eyefish

I'm a new member and I could really use the help
I'm building a mud toy. It has an 80 Landcruzer frame and axles, an Ivan Stuart sand rail body, 8 inches of lift with 15X31.5 inch ditch witch tires.
I put an 88 4runner 30. v6 efi and auto trans in it. I completely rebuilt both.
I'm using a fuel cell with an external 90psi fuel pump. The motor was poped 40over, the heads shaved .020 and the block shaved .015 and it has headers other than that it's pretty much stock.

Now for the problem, it starts and idles ok as soon as I give gas it backfires thru the exhaust. So I'm thinking timing, I've checked the TDC several times, tried setting the distributor a tooth both ways(didn't work) moved the cam settings both ways a tooth(didn't work) Reset it back to factory and it will start and idle, So now I thinking it has to be a fuel issue.

Anyone had anything like this happen? Got any ideas where I can start looking?

Thanks in advance for the help

TNRabbit

So you're saying it won't run except to idle? Is the VAFM connected?

eyefish

I can get the RPM's up a little, but it sounds like the 4th of July when I do. In lue of sounding stupid what is a vafm?

TNRabbit

Vane Air Flow Meter. You have to have all the intake connected or it will not run.

Sounds like other than the VAFM or you wouldn't get more than idle. Timing out of whack will cause what you're referring to. Have you checked to see that the spark plug wires go to the correct cylinder?

Also, is it possible you have the distibutor 180 degrees off?

Did you use the correct timing mark on the crankshaft pulley?

eyefish

Yes the Air flow meter is hooked up.

All new plug wires, rotor and dist. cap, I have checked several times to make sure they go to the right plugs.

I tried the timing 180 out and got a low toned backfire from the exhaust.

On the cam pulleys I set them to the factory marks, then tried them one tooth each way, problem got worse. Set it back to factory

Now the back plate and cam pulleys came off a 1995 and the trottle body came of the same motor. They all looked the same. I did put the throttle positioning sensor off the 88 on the newer throttle body

blake.nemitz

maybe you shaves too much off the heads and block and arent getting a correct timing reading, i mean if it says 10 btdc you could be at 15 beacuse the cam gears are closer to the bottom of the block who knows just an idea

eyefish

Hopefully thats not the case, I had the machine work done locally.

OMG that was here in Florida, what was I thinking.

No really the machinist said he had done several exactly like mine with no problems.

TNRabbit

Not likely. It would have to be decked/quenched a TON to change the timing. You'd have more problems than timing if that was true.

Not sure what to tell you at this point. It sounds like a timing (valve or spark) issue.

eyefish

OK thanks, Could running to lean cause the rapid backfire, I put a snorkle on my polaris 6 wheeler and had to install a ballcock valve on the intake tube to slow the air intake, it lost power and started backfireing with out it. Once the valve was installed and I choked down the air flow it ran great. I do not recall if it was fuel injected or not.

TNRabbit

I can't imagine that would cause it. The VAFM simply adjusts fuel metering.

What makes you think it's running lean?

eyefish

I have heard that a small crack in the hose from the airbox to the throttle body could cause back firing thru the exhaust.

I looked at another motor like mine and noticed a plug where I dont have one and of course it would be a 1/2 inch hole going right into my throttle body.

So tomorrow I will check that and the fuel pressure, worst case I'm back to looking.

I guess when you take several different vehicals and piece them together to make one mud toy your going to have some challenges, next I get to work on creating a new exhaust system for it.

blake.nemitz

the vafm makes it or breaks it if you have one and dont believe me try unplugging it and running your motor, i would satart there

blake.nemitz

hey eyefish where are you i have an extra air flow meter laying around

eyefish

Thanks Blake, I have 2, tried both same result. I'm in SW florida, Cape Coral to be exact.

MB4runner

Well whats controlling the fuel, did you put in an ecu from the 88 v6 3.0 4runner or do you have some sort of standalone?

eyefish

The ecu is from the 88. I could not get constance power source from the fuel pump wires so I ran a hot wire from the ignition, so it would turn on and off with the ignition. I believe the pressure regulator is vacume driven, so there is no wires there. The only things electric I can figure run the fuel is the cold start relay, the mass air flow and the throttle positioning censor. Unless there is something I'm missing

eyefish

UP DATE

I worked on the toy today, I found several vacume leaks and fixed them, made sure my cam and crank pulleys were at the factory marks checked the timing and tried it again, a little stronger but same rapid back fire. Moved the distributor a tooth forward and she got stronger and most of the back fire was gone but shes still not right, I'm getting closer, I may need to re-adjust the throttle positioning sensor.

I,d probabally be smart to hire a good wrench