I recently got rid of the built b20 vtec setup that I had, for something more mild, and streetable, and more friendly at the pump. I purchased a stock b18b longblock from a user on here. The motor started instantly and seemed to be running nice. Wasn't burning oil, wasn't knocking, etc. After driving for a short period of time, I noticed a good amount of black smoke coming from the exhaust when the motor was at or near WOT. The motor is running very rich, and after 2 rides to the next town over, I was empty. The next town over is 30-35 miles. This means the car is getting like 13-14 mpg?! Obviously a serious problem. It has a very bad jerk to it also, until you get to about 3.5K rpms then it seems to smooth out. The jerk only occurs when the accelerator is barely being pressed, like when you are trying to maintain a certain speed, it jerks horribly and feels like all plugs are misfiring(the car feels powerless, obviously because it is getting way to much gas). The idle has the slighest surge, fluctuating about 100 rpms, back and forth sometimes. Now, for the wierdest part...the car has no CELs and hasn't shown one yet. I know the light still works because I disconnected a sensor, just to make sure it was still working. Does anybody have any idea what this could be. Getting that bad of mileage, there must be something seriously wrong with something I have done! Any help will be appreciated!
Thanks!

 

What ECU is running this ? has it been chipped ? if it's using that much gas, a standard o2 sensor would generate a code in no time. Is it running standard injectors and TB ?
Maybe the temp sensor thinks it's cold all the time ?

 

i had something similar.. my rotor in my distributer the screw that holds the rotor fell out i was running very rich.. check that b4 you replace anything i replaced plugs and all b4 i looked at that.

 

check out ur distributor and plugs just like the other guy said

 

A clogged or broken MAP sensor can cause severe drops in gas mileage. It thinks the motor is going to stall, so to compensate, it dumps fuel like crazy. When mine wasnt hooked up right after a swap years ago, i was clocking 103 miles to a tank, thats about 10mpgs, for a good 2 weeks.

Also, that jerk you describe at the low end may be due to a mix of a vaccum leak and bad IACv, which can cause the throttle response to feel sudden and jerky under 3k rpms. Its also notorious for that "2-step" flutter you may get if you try and hold an RPM under4k rpms. Keep in mind a bad vaccumm leak would surely affect gas mileage as well as your idle.

 

All of these suggestions on the solution to the problem sound exactly like some of the things I had thought to check on! I will definitely look into all of these things as soon as I get the time. As far as some of the questions above. The ecu is stock, the injectors are stock, and the throttle body is stock. I already checked the plug/gap, they are perfect, the wires are brand new, as with the distributor. I have not looked at the screw that holds the rotor insde of the dist., as mentioned above! I will look into that! There were like two very small nipples on the manifold, that I capped off, they originally ran to the charcoal canister, but that has been removed. That didn't have any effect on the running of the motor, just capped off the very small vaccum leak. My neighbor, an old man, who has been a mechanic for around 45 years, said something about that temp sensor? Anybody have more on this? Thanks already guys for the awesome input!

 

how did you make out get it fixed?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">said something about that temp sensor? Anybody have more on this?</TD></TR></TABLE>

If referring to the engine coolant temperature (ECT) sensor, I don't think it'd be quite the same symptoms. When mine was out, I had rough starts and such, but it also was always in cold idle, as in I'd be 1500 rpm just sitting there.

Your situation sounds like something much different than ECT sensor, but it's a $25 sensor if you'd like to try it anyway.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by miguel329 &raquo;</TD></TR><TR><TD CLASS="quote">how did you make out get it fixed?</TD></TR></TABLE>
about to work on it today man!
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Davus &raquo;</TD></TR><TR><TD CLASS="quote">

If referring to the engine coolant temperature (ECT) sensor, I don't think it'd be quite the same symptoms. When mine was out, I had rough starts and such, but it also was always in cold idle, as in I'd be 1500 rpm just sitting there.

Your situation sounds like something much different than ECT sensor, but it's a $25 sensor if you'd like to try it anyway.</TD></TR></TABLE>
yeah i am almost positive it is a bad map sensor or bad wiring on the map sensor. The sensor is like $25 at my work, then my discount, so it will be the next thing I try after I dick with the map sensor. So far, I have heard from almost everybody that it sounds like the map. Thanks for all the help guys! I'll update after some wrenchin.

 

well I checked out my wiring on the map sensor and it was fine. I won't know if it is the actual sensor until my buddy comes over and we swap his in to check. I used to recall how to check it with a multimeter, but i left my manual about 40 miles away.Anyone have a link to proper way to test it? Thanks

 

did you switch the MAP and TPS plugs?

Did you switch the VTEC solenoid and CTS plugs?

It's a common mistake.

The MAP and TPS plugs are the same. Check the wire colors for your year and model. I forget what they are right now.

The VTEC plug and coolant temp sensor plug are the same plug also. They are right by each other. If your VTEC solenoid plug is plugged into your CTS, the CTS will read -40degrees (full rich).

Sounds like a wiring problem either way. Does your car throw any CELs?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by B serious &raquo;</TD></TR><TR><TD CLASS="quote">did you switch the MAP and TPS plugs?

Did you switch the VTEC solenoid and CTS plugs?

