85gsl2ndtimearound

So i just want to know where to start looking. I have a 85 gsl 12a bone stock. Whyle on my way back from the store it started running rough (almost like it was mkissing) only at crusing speeds not doring acceloration? any thoughts, im thinking its the coils or cloged cats? I dont know please help or tell me here to start or what to eleminate first. Also it doesn't idle or idles real rough.
thanks in advance Peter A. Trapino

darkfrost

iTrader: (1)

Have a look at the timing, and make sure your coils and ignitors are all okay.

Kentetsu

Could be a clogged circuit in the carb....

You could try this; get her down to 1/8th of a tank, then dump in a full can of SeaFoam. Don't add any gas to it afterwards, just drive it like you stole it for a couple dozen miles. Then, park it overnight.

This might be enough to clear out your carb, and will certainly do wonders for your apex seals. I got huge HP gains when I did this, but I'm sure results will vary.....

64mgb

iTrader: (1)

I have the same problem with my '79. It stumbles (like a miss) when maintaing speed...it's ok when accelerating (or maybe the symptoms are just hidden). You can also here it "missing" wen the choke is on. I rebuilt the carb and that took care of the idling problems, but it still stumbles when cruising. Haven't been able to figure it out.

Rich

ray green

iTrader: (14)

Did you all check your fuel filters?

85gsl2ndtimearound

Did not check the fule filter but it pulls very nice should and will check anyways. just took it around the block and like i said it pulls nice all the way to 7k just hesatates and shutters at crusing speed and below 1800 rpm. cleaned wires there new anyways. going to change pulgs well see what that does. how do you test a coil ?

ray green

iTrader: (14)

That's exactly the problem I was having, there's a long post on it in here someplace. The filters didn't look that bad, you could suck gas through them easily and the car had plenty of ***** on the low end accelerating through the gears up to highway speed. The problem would always start after a few miles on the highway, when you ask for a little more power, like passing or going up a hill. Besides, what have you got to loose? If you haven't replaced the filter lately, you probably should anyway, and it just might fix the problem. And if the hesitation at high speed comes back after awhile, replace the filter again. I went through five filters in about 4 months before it finally seems to have worked itself out, about $20 and some time invested (you get real good at swapping out the filters, takes just a couple minutes).

Ray

Yark79

I think your just not supposed to cruise at less than 2000 rpm's. I would stick with cruising at about 4000 in fifth gear, that's a good cruising speed.

85gsl2ndtimearound

Sorry let me clarify Car hesatates when im at crusing speed ie when im trying to maintain speed. There is very little loss of power while excellorating but hesatation when trying to maintain speed. I just drove it 35miles to my warehouse and it did fine in fifth at 4000 but if i let it get near 2500 than it starts to miss also im niticing a lot of backfiring in the cats? Just changed the trailing coil and no change. I dont think its the fule filter cuz like i said i can pull all the way to 80mph if i want. someone please help also i took out two plugs and they did not look fouled?

85gsl2ndtimearound

plugs changed w/no help COULD IT BE A CLOGED CAT????????

Keith13b

iTrader: (6)

Check the floats and air bleeds in the carb and make sure they are in spec.

85gsl2ndtimearound

someone please help should i use the seafoam could it be the cats?

SSRx7

Check the mechanical linkage for the 4 bbls on the back side of the carb. It is designed to release if the car backfires, keeping the secondaries closed to help prevent further damage caused by the backfire.

If you are standing beside your car, looking down at the carb there is what looks like a linkage that has 2 flat arms that are pointed towards the drivers side of the car . Looking down just past that you should see the end of a cable with a little "t" end on it. That "T" hooks over the end of the linkage, and operates the 4 bbls. It pops off and then it start running like crap.

Also, just because the fuel filter "looks" clean, doesn't mean it is. I was having problems that I blamed on everthing except the filter, because the car would accelerate great. It was at cruising speed, especially just after going through a curve in the road, that it would start missing and backfiring like crazy- sometimes to the point where I would have to pull over and stop, at which point, the engine would die. It would then start back up, and I would be fine again for anywhere from a couple of miles to a couple of weeks, then it would start allover again.

What I figured out is this: The filter is before the pump on these cars. if there is trash in the filter, especially trash that floats easily, the vacuum provided by the electric pump pulls the trash against the filter element, thereby either partially or fully blocking it off, at which point the engine is starving for fuel. when you rock the car side to side or shut it off or let off the gas, the debris shift on the element, allowing partial to full flow for a bit.
WHat happens during acceleration I figure is this, the weight of the fuel forces the debris towards the side of the filter bowl that is towards the back of the car, allowing flow at the front side of the filter. Then, when under normal cruising speed, the debris settlles again around the element.


Or I could be totally wrong and way off track, but when I went to Advance/Discount autoparts and bought a new filter (Purolator) for about $3.75 or so and put it on, THe car has run flawlessly from idle to redline in all gears, and cruising at any speed.


Or you could just pull that 12A out and throw in a 350 like I am doing.

later,
Bill

SSRx7

64 MGB: Nice car. a good friend at church is doing a ground up resto on a 61 MGA. He thought at first it might be a 58 or 59, but little odds and ends keep pointing to a 61. He is hammering all the dents out and smoothing all the pnls by hand. I think this is his 3rd or 4th one.

Sorry guys, back to the subject.....

Later,
Bill

Kentetsu

Okay, its not your cats and its not your fuel filter or fuel pump.... Due to the fact that it pulls hard at full throttle, you can eliminate those along with the secondary linkage that was suggested above.

Check your timing if you haven't already, then use the seafoam. Wait for Sterling or Carl to come along, and they will probably tell you exactly what's going on with it. I'm pretty sure it is carb related though, assuming that your timing is correct.

Good luck...

Kentetsu

Just saw additional information in your other thread. I believe that you are dealing with a vacuum leak....

SSRx7

Not to say your are wrong, but I beleive he should check those items first before tearing into the carb or ignition system.

1 They are very easy to check and very inexpensive and cant do more damage by misadjusting something
2 The almost same symptoms happened to me. mine would run great under full acceleration- until a big backfire disconnected the linkage I mentioned. I changed the filter and hooked the linkage back up and presto.

Now if it isn't those things, pull the top of the aircleaner off and with the engine running, put your finger over the hole that supplies air to the shutter valve. see if it smooths out. (I believe that is the one) It is the large vacume line coming up on the driversside rear of the carb. The diaphrams on these actuators are known to go bad and it will be like a wide open vacuum leak to the intake. If it is sucking hard and the engine smoothes out , then you need to replace the vacuum actuator. Also, make sure that the vacuum lines that supply vacuum to this actuator are in good shape. (Small vacuum hose that comes from a T in a line from a vaccuum port at the carb base.

Later,
Bill