I've never owned a car that aggrivated me more....misfires bad when warm

[letitsnow]

Apparently it has convinced itself that it's a honda and should only have 4 cylinders. When it's cold, it runs on all 6 great, after it warms up to ~140°, 1 and 2 drop out intermittently. It pops out the intake if you rev/try to drive it.

 

 

Fuel pressure is ~25psi at idle with the reference line hooked up, ~35 with it disconnected, increases with boost as well. Also checked while driving, it operates as expected.

 

Spark plugs were new, the ones that come out of the offending cylinders are always wet.

 

Spark plug wires are brand new carquest oe replacements, did the same thing with the old wires, but they leaked visibly at night with a little water

 

Idles at 13.5:1 when running on all 6 according to the wideband

 

No datalog because I really don't think it's a problem with the tuning/megasquirt, I'll get one if you guys want

 

Valve lash was set to the factory settings

 

Injectors were cleaned/flowed by a local shop, I'm going to move them around and see if the misfire follows

 

Compression is ~115 across the board, seems a little low, but the engine has 7.4:1 compression.

 

New msd blaster coil, does the same if I borrow my dad's blaster from his firebird.

 

Dizzy cap looks good, but I'm going to get one tomorrow anyhow.

 

 

I had it running decently before, but as soon as you got into boost, it would go DEAD lean, like hitting fuel cut. I was driving around trying to figure it out and it just started to drop cylinders. Maybe it detonated and blew the headgasket between 1 and 2, anyone know anywhere to get/rent a leakdown tester?

[Drax240z]

I can only assume you have a turbo engine swap in the 77 in your signature, and that is the car you are talking about. How about a rough description of the car first?

[letitsnow]

'77 bottom end

p90 head (solid lifters)

n47 intake

zxt turbo/manifold

msa downpipe

3" exhaust with turbo muffler

turbo injectors

ms1 v3

walboro 255

'83 turbo dizzy

zxt charge pipe

 

That should about cover it.

 

Did some testing, got a leakdown tester from harbor freight, but I think i'm either doing it wrong, it's junk, or my engine is junk. I'm increasing the pressure until the % guage reads 0% leakdown(~18psi on the other gauge), then attaching it to the cylinder at tdc on the compression stroke(verified by looking at the cam lobes).

 

cyl 1

exh temp 175°F measured on the exh manifold with an IR gun

cold comp 115psi

hot leakdown 70%

hot compression 125psi

 

cyl 2

295°F

100

52%

115

 

cyl 3

500°F

110

42%

120

 

cyl 4

515°F

110

45%

120

 

cyl 5

435°F

100psi

40%

115psi

 

cyl 6

550°F

110psi

55%

120psi

Edited April 18, 2010 by letitsnow

[FlatBlack]

What FPR are you using? Mine is 36 vac ref'd and 40 with it unplugged.

[letitsnow]

'77 l28e regulator.

 

The head is going to come off tomorrow unless somebody has a really good suggestion...

[FlatBlack]

'77 l28e regulator.

 

The head is going to come off tomorrow unless somebody has a really good suggestion...

 

Your cylinder compression seems within close range of each other? I'd swap in a new 255 before pulling the head...

 

You aren't getting proper fuel pressure it seems. Pull the filter and see if it has any rust/crap in it.

 

My walboro's filter got clogged and made my car run lean under boost o_o It runs 40 without a vac ref at idle but I think the clogged filter might have killed it. It's much quieter now which is scary. I am loosing power up top and I think I might be running lean [still working out wideband issues ]. I need to pull the pump sometime this week and see if there is something in the pump.

Edited April 19, 2010 by flatblack280

[MAG58]

I'm interested to know why 1 and 2 are running really cool compared to the back 4. I'd expect something a little closer than 175 to a max of 550, as well as why 5 is running at least 80 degrees cooler than the adjacent cylinders. Seems backwards to me.

[letitsnow]

Tank was just pulled, cleaned, and coated. The pump has less than 100 miles on it. The regulator is clearly regulating at the pressures I said earlier.

 

I'm assuming 1 and 2 are so cold because they're not firing reliably.

 

To humor my dad, I'm going to change the oil pump for a turbo pump in hopes that the timing chain tensioner isn't tensioning correctly because of my relatively low oil pressure.

