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Carb Conversion On A 93'


bigtimemcc
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Mine doesn't have a cat either, no emissions testing at all here. I welded a glasspack in it's place after the bolts and flanges got rusty. One drawback to hollowing out a cat is that it causes turbulence in the exhaust path which can hurt performance at lower RPM's, plus it rumbles more and might produce a bit of a resonant vibe through the floor. No biggie.

 

We dont even have inspection here anymore. They stopped that 10 years ago, but even then they didnt check emissions. I kinda like the thunder down yonder, keep you awake on the long trails.

Edited by bigtimemcc
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So, any updates?

 

GOOD NEWS!!! I replaced the computer and that seems to have solved the biggest problem. Starts up with no smoke, runs much much smoother at idle, the idle is at the correct rpm, runs cooler and uses much less gas.

 

But there is a new problem. (had to be, huh)

 

I lose power under load. If I do anything but gently ease on the gas pedal it will bog down. Almost like the fuel pump is not putting out enough pressure and its starving for gas. But I seriously doubt that because it was getting way to much fuel before the new computer. I know the timing is off, but I havent had a chance to buy or borrow a light.

 

If I accelerate slowly I can get it up to any speed. I put almost 200 miles on it today. With the a/c on it was very hard to keep it in overdrive. It would shift into OD when I got up to speed and eased off the gas, but there was not enough power to maintain that speed in OD (70 mph), and it would kick back down into 3rd.

 

I noticed while applying light pressure on the pedal maintaining a constant speed, I could press on the pedal slightly more and the rps would drop by about 200 when it would "bog". I can punch it and it will speed up, but very slowly and sometimes stumble. Its like I'm hauling a trailer with a 2500 lb car on it.

 

Any ideas? Would timing do all of that? Timed it by ear and got it as smooth as I could, testing by setting it and gassin' it till it ran the smoothest. Cap and rotor maybe? I thought I could hear maybe plug wire arc at times while sitting at idle. Coil? Could it not but putting out enough fire? Would seem odd since it was making fouled plugs burn a super rich mixture.

 

I dont know. Do you?

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Timing could do all of that. Get it timed right, and then report back. I'll be willing to bet that it'll be running MUCH better.

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Timing could do all of that. Get it timed right, and then report back. I'll be willing to bet that it'll be running MUCH better.

 

Gonna time it tomorrow. I have no idea when and if the timing belt was changed last (133k miles so far). How much is a belt, and how hard is it to put on? Should I buy a new tensioner while I'm in there, or just check the one in it?

 

Also, where should the mark show on the balancer? Couple degrees to the left or right?

 

Does anyone think I should start a new thread on this or maybe visit and existing thread?

 

Ghostpath, any thoughts?

Edited by bigtimemcc
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Doing the belt is fairly easy. There are many threads on it here on the board - there's one in the How To section at the top of the Garage forum. You should replace the belt, tensioner, water pump, and hoses while you are in there.

You need to find out if you have the round or square toothed belt to get the right one; there are aftermarket kits available out there, but I personally prefer replacing everything with genuine Nissan parts. Here's a kit from a dealer:

 

http://www.courtesyparts.com/Merchant2/mer...ode=WD21-TBKITA

 

To that, I would add a crankshaft timing belt drive gear, two new keyways (also known as Woodruff keys) and two new guide plates for the belt. I find that the pulley and belt guide plates are easy to screw up when doing the timing belt on a VG30, and the keyways are just cheap insurance. All told, from Courtesy or similarly priced dealer, you can get every Nissan part you need to do the job for under $300.

 

See the EC section on the manual I referenced you to earlier - it has the procedure on setting timing. And there's a pic of how it's supposed to be set and what it's supposed to look like.

 

Ignition timing should be 15 BTDC plus or minus 2 degrees.

Edited by GhostPath
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Ok, I timed it with a light today. I got it to 15 degrees BTDC and it doesnt run any better, maybe a little worse. I replaced the cap and rotor because I could hear it arc in the cap. What do you guys think.....

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Ok, I timed it with a light today. I got it to 15 degrees BTDC and it doesnt run any better, maybe a little worse. I replaced the cap and rotor because I could hear it arc in the cap. What do you guys think.....

 

 

What RPM did you check the timing at, and did you remember to warm the engine up to operating temp first?

 

Also, is the TPS properly adjusted?

Edited by GhostPath
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What RPM did you check the timing at, and did you remember to warm the engine up to operating temp first?

 

Also, is the TPS properly adjusted?

 

The engine was up to temp, drove it for 10 min.

 

It was at about 700-800 rpms.

 

The tps is in the middle, how do you adjust it properly.

 

Ran diagnostic on the tps, and it works (red light comes on when you hit the gas)

 

I ran the codes and it came back with 33, for Heated Oxygen Sensor.

 

I reset the computer and ran it for about 5 mins, and checked the codes and it was 55, all good.

 

I pulled the O2 out and cleaned it with CRC Electronics Cleaner (the stuff recommended on this site) a couple of weeks ago, before I put the new computer on it.

Edited by bigtimemcc
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The engine was up to temp, drove it for 10 min.

 

It was at about 700-800 rpms.

 

The tps is in the middle, how do you adjust it properly.

 

Ran diagnostic on the tps, and it works (red light comes on when you hit the gas)

 

I ran the codes and it came back with 33, for Heated Oxygen Sensor.

 

I reset the computer and ran it for about 5 mins, and checked the codes and it was 55, all good.

 

I pulled the O2 out and cleaned it with CRC Electronics Cleaner (the stuff recommended on this site) a couple of weeks ago, before I put the new computer on it.

 

 

Your O2 sensor has probably been poisoned/killed by running so rich for so long. I'd replace it as a matter of course.

 

There should be instructions on how to properly adjust the TPS in that manual. See page EC 144 and adjust your TPS until you achieve the specified resistance.

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Your O2 sensor has probably been poisoned/killed by running so rich for so long. I'd replace it as a matter of course.

 

There should be instructions on how to properly adjust the TPS in that manual. See page EC 144 and adjust your TPS until you achieve the specified resistance.

 

I checked resistance on the tps and it is in working order.

 

I also checked to temp sensor and the maf sensor

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I would check your fuel pressure, see what it does when you rev it.

 

Fuel pressure is correct.

 

Seems to run great first thing in the morning before it warms up.

Edited by bigtimemcc
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