulation overall is not recommended.

I'll try that. I think I can still get to that connection. (close to Battery voltage when running) what is it's different ?? thanks

I'm kinda late to the game but did you change the fuse out for your injectors to a larger one? I had an issue similar when I got my swap going and had forgot to do that. Figures it never hurts to check the small stuff.

Yea, I checked all the Fuses, nothing blown. 1 thing I'm going to try, I'm going to drain the fuel tank dry and try new fuel. Last week my lawnmower started running crappy and the fuel I drained looked like something that had been in there for 20 years, but was only a month old. the fresh gas is clear, the fuel drained was amber and cloudy. Maybe the gas turned or something. can't hurt to check.

Did you change it to a bigger fuse though? The stock fuse is 5amp and not big enough. It won't blow, but won't be able to keep up with the increase amperage demand. It should be changed to at least a 10amp fuse.

quote Originally posted by Lou6t4gto: Is the ICM the" same" for a 3800SC and a N/A 3800 ??? 3800 N/A are all over the place in the bone yards. (The ECM was programmed for 1998 Grand Prix)-- the MAF, Because of the "hole size" in the throttle body, I think I'm "Limited to" a 1998 MAF. much harder to find

I have switched the ICMs on my 3800SC and 3800 multiple times with no issues.

when I have the time, I'm going to go to the boneyard and pick up a couple of ICm's. till then, I'll try draining the fuel and refill, still haven't checked the pink wire for voltage. House problems are First in line. LOL

bump

UPDATE, today I tried 3 different MAF sensors, no change. All 3 coils are new and sparking every cylinder ,(not likely the ICM)). I've already tried a different ECM, no chaange. The fuel pressure is 47 PSI and steady at any RPM. The car idles fine, will hold any RPM "standing still". The engine is "ACTING" Exactly Like a "Carbureted engine" with a Non Functioning "Accelerator Pump" ! Either it is not getting extra fuel to keep up when the throttle is opened (most likely), or there is no Advance when the throttle get opened. At ANY rpm, if I open the throttle Quickly, it falls on it's face until I let off. Puleeze, HELP !

is it possible that it's the MAP sensor ??