It's been a while and I really need this fixed.

[Mean Green]

I've made many threads on 3si with not a single one leading to a solution.

The car is a 1993 VR4 in all stock condition. The engine is fresh also.

The car drives fine out of boost but once you hit boost I can hear it backfiring through the intake from time to time and very loud backfires through the exhaust when the throttle is pressed 100%.

--------------------------------------------------------------------------------------------------------------------------------------------------------------------

The data logger says the TPS is set at around 12.5% when the switch has continuity. The TPS also has a nice path on the data logger with no interruptions so it is not the TPS.

----------------------------------------------------------------------------------

Me and Echo419 tested the ECU today in his car and my ecu ran better in his car than his own...lol...

--------------------------------------------------------------------------------------------------------------------------------------------------------------------

The fuel pump is the only upgraded mod on the car right now. It is a walbro 255 but the pressure is perfect at idle and changes when the vacuum line is removed from the FPR so that is not the issue but was part of the issue before.

----------------------------------------------------------------------------------

I changed out the MAF with another one I had laying around and now the car will rev past 4000rpm but still has the stumbling issue.

--------------------------------------------------------------------------------------------------------------------------------------------------------------------

I replaced both front and rear O2 sensors with brand new units and they are both reading correctly according to the datalogger.

----------------------------------------------------------------------------------

The engine temp sensor is a brand new unit also. I tested it in accordance to the FSM just to be sure.

--------------------------------------------------------------------------------------------------------------------------------------------------------------------

I replaced the injector resistor pack with a brand new OEM unit as the old unit was reading an abnormally high ohm level but it is now correct.

----------------------------------------------------------------------------------

I swapped the injectors out with known to be working OEM 360cc from another VR4 and no change at all.

--------------------------------------------------------------------------------------------------------------------------------------------------------------------

The mechanical timing is spot on and the electronic timing is perfect according to the datalogger.

----------------------------------------------------------------------------------

The car does not read any knock, only catches a few counts in the mid RPM range but it appears to only be hiccups once in a blue moon.

--------------------------------------------------------------------------------------------------------------------------------------------------------------------

The compression is perfect with not a single pound of variance between cylinders which to me, is badass.

----------------------------------------------------------------------------------

I boost leak tested all the intercooler piping to 30psi with just a car air compressor and it held 30psi...yea I wanted something to blow and expose a weak point but no success.

--------------------------------------------------------------------------------------------------------------------------------------------------------------------

I took the K&N air filter off and cleaned it and noticed a small difference but nothing that changed how well it drives.

----------------------------------------------------------------------------------

Now, the car has no power at all if I give it more than about 30% throttle. If I go to 80+% the car will backfire really bad. The rear turbo will be visibly glowing when I get done driving it but that's only after I boost it.

Gimme some more idea's as I only have 250$ to throw around.


EDIT: Also, all updates to reply's will be posted here and a bump added.

The pump is hot wired and getting around 13 volts.

----------------------------------------------------------------------------------

The car also has no cats what so ever and full egr delete.

--------------------------------------------------------------------------------------------------------------------------------------------------------------------

The spark plugs are new NGK platinum's and they are gapped at 35 already. I did have them at the OEM gap and the car did run worse. Closing the gap to 35 did make it alot more drivable out of boost and it idled better.

----------------------------------------------------------------------------------

It goes to 7 pounds of boost and will hold that but it pushes and pulls as if it wants to go but something is holding it back. The car is running on wastegate pressure as in the vac line goes from the intercooler piping to the wastegate actuators.

--------------------------------------------------------------------------------------------------------------------------------------------------------------------

When I took the plenum off to replace the plugs again, I noticed alot of soot / carbon build up and its all new. The old plugs looked great with an identical pattern on all 6 and no carbon build up what so ever.

----------------------------------------------------------------------------------

[RL7]

Try testing the voltage at the pump itself. You will have to pull the fuel pump assembly to do this. I had a bad in-tank ground wire and I was getting low voltage to the pump.

[Midnight92Vr4]

Spark plugs? Maybe your having a dramatically worse version of what I was having: I couldn't rev past 5000 rpm w/o misfire (no knocking though) at greater than 12 psi boost solely due to spark plug gap. I got some new plugs in at .035 gap now and she'll rev as far as I need at whatever boost I want. Good Luck ;)

[futurevr4man]

yeah, plugs are my question as well.

