Christian's build in MA; US Exocet #148

[buildercg]

I found the diagram showing the dashpot and adjustment screw on miata.net.

[buildercg]

I got some work done on the car tonight.

My sender is working, I just forgot how slowly it changes. I have about 2 gallons of fuel in the tank which registers just above empty. I'll have to learn the adjusted gauge.

I sprayed some carb cleaner around each of the vacuum lines while the engine was idling but I didn't notice any changes in RPM.

I cannot reproduce the loss of power issue when the car is not moving. I adjusted the throttle cable back down to the point where I have a stable idle around 850-900 rpm, which nearly bottoms out the cable. There's about 1-2mm of play in the cable. I then brought the engine up to 7000 rpm numerous times by activating the throttle manually and did not experience any lag or stuttering. This was true both when the engine was cold and warm. I then took the car for a short 2 mile drive and drove it up to around 6500 rpm in 2nd and 3rd gear. There's distinct lag - best described as the car seeming like it wants to stall but then recovering on its own -  around 2500 rpm and again around 3500 rpm in both gears. It seems to be happening every time the car goes through those RPM ranges. I got over 6000 rpm a couple times and only noticed it between 2500 and 3000 and again between 3500 and 4000. However, I did not experience the earlier issue when the car tried to stall when coming to a complete stop. 

I did not get a chance to check the codes or attempt any adjustments to the dashpot or adjustment screw. I'll investigate that tomorrow.

I don't have a GoPro but I might try setting up my phone to record another test drive to record the issue.

[gwnwar]

You wrote.. "I adjusted the throttle cable back down to the point where I have a stable idle around 850-900 rpm, which nearly bottoms out the cable. There's about 1-2mm of play in the cable".
Are you using the cable to adjust the idle speed??
If so don't.. adjust the cable play with throttle linkage on the stop and throttle fully closes and then use the idle adjustment screw on the throttle body to set it with Ten and Grd jumped in Dia box..
Just spit balling.. Put a few more gallons of gas in the tank.. Under acceleration fuel will move to rear of tank some..
Have you tried a injector cleaner in the gas tank I like "Lucas" small bottle..
The adjustment screw for the dash pot is under it not the idle adjust screw..
Does the AFM door move freely not binding at all..
The engine might just need a good Italian tune up..

[gwnwar]

Have you put more fuel in yet and test drive..
Are your plug wires new.. use NKG Blue wires.. wires break down under load first, then when really bad just sitting and reving engine rpms won't climb and bad miss/bog..
Seeing you don't have the OEM intake tube in place.. What did you do with the extra wire needed for the JR intake for the AFM..
leave them or cut an shorten harness back to OEM length..
What did you do with the 1" hose from the intake tube throttle body end to the ISC valve..

[buildercg]

I did diagnose the problem: it is fuel related. I filled up my gas tank this morning and went for a short drive. Unlike prior test drives, the car ran perfectly all the way to red line in 2nd and 3rd gear (drive too short/speeds to low to warrant higher gears).

As my car has non-OEM tank/fuel lines, I suspect the lack of a check valve/regulator on the feed line to the engine coupled with a lack of a sump is leading to fuel starvation in the tank while accelerating and with a low tank due to the movement of the fuel in the tank. I'm going to start looking to add a swirl pot to maintain input fuel pressure to solve the issue. In the meantime, I'll keep the tank at least 25% full.

[buildercg]

I got a few more test drives in today. This morning's was brief, just a couple miles and then I had to head off for work. I just returned from a 20 mile test drive, which included getting up to highway speeds. Overall, the car was a lot of fun but it's a bit loose because I probably don't have the alignment setup correctly. I have an appointment on Monday to get the alignment professionally done.

A very worrying point I did notice was that towards the end of latest drive was that as I was coming off the highway coasting down a long ramp from 65mph to a 30mph zone I noticed my oil pressure had to dropped to zero while the car was in neutral. Obviously, this is very worrying. It had been around 30 with the car in 5th gear while driving at 65mph and when I started my drive it was between 30 and 60, occasionally getting up to 90, until the engine warmed up. I don't remember looking at it again until I was on the highway and then again coming off the highway. I had to drive a few miles to get back home and every time I had to get into neutral it dropped to 0 and it was barely 30 otherwise.

The car did not overheat - the temperature gauge was slightly on the cool side from the center of the gauge.

