IMSAaspirations

Hello all,

A problem with my daily driver, an 83 GSL, has popped up. The car was running very well and accelerating very well all the way up to the 7000 RPM redline, but lately its started hesitating when I put my foot down, then after a moment or 2 it seems to finally start pickup up as expected. When it comes time to shift, however, the engine continues to rev up after the clutch pedal is depressed and the gas has been let off entirely, so much so that I've ended up with the engine revving up to 7300RPM on an occasion or two! I have no idea what could have caused this to start happening out of the blue. Even stranger is it only happens some of the time. Other times it revs up and down exactly as expected!

The only issues with the carb I was aware of before this new issue started occurring were a small vacuum leak somewhere causing a slightly rough idle, a broken shutter valve that has been plugged (steel stick epoxy over the hole in the air cleaner) and a slight bog when pulling away from a stop, and those issues remain unchanged.

Does anyone have any idea what's causing the hesitation and continued-acceleration issues? My assumption is that the vacuum leak could be worsening and causing further problems with the air:fuel ratio, but if one of y'all knows better I'd love to be taken to school over this! I have another crarbb off of an 83 automatic that I'm going to clean and get ready to swap out if need be, but I hope someone here can perhaps help me get the one on the car sorted!

mazdaverx713b

iTrader: (91)

It sounds like something is binding and holding the throttle open. First, ensure your floor mat is not touching the gas pedal and holding it open. I've seen this on more than one occasion on customer cars.

Inspect the throttle linkage and accelerator cable to make sure the cable is not bound or that the linkage is not sticking. You'll want to work the linkage by hand with the engine off to ensure that the linkage returns to a resting position.

A super long shot, but look in the top of the carburetor to make sure nothing has fallen down and is holding the throttle plates open. I've seen chewing gum in a carb once and it would roll around and it lodged the throttle plate open.

diabolical1

iTrader: (3)

just to add to the above post, another thing to look for is make sure the return spring is not disconnected, broken or otherwise non-functional.

LongDuck

Is the car equipped with Cruise Control? If yes, there's a Main Switch near the key position that can be turned off to disable the system. In some cases, a vacuum leak in the diaphragm valve will cause the actuator to pull the accelerator cable thinking the car is decelerating and tries to compensate. Operating the clutch should disable the action of Cruise Control, but a failing system will behave erratically.

This is admittedly a long shot, but the other guys have the most likely causes covered.

peejay

I don't know where it is on Series 2s, but on Series 3s the cruise computer is under the driver's side bin. I had a car with light rust perforation get enough water in there that one day I was sitting at a light and the engine went for 7000rpm because the cruise unit finally got enough internal corrosion to wig out. And I had the cruise enabled all the time. Ooops.

IMSAaspirations

Alright gents, a problem had been found that may or may not have been the cause: the carburetor had a MASSIVE fuel leak coming from what looked like the rear float bowl! I'd swapped complete intake manifolds/carbs when I first got the car and at the time that carb was functioning properly it seemed. I'm not sure when or how this leak started but I was only able to find it with some help. I had my girlfriend on the driver seat actuating the gas pedal while l watched the cable for binds or twists when I saw the leak. Thankfully I had an extra carb sitting around my garage so I spent the entire afternoon replacing the carb, and while I was at it all the vacuum lines and fittings. The car seems to be running much better now and the problem that I had started this thread about seems to have disappeared.

To those who posed the questions about the cruise control, I now have some questions. Yes the car is equipped with cruise control, though it doesn't seem to work. On my 83 I believe that the cruise control power switch is located on my centre console by the power window switches, though I could be mistaken. Located close to the clutch master cylinder, on the inner fender is a box with a cable that runs to the carb. Is this the cruise control actuator of which you guys are referring? My car currently has the spade connector that connects to this box disconnected because every time I start the car with everything hooked up the carb makes a gnarly howling/squeaking sound.

IMSAaspirations

I won't start a troubleshooting-my-cruise-control thread here but since you guys mentioned potential problems with it I may as well check them out just in case! I definitely don't want a run-away acceleration event like peejay had!

KansasCityREPU

iTrader: (9)

The cruse actuator is a round can like vacuum with cable on the passenger side tower. The actuator on the drivers side tower is the hot start assist.

Orbitstrider

Mine has been having a similar issue but with the secondary plates not wanting to open consistently, but when they would they would remain open until the vacuum actuator decided to stop actuating. Just got a second carb with mechanical secondaries so hopefully that solves my issue.

jp.gilroy

Had this happen about 37 years ago turned out to be a carb issue. buddy redid it and never had a problem again

IMSAaspirations

Hello all! Sorry to resurrect this old thread but I wanted to let y'all know that after I changed out the carb for a rebuilt one the problems ceased. The car has been running very reliably ever since. It was definitely a carb issue it seems. I just wanted to post the resolution incase someone else runs into a similar problem.