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Mean Green
10-08-2010, 11:21 AM
I got the car all put back together. Now I'm getting about 16hg / 17hg vac but the car still hits something like a fuel cut around 4300rpm.


Compression is about 155ish on all cylinders, plugs gapped at 35, no vac leaks, tested ecu...what gives, I have run out of options.

CoreyB
10-08-2010, 11:23 AM
Test the voltage from the TPS across its full swing to make sure its smooth.

Mean Green
10-08-2010, 04:58 PM
Test the voltage from the TPS across its full swing to make sure its smooth.

The tps and all other sensors are reading right. It just does not make sense. I've got good compression, good fuel pressure and good ignition...WTF.

CoreyB
10-08-2010, 07:44 PM
Are you reading knock ? Sounds like the ECU senses something is wrong and is pulling fuel or timing.

Mean Green
10-08-2010, 08:17 PM
Yea, when it hit the fuel cut, it read 2 counts but was just a hiccup.

Mean Green
10-08-2010, 09:22 PM
I just drove the car around and it has the same exact symptom as before, rear turbo glowing, no power. I'll go out and check the plugs when it cools down.

CoreyB
10-08-2010, 09:33 PM
Do you have a cat on it ? Sounds plugged.

Mean Green
10-08-2010, 10:49 PM
No cats at all.

Could stuck exhaust valves cause this but still show good compression?

CoreyB
10-08-2010, 10:51 PM
No. A exhaust cam out of time might though.

CoreyB
10-08-2010, 10:55 PM
My guess is that for whatever reason as you get closer to high RPMs the ECU is either not changing timing or changing it in a bad way. So that your spark is happening closer to when the exhaust cam is slightly open than when you are at TDC.

Mean Green
10-08-2010, 10:58 PM
The front turbo seems unaffected but the rear glows. I was thinking the same thing as you posted above but I cannot find the problem.

CoreyB
10-08-2010, 11:03 PM
Definitely seems that the rear bank is getting combustion into the exhaust but only at high RPMs

Mean Green
10-08-2010, 11:03 PM
Definetly seems that the rear bank is getting combustion into the exhaust but only at high RPMs

No, the turbo will glow regardless. It just hits something like a fuel cut around 4300.

well, it doesn't glow at idle but its really really hot in comparison. Also, while the car is idling...I can hear a popping through the intake occasionally and the rpms will shudder and then stabilize.

CoreyB
10-08-2010, 11:08 PM
Have you verifiyed the rear exhaust cam is timed correctly ? The rear turbo should not glow as you already know. This has to mean either unburnt fuel is entering the exaust, the exhaust is restricted, or combustion is entering the exhaust. Sticky valve guides may cause this.

Mean Green
10-08-2010, 11:11 PM
Have you verifiyed the rear exhaust cam is timed correctly ? The rear turbo should not glow as you already know. This has to mean either unburnt fuel is entering the exaust, the exhaust is restricted, or combustion is entering the exhaust. Sticky valve guides may cause this.

The timing is spot on, I've verified that many times. That's what I was wondering was sticky valve guides as when I started the car it only ran on 5 cylinders. After trying to investigate it just kinda fixed itself I guess...lol. It runs on all 6 cylinders and has great compression. I've just never run into a problem like this before.

I've never diagnosed sticky valve guides before, how do I diagnose this and correct it? I am assuming I would HAVE to rebuild the head.

CoreyB
10-08-2010, 11:24 PM
I have no idea how to diagnose it. Seems they are only doing it at high RPMs, so you cant just pull the valve cover and check. And that may not even be the issue. Wish I was more help man. Maybe seafoam will fix it ?

Mean Green
10-08-2010, 11:27 PM
Well, the car hesitates really bad. At idle it has 12.2% throttle. If I give it say, 5% throttle, it actually goes down in RPM, then if I give it a hair more, it will finally shoot up in RPM. When I go to drive off, it will do the same thing except I can feel it kinda having a tug of war with itself where it has power then it doesn't. If I start to go and give it around 40% throttle, it will boost and have some power but not full and if I give it 100% throttle, it will kick, backfire and hit what seems to be a fuel cut.

I have a few spare heads laying around, if I have to, I can swap the rear head but jesus that's alot of work and I just did that with a faulty front head.

