Fitro

Hi all, a little while ago i bought a 98 civic dx 5 speed for cheap, knowing it had some issues. The problem I'm having trouble figuring out right now is the fact that anything over 50% throttle seems to bog the car down to the point of 500ish rpm while driving and while in neutral I can get it to rev all the way up if i increase throttle gradually but if i stomp on it, it basically cuts nearly all throttle and bogs hard and backfires for about 3 seconds then pulls out and revs up. While driving it does this in all gears and does not matter the speed I am going. The car idles fine and starts fine with a few cranks.

I have done the following so far.
New distributor cap, rotor, plugs, wires, new tps, new upper radiator hose that was cracked (although barely since not much coolant was missing and only seeped some under heavy throttle) and cleaned throttle body.

One other issue I'm having is that the tps only reads .33 volts at 0% throttle and 3.73 volts at 100% and I know it's not the tps because this is my second one to make sure of that, but the power wire has 5.05 volts and the ground has continuity. So could the signal wire be bad at some point and be causing this? Also the battery reads 12.5v with the car off and 14.3v while running.

Supposedly the last owner had a new fuel pump and filter installed and I work with the last two owners so I don't think there's anything they left out.

The next things on my list are to check the fuel pressure regulator, fuel pressure, engine compression and timing, probably in that order, but I wanted to pick your guys' brains first since this is my first Honda and is just going to be a good mpg commuter to save miles on my diesel.

So far I have got the check engine light for P0171 (too lean bank 1) and P0300-P0304 which is misfire for all four cylinders

Thanks for any help.

civic402lx

Have your injectors clean. Verify timing mechanical and with light. Make sure plugs are gapped correctly.
valve adjustment.
as you said, compression and leak test to confirm health condition of motor.

Fitro

I forgot to mention that I did make sure that each individual plug was getting spark and I gapped them before I put the new ones in, so that's not it. When you mentioned to have the injectors cleaned, that reminded me that I meant to test them, but have not yet, so next I'll check for any dead cylinders, then check the the resistance of each injector to make sure none of them are dead, but since I'm getting a misfire on all cylinders I would guess it wouldn't be one individual injector. Honestly I was considering just replacing them all anyway because a reman set is only like $70-$100 and I'm positive they're the original ones and the car has 165-170 thousand miles.

As far compression and timing those are next and I was planning on cutting off the lip on the valve cover that holds the cover on over the belts so if I ever need to check the timing again it will be quick and easy.

Any experience with the throttle position sensor? I read the tps sticky but can't figure out why the volt readings would be low when everything else with it seems to check out ok.

Fitro

So I tested the injectors last night and all of them are good and spraying what seems like a similar amount of fuel, at least at idle.

Is there any common areas where these cars have vacuum leaks? I also sprayed carb cleaner all around the throttle body, intake and surrounding lines to see if I could hear a change in idle and I couldn't pick anything out.

I suppose I'll try and do a quick compression test after work today and if that comes back good I'll be pulling off the valve cover and checking timing.

I also noticed there was no ac compressor belt, is this the only accessory that belt runs or is it tied in with something more important?

civic402lx

Do a smoke test to find leak. Blow smoke in through the brake booster line on the manifold. Your leak will show up very clearly where.

civicservice

What do your long/short term fuel trims look like?

Fitro

Going to build myself a little pickle jar smoke machine tonight so I can try that out tomorrow.

Fitro

Here's the only freeze frame data my cheap $10 eBay code reader would give me, not sure if it would be any help though.

Fitro

So I finally got around to doing the smoke test after being out with the flu and no dice there either, the only place I could see any smoke coming out was the front of the intake system where air enters, so I plugged that up to get a little more pressure in the system, and nada. This was with the smoke going into the brake booster vacuum line.

So on to compression test.

Fitro

Compression test came back good, 180-190 on all 4 cylinders by the fourth stroke, First stroke was around 75, second was about 150, third was about 165 and by the fourth they were all seeing around 180-190 and stayed there after that.

I guess timing is next, and after that I'm out of ideas, does anyone have anything else I should be looking at?

eghatch9295

iTrader: (1)

distributor is possibly failing. good spark is not enough to rule it out. there is a guide on here to test the coil and some parts stores can test the ICM.

Fitro

I suppose that I forgot to mention that I either tested or replaced the coil when I was doing the cap and rotor, but either way, that's good, the distributor body could still potentially be the issue seeing as how I didn't replace the whole thing though. I have not had the icm tested yet, is there any way I can do it? Or do I need to take it to an auto parts store?

s13-1uz

Check the MAP sensor as well, a bad sensor can give an incorrect pressure reading to the ECU.

eghatch9295

iTrader: (1)

no diy test for theicm, unfortunately

Fitro

So I got some more time to mess with it and I was checking for fuel pressure just by loosening the banjo bolt on top of the fuel filter. When I turn the key I can hear the fuel pump priming but nothing comes out at the filter, but then to make sure I tightened that one and loosened the banjo at the fuel rail and when I turned the key fuel did consistently come out there????? (I tried it about 3 times to make sure it wasn't residual fuel left in the system or something) So then I unhooked the line at the bottom of the fuel filter and fuel came out there too.

So why would fuel not come out at the top of the filter, but it will further down the system at the rail?

So next I checked the pump to make sure it was new like the previous owner said, and it appeared to be. I took the whole assembly out and it all appeared to be hooked up properly and newish at least.

So now I'm waiting for my banjo bolt adapter to show up for for my fuel pressure gauge, but now the problem is that the car won't start at all anymore unless I spray in starting fluid to get it started then i have to run out and keep spraying starting fluid to keep it going?

