stealth723

I bought a 94 civic EX with a blown D16Z6 engine, and put a 92 D16Z6 back in. Same engine, but small differences.
The yard told me the engine surged, so I did some research and thought I'd replace the intake manifold gasket just in case, and I used the old intake manifold, 94 civic engine, on the new 92 civic engine.
I was in for a surprise when I went to fill the coolant. There was a node on the pipe that runs between the water pump and the thermostat behind the block. Upon looking at the old manifold, I realized the difference was how the coolant lines are routed through the throttle control and cold idle sensors. The new design omitted the node on the pipe adjacent to the water pump. So, I just stuck a hose over the outlet, and blocked it with a bolt and clamp. Now, the engine is surging.
So, as far as I can tell, no white smoke or anything to indicate a blown head gasket. I replaced the PCV valve. I couldn't find an EGR valve anywhere along the fuel lines, unless it is really unconventional looking. Also, I found an article where someone used this intake manifold on another block, and had the same issue with the coolant line, and they rerouted it, but their pics are kinda vague:

https://honda-tech.com/zero...09513

So, if anyone knows anything about what could most probably be causing it to surge in this situation, or if you could better explain the scheme of the coolant line routing, the help would be hugely appreciated.
I adjusted the throttle cable, and at low RPM's it's fine, especially after it gets up to temperature, but it still does it when cold. I guess it actually did start doing it once even after it got hot. So, I am pretty much at a loss for what to do. Again, thanks in advance.

stealth723

Also, the engine I put back in was coupled with an auto tranny, it now has a stick on it. And, upon reading, it says that only the auto has an EGR valve, so does the EGR valve go someplace to the block that it's not going now that there is a manual intake manifold on an automatic block? Or would the EGR system have nothing to do with the surging?

Pothole987

I had the same problem with mine and i had the coolant lines hooked up wrong.
http://www.slhondaparts.com/br...=true

i used this diagram to understand how they went on the engine
also, my car was an automatic (1995 civic ex) and doesnt have an EGR valve.

and also, the car may be airlocked causing the surging.

stealth723

Thanks man, you're a lifesaver! I have been hard pressed to find ANYTHING about this at all, let alone someone who has had this specific problem. Also, is there more to bleeding the system than just opening that valve on the front of the head? And should you have the car on or off? Warm or hot? Bleed multiple times?

stealth723

Also, the brokenness of the photo is kinda confusing. Do you know of another source for a diagram?

Pothole987

for bleeding the system, i'd take the rad cap off and squeeze the hoses (when the car is cold) usually what i do when i have to bleed the system. the bleeder on the front of the head works too ( if it has one, mine doesnt )

and that was the only diagram i could find. i used that one (printed it off) and just looked where the hoses where heading.

fastazzcivic08

your problem is your IAC valve (idle air controll valve) it reads the temperature of the coolant running thrue it and adjusts your idle. you probably just dont have it hooked up to a coolant feed or something. it is the bigger sensor on the back of the manifold that has 2 10mm bolts mounting it there. all it needs is a coolant feed and return to your coolant plumbing and it should fix the fluxuating. i have never seen one go bad but there is always a first.. good luck

stealth723

Alright, I observed the layout of the coolant lines, and it is completely factory for 94. I took both the fast idle and the idle air control valves off and cleaned and reassembled them, and put them back on the car, and now it surges drastically when cold, but as soon as it's warm, bam, smooth idle. Now, when it's surging, if I unplug the idle air conrol valve, it smooths right up. And while it's loping, it I pinch the coolant feed line off, it doesn't change anything, so it's like the coolant line coming out of the intake manifold to the two valves is somehow obstructed. Would having the exhaust gases introduced into the coolant the way Honda has it cause crap to fill the cooling system lines, or cause it to surge? At least one of the hoses needed replaced where it was virtually closed off from carbon. I thought that would fix it, but it didn't.

stealth723

For the record, there is a hole in the exhaust side port on the head, and it leads to the cooling system outlet in the intake manifold. I can't figure out if it's to provide vacuum/pressure, or if it's to warm up the coolant quicker. I just knw it's super dirty, ad unless coolant just doesn't go in there, I can't imagine it not dirtying coolant like mad.