Drew Covington

Trying to get my se back on the road after sitting for several years. It's been run and driven short distances throughout this time. The problem is that it runs really good at first but after getting fully warmed up, about 10 to 15 minutes of driving, the throttle starts cutting past about quarter throttle. It still idles good but just cant give it any throttle almost. Doesnt seem rpm related, it will hold rpm. Completely throttle based. Any ideas? Kind of a strange thing. Thanks for any help

GSLSEforme

Get a replacement fuel filter,jack car up and drain filter into a clean container. What's gas look like that comes out? Get some paper towels down on ground and bang filter on ground both ends and see what comes out.
Post findings,pics here,will give further direction.

Drew Covington

Thanks for the reply. Unfortunately the car isn't close by anymore so I cant work on it again anytime soon. However the fuel should be good. I completely drained the tank and replaced the filter. Fuel was old but clean and the old filter didnt look bad, and it had been run recently before this. It feels like an electrical problem. It's not just a misfire, it's like a complete fuel cut. I was thinking it could be a bad TPS. From what I've read there should be a constant 5v on 1 wire and varying volts on the green wire depending on engine speed? I have the constant 5v but 0v on both other wires. Maybe I'm way off though.

KansasCityREPU

iTrader: (9)

It can be hard to troubleshoot when all the information isn't given. GSLSEforme is an expert in all things GSL-SE. Heed his wisdom. He might have more for you to try, but I can tell you he's going to say to change that filter before continuing.

GSLSEforme

Can you post a video duplicating problem so engine can be heard? Possible to do so at engine,using throttle linkage at throttle body to raise rpm slowly to @4k rpm,then open throttle abruptly to achieve that rpm? Can you do this"cold" and then hot to illustrate difference?
Can this only be duplicated with car under power,under way?

Drew Covington

My car is in another state at the moment unfortunately. My brother is storing it while we restore it. So I cant take any videos or work on it right now. I'm just looking for any ideas. I'll describe it the best I can.
It runs really runs good when cold. Idles up and idles down as it warms up. Revs/drives normally. After fully warming up(seems to be about 15 or 20 minutes after starting and driving some) anything past about 1/4 throttle and power cuts out completely but it will go right back to idling when throttle is released and I can slowly bring the rpms up as long as I dont give it to much throttle. I could cruise on flat ground but cant go up a hill basically. Same thing wether it's under load or not That's about all the details I can give at the moment. I was hoping it might be an easy problem to diagnose for someone who knows the gslse well. I know rotaries fairly well but the fuel injection system on that car with all its sensors and pollution crap on it seems so complicated, lol. Are there any general things that I should check besides the basic fuel filters and spark plugs and common since kind of things? Anything would help.

I really appreciate your time. Maybe it would be better if I contact you through here when I'm actually working on the car next time. I'm ok dropping this for now. I honestly didnt think I'd get any replies. 1st gens are getting less and less common. Thanks again.

GSLSEforme

I am familiar with them. The amount of emissions components on an SE is less than carbureted 12A cars.
I can assure you everything on that engine is needed for the car to run properly.
Your description of problem is still somewhat vague,personally I wouldn’t assume it’s a particular part or system and start replacing parts trying to fix it.It gets expensive fast.
Your statement it ran fine on short drives previously,what changed,tps didn’t magically go out of adjustments. If it had a defective tps,it would hardly run cold or hot,you couldn’t drive it without lurching,hesitating.
Resist temptation to adjust things, it can make matters worse and near impossible to get adjustments back where they were
Again,I can get a lot from hearing the car run using the method I outlined in previous post,it could be a lot of things causing the issue,I could eliminate several by hearing it duplicating the complaint.
When you are with the car and can do this,post you are soon to be able to get some video,or pm me to get my attention and i’ll Look for your posts.

t_g_farrell

iTrader: (1)

My bet is on the ignition, but I'm an SA owner so not hip to all the GSL-SE issues that can crop up. Heed GSLSEformes' advice, he is a master mechanic.

