Junior Member
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Join Date: Sep 2013
Location: California
Posts: 7
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Junior Member
Join Date: Sep 2013
Location: California
Posts: 7
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Strange pulsing when applying throttle - coils or injectors?
TLDR - how can I confirm whether a 'pulsing' when accelerating is due to bad coils vs. injectors? (or other)
Hi, in the past couple weeks my 1997 TR4 (260k) has started to do a strange "pulsing" when I apply [steady] throttle/gas... usually most noticeable when under 3000 rpm.
I thought it was clutch slippage (it's a manual), but when I brought it to a shop they said they didn't think it was the clutch (not sure how they ruled it out), and it was more likely the ignition coils gone bad and/or combination of OE/loosening control arms (which apparently the play could give the sense of "pulsing").
They couldn't fix it before I needed to drive head out of town, so I did a quick diagnostic of the coils. One or more of them were changed around 195k -- so only about 65k ago (I've heard they can last quite long). In checking the ohms, the primary readings were 1.2-1.3ohms -- which is above the 1.05ohm specified in the FSM, so I was planning on changing them. However when I checked my multimeter against actual 1ohm resistor, it also read around 1.2ohms, so I'm wondering if the multimeter is off and the coils are fine. I did notice a bit of corrosion on the pin where the plug wires connect to the coil and so cleaned it up (I'll be replacing wires as they probably have ~60k on them as well).
When driving out of town, I added Seafoam to gas when fueling up. Interestingly since getting to the mountains (~6000ft), I no longer experience the pulsing when accelerating (or it may be very subtle), but acceleration feels pretty anemic (could be normal for being at higher elevation).
However, I'm now wondering if the issue could have been dirty/clogged injectors and either A) the seafoam did the trick cleaning them, or B) something about higher elevation helps reduce whatever is causing pulsing.
I still plan on changing plugs & wires when I get back home, but would rather not replace coils that may still be fine, especially if they may not be the actual issue (worth noting: shop said they didn't see any codes from the OBD)
Are there any recommendations around how to further troubleshoot the issue, either while at higher elevation or once back a sea level? Many thanks
Last edited by Erics4569; 02-29-2024 at 03:45 AM.
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