by "way2blu does a rev update" (way2blu)
Published 04/15/2017 at 12:49
by "way2blu does a rev update" (way2blu)
Published 04/15/2017 at 12:49
Tags: Toyota MR2
; Uneven acceleration
STARS: 0
Long time no see, Oppo! Summer is approaching so I’ll be posting a little more frequently now that I have time to spend with my MR2 . That being said, it started accelerating unevenly yesterday and I’m not sure what’s wrong.
For reference this is a 1991 MR2 (2nd gen) with the stock non-turbo 5S-FE 2.2 liter 4-cylinder and the 5-speed manual transmission.
Under heavier throttle inputs, let’s say 50% throttle or more, the car accelerates unevenly. It seems to alternate between full power and no power about two or three times per second on the gas.
From what I’ve been able to google, this could be one of three things:
-Clutch could be slipping, resulting in uneven acceleration. This could make sense under hard throttle, but the engine isn’t revving higher during the delays in acceleration. I’m fairly sure it’s not this one but I’m including it just in case.
-Something is wrong with the ECU. Maybe a sensor isn’t reading properly.
-Throttle cable or some linkage. It seems to be alternating between wide open throttle and no throttle and that’s what results in the uneven acceleration.
Taking the derivatives of the original graphs I get what I think the throttle position looks like over time. These gaps in power delivery are alarming and I haven’t yet found a conclusive diagnosis.
Any thoughts? Is this an issue I can avoid simply by driving the car gently until I find a fix for it, or is there a risk of greater problems arising if I continue to drive it? Any and all input is greatly appreciated.
Picture of the car for your time:
"EL_ULY" (uly)
04/15/2017 at 12:54, STARS: 4
it could even be something as simple as spark plugs. When they are worn bad but not enough for a misfire, they cause a very similar symptom (hesitation under heavier acceloration). Check plugs and wires/coils
"way2blu does a rev update" (way2blu)
04/15/2017 at 12:57, STARS: 0
I’ll take a look at that for sure, thank you!
"sony1492" (sony1492)
04/15/2017 at 13:25, STARS: 2
If you have a multimeter check the resistance of the spark plug wires, a break internally can cause issues like what your explaining. Also could be a coil thats internally shorted so when the voltage increases it is enough to arc from the primary to secondary winding internally. You can really figure that problem out though, you’d just need another coil and if it dosent work return it. Dont condemn the ecu
"I have another burner, try to guess it!" (ihaveanotherburner)
04/15/2017 at 13:30, STARS: 0
My first guess would be ignition, like everyone else is saying, my second would be something wrong with the fuel system. Third would be emissions and catalytic converter.
"jdrgoat - Ponticrack?" (jdrgoat)
04/15/2017 at 13:57, STARS: 1
Did you recently fill up with fuel? Could be a bad tank. Does the MR2 have knock sensors? It could be pulling timing if it senses knock. I’m going to guess that it has something to do with fuel or, as others suggested, spark.
Plugs, wires, distributor (I’m guessing it’s old enough to have one) cap and / or rotor. How many miles/years are on the ignition system? Could it be something with the coil?
I don’t think it’s anything with the physical throttle itself. And if it were a sensor issue, I wouldn’t expect it to be on/off, especially in a pattern like your graphs suggest. A sensor would, I think, be more intermittent and not as predictable. I had a TPS sensor going bad, and it just resulted in a somewhat high idle some, but not all, of the time.
Easiest thing, though, would be if you recently got some bad gas (not from Taco Bell).
"way2blu does a rev update" (way2blu)
04/15/2017 at 14:31, STARS: 0
I haven’t refueled the car in the past few days so I’d hesitate to think it’s the gas that’s the issue. I’ll take a look at the ignition system, far as I know it’s either the original system or replaced a while ago (As in it’s not new by any means). Thank you for the advice! Taco Bell gas is definitely a problem...
"way2blu does a rev update" (way2blu)
04/15/2017 at 14:33, STARS: 0
Sounds good (the advice not the coil shorting), I’ll look into that! Glad to hear it’s not likely to be the ecu.
"Eric @ opposite-lock.com" (theyrerolling)
04/15/2017 at 14:44, STARS: 1
Logically, it’s more likely the coil or a fuel problem.
A plugged fuel filter, weak fuel pump, clogged line, etc, can do this because enough gets through the bottleneck with lower throttle input that it seems fine, then the engine gets starved with higher throttle input.
"sony1492" (sony1492)
04/15/2017 at 14:52, STARS: 0
The reason I mentioned plug wires is because it Fixed this exact issue on my car but yes fuel filter,fuel pressure, coil, generally something simple. The main point would be to hold back on replacing expensive sensors/ECU until the basics are crossed off.
"Eric @ opposite-lock.com" (theyrerolling)
04/15/2017 at 14:56, STARS: 1
The only reason I’d bet against the wires themselves is that he should be experiencing a pretty distinct misfire if it was a plug wire. I’ve never seen all the wires go simultaneously, so working back to a common point you end up at the coil.
Modern cars with a coil for 1-2 cylinders each would have a very distinct and jarring misfire if a coil was getting marginal. With a car of this age, it would just be a loss of power.
"Eric @ opposite-lock.com" (theyrerolling)
04/15/2017 at 15:00, STARS: 0
As I mentioned in a response to a comment, my money is on something common to all your cylinders. Ignition coil, for example. I would also say that there’s a good chance it has something to do with the fuel system. Fuel pump, fuel filter, fuel lines, or injector. If the filter is plugged, it might let enough by at lower throttle and that’s why you only experience it when under higher throttle. Has the car been sitting a while?
It could also be something as simple as a plugged up air filter. Poor airflow at higher load would do similar things to a plugged fuel filter.
"sony1492" (sony1492)
04/15/2017 at 15:05, STARS: 0
That’s a good point I misread the article to be just one misfire. But it’s a total loss of power so coil would definitely be the primary suspect.