Hey all,

Posting this will expose how naïve I am, but I installed some new spark plugs on my 1982 Trans Am (4BBL V8). But when I took it for a test drive I immediately noticed the idle was down to about 400 - 500 rpm, when previously it was around 600 to 700 rpm. It actually stalled once. However, once the engine is warm it seems to idle around 750rpm no problem.

Here are the plugs I installed: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

I chose this set for no other reason than it came in an 8-pack and was suggested by the Amazon compatibility filter. Now I realize that was probably a mistake and the cold-start engine idle is crappy. I feel like I could adjust the electronic choke to stay on longer, but please confirm if that's not just treating a symptom of the problem instead of the root cause (wrong spark plugs).

After digging up my owner's manual, I read that the official manufacturer's spark plug for my Trans Am is R45TS. Is this correct? If indeed I installed incompatible plugs then I'll replace them with these R45TS ones.

EDIT: Yes, I verified the correct gap of 0.035" (35 mills). And I was careful to make sure the ignition wire boots were properly seated.

Thanks in advance

PS - I changed the plugs because the car is new to me and the previous owner has no idea when they were last replaced. The car has 241k miles on it. So I just decided to proactively replace them as part of my tune up.

 

Did you confirm the electrode gap is correct?

 

I did, yes. I set them to 35 mills (0.035").

 

I would always go with good ol' ac delco plugs with these cars.

is it possible you put one of the plug wires on the wrong plug and messed up the firing order?

 

ACCEL plugs aren't known for being great to start with. The heat range is another big question. The heat range of the AC Delco plugs is the number 45. R means resistor plug. TS is tapered seat. Definitely swap in the AC Delco plugs. Once you have the correct plugs in, if you still have an issue, we can work from there. Are your wires in good shape, as in replaced in the last few years and no damage or corrosion?

Be sure you have the firing order right and make sure you didn't disconnect or break any of the vacuum lines. Recheck your work.

 

Good suggestion, but not possible. I only did 1 plug at a time.

I drove it again this morning and the issue is gone. I think the recent cold snap may have been the real issue. If nothing else I'll just tweak the electronic choke a bit to compensate if the cold-start idle is too low again.

 

Thanks for your reply! I was very careful to check the condition of the wires, ensure they were fully seated, and in the correct order.

What you said about the heat range and 'R'-type plug is what interests me. These are variables I didn't know to consider. Looks like I'll be doing some research.

I'll drive it a couple more days until the weekend and if the issue persists now that the cold-snap has passed I'll go ahead and replace with the R45TS plugs as you suggested.

 

Just noticed that this is a carb engine. I assume the choke works. Otherwise it will have a very tough time starting and running when cold. On a carb with an automatic choke, you need to press the pedal fully to the floor before you start it cold. That allows the choke to close and the fast idle cam to move into position. When the engine first starts, it should climb right up to about 1,800 rpm. Then you want to snap the throttle right away to bring the fast idle cam down to the second step. This should bring the idle down to about 1,200 or so. From there it will warm up and the idle will come down to normal.

If it doesn't work this way when you do as instructed, there is a problem with the carburetor.

EDIT: I mean to say press the pedal to the floor and release it before you start the engine cold. Not hold it to the floor. I want to be sure I stated this correctly.

 

Make sure you didn't dislodge or break a vacuum line in the process of working under the hood.