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Discussion Starter · #1 ·
So I bought someones project d16z6 Del Sol si. Yea probably a bad idea but anyways he says he replaced the fuel pump and filter, full exhaust and the timing belt when the issues started. Not sure if he was being truthful about this though. It barely starts (takes about 5-10 minutes of cranking and stopping with some starting fluid), and cylinder 4 starts firing before the rest exhaust pipe gets hot first. Once started it idles ok, but bogs down above idle and barely makes any power (can maybe hit 35mph by blipping the throttle right above idle). It runs best with the distributor adjusted all the way counterclockwise (I forget if this is advanced or retarded) and with the vacuum hose off the fuel pressure regulator. So far the things I've tested are:

Only engine light code is for the water temp sensor (looks like it was cheaply replaced)
Mechanical timing is good (I triple checked)
all cylinders make compression right above 180psi
Spark is consistent on all 4 when turning it over (used an inline spark tester).
I checked fuel pressure and it is a little above 40 when the car is turned on and stays there when turning it over. However, the fuel pressure drops really quickly when turned off (below 20 psi after like 10 seconds).

Could this have something to do with it? My guess is that the injectors are leaking fuel when closed, causing it to run rich and the pressure to drop off. Also, it looks like the cylinder 4 injector was replaced at some point, possibly explaining why it fires before the rest. Before I buy new injectors, does anyone with more experience think this is really the issue, or do you think it could be something else?
 

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Formerly weebeastie
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The engine coolant temperature (ECT) sensor directly tells the ECU how cold it is, and the ECU adjusts fuel based on the values given by the ECT. So if the ECU thinks its -40 degrees outside its going to dump a ton of fuel to compensate, even though it is not actually -40 outside. I would replace the ECT with a Honda genuine part, make sure the wiring is working properly, fix the CEL and then see what happens.

Sensor is simple to replace, but buy a good one. You will lose some coolant when you pull it out.
 

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Sloppy Jalopy
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have a look and see if the mechanical timing is correct ...you sure..

faulty clt sensor signal or wiring will give troubles..


check the tps and map plugs maybe got switched.
 

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The engine coolant temperature (ECT) sensor directly tells the ECU how cold it is, and the ECU adjusts fuel based on the values given by the ECT. So if the ECU thinks its -40 degrees outside its going to dump a ton of fuel to compensate, even though it is not actually -40 outside. I would replace the ECT with a Honda genuine part, make sure the wiring is working properly, fix the CEL and then see what happens.

Sensor is simple to replace, but buy a good one. You will lose some coolant when you pull it out.
This ^. We had the temp sensor fail at our last event. The ECU thought the engine temp was 180F all the time (better than 0F I guess). It made cold starts difficult.
 

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Unplug the coolant temp sensor that is nearest to the upper rad hose. This is the one the ecu cares about. You can toss in a resistor and bridge the pins if you want it to "act" cold. Online civic manual in my signature, find the troubleshooting section to find the resistnace table for the sensor.

I would unbolt the exhaust manifold, and try to fire it with no flow restrictions. its gonna be super uber rice loud, but it will immediately determine if you have something plugging up the exhaust.

A shitty O2 sensor can make it run weird, but it would never be out of line enough to cause sputtering or shitty firing symptoms.


My bet is ignition module, or you have a stuck fuel injector.



See if it starts with starting fluid sprayed around the fuel injectors. If it lights off easily, you have a big vacuum leak.
 

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Formerly weebeastie
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Unplug the coolant temp sensor that is nearest to the upper rad hose. This is the one the ecu cares about. You can toss in a resistor and bridge the pins if you want it to "act" cold. Online civic manual in my signature, find the troubleshooting section to find the resistnace table for the sensor.

I would unbolt the exhaust manifold, and try to fire it with no flow restrictions. its gonna be super uber rice loud, but it will immediately determine if you have something plugging up the exhaust.