[Mean Green]

bump....added more info

[vr3.9]

Did I miss it or did you say anything about the coil pack. You might want to test it. or try swapping with a known good one.

[Mean Green]

Did I miss it or did you say anything about the coil pack. You might want to test it. or try swapping with a known good one.

That or the PTU is what I'm thinking..

anyone have a video of what bad coil packs do on these cars?


I was going to order a set from IPS but I have seen to many horror stories on shipping so I am hesitant to order from them as they are the cheapest.

[Midnight92Vr4]

Yep, agreed with above. Coil packs, spark wires, and I think ptu(?)
The fact that closing the gap improves the situation makes me think its ignition power related even more than before.

[Midnight92Vr4]

Bad coil pack would do the same thing as having too high of a gap on 2 of 6 spark plugs (at least, but in multiples of 2)
Eventually it would stop firing altogether in multiples of 2 I believe.

P.S. you ninja posted... -.- lol

[Mean Green]

Bad coil pack would do the same thing as having too high of a gap on 2 of 6 spark plugs (at least, but in multiples of 2)
Eventually it would stop firing altogether in multiples of 2 I believe.

P.S. you ninja posted... -.- lol

LOL... I'm quick with that shit huh?...lol

I just want to be 100% sure it's that. Like I said, I only have 250$ to play with as I have no more spare funds for the next 2 months. I've already wasted over 3k in the past 3 rebuilds.

[Midnight92Vr4]

Well, Fortunately both the coils and PTU can be tested :) and a multimeter can be had for like $2

http://stealth316.com/2-ignitioncoils.htm
http://stealth316.com/2-pwrtransunit.htm

The inspection bit is at the bottom of the pages.

[Mean Green]

What are the symptoms of bad PTU?

out of all the years working on cars, I have never run across a bad ignition control module / transistor unit..lol

[Midnight92Vr4]

I'm not as familiar with the ptu as some other members, but I know it was one of the things I was worried about when my ECU failed (before I knew it was the ECU lol) The PTU is told by the ecu when to fire the coils, so if the ptu goes out then the coils will not fire or not fire at the right time. Usually this results in the car cranking but not starting (same as if ECU died.) I'm not sure but if the current going to the coils goes through the ptu first then a worn-out ptu may cause the same problem as improperly gapped plugs but i'll let a more informed member say whether that is true or not.

[Mean Green]

I'm not as familiar with the ptu as some other members, but I know it was one of the things I was worried about when my ECU failed (before I knew it was the ECU lol) The PTU is told by the ecu when to fire the coils, so if the ptu goes out then the coils will not fire or not fire at the right time. Usually this results in the car cranking but not starting (same as if ECU died.) I'm not sure but if the current going to the coils goes through the ptu first then a worn-out ptu may cause the same problem as improperly gapped plugs but i'll let a more informed member say whether that is true or not.

I'm going to get some 300m coils tomorrow and just convert it to COP's. That will be a cheaper option for me now. I just wish the plates where cheaper that mount them as I'll have to make my own.

[Mean Green]

I got the 300m coils installed but it's only running on 4 cylinders. I'm to tired to diagnose it tonight so tomorrow I'll jump back into it.

On the other hand I did notice something very strange...I readjusted the TPS and the car runs worse...I put it back, runs better but its out of spec until I readjust it. According to the data logger its at 12% without me pressing the peddle.

[RL7]

That's normal, as long as it's under 15% at idle and over 90% at WOT, you're pretty much ok.

Just in case you misunderstood, the fuel pump voltage I was talking about earlier was the voltage at the connector in the tank. I was getting 12.5V (engine off) to the connector at the top of the fuel pump, but only 3V at the connector in the tank because the little ground wire in the tank had gone bad. That's unlikely to be the issue, but it could be worth a shot.

[Midnight92Vr4]

^On the TPS, what he said. Mine reads 13.2% at idle and 98% at full throttle but no matter how i adjust it, it won't go above 98% at full throttle. Moreover, if the key is turned to on but the car is not started then the datalogger reads only 80% TPS if my pedal is pushed to the floor.

[Mean Green]

I put the 300m coil packs in tonight with no change in performance. I have a log to post but it says the file is to large. The car did something it has never done before, I went to drive it and then all of the sudden it literally just about shut off. It seemed as if it just started running on 2 cylinders and had suck a small amount of vacuum that I didn't have brakes, well power brakes. After a few seconds with playing with the throttle, it started running on all 6.

