85 Civic Si idle again

I posted about this a while ago. After it has warmed up the car will not sit at idle. The revs cycle between about 1200 and 2000 every second approx. Following suggestions here I drained the radiator and
refilled it with 50/50 coolant/water, and I inspected all the hoses/lines looking for leaks. Everything looks fine. I also blasted carb cleaner into the manifold. I have seen suggestions that I need to inspect the O2 sensor and an idle control valve, but I don't know how to locate these. The engine layout pictures I've located are from the US, while this car was sold in Japan, 1.6L engine.
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Gib Bogle wrote:

BTW, I'm having trouble finding out the designation of the engine in this car (because it is a Jap import). It is definitely a Civic Si, 1.6L, DOHC, PGM-FI, and the NZ registration shows it as 1985. On the tag in the engine compartment, among the Japanese characters I see: E-AT AT-1024071 ZC-1032126
The closest match I've found (Wikipedia) is the D16A3 engine, which was in the 86-89 Acrua Integra, but the fuel control of this engine is OBD-0 MPFI, whatever that is.
I need to know the engine series ID in order to locate an engine diagram, so I can find the IACV etc.
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On Hondas sold in the U.S., the engine type is stamped on the block, a little below and to the right (as you stand at the front of the car, facing it) of the distributor housing. You may have to wipe off old grease to see it. The letters etc. are around an inch high.
The parts diagrams at bkhondaparts.com may help you find the IACV.

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Elle wrote:

I've tried to locate the number stamped on the block, but it isn't possible to see the block because the camshaft housing is wide (this is DOHC) and there is hardly any clearance between it and the chassis at the front.

Thanks, I'll have a look. I'm not even 100% sure that this engine has an IACV, BTW.
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Elle wrote:

This doesn't work.
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http://www.bkhondaparts.com/billkay/jsp/home.jsp
Try also the free Factory Service manual linked at http://www.honda.co.uk/car/owner/workshop.html , under PGM-FI system.
The 1985 Civic does not have an IACV nor EACV. The 88-92 have an EACV. The 93-95 have an IACV.
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Elle wrote:

Thanks Elle, that's very useful, especially the service manual.
I have (fingers crossed) fixed the cycling idle problem. Following advice I found online, I screwed down the plastic part inside the FITV (fast idle thermo valve) and blasting carb cleaner through the small throat within the main throttle throat (I'm not sure how to refer to this - it houses the butterfly valve that is directly controlled by the throttle cable). Now the idle speed is down to about 1000 when hot, a bit excessive but I can live with it.
There is another problem that I have started to track down, possibly related to the idle issue. The car runs fine but misses (stutters) under load. If I accelerate moderately it goes up to motorway speed without complaint, but under hard acceleration, or up a hill, there is a lot of misfiring. I'll start by replacing the sparkplugs, then check the sparks with a timing light. A question: I've seen the PCV mentioned as a possible factor in misfiring under load. Do you know if the DOHC ZC has a PCV?
BTW, in my defence, I haven't looked at this car for about 3 years. I gave it my daughter to use, and she probably didn't want to bother me with it. Now I have it back again, and want to get it in a fit state to sell (which I will do reluctantly, because it's a great little car that I inherited from my dad).
Thanks again.
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wrote

most likely.

don't forget your plug wires and distributor cap/rotor. Wire insulation breaks down with age,can cause loss of spark.
--
Jim Yanik
jyanik
  Click to see the full signature.
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You saw in the service manual how to make an adjustment to the idle, right? http://media.honda.co.uk/car/owner/media/manuals/WorkshopManualCivic84-87/62sb200/11-22.pdf
Small caveat about the cooling system: After replacing the coolant, one has to follow to the letter the instructions on purging it of air. Where it says to make sure the fan comes on twice, I learned the hard way this means letting the engine idle for typically 40 minutes, even in summer temperatures, until the fan does this. This is for my 91 Civic.

I would not bet the problem is the PCV. OTOH, if it's never been replaced, it's due. It's cheap enough.
It should. See for example http://www.bkhondaparts.com/billkay/jsp/prddisplay.jsp?catcgry1=CRX&catcgry2 85&catcgry3-R+SI&catcgry4=KA5MT&catcgry5=BREATHER+TUBE-OIL+FILTER&ListAll=All&vinsrch=no&systemcomp=List+All&prdrefno=&quantity=0&act=&count=0&hidSwitch=&hidIrno That's for the 85 CRX Si, which according to http://www.superhonda.com/tech/honda_engine_codes.html , has a ZC engine.

