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Installed UIM gasket, now my engine won't run

Old 08-11-15, 12:15 AM
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Installed UIM gasket, now my engine won't run

There are more details to it than that of course
I have been swapping an s4/s5 hybrid turbo 13b engine into my s4 NA chassis for over a year now, working mainly on weekends. Emissions components are removed. N332 ecu.

Recently I finally got the engine running after installing new stock 550cc injectors, an aeromotive fuel pressure regulator (set to 40 psi before the vacuum line is attached), and fixing a bunch of melts in both my front and engine harnesses. I have a walbro 255lph fuel pump installed and it was recommended to me last year on this forum to install the FPR to prevent it adding excess fuel and causing flooding.
(discussed here: https://www.rx7club.com/2nd-generati...t-run-1073012/)
Other things I replaced before getting the engine running were the TPS and installing a boost pressure sensor. The primary and secondary injector connectors were also connected backwards by the guy I bought the engine from, so that was fixed and new injector connectors were installed. knock sensor was plugged into where the o2 sensor should be. I bought and installed an o2 sensor and connected it.

After doing that, the engine started every time, even if I turned it on and quickly turned it off, then back on again. It wouldn't flood and would always start.

However it was misfiring all the time. I didn't try to drive it because of the misfiring and because I had an oil leak from the turbo oil return line which I have fixed now. Here is a video to hear the misfiring

my wideband was showing idling just below 15 but would increase up to 17 as it idled. This video shows the wideband increasing to 17

Thinking about the lean idling and misfiring, and knowing I still had an upper intake manifold gasket to install, I installed it hoping it would clear up the misfiring. However, since I installed it the engine won't start or idle.

I tried disconnecting the fuel pump connector and cranking a few times, with and without the EGI fuse. Once it was the engine would make short attempts to start while cranking. But once I hooked up the fuel pump again it would flood and I would have to try again.

I have a second variable resistor, so I read the resistance of my stock jb welded variable resistor and it was 1.3 ohm one one of the pins. I set my second variable resistor to that value and tried to crank the engine and it flooded. I de-flooded and tried setting the variable resistor to each of the three 1/4 turn options that the variable resistor has but none of them made any difference so I reconnected my stock variable resistor.

I thought this could be due to the throttle body settings being all messed up so I disassembled it and found that the primary throttle valve was basically shut at idle. I adjusted the screws as per the FSM to have a clearance within the range of 0.016-0.020". I hoped this was the problem since the vacuum leak previously was post-throttle body and could explain why the engine was getting enough air before, and not enough now. I reset the TPS to be close to 1.0 ohm (1.2 ohm at idle) knowing I would probably have to adjust it later, and re-assembled everything. However it continued to flood.

I tried removing the spark plugs and cranking with the EGI fuse out and fuel pump unplugged until all the mist/vapor stopped coming out of the engine. The two lower spark plugs seemed a bit fouled, and all were wet. I dried them off and reinstalled them but it just flooded again. I ordered new spark plugs just now. I didn't try injecting ATF.

One time after cranking to de-flood the engine, I tried spraying quick start into the AFM, and it make some attempts to start. (while the throttle was WOT)

I did compression testing at the end of working on the car last year, I've only started it about 12 times in my garage since then. As I said the engine was just running two weeks ago, installed the intake manifold gasket, and now its not.
Compression test values were:
rotor 1 ~90 psi release valve held
rotor 1 ~ 120 psi
rotor 2 ~100 psi release valve held
rotor 2 ~120 psi
I have the videos should anyone want to see them for clarification.

Should the fuel pressure regulator be set to 40 psi without the vacuum line attached at idle (or while jumping the yellow connector at the passenger strut tower)? In the FSM it shows two values, 28.4 psi while idling (which of course I can't do) or 34.1-39.8 psi while jumping the EGR pressure regulator solenoid valve (Which I don't have)


What should be my next steps? Should I install a fuel pump cutoff switch? I can only answer questions until the weekend, but if I get a good set of guidelines during this week I can check or try anything and give replies with the results on the weekend.

Last edited by trickster; 08-11-15 at 12:29 AM.
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Old 08-11-15, 07:47 AM
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vacuum leaks generally cause these problems and often small to very large leaks are overlooked.

it's funny how people ignore the obvious which is to backtrack the steps they did that created the problem, instead turning it far more complicated by tearing things not even remotely related apart and changing the outcome even further.

did you touch the fuel system when you had the UIM off? why are you now? scratches head.


your car idling with the misfire was actually normal considering it was idling over 1000 RPMs and out of idle timing mode.

Last edited by RotaryEvolution; 08-11-15 at 07:53 AM.
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Old 08-11-15, 09:36 AM
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the fuel pump has 3 tests. the first is deadhead pressure. you're supposed to hook the gauge to the pump and see what it does, 71-92psi is the spec. third is with the FPR vacuum line disconnected, 34-40psi. second is with the vacuum line hooked up, and the fuel pressure should then be base pressure + intake manifold pressure.
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Old 08-11-15, 02:06 PM
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Did you take out the engine? Have you also checked your transmission?

