Spark plug and carburetor questions

nottheactress · Post by **nottheactress** » Sat Feb 16, 2008 3:04 pm

So, my car is getting very poor gas mileage--20.8 MPG on my first tank--and from talking about this with the old boys at the pub where I work as well as reading old posts on this site, it sounds like putting in new spark plugs is the first thing to do to try to fix this. But according to the repair history I received from the previous owner, the spark plugs were replaced about six months ago (as well as a new timing belt and a compression test). Is there an easy way to check if the spark plugs are still working properly, or are they so cheap that I might as well just replace them no matter what?

And if it's the carburetor, what kind of repair job am I looking at? Would it be expensive to get from a parts shop and have a friend install for me? Should I get the mechanic to do it?

Thanks.

Neu · Post by **Neu** » Sat Feb 16, 2008 6:25 pm

well remember, it's an old, old car. It does kind of wear out.

That being said, here's a nice check list.
1. Filters (air, oil, fuel)
2. Plugs/Wires/Distributor(rotor/cap)
3. TIMING
4. Vacuum lines.
5. Carb

Post by **ARCHINSTL** » Sat Feb 16, 2008 8:05 pm

There are opinions on plugs - but I installed NGK to replace the Bosch I had first installed in Goldie - and was really surprised at the difference. Now, it was not night-and-day, but the improved smoothness was noticeable. Apparently the NGK and Denso plugs are the way to go with these (and other '80s Japanese engines...).
From an earlier thread:
Both NGK and Denso are in the Owner's Manual.
Specifically, for all Cali and Canada w/AT :
_____NGK BPR5EY11
_____Denso W16EXR-U11
And for USA/non-Cali and Canada w/MT :
_____NGK BPR5EY11 or BPR4EY
_____Denso W16EXR-U11 or W14EXR-U11
It does not explain the difference, or when to use the cooler plug (or a hotter one either, for that matter).

And from another thread:
Well-
When I got my '86, I installed the least expensive Bosch Platinum (I think around $2.25 each), as I had no problems with them in other cars.
Later, in my shotgun approach and desperate attempt to get the thing running decently, I tried the least expensive NGK ($6.32/set), and was amazed at the results; not just a "I-spent-the-money-so-it-must-work" reaction, but truly a noticeable diference. Mind, not 25% more power or anything, but it did run smoother.
Members - and other Toy sites - made the claim for NGK and NipponDenso, and I was pretty dubious about the assertion that "Japanese engines needed Japanese plugs," but - it's apparently true - at least with our cars.

And also replace (one at a time) the many, many vac lines, as Neu mentioned as well. It's easy, but tedious. These Medusa-tubes do get brittle with age. Also review the correct placement of same, either from our site or from the AZ site. Check under your hood for the OE diagram; I presume you have the Canadian version?
Tom M.

Neu · Post by **Neu** » Sat Feb 16, 2008 8:35 pm

Yeh, i forgot all about the japanese plugs for plug engines

Ford - Autolite
GM - NGK, AC delco
Chrysler - Champion Plugs

The reason? they design and test the engines with these plugs. So use those.

otter63 · Post by **otter63** » Sat Feb 16, 2008 11:02 pm

When my engine started having very low compression, even the NGKs would foul quickly, so I asked at the auto parts store, and a lady there recommended Autolite AP64 platinum plugs. They are the wrong heat range, but they work great, and never foul.

Once I get the motor overhauled/replaced, I will go back to the NGKs.

As far as the vacuum lines, make sure you get the exact size, and yes, go ahead and replace them all. I got mine from Toyota so I could be sure of the size, but there may be other places, too.

Any Chilton manual should have a section on fuel saving tips. Tires, brakes, oil, air filters, thermostat - they all contribute.

nottheactress · Post by **nottheactress** » Sat Feb 16, 2008 11:42 pm

Specifically, for all Cali and Canada w/AT :
_____NGK BPR5EY11
_____Denso W16EXR-U11
And for USA/non-Cali and Canada w/MT :
_____NGK BPR5EY11 or BPR4EY
_____Denso W16EXR-U11 or W14EXR-U11

Just to be really, really sure: AT is automatic transmission and MT is manual?

I had no idea that anything to do with a car could be so cheap... In my experience car repairs either cost $250 or so they cost much you just want to cry. I will definitely put in spark plugs asap. The vacuum lines I think I will save until I have a few days off from work and don't need to drive anywhere.

Thanks again for the great advice.

Post by **ARCHINSTL** » Sun Feb 17, 2008 12:57 am

Yup - AT = automatic and MT = Manual.
And DO check out this AZ link:
http://www.autozone.com/shopping/repairGuide.htm
In many ways (pix) it is better than the FSM and pretty all-encompassing!
Tom M.

Post by **Petros** » Wed Feb 27, 2008 7:40 pm

20 MPG is too low (unless it is an automatic trans). The plugs might help is they are not proper type and heat range, also replace the spark plug wires if they look old. Ignition timing is an easy check, set it a 10 deg BTDC (not the factory 5 deg).

