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Old 08-14-2020, 01:08 AM   #51
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It might be worthwhile to measure the resistance on each wire and see if one is way out of range. I wish I'd tested my failed wires when I had them so I could give you some numbers to look for.
But the symptoms really do sound similar. It bucks and struggles until you get up to speed and then it does fine, right?
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Old 08-14-2020, 01:33 AM   #52
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It doesn’t really buck, but it just feels like it has no power. Then at around 3k RPM, it all of a sudden starts moving. Then of course the horrible idle.
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Old 08-15-2020, 01:00 AM   #53
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Checked the resistance in the wires today, nothing crazy. They were all relatively similar, going down slightly on each wire according to length. Pretty much as I expected. Not really a way to totally rule out bad wires, but reistance wasn't excessive. They were between 4.5K ohms and 9.64K ohms.

From my reading on the LH 2.4 books, I'm down to a few things aside form mechanical.

Radio suppression relay (unlikely since the injectors are getting power)
Fuel system relay (how often to these intermittently fail like this? I figured these usually just die and that's that)
O2 sensor
IACV signal (I'm going to check this tomorrow)

I will try to do a running compression test tomorrow as well, hopefully the rain holds out for me. Its timing wasn't in my favor today, and of course I had something else in the garage.

All else aside, could my cam timing have anything to do with this? The sluggishness started before I installed the cam (along with everything else) but I want to put it out there in case it’s a problem. It’s an iPd turbo cam at stock 0*. I read that it could a little rougher, but unless my engine mounts are just that shot, I don’t think it should idle this bad. And it certainly shouldn’t be so sluggish from a stop.

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Old 08-17-2020, 10:32 AM   #54
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Absolutely.
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Old 08-17-2020, 10:47 AM   #55
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Absolutely.
Interesting... I've heard that the iPd cam at the stock position is pretty good. The sluggishness from a start is unbearable.
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Old 08-17-2020, 01:35 PM   #56
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Are you absolutely certain it's straight up?
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Old 08-17-2020, 01:47 PM   #57
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Yes, the gear is mounted properly and the timing mark is perfectly lined up.

Just did a dynamic compression test. Here are the numbers...
The first is the running compression, the second number is when I blipped the throttle
1- 10-50 PSI/~90 PSI
2- 10-80ish PSI/100 PSI
3- 10-80ish, averaged around 50-60 PSI/110 PSI
4- 45-85 PSI (the check valve appeared to hold this time)/105 PSI
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Old 08-17-2020, 05:08 PM   #58
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Maybe a stupid question... maybe not. The engines shakes like hell. It looks like it's about to jump up and flip around. Like an out of balance washing machine. I know it needs engine mounts, but could those cause the vacuum to flutter like it does?

Aside from that and the down low sluggish-ness (possibly cam timing now that I think about it more) it feels good in the higher end. The gauge flutters a little in boost as well, but when cruising at speed, it stays pretty steady around 20 in-hg. I'd still expect it to be higher (25ish in-hg) though.
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Old 08-17-2020, 08:03 PM   #59
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I understand that the cam gear is lined up, but are you certain about the crank gear too? And for reference, my kid's '93 940T with an Enem V15T (stock beyond that) draws 18-19 in/hg at idle, so you should very much be in that neighborhood. Also, I see you said your valves are adjusted, what clearance did you use?

Last edited by shoestring; 08-17-2020 at 08:11 PM..
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Old 08-17-2020, 10:51 PM   #60
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Originally Posted by shoestring View Post
I understand that the cam gear is lined up, but are you certain about the crank gear too? And for reference, my kid's '93 940T with an Enem V15T (stock beyond that) draws 18-19 in/hg at idle, so you should very much be in that neighborhood. Also, I see you said your valves are adjusted, what clearance did you use?
Yes, crank is perfectly aligned. Cylinder 1 is definitely at TDC with the crank marks aligned. Yeah, my vacuum is definitely way off.

I believe I have them all at 0.015". The cylinder 1 exhaust valve may have been at 0.013" IIRC, but that's still within spec. I know it's not ideal, but I didn't have any shims to correct that. Worst case, it's not hard to order the right one and swap it out. I need to check my notes again to make sure.
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Old 08-18-2020, 01:29 AM   #61
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Huh, this is interesting. http://turbobricks.com/forums/showthread.php?t=233878

So maybe my vacuum isn't as crazy as I thought? It's definitely lower than before the iPd cam, but the fluttering boost gauge is the same as before with the T cam and out-of-adjustment valves.
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Old 08-18-2020, 12:58 PM   #62
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I unplugged the 2-pin connector for the O2 sensor and noticed absolutely no difference in the way it ran. Is that normal or am I just being hopeful that this just might be the problem?
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Old 08-18-2020, 01:59 PM   #63
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does it consistently run better at higher rpm, like you're flicking a switch, on or about 3000 rpm, based on throttle angle?