Like"lyger" said; it was running, you changed something, and now it won't run. You should've checked all of the intake before anything.
Probably some hose that fell off or something
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Old 08-11-15, 02:21 PM
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Originally Posted by Lyger View Post
vacuum leaks generally cause these problems and often small to very large leaks are overlooked.

it's funny how people ignore the obvious which is to backtrack the steps they did that created the problem, instead turning it far more complicated by tearing things not even remotely related apart and changing the outcome even further.

did you touch the fuel system when you had the UIM off? why are you now? scratches head.

your car idling with the misfire was actually normal considering it was idling over 1000 RPMs and out of idle timing mode.
No you're right, I didn't change the fuel system when I had it off. I was just guessing that due to the lack of unmetered air coming in after the TB, the engine might be suffocating. After, I couldn't think of anymore steps to backtrack (throttle cable adjustment, throttle settings, which would have been disturbed when I removed the UIM) I moved on to other things like fuel. Maybe I should have just stuck with vacuum related items. Interesting what you said about the idle. Can I adjust the crank angle sensor to allow it to idle more smoothly at an rpm around 1000? If not, what can be done to fix the misfiring?


Originally Posted by fc323 View Post
Did you take out the engine? Have you also checked your transmission?

Like"lyger" said; it was running, you changed something, and now it won't run. You should've checked all of the intake before anything.
Probably some hose that fell off or something
It's confusing since I've never really had the engine running correctly so I just keep thinking that there are more settings which need to be adjusted in order to have it running smoothly. I will smoke test the engine again and see what vacuum leaks come up.
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Old 08-11-15, 02:21 PM
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Originally Posted by j9fd3s View Post
the fuel pump has 3 tests. the first is deadhead pressure. you're supposed to hook the gauge to the pump and see what it does, 71-92psi is the spec. third is with the FPR vacuum line disconnected, 34-40psi. second is with the vacuum line hooked up, and the fuel pressure should then be base pressure + intake manifold pressure.
thanks for that explanation
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Old 08-11-15, 02:32 PM
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No fuel to 1 rotor.
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Old 08-11-15, 02:40 PM
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Originally Posted by Fuhnortoner View Post
No fuel to 1 rotor.
this is the cause of my misfiring issue? or my no run issue? how can you tell?
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Old 08-11-15, 02:50 PM
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Originally Posted by trickster View Post
this is the cause of my misfiring issue? or my no run issue? how can you tell?
Misfire issue and lean issue, possibly no run issue. I had the same problem. One rotor is burning and one is pumping air into your exhaust, making your AFR meter read lean. Try unplugging 1 leading wire at a time when its running. The one that kills the engine is the one that is GETTING fuel.

Also make sure you didnt cross your injector wires.
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Old 08-11-15, 02:55 PM
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Originally Posted by trickster View Post
No you're right, I didn't change the fuel system when I had it off. I was just guessing that due to the lack of unmetered air coming in after the TB, the engine might be suffocating. After, I couldn't think of anymore steps to backtrack (throttle cable adjustment, throttle settings, which would have been disturbed when I removed the UIM) I moved on to other things like fuel. Maybe I should have just stuck with vacuum related items. Interesting what you said about the idle. Can I adjust the crank angle sensor to allow it to idle more smoothly at an rpm around 1000? If not, what can be done to fix the misfiring?
well technically you're thinking backwards. a vacuum leak would cause a lean condition, so if there was a leak and you fixed it then it would run richer. if you created more vacuum leaks than were possibly present before then it may be enough to cause the car to no longer run.

if you have all the idle controls such as BAC and thermowax functioning then all you need to simply do is lower the idle and readjust the TPS. however youd have to get the car back to at least how it was before.


the car isn't running on one rotor, i can guarantee you that. it actually sounded rather normal in the video, just the idle was too high. don't adjust the CAS to retard the timing to smooth out the idle because you will lose 20 degrees of timing all around and the car will be sluggish. if it had a standalone, you could tune the timing out.

the wideband is reading lean most likely because he has a smog pump installed, those are proper numbers if so. if no smog pump is installed then they indicate a vacuum leak or low fuel pressure.

most of the time the problem is as simple as forgetting to reinstall the brake booster hose or other large vacuum line. i mean this may also be a stupid question but you did put the AFM back on right? the turbo intake ducts also like to crack and create massive leaks and no start conditions.

