Intermittent miss up to 2k and idle when warm NA-T

[pwpanas]

Originally Posted by Travis89Turbo

Only thing I can think of that is left would be ECU possibly. Hopefully I can talk my friend with the mk2 to let me swap ecus.

How is your valve shim clearance?

Originally Posted by interested!

Hi! , No problem ! Question ? : is the engine a high miler from new without top-end overhaul ? -- The valve seats and valves may have some pitting and this is letting the pressure through , my 7MGTE head needed an overhaul ,the seats and valves desperately needed recutting/refacing following a BHG as they were severely pitted ,a leaking ( oil ) turbo and general clean-up . I've had two engines where the inlet valves have split at the seat and burnt away , one was nearly new , the other a high miler . both were misfiring .

True. I've seen a VERY badly pitted head from running higher boost on pump gas. In fact, (among other damage) it punched right through from one combustion chamber to the next! Lots of welding and machining was required to get that head back in shape.

[Travis89Turbo]

Originally Posted by pwpanas

How is your valve shim clearance?

True. I've seen a VERY badly pitted head from running higher boost on pump gas. In fact, (among other damage) it punched right through from one combustion chamber to the next! Lots of welding and machining was required to get that head back in shape.

I checked valve shim clearance and all were to the lower side of the limits per FSM.

Mileage is only 71,000. I purchased the car from an elderly man that was original owner. All factory service records.


I have an idea. Thinkin back a few post when I had pulled all my turbo stuff off and put the header on to determine which bank of cylinders was giving me trouble. I am wondering if its just the differential pressure between the rear bank that causes the ecu to go hay wire.

What if I weld an 02 bung pre turbo on one of the front bank cylinders to trick the ecu. I know this would cause 6 cyl. To run rich but it should keep the ecu out of lean mode. And the worse that could happen is I blow a motor that I am ready to pull out anyways.

Looking way back when I first bought my na header way before the turbo kit I noticed 6 cyl. Was not near as colorful (almost ss still) compared to the others. I think that has been a weak cyl. For a long time? But the turbo pushed it beyond the ecus threshold after the boost. It did run great and not skip a beat when I was running o2 on the front bank.

[pwpanas]

Originally Posted by Travis89Turbo

I checked valve shim clearance and all were to the lower side of the limits per FSM.

Mileage is only 71,000. I purchased the car from an elderly man that was original owner. All factory service records.


I have an idea. Thinkin back a few post when I had pulled all my turbo stuff off and put the header on to determine which bank of cylinders was giving me trouble. I am wondering if its just the differential pressure between the rear bank that causes the ecu to go hay wire.

What if I weld an 02 bung pre turbo on one of the front bank cylinders to trick the ecu. I know this would cause 6 cyl. To run rich but it should keep the ecu out of lean mode. And the worse that could happen is I blow a motor that I am ready to pull out anyways.

Looking way back when I first bought my na header way before the turbo kit I noticed 6 cyl. Was not near as colorful (almost ss still) compared to the others. I think that has been a weak cyl. For a long time? But the turbo pushed it beyond the ecus threshold after the boost. It did run great and not skip a beat when I was running o2 on the front bank.

If the #6 valves are bent, you could get 4 new valves, seat them with lapping compound, and then re-shim just those four buckets. *shrug* just brainstorming ... like you said, it's a good time to try options since you're at the point where the engine may have to come out anyway.

[Travis89Turbo]

Originally Posted by pwpanas

If the #6 valves are bent, you could get 4 new valves, seat them with lapping compound, and then re-shim just those four buckets. *shrug* just brainstorming ... like you said, it's a good time to try options since you're at the point where the engine may have to come out anyway.

Well here's where it gets even trickier. I was doin the leak down on the wrong stroke. I turned engine 180 and then leakage was in the 30s?? No blowby past the valves but some out of the bottom end past rings. The motor hasn't even ran enough for the new rings on 6 to seat. So now I don't think its a valve issue anymore. Lol. This dang thing.. I'm determined to figure it out.

What I did last night is pulled all the turbo equipment off and put my NA header back on with the ECU's Narrow band O2 sensors wired into the front bank. And then My AEM wideband in the rear bank. And wouldn't you know it. Ran perfect. Doesn't skip a beat or run rough at all. And like I was figuring the rear bank is running just slightly rich 13.4 vs before issue idle was about 14.5. I was able to run the engine up to operating temp hoping to help seat the new rings. Although I found my brand new cam seals are leaking like crazy so I am addressing that issue first today.. And I mean leaking bad. Wondering if I blew them out with leak down test? But not a big deal to change.

