Hi all

I have a 97 civic with a pretty bad misfire. It a random misfire

It idles perfectly, then when I open the throttle it bogs and misfires. Sometimes it cleans up and revs and sometimes not

things I have done:

1 Fuel pressure is 36 rising to 42 when throttle is opened

2 removed each spark plug wire one at a time. All are contributing to engine power

3 changed cap to new cap-it was messed up pretty good. No improvement. rotor is fine

4 pulled exhaust to check for clogged catilitic converter. No improvemnt

5 checked map sensor. 3v key on engine off. 1.x at idle. Respond quickly when throttle is blipped

6 throttle position sensor checked. .52 at min throttle, 4.4 at full throttle. No gaps or jumps

7 I checked the tps and map signals
at the ecm-they are getting there ok

8 changed plugs and wires for known good set from my teg. No improvement

I haven’t checked spark advance yet but it’s my next check

Anyone have other ideas???


Thanks

Chay

 

possibly a failing ignition coil

 

How about a bad ECT or IAT sensor ? There are OHM values to check proper function in the FSM.

 

Compression test and if all cylinders are low then valve adjustment and check your timing belt timing, straight away replace coil with the one from teg and check. Your fuel pump may be putting out enough pressure but not enough volume. If you have a preasure gauge with a bleed valve/ tube while car is running press bleed button with bleed tube into a 500 ml or 1/2 quart transparent bottle it should do pretty close to 500 ml in less than 25 seconds without the car dying to affirm enough volume. With the engine cold hook up a scanner and see what the ECT temp is obviously should be close to ambient temp. I would also do an injector balance test to check if restricted.Just what I would do.Good luck

 

Right, I had this problem on a non-Honda and it was the coil(s). If you are getting fuel, your spark plugs, cap, and rotor are good, no exhaust problems, then it might be the coil.

 

I have ordered a new distributor, and a map sensor. Hopefully it's one or the other. Suspect distributor over the map but we'll see.

I scanned the IAT and the ECT. Also the TPS. They all look fine. I don't have a scanner sophisticated enough to do a cylinder drop.

It sure acts like a bad map, so even though it tested ok, I'm suspicious. I did look at the injector duty cycle. Out of gear the DC went from about 5% at idle to about 25% when the throttle was blipped. So I am injecting more fuel---this also leads me to believe it's spark somehow.

I forgot to mention it, but I did a compression check as the first thing I did- My tester is a bit suspect but I measured 120+-5 across all the cylinders...certainly enough that they should run. I might do a leak down test but the compression tells me it should run ok.

I would expect if there was a volume issue with the fuel I would see a drop in pressure when I get the misfire-There is a gain not a drop-fuel is not the issue. I did just have a fuel pump failure-the new pump is literally 2 weeks old. If the distributor doesn't fix it I'll run a volume test.

Interesting idea about the timing belt-it could have slipped....Maybe that's what is going on. It is certainly a weird one like that. I'll check the timing marks.

Thanks,

Chay

 

Try the new distributor, then go from there. I’m thinking it’s that, and probably not timing or fuel.

 

I’m not that lucky. Added new distributor and map sensor. Still misfires. Now it will misfire when it idles down.

then sometimes it will clean up and other times not

i checked the flow on the fuel pump by disconnecting the fuel gauge and putting it into run mode. Fuel squirts out very vigourously

I had a small problem with my comp gauge last time out so I rechecked it. 170-180 on all 4 cylinders

im starting to think ecm or something weird. With the injectors. I may pull them and check their spray pattern next

chay

 

[QUOTE=cfoss;52365373]Hi all

I have a 97 civic with a pretty bad misfire. It a random misfire

It idles perfectly, then when I open the throttle it bogs and misfires. Sometimes it cleans up and revs and sometimes not

things I have done:

1 Fuel pressure is 36 rising to 42 when throttle is opened

2 removed each spark plug wire one at a time. All are contributing to engine power

3 changed cap to new cap-it was messed up pretty good. No improvement. rotor is fine

4 pulled exhaust to check for clogged catilitic converter. No improvemnt

5 checked map sensor. 3v key on engine off. 1.x at idle. Respond quickly when throttle is blipped

6 throttle position sensor checked. .52 at min throttle, 4.4 at full throttle. No gaps or jumps

7 I checked the tps and map signals
at the ecm-they are getting there ok

8 changed plugs and wires for known good set from my teg. No improvement

I haven’t checked spark advance yet but it’s my next check

Anyone have other ideas???



Chay[/QUOTE

Thanks



remove the fuel injectors, send to RC injectors, they will clean and replace parts and return. It helped my 94 Delsol Vtec B16 motor with the problem you describe. Search YouTube for videos.Please update me on results. Good luck.

 

I'm surprised you haven't checked your ECT sensor like was suggested. You say you get more fuel when it's missing. And it's doing it when warm. If the ECT says engine is still cold it pumps too much fuel (open loop) instead of proper fuel trim. Sort of matches up to everything you've mentioned.

 

Ended up being injectors. 2,3 had poor spray patterns to say the least. There are screen filter in the tops of the injectors. They were pretty gummed up

i used the spray can/9v battery method to clear the injectors. Didn’t take long

Runs great now. Ready for another 200k


Chay