It's a common mistake.

The MAP and TPS plugs are the same. Check the wire colors for your year and model. I forget what they are right now.

The VTEC plug and coolant temp sensor plug are the same plug also. They are right by each other. If your VTEC solenoid plug is plugged into your CTS, the CTS will read -40degrees (full rich).

Sounds like a wiring problem either way. Does your car throw any CELs?</TD></TR></TABLE>
Well I know that I didn't switch the MAP and TPS...because I had to hardwire a MAP plug into the car because my new harness didn't come with one on it, as it is supposed to be in my chasis harness...and I am positive that is right, that is the one thing I have checked over like 5 times. Now I am pretty sure the harness I have wasn't even a VTEC haress anyway, although I am not positive. I will double check the temp sensor and VTEC plug to make sure that didn't happen. And as far as check engine lights, don't have one, never had one, since the motor was put in 3 days ago...which is what is bugging the S out of me, if something is wrong, just show me on the dash, and I'll fix it! It never works like that with my luck

 

well i just checked the wiring on that and it was fine. I don't even have a plug for a vtec solenoid. I'll just have to wait until I get that other map sensor so I can swap em out and see what is up with it.

 

maybe you have a leaky injector or too much fuel pressure. Do you have an adjustable FPR?

If you have a stock FPR, the diaphragm might have torn or ruptured. Try switching one out if you have one laying around.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by B serious &raquo;</TD></TR><TR><TD CLASS="quote">maybe you have a leaky injector or too much fuel pressure. Do you have an adjustable FPR?

If you have a stock FPR, the diaphragm might have torn or ruptured. Try switching one out if you have one laying around. </TD></TR></TABLE>
Man, you are thinking exactly like me! I have already thought of these things, I just need to get to the junkyard and pick up some spares and switch em out and maybe get lucky? I seriously can't think of what else it could be. I used to have an adjustable on my old setup, but I got rid of it.

 

I was thinking this was a stupid question, but I just want to double check! If I have like a Walbro aftermarket fuelpump, because of my old setup. Could that be causing this problem? I thought that wouldn't matter, because I figured that the motor was capable of figuring out what amount of fuel it needs...or is that not the case when using a high output aftermarket pump?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by schpiel &raquo;</TD></TR><TR><TD CLASS="quote">I was thinking this was a stupid question, but I just want to double check! If I have like a Walbro aftermarket fuelpump, because of my old setup. Could that be causing this problem? I thought that wouldn't matter, because I figured that the motor was capable of figuring out what amount of fuel it needs...or is that not the case when using a high output aftermarket pump? </TD></TR></TABLE>

Nah. The system has a return line. The ECU tells the fuel injectors to open up at a certain time frame. The FPR keeps the fuel pressure at a certain level. So everything is calibirated for that. The pump just supplies volume. Any residual fuel goes back to the tank via the return line.

 

that would kinda matter whether its a 190 or a 255 a 190 probably b ok but a 255 probably not. just get an adjustable FPR or switch the pump!

Remeber there is a code for "too rich/lean".

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by B serious &raquo;</TD></TR><TR><TD CLASS="quote">

Nah. The system has a return line. The ECU tells the fuel injectors to open up at a certain time frame. The FPR keeps the fuel pressure at a certain level. So everything is calibirated for that. The pump just supplies volume. Any residual fuel goes back to the tank via the return line.

</TD></TR></TABLE>
So basically even if I hooked up an adjustable, I would only be able to sort of bypass the problem, but not really correct it?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by hon2984 &raquo;</TD></TR><TR><TD CLASS="quote">
Remeber there is a code for "too rich/lean".</TD></TR></TABLE>
Yes, which is why I am pissed that I can't figure this out considering I should definitely have a code although I don't!

 

Anything more on the fuel pump/regulator? More input?

 

Figured out the problem!!! Well, I am almost 100% sure. I took my MAP to work today, and checked it out. For the sensor to be in spec with what it is supposed to, the manual says it should be at or very near 5.00 volts, on both the signal, and power. Mine was at roughly 3.5 on one side, and 6.5 on the other! Looking for a new MAP and after that, should be rolling smooth...now just finding one of these..ugH! Thanks for all the help!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by schpiel &raquo;</TD></TR><TR><TD CLASS="quote">Figured out the problem!!! Well, I am almost 100% sure. I took my MAP to work today, and checked it out. For the sensor to be in spec with what it is supposed to, the manual says it should be at or very near 5.00 volts, on both the signal, and power. Mine was at roughly 3.5 on one side, and 6.5 on the other! Looking for a new MAP and after that, should be rolling smooth...now just finding one of these..ugH! Thanks for all the help! </TD></TR></TABLE>

You can find a map on ebay for $25. Or at any junkyard for $ free - $5.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by B serious &raquo;</TD></TR><TR><TD CLASS="quote">

You can find a map on ebay for $25. Or at any junkyard for $ free - $5.

</TD></TR></TABLE>
Yeah, I was just gonna ride to the junkyard on my day off this week...but honestly with gas prices and the fact that it is 100 degrees here, I am thinking ebay! lol

 

Wont taking out your charcoal canister kill gas milage?