[DocWalt]

Have you tested the PTU?

[Mean Green]

Have you tested the PTU?

Replaced it today. Now I am thinking something is up with my mechanical timing. Anything look wrong with this picture to you?

http://i101.photobucket.com/albums/m74/nismo200r/Picture003-1.jpg

[SpdDmnVR4]

both valves are going to be compressed at the same time. so no compression on 1 cylinder. And This leads me to believe that you have 2 exhaust cams on the front and two intakes on the rear. IDK if that is possible, but thats what it looks like.. I would definitely check mechanical time! and then check compression. Bent valves would suck!

[Mean Green]

both valves are going to be compressed at the same time. so no compression on 1 cylinder. And This leads me to believe that you have 2 exhaust cams on the front and two intakes on the rear. IDK if that is possible, but thats what it looks like.. I would definitely check mechanical time! and then check compression. Bent valves would suck!

The compression is perfect. The cams are in time...I checked them against a set I have that have a broken key guide. Any other suggestions..lol

[Mean Green]

I'll give someone an Ipod touch if they can fix this thing. It's the only thing I have left that has any value, that's how bad I need this fixed.

[Mean Green]

Ok...so I have been going through my logs like crazy and found some very interesting things.

When I first start the car, the logs read 14volts going to the pump. 5 seconds in and everything changes...it says the MAP reads 1.81 BAR, says the OILP reads 4.07, EGT reads 144, OILT reads 144, PUMP reads 0.0, WBO2 reads 48, PLEN reads 32.

All those values are either what I listed or 0.0 and nothing other than that. They also come on very randomly and for many seconds at a time also. WTF does that mean?

It also says I have 7 CUS

TIME FLG0 FLG1 TIMA COOL FTR FTRM FTRH FTO2 EGRT O2-R BATT BARO ISC TPS MAFS ACLE ERPM KNCK INJP --- AIRT O2-F VSPD CUS0 CUS1 CUS2 CUS3 CUS4 CUS5 CUS6 CUS7
20:51 241.00 243.00 29.00 25.00 99.84 99.84 99.84 99.84 228.00 0.76 13.59 198.00 47.00 11.76 62.90 49.80 843.75 0.00 2.82 2.00 94.00 0.06 0.00 66.00 192.00 66.00 192.00 64.00 192.00 64.00 192.00

20:51 241.00 243.00 31.00 28.00 99.84 99.84 99.84 88.14 228.00 0.84 13.63 198.00 35.00 11.76 62.90 49.80 843.75 0.00 2.56 2.00 90.00 0.76 47.00 146.00 0.00 146.00 0.00 144.00 0.00 144.00 0.00


something else...the "VSPD" goes from 0 to 56 and other various speeds randomly when I never got over 20 mph.

[colt45 gto]

put your plug wires on in the right order that might fix something. :p

[Mean Green]

put your plug wires on in the right order that might fix something. :p

LOL...I have Coil On plug setup now..http://www.3sgto.org/showthread.php?968-300M-Coil-On-Plug-COP-Setup&p=14017#post14017

:p:p:p

[colt45 gto]

you got the other reply you posted in work safe?

what year is your car?

[colt45 gto]

LOL...I have Coil On plug setup now..http://www.3sgto.org/showthread.php?968-300M-Coil-On-Plug-COP-Setup&p=14017#post14017

:p:p:p

are they firing in the right order? i couldn't care less if you had the queen mary sat on each plug if they aint firing right :p

[Mean Green]

If your exhaust is glowing red, that's your ignition with not enough advance.Unless you got too much compression when you tested it, meaning that your cam timing has slipped.


If it's OK with a timing light then either the ECU is on it's way out or the timing marks have shifted due to a front pulley not tightened properly.
If you advance the timing while it's idling, the vacuum will get better if it's noticably retarded to start with.Otherwise it will get worse.

But then if it's a 4 bolt with fixed sensors, it's a bit different.

Murphys law says that a newly built motor that doesn't go was built wrong.

Steve

It's 4 bolt with fixed sensors. The Vac reads 15hg at idle at operating temp and when its cold it reads around 12hg.

[Mean Green]

are they firing in the right order? i couldn't care less if you had the queen mary sat on each plug if they aint firing right :p

Yea, they are firing correctly. I also tested the ecu in another VR4 and it worked great.

