1990 motor swap

[retard_ed_1]

i recently swapped a 92 H.O into my 90, i put a comp cam (4x4 extreme) in,

my question is : is there any way to change the air fuel mixture because in going thru a lot of gas ( 200km to a tank). and the exhust has a really heavy gas smell, also leave i nice black spot in the snow from the tail pipe.

motor way totally rebuilt, am using stock every thing except the cam, now i know the cam will give me less gas milage but i just want to get rid of the stink

thanks
tim

 

[Dr. Dyno]

Check the voltage from the O2 sensor signal wire with the engine at idle. Since the engine is running pig rich, a properly functioning O2 sensor should produce a signal very close to 1.0v (full rich). If it's producing close to 0.0v (full lean), either the sensor is dead or there's a problem with the wiring to it.

 

[retard_ed_1]

ok ill start there, thanks, if its not that that what can it be?

someone told me to ask you about a home made adjustable map sensor

tim

 

[BLSXJ]

I'll own up to be that person. I think?

 

[retard_ed_1]

lol :wave:

 

[Dr. Dyno]

ok ill start there, thanks, if its not that that what can it be?

someone told me to ask you about a home made adjustable map sensor

tim

Yeah, I do have a homebrew MAP adjuster but that's not what you need to cure your problem. You need to find out what's wrong with your existing system and the O2 sensor is the best place to start.
You can also check the vacuum tube going from the MAP sensor to the intake manifold. If this is cracked or broken, the MAP sensor won't sense any vacuum in the intake manifold so it'll falsely interpret that as the engine being under load (WOT) and tell the engine computer to richen the A/F mixture. If that checks out OK, backprobe the middle (signal) of the three wires coming from the MAP sensor and check the voltage from it while the engine's idling. It should read somewhere around 2.0v.
Let me know what you find and we'll take it from there.

 

[retard_ed_1]

what if the map is getting to much vacum? like i said i put a 92 H.O into a 90.
the 92 TB didnt have a spot for the map vacum, so i was told to just stick it somewhere on the intake that had roughly the same size hole as the 90 TB.

could to much vacum be leading to a rich mixture?

anyway i will try what you said
thanks

tim

 

[Dr. Dyno]

No.
Higher vacuum = lower manifold absolute pressure = lower MAP voltage = leaner A/F mixture
Lower vacuum = higher manifold absolute pressure = higher MAP voltage = richer A/F mixture

Does that make sense?

 

[retard_ed_1]

ya thanks

 

[retard_ed_1]

hey dr dyno

could engine temp be causing the problem, i started checking around a notice my thermostat was stuck open

just wondering

tim

 

[Sarge]

A thermostat stuck open would cause the motor to not come up to temp which could cause some problems. Not sure if it would put it into a limp home type setting but those are usually fairly rich. I think.

sarge

 

[Dr. Dyno]

hey dr dyno

could engine temp be causing the problem, i started checking around a notice my thermostat was stuck open

just wondering

tim

I'd say almost certainly, especially since the weather's very cold and the engine will barely warm up. Replace the old factory t'stat with a Robertshaw 195* t'stat from http://www.flowkooler.com and see if that improves things. At least it's a cheap fix.