Trouble accelerating, terrible gas mileage..??

Technical Topics specific to the Hatchback body - NOT where you post pics/build specs of your car.
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Trouble accelerating, terrible gas mileage..??

By Crabloc93
- Sun May 31, 2015 7:13 pm #353980 My eg has a loss in power, it lags in 2nd/3rd gear up but when it hits about 2500 rpms it kicks in and accelerates normal again, almost like VTEC kicking in(I have a non VTEC block). I also get terrible gas mileage, I filled my car up two days ago and drive about 20 miles a day, its close to E already. Here are some things I do know about my car that may be causing this.

I have an exaust leak behind the drivers seat (not sure if this is the reason why theres a lot of carbon build up all over the back of my hatch)

The guy who put my used block in adjusted the clutch a little, very soft compared to when I first got my 5 speed swap done, tranny also smokes at times, I know it has a leak maybe clutch slippage?? I know it needs a new input shaft bearing.

Yesterday pulling out of a parking lot my car died and wouldn't start after at least 5 attempts. Just put a new dizzy, plugs, and wires in...

Id like to receive more feedback on what is causing the terrible gas mileage and lack of power, its much appreciated
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By teal_dx
- Mon Jun 01, 2015 4:14 am #353986 If clutch was slipping, you would notice the RPM's rising without additional acceleration. If you have a tach, then that wold let you know for sure.

You have some issues which need to be fixed but I don't think this is related, although all of the issues you mentioned are combining to hurt your mpg.

The carbon build up is from your engine running too rich = too much fuel. Most common reason for this is a bad o2 sensor. Assuming your engine is stock, I'd check that out first. Even if you don't have a check engine light, an o2 sensor can be going bad. a bad o2 sensor will tell the ecu the wrong air/fuel readings, which can cause the ecu/injectors to dump too much fuel into the engine.
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By suspendedHatch
- Tue Jun 02, 2015 6:09 am #354001 The only adjustment on the clutch is the pedal height. Was the clutch replaced? Aftermarket clutches will often feel softer than OEM. It takes some getting used to.

If the transmission leaks, fix the shift shaft seal, axle seal, or the sealant between the two halves of the housing. Trannies shouldn't leak.

Tell us more about this "used block". Did it ever run well afterward? For how long?
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By Crabloc93
- Fri Jun 05, 2015 7:43 am #354046 I bought a used d15b7 with 160k and runs fine, the cell light does come on after 20 minutes of driving, I don't have a speed sensor hooked up, I'm thinking I have an bad o2 sensor as tealdx stated. I did just discover I have an axle seal leak, not sure if this is causing the tranny to smoke. This happens after driving up a steep hill or driving it hard after 15 min straight. I have an 97 EX tranny with about 230k, it grinds due to the input shaft bearing being worn out, heard it causes the internal gears to match not right? I know it needs replacing, makes a noticeable noise that goes away with the clutch engaged..
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By Crabloc93
- Fri Jun 05, 2015 6:22 pm #354058 I haven't had time to check, I'll see tomorrow morning
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By Crabloc93
- Sun Jun 07, 2015 2:44 am #354076 Today my cars idle was running rough, at 400 rpm, it hesitated trying to take off, like it wanted to stall, this happened a week ago but the car stalled and had trouble starting up. The suction from my intake isn't as loud like it used to be before I swapped in my last motor, thinking it could be a bad tps sensor?? Haven't had time to check my codes still...
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By FlopUrDonk
- Mon Jun 08, 2015 7:55 pm #354097 You could always test it. Have a volt meter?
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By Crabloc93
- Tue Jun 09, 2015 1:11 am #354102 I don't have one, I tried checking my codes but my CEL stays on, I heard this means I have a bad ecu. I have another ecu in the garage I was gonna use when I put my z6 head on, I'm sure its compatible with a non VTEC block right?? Apologies if that's a stupid question lol
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By teal_dx
- Tue Jun 09, 2015 4:52 pm #354108 Yeah, you can plug the vtec ecu in and start the car up. :thumb:

Fuel curves will be off, so I wouldn't recommend driving around on it though. You might also get a CEL due to the ecu not seeing the vtec/oil pressure sensors on the back of the head.
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By Crabloc93
- Sun Aug 02, 2015 5:13 pm #355117 I have a new o2 sensor, got my valves readjusted, so it runs a lot smoother, but still has a tough time on acceleration. It will start accelerating and just die down, then suddenly go back to normal rate of acceleration. Maybe it could be bad injectors?
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By suspendedHatch
- Sun Aug 02, 2015 9:07 pm #355123 Have you put a speed sensor in and checked the CEL yet? There's no reason to pursue anything else until you tackle the obvious stuff.
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By Crabloc93
- Mon Aug 03, 2015 3:50 pm #355160 I've tried the CEL light doesn't even blink to throw out codes, it just stays on the whole time
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By EconoBox
- Tue Aug 04, 2015 6:20 pm #355177 OK before I go into troubleshooting a solid MIL let's double check and make sure thats actually the issue.

Unplug the ECU for a couple of minutes and plug it back in. Once you plug the ECU back in turn the key without starting the car, the MIL should come on and then turn off. If it does that start the car and let it run/drive it until the MIL comes on. When you turn the key, If the MIL comes on and doesn't shut off skip to my second post.

Turn your car off.

Use a jumper wire to check the MIL codes by jumping the pins together of the blue SCS connector found under the glovebox against the passenger side of the dash. Turn the key to ON without starting the car while this SCS connector is jumped. If the lights flash, match them up to a DTC list and see what the issue is. Or you can post the code here.

If the MIL stays solid see my next post.
Last edited by EconoBox on Tue Aug 04, 2015 7:08 pm, edited 1 time in total.
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By EconoBox
- Tue Aug 04, 2015 7:06 pm #355178 Before doing any of this make sure the SCS is no longer jumped.

This is an involved troubleshooting process. You will need a volt meter and an OBD1 ECU pin-out to follow where I am telling you to probe for voltage and grounds.
- Try to start the engine

-- YES it starts
---turn ign off, turn switch back to on without starting the car
----check voltage between D4 (+) and D22 (-)
-----is there around 5v?
------NO, repair body ground to BRN wire between ECM (D4) and the SCS
------- YES, connect the SCS
-------- measure voltage between D4 (+) and D22 (-)
--------- is there around 5v?
---------- YES, repair open in BRN wire between ECM (D4) and SCS, repair open in BLK wire between SCS and G101 (Ground on the thermostat housing)
----------- NO, remove the jumper from the SCS
------------turn the ignition switch off
------------- disconnect ECU connecter 'A' from the ECM
-------------- turn the ignition on, is the MIL on?
--------------- NO, subsitute known working ECU, if symptom goes away replace ECU
---------------- YES, repair short to body ground in GRN/ORN wire between ECM (A13) and MIL

--NO, the car doesn't start
---remove and inspect the ECU (15A) fuse in the under hood fuse/relay box, is the fuse OK?
----NO, replace the fuse
----YES, inspect the ACG (ALT)(S)(15A) fuse in the under hood fuse/rea;y box, is the fuse OK?
-----NO, replace the fuse
-----YES, turn the ignition to ON without starting the car
------disconnect the 3p connector one at a time to each of these sensors and check the status of the MIL. MAP sensor, TPS (throttle posistion), EGR if equipped, Did the MIL shut off?
-------YES, replace the sensor that when disconnected the MIL shut off
-------NO,turn the ign off
--------Disconnect connector 'D' from the ECU and on the connector (NOT ECU) check for continuity between D19 and the Body ground, and between D20 and a body ground, is there continuity?
---------Yes, repair short to body ground YEL/GRN wire between ECM (D19) and Map sensor, repair short to body ground in YEL/WHT wire between EMC (D20) and TPS or EGR lift valve if equipped.
---------No, reconnect 'D' Connector to ECU
----------turn the ign swith to ON without starting the car
-----------measure voltage between body ground and each of these terminals (measure them one at a time) A26 and B2, is there less than 1.0V
------------NO, repair open in BLK/RED (A26) or BRN/BLK (B2) and G101 (Ground on thermostat housing)
------------YES, measure voltage between A26 (-) and B1(+) and A25(+), is there battery voltage?
------------Yes, substitute known good ECU
------------ NO, repair open in YEL/BLK wire between EMC (A25,B1) and PGMFI main relay. Check the PGMFI main relay and all connection at the PGMFI main relay.

That's literally the whole section on a solid MIL from Honda.
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