Also check for vacuum leaks and that everything is running properly with the carb. It is not necessary to replace all of those vac lines, only the cracked, brittle or questionable ones. Use a spray can of carb cleaner to look for a vac leak: With the engine running, spray it over the carb, vac lines, and other components and see if there is a change in the running speed. You can narrow it down and isolate the leak if you get a change in engine speed with each squirt of carb cleaner.

You should also make sure all the tires are inflated proerly and your brakes are adjusted properly (not dragging, easy to check with a jack, you spin each tire).

Good luck.

nottheactress · Post by **nottheactress** » Thu Feb 28, 2008 11:40 am

20 MPG is too low (unless it is an automatic trans).

It *is* an automatic--but to me 20 MPG is too low nonetheless. Do I have unrealistic expectations for my beloved little car?

My mechanic discovered that the choke was sticking open, and charged me CDN$70 to clean and lubricate the carburetor. The car sounded infinitely better for about a day, but I think the choke must be sticking again because it now sounds as bad as before and I'm still getting crap mileage. I am definitely going to take him to task for this. I guess I'm just going to have to suck it up and get a new carb?

The vac lines look okay--no obvious signs of wear, cracking, corrosion...

Ignition timing is an easy check, set it a 10 deg BTDC (not the factory 5 deg).

Actually, a quick scan of the Autozone repair guide tells me that this one is way out of my league. Heck, I bought those recommended spark plugs about a week ago and haven't had the guts to put them in yet, despite hearing how easy they are to install... but I will mention the timing thing to my mechanic (who is definitely on his last chance).

Post by **Petros** » Thu Feb 28, 2008 11:54 am

Get someone to help you with the plugs and the ignition timing check, both are easy compared to a lot of other things that need to be done. You will also need a timing light (many auto parts stores will rent them cheap). After you have someone help you with it once, you will know what to do with it next time (and replacing the spark plug wires too if necessary).

The carb is more complicated, but your mechanic should have fixed the choke right the first time (the choke is a relatively simple device). If the choke is sticking it would cause poor economy. I would not replace the carb just yet, they are pretty expensive, but fairly durable. But they do need maintenance, cleaning, adjustment, etc. regularly.

Good luck

Neu · Post by **Neu** » Thu Feb 28, 2008 2:12 pm

I was actually thinking about this the other day, I get 22mpg on a stick, albeit i only have 1st, 2nd and 5th gears, but i should get better than 22mpg, and 22 is on a good day.

The carb is original, i'll spray some cleaner through it, the vac lines are all good, i did those incredibly well, tires are all inflated well, brakes should get good, filter is new, plugs and plug wires are all good. I think I might need to redo my timing.

Someone wanna walk me through doing 10degrees?

Neu · Post by **Neu** » Thu Feb 28, 2008 5:33 pm

k, did my timing, i think itll be better. it was 5 degrees retarded. its about 7 advanced now.

neonsport · Post by **neonsport** » Thu Feb 28, 2008 7:10 pm

The best I ever got out of an automatic Tercel wagon was 28mpg on all-highway driving, and that was 14 years ago on a Tercel with only 130k miles on it, with a great carburetor. If you're getting 20mpg in highway driving, you're at least 5mpg shy of what you should be getting. If that's city driving, it's fairly close to right. A fresh set of NGK or Nippondenso plugs can make a 1-2 mpg difference, and timing, plug wires, distributor car and rotor, etc, can all make a difference. Likely your biggest loss is coming from the carburetor.

nottheactress wrote:
20 MPG is too low (unless it is an automatic trans).
It *is* an automatic--but to me 20 MPG is too low nonetheless. Do I have unrealistic expectations for my beloved little car?

My mechanic discovered that the choke was sticking open, and charged me CDN$70 to clean and lubricate the carburetor. The car sounded infinitely better for about a day, but I think the choke must be sticking again because it now sounds as bad as before and I'm still getting crap mileage. I am definitely going to take him to task for this. I guess I'm just going to have to suck it up and get a new carb?

The vac lines look okay--no obvious signs of wear, cracking, corrosion...

Ignition timing is an easy check, set it a 10 deg BTDC (not the factory 5 deg).
Actually, a quick scan of the Autozone repair guide tells me that this one is way out of my league. Heck, I bought those recommended spark plugs about a week ago and haven't had the guts to put them in yet, despite hearing how easy they are to install... but I will mention the timing thing to my mechanic (who is definitely on his last chance).

otter63 · Post by **otter63** » Thu Feb 28, 2008 8:32 pm

My car has really low compression, but is still getting 32 miles per gallon.

nottheactress · Post by **nottheactress** » Fri Feb 29, 2008 12:00 am

If you're getting 20mpg in highway driving, you're at least 5mpg shy of what you should be getting. If that's city driving, it's fairly close to right.

Hmm... I have to admit I had higher expectations than that. My car--I call it the Inconvenience, which is actually supposed to be a literary reference and not a mention of how much trouble it causes me--is actually the first car I've ever owned by myself. In the past I've shared cars with friends and haven't been quite so strict with my MPG. These cars (first one possibly a Terc, the second a Subaru wagon) were stick shifts and I guess I just didn't realize how much of a difference that can make in fuel economy. I think it might be time to sit down with a calculator and figure out how cost effective a new carb would be. And I am going to get brave and put those spark plugs in... soon.

Thanks so much for all the great advice and comments.