LongDuck

Like a smart person, I defer to GSLSEforme - as he worked extensively on RX7s back when they were popular - and from your description, I'll throw a few ideas out there that may help with differential diagnosis (ruling out one thing to focus on another), that are NOT fuel-related, and specific to the -SE model;

1) Double-Throttles (choke) not releasing - The -SE has double-throttle plates in the Throttle Body which are engaged when the engine is cold. These are located in front of the normal operation throttle plates, and function as a choke which is operated via vacuum pressure through the Thermo-wax Pellet based on coolant temp flowing through the throttle body. If the Double-Throttles are NOT releasing after engine warm-up routine, it would heavily restrict air flow into the engine, and dramatically affect performance. An easy check for this is to replicate the problem, then remove the 2x chrome plated acorn nuts that hold the Air Pipe onto the Throttle Body and view the Double-Throttle plates directly. They'll be the one on top, and after the engine is warm, they should be flat to the incoming airflow (i.e., passing air to the Primary Throttle Plates behind them), and not restricting airflow. If they are closed, try rotating the Double-Throttle rod which is connected to the vacuum pot on the front-facing, right side of the Throttle Body when viewing from the passenger side of the car. If this linkage is binding, or won't move freely, the Double-Throttle plates or actuators may be frozen, corroded, or not functioning properly.

2) Coolant Temp Sensor(s) - The 2 in question are A) at the back of the Water Pump, and B) at the bottom of the engine block. These Coolant Temp sensors are used by the ECU to determine Fuel Injector Pulse Width for the purpose of defining the right mixture. If one of these sensors is not working correctly, the ECU may assume the engine is cold all the time, resulting in excessive Fuel Injector duty cycle and an overly rich mixture. This would primarily affect overall fuel mileage and driveability after being warmed up.

3) Intake Air Temp Comparison - The SE has 2 Air Temp Sensors located A) at the Air Flow Meter, and B) at the RE-EGI chamber. These 2 signals are compared to determine if the engine is hot on restart to help set the mixture. If one or both of these sensors are not functioning correctly, the ECU will always set a cold engine condition, and / or cold intake air temp, which will result in a higher Fuel Injector duty cycle and an overly rich mixture. This also primarily affects overall fuel mileage and driveability.

Again, these are alternate things to look at, but definitely follow GSLSEforme's suggestions, first and foremost. He used to make his $$$ on diagnosis on these cars, and I'm just an enthusiast. Good luck,

Drew Covington

Thanks for the help everyone. GSLSEforme, I will message you and try and post some videos when I get the chance. Could be a couple months before I'm working on the car again, fyi. Not going to lie, you have worried me a little bit. That car has been tampered with quite a bit over the years, lol. And things have been removed that maybe shouldnt have. I have kept most of the parts I think though. So hopefully I can get it running decent again. Luckily I also have some good mechanics helping me. I guess worst case scenario I can just slap some Weber's or a Holley on that sucker, lol. Would be cool to keep the fuel injection though, if possible. Thanks again!

GSLSEforme

Don't let anxiety get the better of you-you're starting with a running car,always easier to diag a running car than one that doesn't. You're several steps removed from a non running engine.
Can you take pics of parts you have that have been removed from the car when time allows. The pieces removed may shed some light on problems you're having now and where to start.

Drew Covington

I can tell you what was removed. I got a full racing beat exhaust system. There wasnt a spot in the header for the o2 sensor. Called racing beat and they said it was fine not to use the o2 sensor and to just run it as an open loop, which I assumed meant to just remove it. Also I removed the air control/check valve and used a block-off plate. I have no idea what that valve does, so that might have been a stupid mistake. I did save it so I could put it back on if needed. Other than that, everything else should be stock.

GSLSEforme

The Racing Beat Streetport system comes with their roadrace header which has no provision for O2 sensor. Removing ACV and installing a block off plate is correct thing to do. Not having an O2 sensor will not cause your symptoms. It will cause a slight loss in fuel economy.
The ECU doesn't look for input from O2 sensor until car is in 5th gear. The O2 sensor allows the ECU to adjust fuel trim for best economy. When i drive my SE it's usually for some distance. I welded a bung into header for O2 sensor to maintain mpgs.

Did you get a chance to do videos of car?

Drew Covington

Ok, that's good to know. I do have the streetport system. Maybe in the future I'll put the o2 sensor back on like you did. No video yet. Like I said, the car is in another state, stored at my brother's house. I've been making trips there to work on it every couple months. So unless I can get my brother to take some video for me, it could be a little while before I can get them, unfortunately. I did think of something though. The gas tank is not venting and is building a lot of pressure in it while running. Blows out pretty hard when you crack the gas cap. Obviously the tank vent is clogged and needs to be cleaned out/fixed. Which I plan on doing. Could that maybe be causing any problems?

GSLSEforme

It’s possible the charcoal canister is clogged causing the high tank pressure condition. When fuel tank gets pressurized like this it’s usually associated with fuel pump whining. Do you hear that?