CoreyB
10-08-2010, 11:33 PM
I dont think is mechanical really. What are you running for mods if any?

Mean Green
10-08-2010, 11:35 PM
Bone stock except for a Walbro 255.

CoreyB
10-08-2010, 11:37 PM
Guessing you have tried this but what happens if you unplug the electrical connector from the MAF and then drive it ?

Mean Green
10-08-2010, 11:38 PM
Guessing you have tried this but what happens if you unplug the electrical connector from the MAF and then drive it ?

Runs much worse.

CoreyB
10-08-2010, 11:40 PM
Thats weird. My VR4 will run decent without the MAF, just rich. Do you have any readings from the rear O2 ?

Mean Green
10-08-2010, 11:41 PM
Thats weird. My VR4 will run decent without the MAF, just rich. Do you have any readings from the rear O2 ?

Yea, the O2's read. I will go out and drive it with the MAF unhooked again and see what the datalogger says. brb.

Mean Green
10-08-2010, 11:54 PM
wow...it drove like total shit. If I touched the gas, it would die. I'll try to post the log now with the MAF unhooked.

CoreyB
10-09-2010, 12:03 AM
Sounds like its not going into closed loop. I am not much help when it comes to log files as I dont know what things should read. I am more of a mechanical/electrical guy than a settings guy, if that makes sense. I hope someone will chime in on the log file for you.

Mean Green
10-09-2010, 12:06 AM
Sounds like its not going into closed loop. I am not much help when it comes to log files as I dont know what things should read. I am more of a mechanical/electrical guy than a settings guy, if that makes sense. I hope someone will chime in on the log file for you.

What do you think would cause the car to not go into closed loop?

Mean Green
10-09-2010, 12:15 AM
I managed to upload the logs but I had to use the "other" site to host them but that's the best I can do.

http://www.3si.org/forum/f1/see-anything-wrong-here-log-attached-506656/#post6052196

This log is with the MAF unhooked. Any erratic behavior coming from the TPS is me trying to keep the car alive.

Mean Green
10-09-2010, 03:19 AM
I've replaced the FPR one time already but the guy I got it from was unsure what it was from. I did notice a slight difference but that was with the messed up head. Would the FPR cause all the issues I'm having right now? I guess if I understood the logs more I would be able to tell.

Mean Green
10-09-2010, 07:54 AM
Well.........if one exhaust manifold is glowing..... the other isn't........there's a problem with the cams.


Or the valves.

Steve

I went ahead and ordered a new FPR anyway, I'll have it this afternoon and will be able to post results tonight. If that does not help at all, then the rear head will come off as I do not know what else I can do.

The manifolds don't glow at all actually, it's only the rear turbo. Also, if the cams are lined up perfectly, and the compression test and leak down test pass with flying colors, what other things can I do to test the valves?

KeithMac
10-09-2010, 05:04 PM
Only thing you can do is strip the heads down and maually push the valves in and out (no springs in at this point).

Massive timing retard will cause the manifolds to glow but it would do both not just one..

Mean Green
10-09-2010, 08:49 PM
I installed the new FPR and boy what a difference! But...not fixed. It does get into boost MUCH smoother but it still face plants. At cold idle I am getting 10hg vac now and it is very erratic. I can drive it around, stop and let it idle and it has 17hg and then I can drive, stop, let it idle and it has 14hg. The rear turbo is still glowing but I really think that, the rear head has been the problem from the get go. I am thinking that the guides are shot and causing the valves to not work properly. Only thing that is weird is that I had the heads rebuilt.

stealthee
10-09-2010, 08:53 PM
I dont think its a head issue. If it were a head issue I would suspect the manifold to glow. If the turbo is glowing, I would suspect it to be a turbo problem. Maybe thats just me though.

Mean Green
10-09-2010, 08:56 PM
Well, any and all opinions are greatly appreciated at this point. I need all the help I can get with this illusive issue.

stealthee
10-09-2010, 08:58 PM
It could explain the erratic boost issues. :shrug:

Mean Green
10-09-2010, 09:06 PM
It could explain the erratic boost issues. :shrug:

Yea, that's exactly what I'm thinking. I rolled down the windows to listen to the turbos and watched the boost gauge at the same time. The boost pressure will sit at 7 psi but I can infact hear the turbo's fluctuate as far as sound pitch is concerned. I know it sounds weird but that is my assessment.