[colt45 gto]

are you certain the sensor pickup on the back of the crank cog is in line? sometimes they come adrift and spin, just make sure the dot on the cog lines up with the tdc cut out on the pickup disk.

[Mean Green]

Yea, they are lined up perfectly.

I cannot post a log...it says the file is to large.

[jba3]

Wait ... are you running the COP setup you posted here (http://www.3sgto.org/showthread.php?968-300M-Coil-On-Plug-COP-Setup)?

Keith has a good question. Should they be wired in parallel, and not in series? Maybe your firing order is off?

[colt45 gto]

Wait ... are you running the COP setup you posted here (http://www.3sgto.org/showthread.php?968-300M-Coil-On-Plug-COP-Setup)?

Keith has a good question. Should they be wired in parallel, and not in series? Maybe your firing order is off?

which is what i have been saying....but not in as many words lol

[Mean Green]

Wired in series to not put such a strain on the PTU. Also, the OEM coils are wired the same way.

I tested the CAM / CAS today and they are both in perfect working order. That leaves only 3 possible culprits...ANOTHER bad maf, the walbro 255 isn't working right, or the FPR is fubar when boost hits.


Anyone know where I can upload this log file at?

[Mean Green]

http://www.4shared.com/document/OvoN4EvO/September_22nd_log.html

I think that works...well, that's the log I have from when it hit what it seemed like fuel cut.

[jba3]

Wired in series to not put such a strain on the PTU. Also, the OEM coils are wired the same way.

I haven't wired up a COP before, and the only thread I know of hasn't had any measurable results yet. It's wired exactly like yours. Per that thread:

"I did drive it a couple times with the coil on plug and it ran great. However, I did have year old copper plugs in there that were fouled beyond all hope so as soon as I hit 15psi it was misfire city. I'm fairly certain it was just the plugs as that car ran and felt stronger in every other area."

Try gapping the NGKs to 30 and see what happens? Checking out the log now....

[Mean Green]

I'm running only 7 PSI now and my plugs are gapped at 34. I also noticed today that over time I am loosing fuel pressure. If I leave the car off for a long time, the pressure goes down...not within 30minutes or so but after a few hours. It doesn't go down to 0 but more like 10psi or so.


EDIT:

Ok, this is weird...

I was driving the car around trying to log it and then suddenly the o2's started reading 0 and the PUMP on the data logger started reading 16v. It did this for EXACLTY 2 minutes. I tapped the gas and the PUMP started reading 0 again and the o2's started working. For some wierd ass fucking reason the POS logger did not log this event. I managed to take some pictures of it though.

http://i101.photobucket.com/albums/m74/nismo200r/Picture013-1.jpg
http://i101.photobucket.com/albums/m74/nismo200r/Picture012-1.jpg

The line that is the highest on the logger is the fuel pump voltage.

[SpdDmnVR4]

Start tracing your wiring harness... Maybe something is cut into it... I'm really curious to see what the culprit of all this madness is

[Mean Green]

Start tracing your wiring harness... Maybe something is cut into it... I'm really curious to see what the culprit of all this madness is

Actually looking for a 93 harness now but can't find one that is cheap. I also need to get another FPR and fuel pump assembly.

[Mean Green]

Your vacuum isn't enough, Should be more like 18,
What were your actual compression numbers?
My "good" GTO which is basicly standard, a cold start, 1500 RPMs gives 20 in of vac.

Cam timing will be "out" along with the ignition timing, which is dependant on the rear cam.

Steve

I've got the Vac reduction and EGR blockoff plates as well. I was told that 15hg was good for the car. I don't remember the actual numbers but they where well within spec and no variation between cylinders.

[Mean Green]

It would be best to repeat the compression test and come back with some real numbers.
15in of Hg is BAD.

Steve

I'll try to get my hands on another comp checker. Until then I'm going to block off the brake booster and everything else and see if that helps the vac as the brake booster is OEM.

See, I'll be up all night as I cannot sleep. This whole thing is bothering the hell out of me.

[Mean Green]

With the car 100% cold, the vacuum reads 10hg and once the IACV starts to switch as the car warms up it goes to 15hg.

[Mean Green]

ok...did another compression test today with some depressing results.