In engine compartment,charcoal canister located on passenger side rear fender apron. Find vacuum hose coming from metal tank vent line. Remove hose and see if tank pressurization issues subside..

I’d like to see/hear video duplicating the problem(s).
Not common for tank venting issues to cause what you’re reporting your car is doing,but venting issue needs to be addressed.

t_g_farrell

iTrader: (1)

Is it building pressure or producing vacuum? If the vent is clogged then the gas will pull a vacuum as it gets pumped down by driving. If the pump is old or weak it will have problems with this.

Drew Covington

Yes I did hear the fuel pump whining, and it was only after driving for a while and the pressure building. Someone mentioned it could be producing vacuum somehow? Is that possible? I think it was pressure but I could be mistaken. Either way, it seems possible that if the pump is being strained to much, maybe I'm loosing fuel pressure, thus causing my lose of power after driving for a bit...? Just a thought. Might be a good place to start. It ran fine when I parked it years ago and other than adding the exhaust system and removing the o2 and ACV, nothing on the motor has been changed.

GSLSEforme

I had this same scenario occur on a long trip@700 miles home from vacation. Temps in high 90s. 1st noticed it when changing cassettes.Tank level@1/4 full. Don't know how long fuel pump was making noise,til music stopped and no more conversation as i shooshed my girl so i could listen to it. Pulled over into a parking lot and put hands on pump,car running. Considering temps,pump was cooler than ambient temps. Shut car off and popped filler door and cracked gas cap,fair amount of pressure. With cap just cracked,hissing continued for @ 20 seconds.

With cap off,started car and held my hand over filler neck to see if pressure would build for @5 minutes,nothing. Cap back on and drove for @30 miles,no noise. Stopped and filled tank,drove in silence for the most part,lol. Slowly started hearing pump get noisy @160 miles on,got louder as sitting in stopped,1st gear rolling traffic for 1/2 hour. At this time i had a 16" fan on my ac condenser that turned on with ac compressor,kept car cool at idle,ac still cool. While stopped in traffic,hopped out and cracked gas cap and let pressure out,cap back on.Could feel heat on my legs rolling out from under car from electric fan Started moving again,didn't hear pump for @70 miles. Stopped for a meal,gassed up and @170 miles slowed down in traffic and heard pump again. Stopped and filled up,no noise til @1/2 empty tank. Continued doing the fill up soon as i heard noise thing til got home. There was no loss in power,driveability,idle quality when pump was noisy. Was concerned while idling and barely rolling along in traffic that i would soon be another traffic backup. Engine never missed a beat.
Some thoughts:

After vacation trip,car was in garage for a month or so.I didn't fill tank as i thought i'd be taking it down to investigate pressure buildup issue. I took it out and ripped around for @45 minutes,1/3rd tank of fuel,no noise. Ambient temp 75 degrees.
In cooler months,no noise no matter level of fuel in tank. Should be noted,i never park the car without filling tank to neck,**** about this.My car may sit 3-6 months,sometimes longer. In humid summer months,if working in garage ac is on keeping relative humidity @25%. When not in garage have humidier with humidistat set to keep humidity to 28%. All my tools love the environment,certain vehicles benefit from it also. Rust formation on rotors is minimal over several months storage.Being that i always have a full tank majority of time and often don't drive enough to get low on fuel, tank pressure/pump noise doesn't occur.
Reasoning,especially with ethanol fuel,if tank is full,it cannot form condensation and therefore promote rust. Have seen many FB tanks over the years unable to be salvaged due to rust damage from water and low fuel and driver habits. Cost same to run and leave tank low on gas as it does to keep it full.
@ 3 years ago,put car on lift during winter months and did full suspension,brake,exhaust electrical system upgrade. Emissions delete,DFI. In the interest of reliability with 120k on car i replaced fuel pump and filter while car was up in the air. There were no running issues,i take car occasionally on long drives,weekend trips and don't want problems while on the road.I used a oe Mazda pump,seems they last much longer than aftermarket pumps.

Forgot about tank pressure,pump whine condition,though i always listen for the psss as i remove gas when cap filling up. In temps from 40-70 degrees there's nothing when removing cap,above 75 more likely a slight hiss on gas cap removal. It wasn't til @a year later i had occasion to visit my sister about 100 miles away and it was hot outside,i took car to give it some exercise and near home was the pump whine. At gas station,good amount of pressure on cap removal.

