12A Hesitation under acceleration, bad idle, low power and problems revving
06-24-12, 03:24 AM
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12A Hesitation under acceleration, bad idle, low power and problems revving
Hi there! I bought my RX7 back in November. It's my daily driver and I was somehow fortunate enough to find it in great shape. I really love it; despite it not being quite what I was looking for at the time, it's proven to be a riot and turns a lot more heads than I had imagined it would.
Recently, however, it's decided that it doesn't love me as much as I love it. To put it bluntly, it started running like absolute garbage. It idles poorly, it has no power, revs slowly, and past 4k rpms, it struggles to rev more and stumbles (I can hear backpressure in the exhaust with the thing floored, etc.).
Logically, I started by replacing the fuel filter. This accomplished nothing. So I next checked the spark plugs, which were possibly still usable, but showed pretty heavy signs of a lean condition in the engine. This isn't really a surprise, as I'd already thought it may be a starvation issue if it didn't turn out to be ignition related.
I then went and checked the fuel line going into the carburetor with a pressure gauge, which gave me a reading of 2.7. This seems low, but the secondary test I did (rev it way up for 15 seconds, shut it down, check float levels) did not necessarily back up that it's the fuel pump, as the float levels were fine after. If it was the fuel pump, the float levels should be low after doing this, right? I also realized when doing this that the rev issue does not really present itself (or at least isn't as bad) when I rev it in neutral; it shot right to 6k about as easy as it did before this all started. Is it possible that if it was a fuel pump issue that it would only really present itself when it's actually being driven rather than revving it in neutral?
Also, I'm not sure if this is a separate issue or related somehow, but since I bought it, it's had an intermittent issue revving past 3k. For one, it doesn't always do it, and for two, when it does, it only does it a single time over the course of a drive, and only the first time I reach 3k. It gets to 3k, and then seemingly cuts out entirely for about half a second, before picking back up and revving as usual. I poked around looking for someone with a similar issue, but haven't found much. It also still does it now with the new problems, though I've stopped driving the car until this is all sorted.
I'm at a bit of a loss at this point. I'm really hoping that whatever issue it is doesn't require something horrible like rebuilding the carb. More than anything, I just want it back up and running properly, because I'm driving a Ford Focus in the interim and I hate every second in that thing.
Recently, however, it's decided that it doesn't love me as much as I love it. To put it bluntly, it started running like absolute garbage. It idles poorly, it has no power, revs slowly, and past 4k rpms, it struggles to rev more and stumbles (I can hear backpressure in the exhaust with the thing floored, etc.).
Logically, I started by replacing the fuel filter. This accomplished nothing. So I next checked the spark plugs, which were possibly still usable, but showed pretty heavy signs of a lean condition in the engine. This isn't really a surprise, as I'd already thought it may be a starvation issue if it didn't turn out to be ignition related.
I then went and checked the fuel line going into the carburetor with a pressure gauge, which gave me a reading of 2.7. This seems low, but the secondary test I did (rev it way up for 15 seconds, shut it down, check float levels) did not necessarily back up that it's the fuel pump, as the float levels were fine after. If it was the fuel pump, the float levels should be low after doing this, right? I also realized when doing this that the rev issue does not really present itself (or at least isn't as bad) when I rev it in neutral; it shot right to 6k about as easy as it did before this all started. Is it possible that if it was a fuel pump issue that it would only really present itself when it's actually being driven rather than revving it in neutral?
Also, I'm not sure if this is a separate issue or related somehow, but since I bought it, it's had an intermittent issue revving past 3k. For one, it doesn't always do it, and for two, when it does, it only does it a single time over the course of a drive, and only the first time I reach 3k. It gets to 3k, and then seemingly cuts out entirely for about half a second, before picking back up and revving as usual. I poked around looking for someone with a similar issue, but haven't found much. It also still does it now with the new problems, though I've stopped driving the car until this is all sorted.
I'm at a bit of a loss at this point. I'm really hoping that whatever issue it is doesn't require something horrible like rebuilding the carb. More than anything, I just want it back up and running properly, because I'm driving a Ford Focus in the interim and I hate every second in that thing.
06-27-12, 10:10 AM
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Well, I've found two issues that probably conspired to make my car hate me.
First, the coasting valve is bad. I blocked off the vacuum tube and it's fixed several of the issues, notably the idling and the hesitation in the lower RPM ranges. The starvation issues at high RPM ranges persists, however.
I also discovered that my secondary jets are not firing at all. This is certainly the cause of the starvation issues, so where do I go from here? I've read that there's some sort of spring that can pop off and cause this top happen. Where is this, exactly? And if this isn't the problem, what else could it be?
First, the coasting valve is bad. I blocked off the vacuum tube and it's fixed several of the issues, notably the idling and the hesitation in the lower RPM ranges. The starvation issues at high RPM ranges persists, however.
I also discovered that my secondary jets are not firing at all. This is certainly the cause of the starvation issues, so where do I go from here? I've read that there's some sort of spring that can pop off and cause this top happen. Where is this, exactly? And if this isn't the problem, what else could it be?
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