Cyl Compression

1 165

2 160

3 90 dry / 130 wet

4 155

5 162

6 160

[colt45 gto]

thats why its back firing out the plenum. see if you can measur the depth of the valves from the top of the head, if the valves on #3 and lower than the rest then your going to have to pull the head. just get a light and look into the port of that cylinder too just see if you got light down there with valves shut. pull a plug and shine a bright light in the cylinder via plug hole and look down port.

[Mean Green]

thats why its back firing out the plenum. see if you can measur the depth of the valves from the top of the head, if the valves on #3 and lower than the rest then your going to have to pull the head. just get a light and look into the port of that cylinder too just see if you got light down there with valves shut. pull a plug and shine a bright light in the cylinder via plug hole and look down port.

I'm not going to fool with it. Everytime I run into a problem, I have to rebuild the entire engine and I'm done with it. I am going to try to find a complete donar engine.

[colt45 gto]

quitter! lol

[Mean Green]

quitter! lol

lol...I get pissed off for a little bit and had a few choice words with the shop that revamped my heads...that cooled me off a little bit.

I already found another front head and I will be picking it up Monday. Also, already ordered new VSS and a new HG for it as well. I will try and post up pictures of the progress as well.

[colt45 gto]

thats the spirit old boy!

onwards and upwards!?!

[Trab]

I hope its the piston and not the head lol jk

[Mean Green]

I hope its the piston and not the head lol jk

I think the motor is toast to be honest....

[Mean Green]

Piston no 3 will have a broken ringland.
The others are all too high which is what you get when you're a tooth out with the cambelt.

Steve

The timing was spot on...I guess having the heads shaved raised the compression. As for the broken ring land, we'll see, I will be removing the head tonight.

I don't have a leak down tester so I kinda devised a ghetto test...I filled the cylinder with gas after I drained the oil...the gas drained in a matter of seconds but stopped once it got below the valves. The gas went out through the exhaust valves...If it had a broken ring land, wouldn't it have emptied the cylinder pretty fast?

[Trab]

Did you figure it out yet?

[colt45 gto]

Did you figure it out yet?

http://www.3sgto.org/showthread.php?1041-What-the-F
he postin like a deemon. yeah some shit round his exhaust valves.

[Mean Green]

I rebuilt one of the spare heads that I had laying around and it is ready to go in. I went ahead and took the oil pan off and checked the bearings since the car was apart. cylinder 3 had a score mark from a piece of debri but otherwise looked great. I am going to go ahead and throw another set in just because. I am also replacing all my cams and crank cog with that of a 92 as right now I have 92 intake cams and 93 exhaust cams. I am thinking there might be a difference in where the actual cam gears sit.

[Mean Green]

I got a new set of cams and matching crank cog thanks to Echo419. I cleaned the cams off with a chemical bath, rinsed them off with boiling water, then dryed them with the heat gun. I had already prepped the head and checked all the clearances, everything matches up perfectly. I installed new cams seals and the cams along with the exhaust manifold. I prepped the deck and installed the HG right before I sat the head down on top. I placed the head in place and just had to come inside and take a break.

Cleaning all the metal shavings off of the cams was very time consuming as I do not have the right equipment for the job but managed the make do with what I had and what I had purchased from Home Depot. Hopefully within the next few hours I will be done and then Tuesday the new rod bearings come in.

[Mean Green]

I got the head installed, the cams all swapped out in both heads. I got the lower intake manifold torqued down as well. Now..time for BREAKFAST!

The more and more I work on this car, the more I cannot wait to get back into inline 6's.

[Mean Green]

I went ahead and replaced the main bearings and rod bearings despite the fact that they looked to be in great shape...I took the upper mains out and figured why put the used ones back in, so I just got new ones. I buttoned up the underside of the car for the most part and all I gotta do is hook up the down pipe to the main cat, put the belts on, clean up the upper wire harness and then fire it up.

I know one thing is forsure and that is that my fucking arms are killing me...I'm to damn tall and lanky to hold my arms in one spot for a long time and putting those main bolts back in and torquing them down kicked my ass. I already filled the car up with oil and hopefully, I pray, the car runs and drive perfectly and today will be the last day that I own a 3000GT.

I have all the old bearings just to show the possible new owner that the engine is in perfect working order mechanically now.

[Mean Green]

Did you pull that no 3 piston to have a look at it?

Steve

Yep, it was fine thankfully. I'm still kinda confused to the compression going up when I put oil in the cylinder but owell, we'll see what happens here in a little while as I just finished fixing the upper harness...again...lol