My biggest concern is tank being damaged from overpressure condition. Did a lot of fault tracing for cause,nothing concrete. On way home with @1/2 tank,hot outside,let pressure off tank and pulled vacuum hose from tank off charcoal canister. Next day drove car @100 miles to a friend's place,no whine.no pressure,just a little pss when taking cap off. Before i left i reattached hose to charcoal canister, a little below a 1/4 tank,near home,pump whine. At gas station,lot of pressure on cap release. Subsequently replaced charcoal canister with one from my stash and no whine or huge pressure release on cap removal when hot outside. If tank is highly pressurized,you can feel air coming out past your hand. I've never had a vacuum buildup issue on a 1st gen but have on motorcycles and ATVs and trying to open gas door on a bike with venting issues is near impossible requiring something to leverage door open on tank when normally it pops open when key is turned and the hiss sound it makes is different than pressure release sound on my SE.
So if the gas cap on your SE wants to push against your hand on release,that's pressure buildup. If it should resist removal when turned,that's a serious vacuum in tank.

LongDuck

Routinely drive the SE in 115-118F here in the desert and can confirm high temps lead to more PRESSURE being retained in the tank. It would seem the Charcoal Canister is designed to NOT vent under high temps, when fuel vaporized more easily (specific gravity and vapor pressure - Boyles Law). Point being, at least 1/3 of the 242k mi on my car were in similar hot conditions, with no ill effects on performance or fuel tank damage.

I wouldn't worry about fuel tank expansion and contraction, and the fuel pump went 240k miles and was still good when I replaced with OEM.

GSLSEforme

While i have not driven my car in that environment,mid 90s and 72% relative humidity is more than enough,lol. I know it's a "dry" heat-we joke about that here on east coast when we walk out the door and get slapped in the face with humidity.
LongDuck,do you hear your fuel pump whine with tank pressure?

LongDuck

I can't say that I've noticed it at all in the past, but I'll remind that I did a bunch of Dynamat about 6mo ago - right around the time I replaced the (good) original Fuel Pump with 240k miles on it, so it never bothered me.

When the tank is empty and I go to fill up, there's definite pressure in the tank on hot days; not enough to spray fuel out, but a pretty good 'whoosh' of air just as you remove the Fill Cap. Also, with state-mandated emissions testing here, they test the Fill Cap and pressurize the Carbon Canister to be sure it doesn't vent to atmosphere, and the car has always passed easily. This leads me to believe the system is functioning as designed - at least to MVD standards!

Could be, I have so many other mysterious sounds coming from the car that I don't notice the Fuel Pump whine...

GSLSEforme

I 've never had fuel come out of filler neck either but more pressure than i'd like when releasing cap. Charcoal canister resolved majority of pressure issue when releasing cap and no more pump whine. Both my original pump and oe replacement pump exhibited same whine.
I used an oil filter cutter to open canister i took off and both filters in canister wouldn't pass any air thru them. I put all the pieces in a box,didn't pursue doing anything with it since i had a functioning canister.
I recall someone on here not an SE cut one of these apart and rebuilt it and had a thread on it. I think it might have been chuyler.

LongDuck

Common practice in the LandCruiser world to get rid of underhood gas smells is to use a tin can opener (*the type that scores the outside edge) to open the Charcoal Canister, remove the activated charcoal - which has absorbed it's lifetime supply of gas fumes - and then replace the charcoal with common fish-tank filter charcoal. This 'recharges' the filter and it can be reassembled using epoxy to seal it back up. Typically, the paper filters in there are designed to separate the media and prevent it getting sucked into the pressure lines, but the valves are usually in the top of the can, and easily cleaned or tested for function.

In the olden days (pre-80's, before EPA), any fuel tank venting would just go to atmosphere and we wouldn't have to drag around a bunch of crap to try and contain fumes until they could be sucked into the intake to be burned, but oh, well...

Drew Covington

Thanks for all the help guys. I actually learned quite a bit. I think I'll start with solving the tank pressure problem first and see if that has any effect. Check the fuel filter again as well. Change spark plugs, ect. Just cover the cheap and easy stuff. If that doesnt fix the problem then, as soon as I can, I'll try and post some video of the problem on here. GSLSEforme, I'll pm you and let you know if I do that. Might be a couple months from now. I've been restoring this thing for about 2 years now and this is the last hurdle I hope. Cant wait to be driving it soon, fingers crossed!

GSLSEforme

You should focus your attention to filter contents,condition of plugs. Post pics of business end of plugs here,it may provide some clues
I don’t think the pump whine when tank is under pressure is relevant to your problem.
Does the whine stop when you release pressure or is it constant. You should be able to hear pump. Normal sound is a steady zzzzzzzzx.