Also the other day after I finished replacing the front head, I started the engine and it would only run on 5 cylinders. I freaked out and hit it with a compression test and it revealed no problem despite me being able to hear the dead spot while it was starting. I took the front valve cover off assuming it was the front head with the issue but after further investigation, all the front valves where all at the same position when fully retracted. I then took off the rear valve cover and could hear what sounded like a popping noise. The rear valves where in the right spot as well. I put the car back together and fired it up and to my amazement, it was now running on 6 cylinders.

Later that day, the same problem happened again except I let it warm up running like that, on 5 cylinders. I turned it off and let it cool down for about 20 minutes. Came back out and it fired right up on all 6 again. I tried to narrow the compression loss down to a single cylinder but I have been unable to duplicate it when I have the logger readily available.

Mean Green
10-10-2010, 11:37 AM
That's what the "injector disable" feature is for. You disable them one at a time and see which one makes no difference....just go straight to no 3.
Your cams have probably jumped a tooth at the crank since you put it back together, in turn probably because you didn't tension the belt properly.
Just a guess.
You'll know when you pull the covers.

Steve

I wish that where the case. I pulled the covers already and found nothing wrong with the mechanical timing. I put the logger on the car to use the injector disable and started it up but I could not get it to skip again.

stealthee
10-10-2010, 11:55 AM
That's what the "injector disable" feature is for. You disable them one at a time and see which one makes no difference....just go straight to no 3.
Your cams have probably jumped a tooth at the crank since you put it back together, in turn probably because you didn't tension the belt properly.
Just a guess.
You'll know when you pull the covers.

Steve

If timing were off a tooth at the crank then it would affected at all times, every time its running since timing would either be a tooth advanced or a tooth retarded.

I'm still convinced its a turbo related issue.

Keyan
10-10-2010, 08:38 PM
how about a clogged injector? have you tried swapping injectors front to rear to see if you can make the front turbo glow? then try switching the coils. and the spark plugs. might as well make sure its none of that. eliminate things one by one.

Mean Green
10-11-2010, 05:55 AM
yea, I've swapped injectors twice already with a completely different set and also swapped front and rear bank with no improvement. The car is now idling with 8hg at cold idle and goes up to 15/16hg at hot idle.

colt45 gto
10-11-2010, 06:56 AM
that shit that was round the valves may have got into the turbo impellar. just a thought?

blindmist
10-11-2010, 07:09 AM
Are you sure you don't have a vacuum leak? With good compression and no leak, you should get somewhere around 17hg/in constant, regardless of cold or hot, at least thats how it is on my car. I am actually thinking my gauge shows closer to 20hg/in at idle. This just really might be me though. I haven't really paid very close attention lately.

Mean Green
10-11-2010, 07:13 AM
that shit that was round the valves may have got into the turbo impellar. just a thought?

That was on the front head, that bank is fine now...its just the rear with the problem now like before.

Mean Green
10-11-2010, 07:14 AM
Are you sure you don't have a vacuum leak? With good compression and no leak, you should get somewhere around 17hg/in constant, regardless of cold or hot, at least thats how it is on my car. I am actually thinking my gauge shows closer to 20hg/in at idle. This just really might be me though. I haven't really paid very close attention lately.

The intercooler piping was pressure tested up to 30psi and had no leaks. I've plugs the brake booster and removed all lines except for the boost gauge and it does not change.


I just don't know what else to do. I checked the rear turbo also and it spins freely. There is literally nothing else I can replace on the car to eliminate something except the rear head. After I put a brand new FPR on the car, that was the last thing I could buy and replace. I even put a different plenum on the car and throttle body.

I just don't know what else to do at this point except replace the rear head.

Mean Green
10-11-2010, 09:02 AM
YAY! confirmed the problem this morning.

I kinda sorta fixed the low vacuum problem. The idle screw had worked it's way out. I screwed it all the way back in and out 1 turn until I got proper idle and it was reading 16/17hg at idle but I have yet to test it against a cold idle. I also bought a nice big vacuum gauge and cofirmed the sticking valve guide theory. The vacuum suddenly pops from 18hg vac to 10 hg and suddenly back up every once in a while. I also was able to put a 1$ bill against the exhaust and it sucked it in on 1 compression stroke, of course it does not determine which cylinder it is but considering I just replaced the front head and the rear bank is having the issue, that pretty much narrow's it down.

