Possible Mas problem?

[tsd123]

I am having a mis fire problem on my 91 Talon. I swapped the motor out of my 1990 a few weeks ago, and I've has this problem ever since. The only things I didn't use from my 1990 were coil pack, transistor, and the CAS. Today I changed the coil pack, and bought a used transistor. I also put new plugs in. It will randomly bog down at what ever rpm I hold it at, and I'm lucky if it stays idling. I usually have to hold my foot slightly on the gas when I'm stopped (Auto). It usually drops 200-400rpm and quickly goes back to where it was. It is also keeping me from break boosting my car. I can try break boosting after I let it warm up and it will spool right up. Drive it down the road and it doesn't even try to build boost. It runs fine at WOT most of the time, but sometimes it will spit and sputter. The longer I drive the worse it usually gets. When I was swapping pins on my ecu for the 1990 to 1991 car. I accidentally swapped pins 6 and 23 instead of 6 and 14. Would the 5v that's supposed to power the mas mess up the resistor part of the mas on pin 6? Also would the mas cause this kind of problem? I have boost leak tested it and fixed leaks.

 

[92AWDHX40]

First a bad sensor should throw a cel code do you have any>

 

[tsd123]

No the only time I had a code was when I accidentally swapped those pins. After I fixed them it went away.

 

[92AWDHX40]

Well if your asking if the mas is bad, no codes so you could probably rule that out. Kinda hard to say could be wiring, plugs, spark wires, coil, narrow it down a bit to exactly whats going on because so far you think its a mas issue. Maybe the wiring something you did incorrect, could be a bad ecu pull it out and inspect it, recheck all the wiring at the ecu pins, even with my boost leaks my car didn't do what yours did. Ive swapped plenty of engines and have done plenty of wiring, ill do all I can to try to help you figure it out. Any more info..

 

[tsd123]

The ecu had the caps replaced a few years ago. I wasn't having any problems when it was in my 1990. It has ran great for years. It took me 2 weeks to finish the swap, because I was waiting on parts to upgrade my auto trans. So the mas will always throw a code when something is wrong with it? I feel like it is something small.

 

[92AWDHX40]

From using link and loggers over the years when ever mine was bad I got a code, along with everything else I would rule out the mas as the problem the car would run like crap from my experience with my dsm less than I mile I had issues when my gm maf sensor was bad usually I had a bad ground when using the ecmlink cable, I would look for something else. Doesn't hurt to check the ecu caps anyway its easy enough. Also I would do another blt, try another coil pack, and change the plug wires, ,check compression just in case, check fuel injectors, fuel filter.

 

[navyissuedsm]

Thats a strange issue with out any codes. I know someone who forgot he has shoves a rag into his exhaust, and then bolted it right up like that. he had a similar issue, but that was really a freak thing.

 

[tsd123]

I'm going to check everything I can tomorrow evening after I get off work. It seems like it might be getting worse.

 

[buddahboost]

The throttle body should of also been swapped.

Have you tried to adjust your BISS screw on top of the throttle body?

Do you have link or a logger to see where the ISC motor is at?

If you unplug the MAF..it should run shittier..if it doesn't then problem lies else where

Was there a AFC before? Make sure no wires at the ECU are not cut and if they are, solder them together

 

[BlackKnight2013]

the mas/maf doesn't need to throw a code when its bad all the time. i have seen mas/maf go bad without a code and causes hesitations and misfires due to an improper input reading of air flow into the ecu which in turn give the wrong output of fuel and timing advance. a good rule of thumb when testing a maf/mas sensor is to take the vehicle and run it up to the first shift point under load, i.e. getting onto a highway with the pedal all the way to the floor, and taking a maf/mas reading in g/s from a data logger and or scan tool; then take your liter size and multiply it by 40. so for example, a 2.0L engine multiplied by 40 is 80, and 80 would be g/s, and you should be within about 10 to 15 percent -/+ of 80. this will tell you if your maf/mas is reading correctly. though i would also check your timing to be sure its also correct. another test is to tap on the maf/mas with a screw driver handle and see if it hesitates or dies.

 

[tsd123]

Thanks guys. I'm going to try a different mas if I get home before dark. My throttle body has 6 month old seals and biss screw/o ring. No idle control just a block off plate. Been running it that way for a long time.

Okay it wasn't the mas.

I did a fuel pump rewire with an stm kit when I was swapping engines. I noticed my 255 fuel pump sounds louder in this car. I have the same fuel filter off my other car which was pretty new.

 

[BlackKnight2013]

Thanks guys. I'm going to try a different mas if I get home before dark. My throttle body has 6 month old seals and biss screw/o ring. No idle control just a block off plate. Been running it that way for a long time.

Okay it wasn't the mas.

I did a fuel pump rewire with an stm kit when I was swapping engines. I noticed my 255 fuel pump sounds louder in this car. I have the same fuel filter off my other car which was pretty new.

good to hear you found the problem

 

[tsd123]

No I didn't find the problem. I was just stating that my FP was louder in this car or seems like it. Today I soldered every wire I had wired together from the ecu to the fuel pump rewire. I tried my best to set my timing by timing light. It doesn't matter what the timing is it still does it. I have a video. You have to turn it up quite a bit to make out the miss. I'll also put the log in.

Talon problem - YouTube

Just noticed my o2 isn't cycling anymore. I have logs from 11/15 where it is cycling fine.

 

[92AWDHX40]

Glad you found out was wrong.

 

[tsd123]

My misfire is getting worse it is also making my car spark knock at little boost. It's going lean. I have a log showing the knock. I haven't had this much knock in a long time. The fuel pump is holding the 43.5 I set it at when I activate it through link. What would cause this?

 

[tsd123]

I guess I'll change the fuel filter and try that. Then a compression test.

I can't get it to lean out so it looks like it could be fuel related. I took my sliders all the way up. At first it showed 11.5 on a/f, but on the pull I did today it was high 12 to 13 a/f. I just let off when I see it spark knock. I guess it could be the fuel pump, filter or something. I don't see the fuel pump rewire causing it.

I meant I can't get it to richen up.

Okay I did a compression test today, and it looks like I have all low numbers.
#1 124
#2 114
#3 120
#4 129

I drove it earlier, and the misfire is still there, but I can break boost the car now. I am getting knock no matter what my a/f ratio or timing is. It is staying in the 11's and the timings highest point is 18 when in power. I don't understand why I would be getting knock? Here is a log

 

[tsd123]

It ended up being a clogged FP screen.

 

[smoked28]

Mine did that and it was the upstream 02 sensor. However, of course, mine did throw a code.