These old Civics cannot be beat. I keep an eye for buying another.
Over the years the wisdom on tuneups is to use strictly OEM for wires, plugs, distributor cap, and rotor. It's amazing how often a running problem is reported here and a new set of wires fixes it. You sound experienced, so just saying for the archives.
The problem under load makes me suspect either the catalytic converter (based on what others report here and reports on the net) or the O2 sensor. Then again from checking BKHondaparts.com, I am not sure your Honda came with a cat converter.
If it's the original O2 sensor, consider a new OEM one from www.automedicsupply.com. It should go for under $40. Even if the old one still "works," they do degrade over time before full failure. Might improve your fuel mileage. I have used automedicsupply for an O2 sensor and was pleased with the price, speed of shipment, and total cost.
A tuneup sounds very prudent, by the way. If nothing else, it establishes a baseline so multiple problems are less likely to confuse diagnosis. Plus a tuneup is due every so often anyway, so it's not like money is being thrown away.
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Elle wrote:

http://media.honda.co.uk/car/owner/media/manuals/WorkshopManualCivic84-87/62sb200/11-22.pdf
Yes
Thanks, I'll bear that in mind.

http://www.bkhondaparts.com/billkay/jsp/prddisplay.jsp?catcgry1=CRX&catcgry2 85&catcgry3-R+SI&catcgry4=KA5MT&catcgry5=BREATHER+TUBE-OIL+FILTER&ListAll=All&vinsrch=no&systemcomp=List+All&prdrefno=&quantity=0&act=&count=0&hidSwitch=&hidIrno Something is screwed up with that bkhondaparts site. My Firefox says it can't find the server. Google gives plenty of hits for bkhondaparts, but I can't go to the sites.

I don't believe I have a cat converter.

I'll look at the O2 sensor after checking out the electrics.

Yes, I'm sure you're right. I have to overcome my suspicion of mechanics ;-)
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Gib Bogle wrote:

Your engine is not from the car it it's in now. There is no 1985 Civic Si - I had one of the first ones in 1986. They have a fuel-injected 1.5 litre 12 valve engine. Look for the engine (not chasis) serial number. A dealer or mechanic can tell you which engine you have from that.
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mjc13<REMOVETHIS> wrote:

I think you are probably referring to cars sold in the US. This was sold in the Japanese domestic market, and imported used to NZ. According to Wikipedia:
http://en.wikipedia.org/wiki/Honda_Civic_Si
"Honda first adopted the Si badge for the JDM Civic in November of 1984. Mainly offered in hatchback form (four-door Si's existed but were rare), the main aesthetic difference was the slight bulge in the hood, which accommodated for the 1.6-liter I4 DOHC engine. Designated as ZC in Japan and D16A9 in Europe, the new engine put out 130 hp (97 kW). Since compact cars at the time typically made less than 100 hp (70 kW), the Si proved popular amongst tuning enthusiasts.
The United States saw the release of the Civic CRX Si in 1985 with the Civic Si following in 1986, replacing the Civic 1500S-which shared the non-fuel injected 1.5 engine as the rest of the Civic lineup. The trim of the Civic Si was geared toward those who wanted the performance of the CRX Si, but with four-seats. Standard equipment for the Civic Si hatchback included a removable glass moonroof, tilt steering wheel, a full-width taillight panel and color-keyed front airdam and roof spoiler.
Unlike the JDM Si, which had a 130 hp (97 kW) ZC engine, the USDM Si featured a 1.5-liter, 91 hp (68 kW), 12-valve SOHC engine designated EW4/D15A3 (the latter code was used for 1987 but with same specs). [1] The Civic Si also saw a release in New Zealand and Australia in 1987, and sharing similar specs to the USDM Si."
The ZC number I gave is presumably the engine number, consistent with other info I've managed to dig out. The engine seems to get referred to as the ZC DOHC 1.6L. The problem is that although it's easy to get info about the models sold in the US, this is not true for those sold only in Japan. I suspect that something similar was sold in Europe, but I don't know the model name. BTW, the markings on the back of my car say Civic Si Aerodeck, but Aerodeck usually refers to an Accord model. Mine is a 3-door with a very similar shape to Accord Aerodeck pics I've seen, but not so long I think.
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Gib Bogle wrote:

I stand corrected - I passed over your mention of it being a Japanese import, or misunderstood...anyway, what Elle wrote about looking for the engine serial number as stamped on the block, is your best bet. That will give you the specific engine type.
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Gib Bogle wrote:

I suggest you take the car to someone who knows how to diagnose and fix vehicles.
Jeff
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Jeff wrote:

I suggest you read the whole thread before posting ;-)
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