jimcat3

My cars an 86.5 w/AA chip. I just finished painting the intake manifolds. I took off the plastic intake tubes, air filter cover, then removed the 2 cast aluminum side chambers and left the crossover tubes in place. I then preeped and painted and put all back together and Voila! ...now it won't idle, runs fine, but won't idle.
While I was at it: there was 1/2 cup of oil in each side chamber which I drained (is it suppossed to be in there? and I replaced the spark plugs.
I also noticed a rubber bellows was torn (leaking) when I removed it originally and I did a quick fix with another rubber hose and 2 clamps when I reinstalled untill I can order an original part. The plugs that were in there were NGK's with 2 prongs. I used standard Bosch platinum 4's as replacement.

I am perplexed (what else is new). Any suggestions?

no doubt

It's probably just a simple air leak...but there's no harm in disconnecting the electrical plug to your ISV (idle speed regulator). Your ISV has a limp home mode (when disconnected) that is worth testing to see if it helps your idle.

jimcat3

Thanks "no doubt" I think I did find a possible vacuum leak (a bad tube fiiting). I just taped it up and I'm getting a low idle. I have a vacuum gauge that reads -6 psi at idle and bounces up to -20 at 3500 rpms. Is this a normal reading?

aggravation

When you say it won't idle do you mean it idles too high, or it's too low and you have to constantly give it throttle to keep it running, or it cycles continuously from too low to too high?

jimcat3

craig, it quits out/stalls/shuts off completely, unless I give it gas at a stop to keep it running. I just picked up some new hose and a t fitting and replaced some leaky vacumm fittings. It now idles but is idling a little low: idling even at 400 RPM and from the intakes I get a strange "bang" type of noise every 20-30 seconds!

SharkSkin

Is the "bang" in the intake or out the exhaust? If it's out the exhaust it could be misfire followed by ignition of the unburned fuel in the exhaust. Does the exhaust smell too rich, like it's blowing gas out the tailpipe? These cars tend to dislike multi-electrode plugs. Get a set of Bosch Copper single-electrode plugs in there and see where you stand.

One way to check for vac leaks... Get a plastic bottle, like a bicycle water bottle. Attach a hose to the outside of the lid that is of an appropriate size to connect to the brake booster line or other vac hose that would ordinarily see manifold vacuum(as opposed to "port vacuum"). Glue a short piece of fuel line to the inside of the cap of a suitable size to hold a cigarette. Poke a small hole in the side of the bottle. Set your air compressor regulator very low, ~2-3 psi. The bottle/cig assembly should be put together such that air blown in through the side of the bottle has to go through the cig (no leaks).

Attach the outlet of this contraption to your intake manifold. Light the cig and seal up the bottle. Now apply the low air pressure from the compressor to the hole in the side of the bottle. If you use a slow/long burning cig like American Spirit this setup will get you about 10-15 seconds of smoke(the cig burns VERY quickly). Look for the smoke coming out of whatever vac leaks you have.

This worked very well for me -- Less than $15 for all parts if you don't smoke and have to buy a pack just for this(I had the compressor already). I suppose you could also use a mityvac, connecting to the pressure port. Blowing into the hole in the side of the bottle won't be enough; you need more pressure than you can generate by blowing into the bottle.

Or, you can pay $1,000 for a professional smoke machine that does the same thing.
http://www.mainlineauto.com.au/produ...hine/index.htm
http://www.foranythingautomotive.com/smoke.html

[Edit]
I've had a couple of PMs asking about this. I've attached a pic of my "smoke machine". I was inspired by someone's mention of blowing smoke into the intake manifold to check for leaks... unfortunately, my leaks were small and I couldn't accomplish much this way. I just couldn't get the smoke to move into the manifold fast enough to accomplish anything. Then I hit on the idea, why not just use a "power hitter"... these things were common as dirt back in the 70's, any rock concert would have several people passing them around. So I went to a couple of local "smoke" shops, the first attended by a clerk who had no idea what I was talking about. He suggested that I choose from his assortment of ***** pumps after I described what I was trying to do -- I declined. I went to the second shop, and they had two of these on the shelf @ $10 ea. but the girl had no idea what they were for. What's the youth of today coming to, anyway?

All I had to do was tape a piece of fuel line to the fitting on the cap and I was good to go. The hole on the side was already there. This device is easy enough to fabricate out of any plastic bottle, but the reason I went off in search of a ready-made solution is that I recall the original having a check valve on an intake port, and I would have been able to do the job without using the compressor.
[/Edit]

Mrmerlin

I would run a continutiy check on the plug wires looking for about 3 ohms from each connector to connector.

also check the coil wires for corroded ends.

Since you changed the plugs it sounds like you have either a crossed wire ( check the correct plug firing order) or a damaged wire thats letting hi tension leak

Note the best plugs for the 928 are usually the least expensive, Bosch supers with copper tips are the way to go, WR7DC IIRC

. Run a test at night open the hood and look for sparks jumping

Mike B

+1

SharkSkin

JHowell37

Check to make sure you didn't get two plug wires crossed. It's an easy mistake.

marcoturbo

Dave, thanks for the pic

Glenn Evans

Most automotive vacuum gauges are graduated in inches of mercury (inHg), with a range from 0 (atmospheric pressure) to 30 inHg (in the vicinity of a vacuum at mean sea level ambient pressure).

If your idle reading is, in fact, 6 inHg, you definitely have a leak in the intake manifold.

Mrmerlin

or the cam timing is way off

Glenn Evans

Correct, but jimcat3 didn't say that he'd touched the timing belt.

Mrmerlin

that could also account for the bang in the intake, a badly timed cam. So check the timing