14 replies to this topic

[ihscout54]

Well it was running good for a bit but now running poorly. Has good power but intermittent low/rough idle and idle miss. Nasty ping that comes and goes. Checked fuel pressure, timing, TPS, vac system, EGR system and ran check for codes. Nothing out of specs found. I tried to up the idle on the IACV and it did very little. I cleaned the port and removed the screw, it was clean. IACV works fine. I unplugged the MAF sensor and idle came up and smoothed out and ping seems to have gone away. Car seems pretty decent without MAF (or in open loop). I cleaned the MAF, no change, then replaced it with my spare to no prevail. O2 sensor is pretty new...
Im stumped.

[somick]

If this is automatic, check transmission modulator.

Sam

[ihscout54]

No its my ea81 Brat w/SPFI swapped in. Its a 4sp d/r.
Your parents obviously had good taste. Always nice to see another Sam out there
-Sam

[Niku-Sama]

how are the plugs?

pcv system clogged at all?

[ihscout54]

PCV is new. I messed with it too. The plugs are a year old or so, but they are Autolights :-\ Im not sure what brand the plug wires are I replaced them w/plugs but I doubt they are NGK's

[ihscout54]

I checked the plugs, the pass side looked great, the driver side were a bit carbon fouled :-\. I wonder if its possible, that because Im running a cone filter that is sitting under the hood the air going in to the MAF is too hot and throwing off its signal? It doesnt seem possible but it is interesting that this problem has grown now that its redonculously hot outside.
If you remove the filter and cover the lower half of the housing it smoothes out a bit.

[Gloyale]

Check the Coolant temp sensor for output in the proper range.

IIRC should be 2-3K ohms when cold(60-80 degrees F) and less than 500 Ohms when fully warmed up.

If it is more than 500 Ohms when hot, the ECU will be running it too rich and too advanced.

[ihscout54]

CTS is within specs. I guess fooling with the MAF could hide a lean problem caused by something else...

[ihscout54]

Im pulling my freakin hair out with this crap! Im getting a bog under heavy load w/poor acceleration now.
No codes D-Check comes back clean, timing @ 22 deg. Ive checked my TPS CTS & MAF 50 times now. Ive backprobed sensors back to the ECM they are all good. CAT & O2 sensor is less than a year old, vac readings good. Fuel filter is pretty recent, pump screen is clean. Fuel pressure dead on at 21psi. Compression better than expected. Checked - regapped plugs & re-routed plug wires, added ground wire to coil bracket. Tried different coil, MAF, IACV, injector, fuel pump, pressure regulator, plug wires, cap & rotor. I plugged every vac line at source & pvc except power booster. Intake boot seems decent & leak free.
Im outa ideas. Befor, I spend money on new NGK plugs and wires I know Im missing something. I thought perhaps the fuel volume was weak but I imagine that would effect pressure readings. My coil wire is kinda long but it wasnt a problem befor. This just happend.

[4x4_Welder]

It sounds like an ECM ground issue. Make sure your body to engine and body to battery grounds are nice and clean, and that the battery terminals are nice and clean as well.

[GeneralDisorder]

How's the seal on your dip-stick? Oil fill cap?

The PCV is a closed system - it is part of the vacuum system and must be sealed.

GD

[ihscout54]

It sounds like an ECM ground issue. Make sure your body to engine and body to battery grounds are nice and clean, and that the battery terminals are nice and clean as well.

I had already cleaned the ground lug where it mounts to the block and the batt terminal a couple days ago when I went nuts with the grounds. I decided to remove and clean the + terminal and clean it today. I hadnt messed with it yet because it was replaced it a few months ago. It looked ok but I cleaned it anyways. Well after my test drive that seems to have eliminated the ping and bogging. I cant belive I missed that the car would start, drive, lights would work fine 13.9 volts, yet it was a dirty + terminal causing these issues.
If it comes back Ill let you know, but it looks like Ive just waisted usmb space, and alot of energy on something really stupid. :-\
Thanks guys

Edited by ihscout54, 28 July 2009 - 12:54 PM.

[RenaissanceMan]

didn't read the last post, disregard... lol

Edited by RenaissanceMan, 29 July 2009 - 11:56 PM.

[Log1call]

Pinging can be caused by bad fuel, oil burning, too higher compression, too hotter motor in general or a localised hot spot in the combustion chamber, wrong ignition timing and even extreem lean(causing heat).

You mention the compression is better than expected... could it have been planed too many times or could the combustion chanber have a build-up of carbon? I'm not sure if it's possible with your model but have you tried backing the ignition timing off a little?

[ihscout54]

Yea I went through it all. It seems fine now after cleaning the + battery terminal. That and unplugging the MAF were the only things that made a difference. Im still being pretty paranoid about it but I think its solved. A lesson learned, when you have odd issues like this: Clean youre batt terminals/ connections.