I'm going to go pick up a replacement head this morning and hopefully have it swapped out by tonight or tomorrow. I drove the car with the vacuum a little better and it will boost and run decent but still not alot of power and it still hits something along the lines of a fuel cut at 4300rpm.

Mean Green
10-12-2010, 04:47 AM
I got the rear head off and I am dead tired. I sat the head down on the ground sideways and poured gas into the runners. Cylinder 2 and 4 could not hold the gas just in the runner on the intake valves. I could not see any visible damage so I am very unsure as to what has caused them to what would seem to be sticking. I am just glad that I took the head off and found a problem...hopefully I can put some closer on this mystery that has plagued my car for well over a year in a half. The exhaust valves did the same thing as well...

SpdDmnVR4
10-12-2010, 12:37 PM
I hope you figure out what caused that.. That's a strange thing to happen with little to no other damage to the head, block, or pistons

Mean Green
10-12-2010, 05:40 PM
The cam timing was never off to begin with. The guides where not installed right at the machine shop so the valves are kinda overlapping the seal by just a hair. I just don't understand how I did not notice it to begin with.

CoreyB
10-12-2010, 06:56 PM
The cam timing was never off to begin with. The guides where not installed right at the machine shop so the valves are kinda overlapping the seal by just a hair. I just don't understand how I did not notice it to begin with.

This doesnt make any sense to me. Can you clarify?

Mean Green
10-12-2010, 08:04 PM
This doesnt make any sense to me. Can you clarify?

When they drilled out the old guides, they installed the new ones crooked. The valve will snap back into place at lower RPM but would slam against the valve seal at higher RPM. They are only off just a hair but its just enough to cause it to not seat properly. It is really hard to explain without you being able to physically see it, I tried to get pictures but I cannot get enough light in to show it.

Once I removed a valve spring, I was able to move the valve side to side by hand with barely any effort...so over the time of it being installed wrong, it has worn the new valve guides out due to them being installed incorrectly.

CoreyB
10-12-2010, 08:18 PM
I think I follow you. This would mean the head is junk wouldn't it. I thought that old valve guides were pressed out not drilled. Drilling seems to leave the opportunity to not drill straight, which is what sounds like happened if I follow you.

Mean Green
10-12-2010, 09:12 PM
Yea, the head is no good now. Totally not worth rebuilding as it would need sooo much work. The only problem I have is now I have 2 92 heads and my car is a 93 so I have to convert the harness to the 92 single CAS.

CoreyB
10-12-2010, 09:15 PM
Thats really easy to do though.

Mean Green
10-12-2010, 09:18 PM
Thats really easy to do though.

oh yea, I know, I had it converted before but changed it back because I was having this issue with the car.

CoreyB
10-12-2010, 09:30 PM
Good luck man. Let me know if you have any wiring questions. I might be able to help.

Mean Green
10-16-2010, 09:09 AM
I swear I'm cursed...I got the rear head replaced and started the car up. It runs...barely. I turn the injectors off on cylinder 1 and 2 and there is no change. I dunno wtf happened.

If anyone knows of a cheap tt long block, please let me know as I am at my wits end.

CoreyB
10-16-2010, 01:05 PM
Maybe those injectors are not working, wiring issue maybe ?

Mean Green
10-16-2010, 01:06 PM
nah it's not wiring...something happened in the install I'm guessing despite me testing the head with liquid. Cylinder 2 has 0 compression for some odd reason...I'm checking into the reason why now.

CoreyB
10-16-2010, 01:08 PM
That sucks man.

Mean Green
10-16-2010, 01:11 PM
That sucks man.

lol...yea...tell me about it.

ok, so I made a ghetto pressure tester as I do not have an air compressor...worked like a charm.

I pressurized the cylinder to an attempted 40 psi with epic failure...it seems that somehow upon installation, dunno how but it happened, the 2 intake valves on cylinder 2 where bent despite my every precaution. I went ahead and tested every other cylinder with the make shift pressurizer and every other cylinder was fine.

What makes it even more ironic is that cylinder 2 on the old head was the one with the biggest problem. The guides on cylinder 2 felt like sand paper when I tried to push the valves in and out without the springs in.