by "way2blu does a rev update" (way2blu)
Published 06/30/2017 at 15:27
by "way2blu does a rev update" (way2blu)
Published 06/30/2017 at 15:27
Tags: toyota mr2
; miata
STARS: 0
My fellow motorist did ask the question. “Fuel economy is why I rev it so!” I did answer.
My MR2 likes to idle high (2k rpm or higher) if I don’t give the engine lots of revs, and it’s become worse lately. I’ve signed up for autocross this coming month but I’m not sure how to diagnose/fix the throttle issues.
First throttle issue: doesn’t like to idle.
Accelerator pedal feels imprecise compared to other cars I’ve driven.
The engine will hold steady at ~2,000 rpm when lifting off throttle in neutral or putting the clutch in to shift.
Only remedy is on an immediate basis: hit the gas hard while in neutral and lift just as quickly. Revving the engine makes it drop back to normal idle.
This high-idle behavior shows up any time I lift off the gas lightly rather than abruptly.
It’s been getting worse lately, sometimes revving higher than 2,000 when I put in the clutch to shift.
I think this issue is entirely related to the accelerator pedal or throttle cable. I can provide pictures of the assembly as it sits in my car currently.
Second throttle issue: hesitation under hard acceleration
Sometimes (read: randomly and I see no correlation with any other factor) my car will hesitate intermittently under heavier acceleration.
Briefly and repeatedly cuts into throttle output. This shakes the car forward and back due to the rapid changes in the acceleration vector.
The revs and road speed remain correlated. No clutch slippage.
If the issue manifests itself during a drive, it gradually gets worse, showing up even under lighter acceleration.
It goes away entirely if I park the car and start it again later, or if I brake hard and slow down in a straight line.
The way the hesitation shows up is different every time. Sometimes it’s choppier and sometimes it has a higher frequency of hesitation.
I’ve researched this issue and it’s probably a fuel pump issue. I’ve never had the fuel tank serviced, nor ever driven it to below a quarter tank in my four months of ownership (the fuel gauge on the dash seems to get sticky below that level and I don’t trust it).
Currently I’m just looking for an accurate diagnosis of these problems so I can begin to go about fixing them. I plan to autocross it again if I can fix it with a few days left before the event, so I can drive it and confirm it’s healthy again before autocrossing it.
Advise me, Oppo... I’ll get to thank you all for some great autocross adventures if I can fix the throttle issues.
Now that that’s out of the way, here’s an update on my friend’s Miata project :
After 2 days worth of effort, we haven’t been able to bolt the downpipe to the exhaust manifold and form a proper seal. There simply isn’t room in the engine bay to turn a wrench for the 3 bolts. We can’t assemble them outside the car and then connect it through the engine bay because the steering column blocks the O2 sensor that’s connected to the downpipe.
The current plan is to have a local muffler shop assemble it so that it can be smogged and driven. Further wrenching efforts should be easier once the car is assembled properly . I’ll post updates on the project as it develops.
"Sweet Trav" (thespunbearing)
06/30/2017 at 15:36, STARS: 2
Problem 1: you have a vacuum leak.
Problem 2: replace (in this order) Plugs, Wires, Cap, Rotor, Coil. Sounds like ignition problems to me, like you have spark breaking down.
"Smallbear wants a modern Syclone, local Maple Leafs spammer" (smallbear94)
06/30/2017 at 15:36, STARS: 1
Fun is why I rev my engine so.
"I have another burner, try to guess it!" (ihaveanotherburner)
06/30/2017 at 15:39, STARS: 0
Well a throttle cleaning certainly wouldn’t hurt. I’ll bet you need to adjust your idle valve. Should just be a matter of finding it and screwing the adjuster down till it’s snug. You also might have two, a fast a slow idle valve. I doubt it’s the cable, a stretched cable would just make it lag.
Also I’d check for a vacuum leak. That’s my go to for any engine revving problems.
"crowmolly" (crowmolly)
06/30/2017 at 15:40, STARS: 0
Problem 1 could be a vacuum leak or a bad IAC valve. Fix this before you move on to problem 2, they may be related.
"SidewaysOnDirt still misses Bowie" (sidewaysondirt)
06/30/2017 at 15:48, STARS: 0
Shit, I guess it’s time for a 3SGTE....
"way2blu does a rev update" (way2blu)
06/30/2017 at 15:52, STARS: 0
Hehehe, I have crazier plans than that...
Blasphemous, even (soon as the budget permits)
!!! UNKNOWN CONTENT TYPE !!!
I wouldn’t go for the wheels or paint but that’s the conversion kit I’m aiming for.