So what I am goin to do to for a more permanent fix is weld the o2 sensor bung into my number 1 cyl. Pipe on my turbo mani pre turbo to run my ecu. I got thinkin about tuning after that and figured the best way to do it accurately (except for 6) is to weld an additional o2 bung in either 1 or 2 for my wide band. Allowing me to tune accurately to 5 cylinders and 6 be slightly rich due to lower compression which may go up with some break in. Although it will technically only be tuning to one cylinder but the others are within a few psi of eachother and the low amount of boost/power I am aiming for and just daily driving it not beating it up I believe it should work.

Then the thought of passing the emissions smog test. Luckily its obd1 so its the sniffer. How I plan on makin it pass is with a separate tune I will add only for smog and load it to the ecu at the smog parking lot. Is move my wideband to the downpipe after turbo and de fuel the other cylinders to make My exhaust fall within smog limits. What do u think? To pass smog based off other vehicles I have tuned is around 14-14.7


I will be doin tune with MAP.ECU1 with built in map sensor and runnig an IAT sensor. Deleting MAF.

[interested!]

Hi! , Excellent news! just a bit of tweaking now , had us worried for a while .

[pwpanas]

Originally Posted by interested!

Hi! , Excellent news! just a bit of tweaking now , had us worried for a while .

Agreed.

Originally Posted by Travis89Turbo

Well here's where it gets even trickier. I was doin the leak down on the wrong stroke. I turned engine 180 and then leakage was in the 30s?? No blowby past the valves but some out of the bottom end past rings. The motor hasn't even ran enough for the new rings on 6 to seat. So now I don't think its a valve issue anymore. Lol. This dang thing.. I'm determined to figure it out.

What I did last night is pulled all the turbo equipment off and put my NA header back on with the ECU's Narrow band O2 sensors wired into the front bank. And then My AEM wideband in the rear bank. And wouldn't you know it. Ran perfect. Doesn't skip a beat or run rough at all. And like I was figuring the rear bank is running just slightly rich 13.4 vs before issue idle was about 14.5. I was able to run the engine up to operating temp hoping to help seat the new rings. Although I found my brand new cam seals are leaking like crazy so I am addressing that issue first today.. And I mean leaking bad. Wondering if I blew them out with leak down test? But not a big deal to change.

So what I am goin to do to for a more permanent fix is weld the o2 sensor bung into my number 1 cyl. Pipe on my turbo mani pre turbo to run my ecu. I got thinkin about tuning after that and figured the best way to do it accurately (except for 6) is to weld an additional o2 bung in either 1 or 2 for my wide band. Allowing me to tune accurately to 5 cylinders and 6 be slightly rich due to lower compression which may go up with some break in. Although it will technically only be tuning to one cylinder but the others are within a few psi of eachother and the low amount of boost/power I am aiming for and just daily driving it not beating it up I believe it should work.

Then the thought of passing the emissions smog test. Luckily its obd1 so its the sniffer. How I plan on makin it pass is with a separate tune I will add only for smog and load it to the ecu at the smog parking lot. Is move my wideband to the downpipe after turbo and de fuel the other cylinders to make My exhaust fall within smog limits. What do u think? To pass smog based off other vehicles I have tuned is around 14-14.7


I will be doin tune with MAP.ECU1 with built in map sensor and runnig an IAT sensor. Deleting MAF.

Thanks for the update! Please keep us informed.

[Travis89Turbo]

Originally Posted by pwpanas

Agreed.

Thanks for the update! Please keep us informed.

Ok here is the latest on this car. After moving the 02 sensors like I described in am earlier post on the turbo manifold the car ran excellent. Still on factory tune. I put 250 miles on the car with slight boosting at 4psi. All was well and had no issues at all. Until yesterday when I drove it into work just a few miles from home at 430am car drove perfect to work I did not boost at all. No free way even, I work on a base and did not go over 40mph. I parked the car and it was idling perfectly with good afr and good vacuum. I went out to the car at lunch y6 hrs after i parked it and it was difficult to start and when it did only idled at 300rpm with no throttle response whatsoever. Vacuum went way low the best its gotten is -4.5hg now. Afr are way rich at first 11-12. Then falls off to 17. Which tells me the computer is seeing something it doesn't like. I am completely lost what happened to it while it was parked? good fuel pressure and spark. Any ideas? It sure is getting frustrating. 250 miles in almost a yr is all I've been able to put on this car.. And I'm to the point of maybe a new ge motor. But I am not sure that would even take care of this issue. it was running flawless until I came out for lunch.