Also, did you check for codes?

Last edited by shoestring; 08-18-2020 at 02:23 PM..
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Old 08-18-2020, 03:50 PM   #64
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It’s not quite as abrupt as feeling like flicking a switch, it smoothly transitions. Over 3k RPM, it feels good. No issues from what I can feel. It pulls healthy. Throttle angle doesn’t seem to affect it. However in the low RPM, even with low throttle input, it feels and sounds like WOT. It just bogs down.

Checked for codes, ran the diagnostic tests for the IACV, injectors, etc. and everything checks out. No codes.
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Old 08-18-2020, 03:59 PM   #65
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Depending on throttle input, you could be crossing over from closed loop to open loop around 3000 rpm. In open loop it would refer to fueling tables rather than o2 sensor, so yes, it would run correctly.

However, without a code for O2, I'm skeptical. I don't know. I'm signing off this one.
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Old 08-18-2020, 05:31 PM   #66
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Just drove it again, and when I first left and went over 3000, it felt like a switch this time. Interesting.
Good point though, it makes sense. I wonder if the O2 sensor actually has anything to do with it.

It really feels like cam timing, but the vacuum is still a little on the low side. And of course it's jumping around like crazy. The really odd part is that it ran pretty much exactly the same prior to swapping the head and cam.

Basically, this is where I am...

-get an adjustable cam gear and advance the timing a little
-replace the trashed engine mounts
-adjust the valve that was a little tighter than the rest (just ordered the correct size shim)

I've pretty much ruled out anything and everything else. Timing, vacuum leak, fuel pressure, injectors, plugs, cap, rotor, wires, power stage, TPS, MAF (I suppose it could be failing, but typically that'll throw a code, no?), etc. I haven't swapped the fuel system relay yet, but if the pumps are working and I have good fuel pressure, I don't think it's a problem.
The only other thing I can think Same goes for the radio suppression relay.

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Old 08-18-2020, 10:23 PM   #67
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I can tell you when I had a bad O2 sensor, I had both fuel mixture error codes and a rough idle. And the exhaust smelled so bad that my hair and clothes would stink for the rest of the day after a 5 minute drive. I'm pretty sure that one was a pebble inside of an oxygen sensor housing though. There might be other failure modes.
The fuel and radio suppression relay failing will stop the car dead. If you suspect an intermittent failure, it's easy enough to pop them open, clean them and reflow the solder.

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Old 08-18-2020, 10:44 PM   #68
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Right, I figured those relays either work or they don't. I don't think I've heard of them softly failing.

That sounds like a pretty extreme O2 sensor failure! I guess mine could be bad, but it's probably not the main problem.
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Old 08-19-2020, 04:27 AM   #69
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Did you already cover an o2 voltage test ?

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Old 08-19-2020, 10:58 AM   #70
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Did you already cover an o2 voltage test ?

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I have not. I just saw that part of the LH 2.4 manual last night, and I will try that today.
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Old 08-19-2020, 12:02 PM   #71
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Ok, just voltage tested the O2 sensor. On a cold start, it bounced around quite a bit, but after running for about a minute, it settled around .85V. Little high, no? It should be around .5V. But maybe it’s just a little rich?

I had the ECU side of the connector grounded, per the manual. It ran exactly the same as it always does and the CEL didn’t pop on.
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Old 08-19-2020, 02:22 PM   #72
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Google it noob

Pegged at .9v is rich or bad sensor.
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Old 08-19-2020, 11:27 PM   #73
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Google it noob

Pegged at .9v is rich or bad sensor.
I'm used to just looking at an OBD2 feed of the O2 sensors... the newer cars are too easy to diagnose. They've made me weak!
At this point, I have reason to believe it's a bad sensor. Fuel pressure is good, plugs are good, injectors are good, no obstructions to the intake, no vacuum leaks.
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Old 08-20-2020, 01:04 AM   #74
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Quote:
Originally Posted by bmdubya1198 View Post
I'm used to just looking at an OBD2 feed of the O2 sensors... the newer cars are too easy to diagnose. They've made me weak!
At this point, I have reason to believe it's a bad sensor. Fuel pressure is good, plugs are good, injectors are good, no obstructions to the intake, no vacuum leaks.
In theory it should oscillate somewhere in the range of .1v to .9v while at idle

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Old 08-20-2020, 01:11 AM   #75
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Quote:
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In theory it should oscillate somewhere in the range of .1v to .9v while at idle

Right. It fluctuated for a few seconds on the cold start, then settled at right around 0.8V. Iím going to check it again tomorrow, but I think this O2 sensor may actually be the issue. I hope so, Iím sick of this thing running so terrible. Itís terrifying to turn out into traffic because it takes longer to get to 20 than my V70R takes to get to 60.
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