"SidewaysOnDirt still misses Bowie" (sidewaysondirt)
06/30/2017 at 15:56, STARS: 1
"MR2_FTW - Group J's resident Stig" (MR2_FTW)
06/30/2017 at 16:12, STARS: 0
My ex had a 5SFE MR2. Hesitation is likely ignition related. Dizzy cap and rotor, plugs (NGK) and wires should help a lot. 5S’s also wear out motor mounts a lot. Google “kirkosaurus motor mount inserts” and throw those in there to keep the engine from knocking around under on/off throttle. This will also help preserve your shifter cables. The engine can move around enough to weaken them and they can snap. It doesn’t help that they go right next to the exhaust manifold either. Lastly, high idle is almost always a bubble in the cooling system. Download a copy of the factory repair manual and bleed the air out of your system per the factory guidelines. Your description of the high idle also sounds like it could be a fraying throttle cable. Take a close look at the end nearest the throttle body and see.
"way2blu does a rev update" (way2blu)
06/30/2017 at 16:50, STARS: 0
Okay! Let’s discuss. My argument for the EV swap would be as follows:
Faster. Torque is available instantly.
Still manual (their kit hooks up to the stock gearbox).
Mechanically simpler, fewer parts to fail.
Battery & EV tech is advancing very quickly. Further improvements to the setup will become available over time.
It can probably do a burnout better. Stock weight distribution is absurdly rear-biased and the resulting grip prevents such shenanigans with the stock engine. (I know that’s a silly reason but I like silly).
Because the batteries can be put in different places, I can get a custom weight distribution and decrease snap oversteer.
Convince me otherwise, I keep an open mind so I’d love to hear your side of it.
"way2blu does a rev update" (way2blu)
06/30/2017 at 16:55, STARS: 0
Thank you for the detailed response and links. I’ve bookmarked the BGB page now and I’ll take a look at the throttle cable soon.
If I hear a “clunk” from the engine bay when I shift gears when first driving the car each day, could that be a sign it’s moving around? I may need to invest in those motor mount inserts sooner rather than later if that’s the case.
"Bytemite" (bytemite)
06/30/2017 at 16:57, STARS: 1
Faster isn’t a good reason to EV an MR2. You’re not racing to get faster lap times, you’re driving for the enjoyment of it.
If you’d rather drive around basically a full scale RC car...and that sounds more fun to you then sure.
"way2blu does a rev update" (way2blu)
06/30/2017 at 16:59, STARS: 0
Any chance it could be something in the fuel tank? Such as something blocking the fuel pump under acceleration. I think your point is valid about the ignition though, I’ll take a look at that too.
"way2blu does a rev update" (way2blu)
06/30/2017 at 17:10, STARS: 0
You know, you are right. What EVs possess in torque they lack in passion, which is admittedly a drawback. I love the induction note that my car has currently (intake is right behind the driver) and I’d miss that with an EV swap.
But the instant torque and customizable weight distribution could make the car far more hoon-able if I find a good place to make a MR2 Gymkhana video. In my opinion that brings a different kind of fun to the game.
"SidewaysOnDirt still misses Bowie" (sidewaysondirt)
06/30/2017 at 17:34, STARS: 1
Keep driving it. The precursor to snap oversteer will become your friend. Being able to feather the throttle for perfect entry and get on the gas sooner than anyone in a front engine’d car is one hell of a drug and nailing it makes you feel like a god. As far as burnouts, torque, etc, 3SGTEs are super well supported and pretty famously reliable if you keep the temps under control. I see people reliably dailying them with 350 hp past the 200k mark.
"Discerning" (discerning2003c5z)
06/30/2017 at 18:30, STARS: 0
This is the correct answer.
Might want to check iac too
"Frank Grimes" (FrankGrimes)
06/30/2017 at 20:23, STARS: 0
I can fit my exhaust to my car from the wheel well and underneath the car. I had an exhaust leak at the manifold to down pipe and I solved it by undoing the entire exhaust so it can flap around even loosened the cat pipe and then bolted the down pipe back up to the manifold and tightened it up and then only then did I reattach and re bolt everything back together. socket extensions are your friend here.
"MR2_FTW - Group J's resident Stig" (MR2_FTW)
07/01/2017 at 00:49, STARS: 0
Absolutely. They are just inserts, so they fill the voids in the stock mounts, rather than replacing everything with solid urethane. They will still be pretty harsh at first with vibrations and such, but they do settle in over time. I have them on mine and I filled my side mounts as well. I really like the response and clunk-free operation.
"Sweet Trav" (thespunbearing)
07/02/2017 at 09:35, STARS: 0
from my experience, old style non PWM pumps either work, or they don’t. now it is possible that the strainer in the tank, or maybe a fuel filter is clogged.
"Sweet Trav" (thespunbearing)
07/02/2017 at 09:36, STARS: 0
Yes, check IAC. I always forget new motors have IACs