[z-ya]

It is not the pump, or ignition system (distributor) if only 2 cylinders are being effected.

 

Are you using a resistor pack or the PWM in the MS? If you are using PWM, what are your settings? Seems like something is heating up and then failing.

 

When the engine is running on 4 cylinders, pull one injector plug at a time. If after pulling any of them and the engine doesn't stumble, it's not an injector/driver/wiring problem. If it does stumble, you know which injector to start looking at.

 

Pete

Edited April 19, 2010 by z-ya

[Mack]

How old are your injectors? It is poissible that when your car heats up, they could be failing. when it gets hot and starts to stumble, pour ice cold water water on the front 2 injectors and see if they kick back in.

[letitsnow]

injector opening - 1.0

battery correction - .20

pwm current limiting - 30%

pwm time threshold - 1.0

 

It stumbles when I pull 3-6 off, 1 and 2 have little effect. I also swapped injector 1 and 6 yesterday, no change. They are the stock ones from an '83 turbo. I've also switched the channels back and forth.

Edited April 19, 2010 by letitsnow

[z-ya]

injector opening - 1.0

battery correction - .20

pwm current limiting - 30%

pwm time threshold - 1.0

 

It stumbles when I pull 3-6 off, 1 and 2 have little effect. I also swapped injector 1 and 6 yesterday, no change. They are the stock ones from an '83 turbo. I've also switched the channels back and forth.

 

So I guess you don't have a resistor pack?

 

Do you have driver 1 (D1) driving injectors on cylinders 1,2 and 3, and driver 2 (D2) driving injectors on cylinders 4, 5 and 6? And you have swapped them so D2 drives 1, 2, and 3 and you still have the problem?

 

What do the plugs look like in 1 and 2, are they gas fouled or dry? What plugs and gap setting?

[letitsnow]

No resistor pack. Plugs are wet, but not soaking. They are whatever is stock for an '82 280zx turbo, gaped at .045.

Edited April 19, 2010 by letitsnow

[Drax240z]

Without going into all the details:

 

- Don't pull the head yet

- Don't worry about fuel pump/filter

 

- Do pull #1 and #2 injectors. Check for blockage. Check that they click when they see 12v

- If you can replicate the issue, pull the #1/#2 spark plugs and make sure they are sparking

 

With all that said I'm willing to bet it's something to do with your MS/wiring or your injectors. Check, check and re-check!

[letitsnow]

That's what I'm starting to think, I'm going to redo the harness before anything else. Once I have that to a point where I can trust it I'll look elsewhere.

 

Also, as if to add insult to injury, the relay that activates the starter motor when you turn the key stopped working.

[Mack]

did you replace the distributor cap and/or wires yet? I wouldnt rule out something stupid like it warming up and jumping spark between the 2 seeing as how they are right next to eachother. If you swapped injectors between #1 and #6, that rules out injectors. and it 1 2 3 are running off the same bank in MS, that would rule out MS hardware or software as well as wiring, unless solder joints are bad or something.

[frank280zx]

Seems all is within spec ... I had a similar problem with correctly gapped plugs .. they where Bosh platinums .. they did exactly the same!! switched back to NGK's and my problem was gone. (apparantly our l's dont like nifty high end plugs)

So what plugs are you running ? to cold to hot? wrong brand ?

Edited April 20, 2010 by frank280zx

[letitsnow]

I'll get the number later today, but they're the cheapest NGK's. I'll get a new cap, the wires are brand new from carquest. I probably won't be able to look at it much until thursday or friday, but that might not be a bad thing, I've been working on it with every extra minute for a week straight.

[z-ya]

I'll get the number later today, but they're the cheapest NGK's. I'll get a new cap, the wires are brand new from carquest. I probably won't be able to look at it much until thursday or friday, but that might not be a bad thing, I've been working on it with every extra minute for a week straight.

 

If they are platinum plugs, that could be your problem. They are very sensitive to gas fouling. So if it was running pig rich at one point, change all of them. Use NGK BPR6ES gapped to .035 to start.

 

Pete

[letitsnow]

They're not platinums, I'll get the part number when I get home.

 

Nobody has mentioned the massive difference in leakdown that the no 1 cylinder has compared to the rest, or are you guys just assuming that the HF leakdown tester is complete junk?