A shitty O2 sensor can make it run weird, but it would never be out of line enough to cause sputtering or shitty firing symptoms.


My bet is ignition module, or you have a stuck fuel injector.



See if it starts with starting fluid sprayed around the fuel injectors. If it lights off easily, you have a big vacuum leak.

Why would you suggest all of the other checks when the ECU is already showing an engine coolant temperature sensor issue? Take care of the obvious first. Get the light off and it likely runs properly. If not, then some of this you offered is a possibility. But to say its probably an ignition module and that bad O2 sensors won't make one run horribly is a reach at best. I realize this is online diagnosis, so yeah, it could be anything, but if the CEL suggests ECT, and it shows all of the symptoms of a faulty ECT or faulty ECT wiring, then that should be addressed first before the can of worms gets opened.


I guess some just like to chase their elbows?
 

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Because the coolant temp sensor is not going to send it off the deep end like you seem to think.


It will certainly help expose certain things though. Especially if the ignition system is weak.


EDIT I think I got your idea wrong. If its messing with the ECT, might be a wiring fault, not a sensor fault. Yeah, wiring would definitely potentially be more than just the one sensor.
 

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Formerly weebeastie
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Because the coolant temp sensor is not going to send it off the deep end like you seem to think.


It will certainly help expose certain things though. Especially if the ignition system is weak.


EDIT I think I got your idea wrong. If its messing with the ECT, might be a wiring fault, not a sensor fault. Yeah, wiring would definitely potentially be more than just the one sensor.
I sort of thought you knew what you were talking about, but if you don't know that a faulty ECT sensor or faulty ECT circuit can send most any early to mid 90's car off the deep end, then you don't know what you're doing. I can't even begin to describe how many vehicles I have repaired that ran horribly, if they ran at all, solely based on a bad engine coolant temperature sensor. I guess if you've never experienced it, then it can't be true. That seems to ring true with a lot of your posts. They are mostly add ons, repeats, or just outright contradictions for the sake of opening your mouth. I guess that's how you got to 7,014 posts. Cool.


To the OP, make sure when you replace the ECT (and that is where to start) that you get one from Honda. They are still available and cheap. If it is indeed the wiring plug, I'm not sure that they still sell those connectors, but it was the same for a long time, so you might ask about that at the dealer as well. If not, I'm sure you can find one on the internet or at a junk yard.
 

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BATSLOMAN GIVES NO FUCKS.
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I was in the middle of sipping some whiskey, and damn near choked. Ha!

All Ive really owned is late 80s and early to mid 90s cars, most of them being problematic cars being sold for cheap. Ive definitely had my share of things being goofy or off, but never ran into a situation where an actual bad ECT sensor caused a bunch of drama.

Wiring bullshit that made the ECT sensor act up? That becomes more involved than jsut an ECT and can definitely cause some grief.


But no, I stand by my words. A bad ECT in of itself, will not cause a bunch of drama or fuckery. It only serves to act as a data source for the ecu, and all it gets in return is fuel mixture command and idle command. There is a reason ECT and IAT sensors back in the day were manipulated for simple bolt-ons.

That same manipulation was a great tool to verify things. Thinking the ignition system is weak? make the ecu think the coolant temp is super cold, and if it misfires, you exposed the weak ignition.
 

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Formerly weebeastie
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Only engine light code is for the water temp sensor (looks like it was cheaply replaced)

Ok..........


Matt were you in the army? I say that because of past experience and you sure are planting your feet hard, and still not paying attention to what the OP said in his first post.

And just so we all know. A faulty Engine Coolant Temperature sensor (that tells the ECU its -40* or +180* outside) on most any late 80's/90's car will cause the vehicle to either run extremely poorly or not at all. I have repaired this issue on multiple Ford v8's, TPI chevy's, Toyota 3VZE's and 22RE's, and on multiple Honda's. I'm not speaking from ignorance or dreams of fluffy clouds in the sky.