I want to take a sledge hammer to this thing and then just swap the motor, but then that defeats the purpose of what i bought this for originally.

I was also going to check timing today, but now it won't run and I'm pretty sure my starter is just about shot from cranking it over too much............ FML

mk378

Detach the fuel return hose (which starts from the fuel pressure regulator) where it goes to the metal line on the firewall. Point the hose into a container. Turn key on but don't crank. Fuel should come out. If none comes out, you don't have enough fuel pressure. This is the best way to test fuel pressure without a gauge. Loosening the inlet fitting at the rail or the filter doesn't show how much pressure there is.

New parts aren't necessarily good.

Timing seems OK as it does run on starting fluid. Seems to be lacking fuel.

civicservice

In the scanner data you posted, your long term fuel trim is quite lean (LongFT1, 15%).

Get a scanner that will let you collect real-time data. There are lots of them that will connect to an Android or iOS system. For example, this one:


connects to the Torque app:

https://play.google.com/store/apps/d...l.torque&hl=en

and will let you collect real-time data on a sixth generation civic.

If your fuel trim normalizes (goes toward 0%) under higher RPM, that's pretty good evidence for a vacuum leak.

You can learn more about what fuel trims can tell you in this excellent video:


Propane is a clean and simple way to hunt for vacuum leaks. Open the valve (without lighting), then let the gas escape, moving around to different engine locations. Change in idle speed indicates you've hit the leak.

You mentioned doing a smoke test, but that may not catch a leak that only occurs on a running engine.

Also, it might be possible to approach this diagnosis more systematically. FASTTEC is a method that works extremely well, both for no-starts and for poor performance like you originally described:


The idea is to systematically eliminate the sources of your no-start or performance issue (there are only 7). You will eventually zero in on the cause.

To move forward on your current no-start issue, it sounds like you're going to need a fuel pressure gauge. Just watching fuel squirt out doesn't tell you how much pressure there is, nor does it let you see what happens as the engine runs. I've had terrible luck with the rental kit from AutoZone (and I think O'Reilley):

https://honda-tech.com/forums/honda-...ic-dx-3297560/

However, this one has been reported to work well with earlier Hondas:

https://honda-tech.com/forums/honda-...-bolt-1171554/

I'm still interested in getting a good gauge that will work on sixth-generation Civics, so if you get yours to work, can you drop a note with a model # and maybe vendor on this thread?

Fitro

I'll try this tomorrow if I have time after work, but I'm definitely leaning towards a fuel delivery issue somewhere at this point as well. My banjo bolt adapter showed up today, so hopefully it's what I needed to connect my fuel pressure gauge, but don't I need the car running to get any sort of results that I need? I mean I suppose I could keep it running off of starting fluid with the gauge hooked up and see what it shows??

Fitro

I just have a auto parts store $30 universal fuel pressure gauge too, but all I did was search Google for a "M12x1.25 banjo bolt fuel pressure tester" and it was the first result on eBay and it's just a banjo with a schrader valve on top, which just about any fuel pressure tester should be able to connect to it. I'll let you know if it works out or not and take a picture of it hooked up if I can remember.

Fitro

I also ordered the Bluetooth obd II reader, because I figure it will be a good thing to have and I'll probably get a lot of use out of it since I usually have some sort of vehicle project.

Also here is the link to the banjo bolt with the schraeder valve.
https://ebay.com/itm/Banjo-Bolt-Fuel...-/251254996574

But I can't guarantee it will work yet, but I'll report back once I've tried it

mk378

To make the fuel pump run constantly without the engine, disconnect the small wire from the starter and hold the key at cranking position. Or you can jump the main relay.

Fitro

Good info, I had never thought of that, but it makes sense.

Fitro

I was back at it for a little bit today and I disconnected the fuel return line at the hard line by the fire wall and turned the key on without cranking and no fuel came out.

So I disconnected the FPR from the rail to see if it would even come out there (because it would come out at the banjo on the rail) and it would, buuuut I had to disconnect the starter so I could constantly run the pump for a few seconds before any would come out.

Then I reconnected that, then I disconnected the return line right where it connects to the FPR to make sure the line wasn't clogged between the regulator and the hard line at the firewall and no fuel at all would come out of the bottom of the regulator even after a good 10 seconds straight of running the pump.

So obviously my fuel pressure is garbage. Now the question is why?

Is the FPR bad because it won't let any fuel through even though the pressure is weak, it still makes it to the regulator and will shoot out the back of the rail after letting the pump run for a bit.

Or is the pump shot because it certainly doesn't seem to push the kind of fuel it should.

I guess the next chance I get I'll pull the pump back out and re-inspect all connections.

Is there a test I can do on the pump with a voltmeter to make sure everything is good electrically speaking?

civic402lx

Oem fpr or aftermarket?
how old is fuel pump?

mk378

It sounds like the pump is weak.

The regulator is a pressure-operated valve. At low pressures it is closed. When the pressure in the fuel rail reaches the design pressure, the regulator opens and lets fuel out of the rail back to the tank to keep the pressure from rising further.

You need a gauge to absolutely diagnose what is going on, but if you think of the two ways the regulator could potentially go bad -- stuck open or stuck closed -- neither of them would cause what you have observed.

Stuck open, the pressure in the rail would be too low and the engine would not start, but gas would come through the return line all the time.

Stuck closed the pressure in the rail would be too high. The car would probably start but would run very rich with symptoms like black smoke from the tailpipe. If it was too rich to start, the plugs would get flooded with gas and it would not help to put starting fluid in.