gearhead2228

How's it going honda tech. Hope I'm posting in the right spot. Pretty new to posting around here but have been trolling for the past 6 or 7 months ever since I got my 88 hatch and dropped a zc in her. Still pretty new to the honda scene but have gained quite a bit of knowledge in the past year, a lot of which has come off here.

So I've been up and down the forums, and have found a lot of useful tips but nothing that can solidly ID the problem I'm having.
Like I said I have a 88 ef hatch with a zc, all motor. No mods other than header, full catback, and cold air intake.

Basically in a nutshell the problem is that when I'm accelerating, all the way up until around 2-3k rpms the car will hesitate like it's stuttering or bogging (the engine shutters really bad). After 2-3k the engine kinda feels like it finally kicks into gear and gets going. This happens through all gears but is the worst starting in first from a complete stop. If I keep the rpms High, above 3k it drives smooth. Also while idling the rpms will for the most part be constant, but feels like it steps kind of intermittently.

Now I know it can be quite a few things from fuel system to timing or even vacuum leak. But what I'm stumped by however is that this only seems to happen when the engine gets up to operating temp, it doesn't happen when the engine is still cold. The other weird thing is that it gets significantly worse when the engine is under higher electrical load (when the lights, heater, or music is turned up too load). Also When I do turn on the lights or anything not only does it hesitate even worse when accelerating, but it'll start to idle at around 300-500 rpms and the engine will start to shudder like it's going to stall. Lastly, the whole time this has been happening there have been no CEL at all.

To try and fix this I've replaced IACV (fixed my hunting idle problem). the spark plug wires with ngk wires (which helped a little but went back to doing it again). Ngk spark plugs are good. New pcv valve. I've checked for vacuum leaks and found none. the fuel filter and pressure regulator are good. Ran some injector cleaner in three tanks of Gas. Seafoamed the intake through vacuum line. New air filter. Alternator and battery are 100%.

I guess I just can't seem to find what would be causing a hesitation issue that occurs only when at operating temp, and gets worse when under electrical load???

I've recently read that the ECT sensor can go bad, and when the engine is at operating temp. It will be telling the ecu that it's still not warm enough which would cause more fuel to be dumped in making it run rich. Could this be it?

Maybe I'm just overlooking something??

Any advice at all would be immensely appreciated since I've been trying to conquer this one issue for months now; and thank you in advance for any replies!!

gearhead2228

Bump for some help!! Anyone got any ideas??

bambam

Can you pull the spark plugs and post pictures of them?
Youve also checked cam timing?
Have you checked ignition timing with a timing light?

jdmjunkieXL

Inspect tps per service manual

gearhead2228

Thanks for the replies! I have checked the tps with a multimeter and the voltages checked out good when the throttle plate is closed, open, and changes steadily as you go from closed to open.

I don't know if I mentioned earlier but I did check the spark plugs and they were good. Almost brand new ngk's.

If it was the timing wouldn't the hesitation be happening when the engine is cold as well, and not just when it gets to operating temp??

bambam

Not necessarilly. Ignitition timing changes with coolant temp. And there is a relationship between cam timing and ignition timing. Cam timing doesnt change. Ignition timing does....based off of various sensor inputs. So, cam timing being off can have an unnoticable effect when cold, and as the engine warms up and the ignition timing changes, can become more pronounced.

gearhead2228

Interesting, I didn't know that. Thanks for the advice, I'll check timing within the next couple days and post back with the results. Hopefully that's the issue.

jdmjunkieXL

The tps is faulty

gearhead2228

So an update to the problem!!!! I finally got around to checking the timing the other day, as you guys suggested (i hadn't been driving my car at all because I was waiting to get an exhaust on). The cam timing is about as perfect as you could get it. And the ignition timing is pretty spot on as well. There's a few pics of the cam timing below. So back to square one I suppose. Anybody else got any ideas? This problem is really killing me, I even talked to another guy in my neighborhood with the same zc/Pg7 setup and he's having the same issue.
???????

gearhead2228

Also to jdmjunkiexl I checked the tps and seemed to get the correct voltages. Could it still be faulty even though the voltages read ok??

gearhead2228

Bump for any suggestions?!

gearhead2228

Anyone???

daxr

You're a tooth off on each cam, unless there is a lens distortion in the picture. At TDC you should be able to draw a straight line between all four timing marks, that bisects the cam gear mounting bolts. See how a line drawn between the outside cam marks doesn't cross the inside cam marks, or the cam gear bolts?

on edit - boneheaded wrong on the above - my apologies. The inner marks aren't exactly opposite with the outer. To line up, you draw a line between the center cam bolts that crosses both inner marks. Ignore the outer marks, of course. It looks like the timing is set up correctly there, so the problem should be something else.

gearhead2228

Hmm.... are you positive that's how it's supposed to be with the zc dohc? I know that that's true for other motors but I'm pretty sure that it's supposed to be that way on the zc. Even the diagram in the manual shows that the two "up" arrows aren't supposed to be straight up, but rather slanted inward like they are.

gearhead2228

Here's a screenshot from the zc manual.

daxr

Ok, my bad - counting gear teeth they aren't perfectly opposite each other on that one, so there wouldn't be a way or a reason to line up the outer ones. It looks like timing is good...

gearhead2228

No worries, I really appreciate the reply! Any other ideas??

daxr

The thing where its worse with a load on the electrical system - maybe look at the alternator diodes. Its an easy test with an old Sun battery/charging system tester, or if you have a DMM you can set it to ACV. If it shows more than .4V AC, that's where you can have problems. If a diode is going out it throws the wrong kind of voltage into the system, and can cause all kinds of off symptoms. When the alternator is working harder it could accentuate the problem enough to disrupt the ignition system.

Its pretty uncommon, but eays to check for.

fcm

Redo your main grounds, DO NOT just eyeball them, disconnect/clean/reconnect.

Neg(-) batt. post and cable clamp, batt. to chassis ground, chassis to engine ground, rad support to VC ground and the thermostat ground(s).

Poor grounds are affected by temp. and load, even if they are not your problem redoing them is the only way to elliminate them as the possible problem and it sure can't hurt on a 26 year old car. 94

gearhead2228

Awesome thanks for the help! I'll take a look at/clean/replace all the grounds today and see if that solves the problem. Like you said, probably a good thing to do anyways. If that doesn't work I'll check the diodes as well. Thanks for the help guys, anymore, thoughts are welcome?!!

gearhead2228

No luck with redoing the ground wires any other ideas, anyone??!?!

fcm

Have the alt./charging system tested, any batt/alt. shop, [Interstate Batteries] will do it for free in the car.

When was the fuel filter last changed?

What is the fuel pressure, test it? 94

gearhead2228

So i just replaced the fuel filter yesterday, and I readjusted the throttle cable because it was loose. It seemed to help a little; It doesn't hesitate quite as long and the idle picked up to where it's supposed to. The problem is definitely still there though. And now, another weird thing is that, about 60% of the time when I stop at a stop light and go back into neutral the idle will bounce around, up and down from 1000 to 400 for about 15 seconds and then it'll steady out back at ~700. It's almost like the ecu can't find the right air to fuel mixture or something?.... I haven't got the alternator checked yet. Thoughts? Thanks again for all your help!!

gearhead2228

Ran over to interstate battery today and had em check my alternator. They said it checked out 100%.

holmesnmanny

Could be a bad oxygen sensor. I would seafoam and check for an exhaust leak before replacing with a new Denso oxygen sensor.