Read the quote above. Only code is for the ECT. You're saying weak ignition on a car that isn't throwing an ignition code. But being as it is a 90's Honda, I bet the ignition system is a little weak on it. All of them were unless they've been upgraded, but I digress.

There's a process to every repair. Most times that process has branches that you follow. It starts with the most obvious. The CEL, then branches out from there. You went down 2 or 3 branches without fully addressing the obvious starting spot. Most NOOB's don't need all the answers, they just need direction, then they check the one thing, it fixes it, we never hear from them again, or it doesn't and they post, hey I tried this, and need more help. I wouldn't even have said anything, but it seems here lately you either need to contradict, repeat, or non-logically add on to a post, but again I digress you own something with a Northstar in it on purpose, so yeah. And a Ford 4.6.........hows that intake mani treating you?
 

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....

The code just indicates the ecu isnt happy.

If clearing the code makes it pop back up immediately, its electrically not seeing the sensor properly or at all. If it takes a few driving cycles to re-appear, its a condition that is causing the code.

I tend to go for basics first, then work from there. So much is overlooked. Could be as simple as the sensor coming unplugged, or the connector plug getting dirty enough to not conduct through the harness.

Heck, anything coolant related, is worth at least checking to see if the darn thing is even warming up properly, or overheating.



You misunderstand something about why I mentioned a weak ignition system. The only time Ive seen a bad ECT actually cause drama, is because a weak ignition system could not handle the extra fuel coming form the ecu having a bad reading of coolant temp. I simply add that because, generally in these situations, it is never JUST the one issue. It is a combo of multiple small ones that finally let a deaf and numb driver know something is wrong.




As for my personal vehicles, yes, I own a 4.6 2v ford and a gm northstar. Ive always had a car crush on the FWD caddies, and also made a ton of money off the owners back when the cars were still new enough to warrant the money. Customers got a car back with no codes, a clean cooling system, new timing chain components, and a headgasket and headbolt combo that would last a quarter million miles easily if they actually keep up with maintenance. No more dex-kill BS, and simply changing the coolant every 2 years keeps them running. Ive also worked on a few one owner 93 cars (the worst of the batches) that had over 200k miles on the original engine, never opened up. Treat them like glass by changing fluids often, giving it an Italian tuneup every once in awhile to prevent the cam washout and piston ring sludge buildup that happens with gentle driving, and change the cat converter since it is doomed to plug up, causing one of the many overheating conditions. Everyone seems to zero in on headbolts coming out, when its the main problem maybe 10% of the time. Mine plugged the cat at 110k miles, well, whatever mileage it was at last year.

The ford is fine, runs liek a swiss watch, and even fired up a couple nights ago when it was negative 20*F up here in Wisconsin. The all plastic original intake manifold is fine, since a gorilla never worked on it, damaging the mounting inserts, and the cooling system was clean. Only problem I had to really fix on it so far was the failed thermostat. Runnign around town with the coolant temp at 120 degrees nearly 100% of the time meant it got far worse than normal gas mileage. $7 thermostat and $20 in coolant later, it was getting mid-teens for mpg, and running strong. SCT X4 tuner with a MO's tune made it even better. Right rear tire is wearing out quite fast.....





Im not sure what you mean with the Army comment. I would guess you are not, yourself, prior military.
 

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Formerly weebeastie
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Im not sure what you mean with the Army comment. I would guess you are not, yourself, prior military.

And yet again, your guess would be wrong.

I served in the United States Marine Corps
 

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BATSLOMAN GIVES NO FUCKS.
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And yet again, your guess would be wrong.

I served in the United States Marine Corps

whats your favorite flavor crayon?




sorry, I had to. every marine I meet, I have to ask
 

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Discussion Starter · #16 ·
hey sorry for no update but to give y'all closure I cleaned out the injectors using the throttle body cleaner method and it runs great now. I unplugged and plugged back in the coolant temperature sensor while the injectors where off and the code for that went away too.
 
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