Car: 1987 Coupe, Stock TPI Ported, Accel 24 lb/hr injectors, AFPR, AC Delco Plugs Ground electrode, MSD 8.5 mm SuperConductors, stock batch fire computer

I am in the middle of a plug and wire change right now. The #2 and #4 wires melted a few weeks ago because they touched the header tubes and I've been driving around with a band-aid since. Now I'm fixing it. I haven't noticed too much of a problem with how its running.

I pulled the #2 and #4 plugs, and they are completely clean, with signs of white but not too lean. The #6 plug looked healthy, and the #8 plug was less white than #2 and #4, but it wasn't stoich by any means. The left bank all looks great. That what makes it confusing to me.

I started the car up with the right bank plug/wire change complete, and the car idles nice, but within 20 seconds, the right airtubes were too hot to touch, the left side was still cool. it keeps burning the little rubber tube that goes from the hard line from the airpump to the header.

Does this sound like defective injectors?

I've been really gentle with the car because I am leaving for the AirForce on Tuesday and I wanted it in good shape to drive whereever I need to take it.

How do I check injectors? Can I do it in the car?


[Modified by NoWorries, 5:02 PM 2/6/2003]

 

I am thinking a bad o2 sensor... there is one on each bank, right?

 

Thats a good thought, but in '87 they just had one, and it's on the left(drivers) bank.

My Air Fuel guage is running off of the left bank also, with a seperate O2 sensor. It shows on the high end of stoich most of the time...

 

There is only one O2 sensor in the 1987 L98, located on the driver side.


Is the idle a little rough? If so, it could be anything from a burned exhaust valve to worn valve springs to improper valve lash settings...and then it could be a bad injector driver circuit as well.

Generally, if you run a cylinder rich on fuel, or with poor valve sealing, the fuel will burn in the header tube and make it glow red. Stock L98 springs with high mileage are famous for not putting enough closing pressure on the valves to seat them fully.

If it has a bad injector or two on one side, it would make hot re-starts take a long time. Of course, you would also see a blackened sparl plug.

If you suspect one cylinder is not making the power, you can do a balance test. Either follow the official balance test procedure from the GM manual, or just pull one injector clip off while the motor is idling and note the RPM drop after it stabilizes, then plug it back in, and do the same for the others...the one with the least RPM drop is running lean or not firing or has poor valve/ring sealing. The one with the greatest RPM change has either a rich mixture or just makes more power than any other.


As for both sides of the headers getting hot...well I would think they should get hot equally in an ideal world...but we don't live in one of those. :D

 

Thanks for the reply! This is some excellent info, I'm going to head out to the car and see what happens.

The idle is rough, but I'm running a 214/218 duration .452/.465 lift 112 sep cam, (multiplied by 1.6 rockers), it is not any rougher than when the engine was new 90 hours and 6,000 miles ago.

The heads were done at the rebuild, 3 angle valve job, and springs to match the cam, they should be sealing up fine, whether or not one is burned is another matter. I just reset the valve lash about 1,000 miles ago, so maybe I screwed that up.

Hot starts are better than cold starts, so that would rule out a leaky injector, right? Gas mileage is also ok, at about 23 on my last freeway trip. Can an injector get plugged or anything like that?

You made me think about the valve lash now, I'm pretty sure I did it right, setting the cylinder at TDC, and torquing until there is no pushrod spin, then half a turn. If I remember correctly, #2, both valves, was one that needed to be tightened more than the others.

Its too cold to do any actual work on the car tonight, but I'm going to go check the injectors now, and then I'll back all of the rockers off and reset the lash tomorrow.

Thanks again for the comprehensive reply.

 

Ok, I ran into some trouble, and I haven't been able to do the balance test yet because I spilled coolant into the oil! So as soon as I do an oil change, I'll get to the balance test. I relashed all of the valves, #2 may have been a little tight, but not enough to keep it open, I don't think.

I have a new question now though, what would cause the car to not hold fuel pressure with the engine off? I noticed that it goes from 52 psi to 0 psi in less than 15 minutes...where-as I used to notice it still having 30+ psi overnight.

:seeya

 

I would think a 30 minute fuel pressure bleed down is not really bad at all, but other than injectors, the pressure regulator could bleed off fuel as well, but I don't see how it can make one bank run leaner than the other.

Hmmm.....you don't have all 4 injectors on each side banked together do you? I'm not sure but if that is teh design the harness uses...maybe a bad injector driver would effect just one side of the motor. Of course, the injector driver is built into the ECM.

 

Hmmmm...I thought I was onto something when the oil pressure was bleeding off really quick, thinking an injector wasn't closing all the way, but that shouldn't make it run lean, especially since the O2 sensor doesn't even know this bank exists. I still think its bleeding too fast, I just don't know if thats related to the problem at hand.

The stock computer is a Batch fire I believe, no bells or whistles here, just fire off every injector at the same time.

I keep putting things in front of the project, and I'm afraid its going to come back and bite me. I haven't gotten around to the balance test. I had the thought that I'll be picking up the car in the middle of summer, and if I have to drive through any cities, I needed to fix my cooling system ASAP. So I finally got around to installing my new fan shroud and modifying my Permacool fan to fit on the shroud. Now it should be good to go in the hottest of hot climates. That took a lot more time than I was expecting, and I had the hood up the whole time. So I finally got ready to start the car and the battery was dead!

I'm leaving for Basic Training tomorrow at 10:00am, I'm going to get up early and try to do the balance test. That way I'll know if I need to have a new set of injectors waiting for me.

How does this sound as a plan? I was thinking about installing an O2 sensor on the right bank, and put it on a toggle so I can either send its signal to my guage or to the ECM. That way I could see how its running and equally see if the car runs any differently getting its open loop info from the other bank. There is an awesome exhaust shop right down the road that built the exhaust thats under my car now, so it'd be a quick thing to do when I get back to pick up my car for my first duty assignment.

I've known Accel injectors were junk since about a week after I had these installed, I wish I had gone with something else. Oh well, they were relatively cheap, I figure I've gotten my money out of them.

I'm not sure I'll post again on the forum before I leave. Thanks for your help on this, and see everyone in about two months!

 

How is the one way check valve(between the rubber air tube and the header)? Upon start up, the ecm sends signal to the air divert valve to send air from the air pump to the headers. When that air hits the exhaust, it "afterburns" and gets the cats hotter sooner so they do what they are designed to do.
Can you test the pass side one way check valve? Try putting a shop vac suction on it (remove that rubber air line)and see if it allows air to come back up from the tailpipe/mufflers/cats/manifolds.
BTW, thank you for your service to us and our country

:flag


[Modified by 89 Paul in Cal, 1:18 AM 2/10/2003]