When I pulled into the garage I was expecting major oil loss or an obvious oil leak but I spent 10 minutes with a flashlight and I cannot find anything out of the ordinary. I checked the oil level three times and it's right where it was when the engine was cold. I opened the oil filler and looked inside and I could a small amount of oil on the visible cam and there was oil on the inside of the cap as would be expected. I didn't see any evidence of oil in the coolant reservoir.

I don't remember hearing anything out of the ordinary while driving.

Any idea why the gauge would suddenly be dropping to zero when the car is in neutral? It wasn't doing this on my prior drives and it certainly wasn't doing this before. Is this a sign that I should replace my oil pump immediately?

[buildercg]

Reading a couple of posts on miata.net forums. It seems that either the sender might be going bad or the fact that my drive is longer in the past plus it's about 85 degrees outside might be the cause for the low idle readings.

[gwnwar]

I would be looking at to sender unit and wire connections first..
If you remove the sender there is a hex section for a wrench on the back of the sender next to the block. If you spin the case of the
sender and not the threaded part you will break the wires in side unit.. Senders are not cheap.. 89>94 used same sender..
You could put a mechanical gauge on the engine to check it.. If you put a mech gauge on you will need an adapter BNP block thread
to NPT on most senders.
Replacing the pump before ruling out other thing is not the way to go..

[buildercg]

Jun 24, 2017 14:27:13 GMT gwnwar said:

I would be looking at to sender unit and wire connections first..
If you remove the sender there is a hex section for a wrench on the back of the sender next to the block. If you spin the case of the
sender and not the threaded part you will break the wires in side unit.. Senders are not cheap.. 89>94 used same sender..
You could put a mechanical gauge on the engine to check it.. If you put a mech gauge on you will need an adapter BNP block thread
to NPT on most senders.
Replacing the pump before ruling out other thing is not the way to go..

Thanks gwnwar. Always helpful. I checked the car again this morning and there's no obvious oil loss or leaks. I'm going to clean up the wire.

If I put a mechanical gauge on, would it go in place of the existing sender?

[gwnwar]

Just for testing...
You could just put test gauge with a long supply tube into the cockpit take a long drive and check pressures. I don't like mech oil pressure gauges mounted in dash there is always the chance of a leak and a big mess.
You should be able to get a cheap gauge with tubing and fitting at auto stores.
Remember to get the fitting.. 1/8-27 NPT Female to 1/8 BSPT Male Gauge Sensor Fitting.
Yes you can install new aftermarket gauges electrical in OEM gauge space but it is a job..
lets just get the oil pressure checked for now. Other is a good winter job.

[buildercg]

Oil pressure is good. This afternoon when I started the car the gauge stayed pegged at zero. Since I did extensive work on the wiring, I figured I check if I had a bad joint so I ran a brand new wire from the sender to the gauge. With the new wire, I get good signal. I also cleaned up the electrical pickup with sandpaper as it looked a little rusty. I cleaned up the old wire end and signal is restored with the original line. I just finished a 20 mile test and notice the gauge going back to zero at idle and generally staying around 30 except when accelerating hard. I'll re-install the temporary line and go for a ride to see if I get a different result.

[buildercg]

I also don't like the idea of the chance of oil spilling out of the dash. If my new line doesn't work then I'll start looking at replacement electrical gauges..as a winter project.

[gwnwar]

Just a quick question. Is the pic of the car as your avatar, is that the way you are driving it now..Just asking because the left/drivers front wheel looks way toed out and right/pass looks straight.

[buildercg]

Jun 25, 2017 4:35:05 GMT gwnwar said:

Just a quick question. Is the pic of the car as your avatar, is that the way you are driving it now..Just asking because the left/drivers front wheel looks way toed out and right/pass looks straight.

Good eye gwnwar. The alignment was pretty badly off. I don't have the right tools to adjust but I did modify it a couple days ago which helped a lot. I'm having it professionally setup tomorrow afternoon.

[gwnwar]

After you get the 4 wheel alignment done Monday it should drive like a new car..
You are going to want to adjust your tire pressure down some from OEM to around 23>24psi.. Adjust as needed for wear..
What are you going to use for specs to set car to.. Here is what I and a lot of miata owners use . On Miata.net it is call "Lanny's"
setup.. You can read it here or in the Garage section.. www.hummingbirds.net/alignment.html
If you want print it off for the shop.. start the adjustment at the rear of car..
Let us know how the car feels after setup..