Last edited by RotaryEvolution; 08-11-15 at 03:06 PM.
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Old 08-11-15, 04:35 PM
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Originally Posted by Lyger View Post
well technically you're thinking backwards. a vacuum leak would cause a lean condition, so if there was a leak and you fixed it then it would run richer. if you created more vacuum leaks than were possibly present before then it may be enough to cause the car to no longer run.

if you have all the idle controls such as BAC and thermowax functioning then all you need to simply do is lower the idle and readjust the TPS. however youd have to get the car back to at least how it was before.


the car isn't running on one rotor, i can guarantee you that. it actually sounded rather normal in the video, just the idle was too high. don't adjust the CAS to retard the timing to smooth out the idle because you will lose 20 degrees of timing all around and the car will be sluggish. if it had a standalone, you could tune the timing out.

the wideband is reading lean most likely because he has a smog pump installed, those are proper numbers if so. if no smog pump is installed then they indicate a vacuum leak or low fuel pressure.

most of the time the problem is as simple as forgetting to reinstall the brake booster hose or other large vacuum line. i mean this may also be a stupid question but you did put the AFM back on right? the turbo intake ducts also like to crack and create massive leaks and no start conditions.
the emissions components are removed so I don't have the BAC, air pump, functioning thermowax. So I suppose the lean condition is due to vacuum leak or low fuel pressure although my fuel pressure gauge is showing a pretty constant 35-40 psi range.

Its possible that a new vacuum leak came about. All the vacuum lines should be reinstalled as I've gotten pretty used to pulling apart and reinstalling the components. I will smoketest everything, and recheck the ducting areas again. The AFM should be installed correctly, but i'll leave that on during the smoke testing as well. Good to hear the idle sounded fine (without a standalone anyway). I won't adjust the CAS then.
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Old 08-11-15, 05:36 PM
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Originally Posted by trickster View Post
Its possible that a new vacuum leak came about. All the vacuum lines should be reinstalled as I've gotten pretty used to pulling apart and reinstalling the components. I will smoketest everything, and recheck the ducting areas again. The AFM should be installed correctly, but i'll leave that on during the smoke testing as well. Good to hear the idle sounded fine (without a standalone anyway). I won't adjust the CAS then.
Probably some small vac hoses you forgot to plug in when slapping t back together(i know i do). Check twice, cut once.
Also, its safe to presume that the pump would work because it did before. No need for unnecessary steps
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Old 08-11-15, 05:36 PM
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The BAC is not an emissions item.
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Old 08-12-15, 07:56 AM
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you can still have the car idle below 1k without all the idle aids but it will require a warmup with your foot. otherwise the unsmooth idle is just something you have to accept.
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Old 08-12-15, 03:03 PM
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Originally Posted by fc323 View Post
Probably some small vac hoses you forgot to plug in when slapping t back together(i know i do). Check twice, cut once.
Also, its safe to presume that the pump would work because it did before. No need for unnecessary steps
Good point, I won't change the pressure then
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Old 08-12-15, 03:07 PM
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Originally Posted by satch View Post
The BAC is not an emissions item.
thanks for the clarification, I always think of it as one since it is part of the emissions removal on rotaryresurrection
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Old 08-12-15, 03:08 PM
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Originally Posted by Lyger View Post
you can still have the car idle below 1k without all the idle aids but it will require a warmup with your foot. otherwise the unsmooth idle is just something you have to accept.
Good to know, I raised it up since it was the first time I was trying the engine and had oil leaks and fuel pressure to adjust. I'll lower it back down if I can get it going
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Old 08-18-15, 09:16 AM
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I took into account a mix of everyones advice and got the engine to run again. I think it was likely just heavily flooded, but I did find some small vacuum leaks which probably had been existing even when I last ran the engine.

I smoke tested and found a crack at the bottom of the intake duct and patched it. Then I found another on one of the bottom injector seals and I put another rubber seal temporarily in place with a new one being shipped. And finally I found the small factory vacuum leak behind the thermowax which is not being used and I decided to patch that as well. I figured I can always just scrape it out if necessary.

Did an oil change, got new spark plugs, injected ATF into the lower plugs, decreased the fuel pressure to 35 psi, and added a fuel pump kill switch.

The engine turned on immediately with lots of smoke from the ATF but I need to adjust the throttle settings because I think its too low to stay running. Holding the pedal I could get it to run smoothly at 2k with out anymore misfiring which must be due to the vacuum leaks being patched and the throttle settings being corrected.


After this video I raised the idle up accidentally to 3000 and slowly lowered it but it won't let me go below 1500 rpm. Part of the thread on the throttle cable which has the two nuts that mount to the bracket is stripped. This should be an easy enough fix, and then I can further decrease the idle set screw.

I assume the main problem was the fouled plugs, and the fuel cut switch while starting probably helped as well and will help with flooding in the future.

thanks to everyone who commented

Last edited by trickster; 08-18-15 at 09:50 AM.
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Old 03-22-18, 08:29 PM
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Mazda fc differential installing

Can anyone give me a tip on how to mount the differential back on? I can get the front mount on but it does not line up with the rear mounts...1987 Mazda rx7 fc N\A
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Old 03-26-18, 09:37 AM
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Originally Posted by Homie The villain View Post
Can anyone give me a tip on how to mount the differential back on? I can get the front mount on but it does not line up with the rear mounts...1987 Mazda rx7 fc N\A
Theres no reason why it shouldnt line up
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Old 03-29-18, 02:05 PM
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Will that reservoir work on a 90 Vert?
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