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New Atkins engine starts but will not idle/runs rough
Hi there I just finished installing a new engine from atkins on my 91 vert and I've been able to start it but it will not idle or keep running unless my foot is on the gas. It also runs a bit rough and backfires. The other thing I noticed is it doesn't seem to like starting without me holding down the gas and shutting off the injectors but that might have just been me flooding it and not paying attention. I've checked all my vacuum lines, spark plugs, injectors and so forth and they all seem to be just fine. Any other ideas as to what I might be able to do?
Took ignition timing out and reset it with proper alignment and same thing. Any advice as to advancing or retarding it without even being able to have the engine idle? Is that even something you should do?
I would check the TPS, water temp (back of water pump), and all other connectors before trying anything else. Don't forget the MAF. Also verify your grounds.
It's also a good idea to verify spark on all plugs before proceeding. You seem to have fuel based on your description. A compression test won't hurt but I wouldn't worry about the exact numbers since it hasn't broken in yet. Even bounces are good enough for now.
Keep in mind that flooding is especially common with low compression, and as mentioned rebuilds usually have low compression before break-in.
I've recently given similar advice on another thread, but here's the cliff-notes version to set your idle:
- Turn the idle air bypass screw on top of the throttle body outward (underneath the rubber cap) until the car will idle without your foot on the gas. Do NOT use the throttle stop, there is a specific small flat-head set screw for this purpose. This is not usually necessary but a fresh rebuild may need more air during the break-in period.
- Let the car warm up all the way. Keep an eye out for leaks, and keep an eye on the temp gauge since this is the first start and you want to make sure the cooling system is in good order.
- Once it's all the way warmed up (rad should get hot so you know the thermostat is open) shut the engine off. Put a jumper wire across the two pin green connector by the front driver's side headlight (near the coils). Only the two pin connector, don't touch the six pin connector.
This tells the car to lock the base timing and to not use the BAC valve for anything.
- Start the car.
- Use the idle adjust screw that I already mentioned (NOT the throttle stop) to set the idle to 750rpm, within a margin of +/-50rpm.
At this step I should mention if you have a bouncing idle, or an idle that is very high and can't be reduced, you likely have a vacuum leak. Other causes are throttle cable too tight, or hanging thermowax. You can check the thermowax with a mirror (the little roller should fall off the cam when warm), the throttle cable is too tight if pulling up on the pedal reduces the idle. I only mention it because at this stage, the idle control circuitry is completely out of the equation so you are not experiencing the BAC valve messing with the idle level.
- Adjust the timing using a timing light. Lock down the lock nut when done.
- Readjust the idle if it is no longer within the range mentioned above.
- If the idle mixture screw has been adjusted already, there is a procedure in the FSM for it. If it has not been adjusted (or you don't know if it is adjusted), don't touch it. They are set from the factory.
- Shut the car off. You can unplug the jumper you put on the green connector now.
- Set the TPS. I like the two-lamp method. Otherwise voltage and resistance methods work but I've found them to be less successful for me. Get in the car (still with the car off) and mash the throttle a bunch of times, then re-verify the TPS setting.
- Start the car and see how it goes. You may need to tweak things again after break-in when compression increases.
Great I'll do that tomorrow after the snow dies down haha. One question, on the Idle air bypass screw when you say outward would that be counterclockwise?
Great I'll do that tomorrow after the snow dies down haha. One question, on the Idle air bypass screw when you say outward would that be counterclockwise?
Yes, counterclockwise.
One thing I forgot to mention is to not lose the little rubber cap that goes over the bypass screw, and remember to put it back on when done.
Took ignition timing out and reset it with proper alignment and same thing. Any advice as to advancing or retarding it without even being able to have the engine idle? Is that even something you should do?
I'm not sure what you're saying? You need a timing light to set your timing. The symptoms you described sounds like your timing may be too retarded. Of course, it could be other things too.
So I just tried again. I realigned my CAS, verified spark, verified all wires, grounds, and vacuum lines and tried with the Idle air bypass screw and cannot get it to idle. It starts and sounds decent above 1000 rpm but as soon as I let off the gas it sputters and dies. Anything else I might be able to try without getting the car to idle?
I'm having pretty similar issues too, I just rebuilt my engine and it doesn't like to idle. It's definitely flooding quite a bit but once it's started, the engine sounds really healthy in the 1000-2500 rpm range. On the first day it wouldn't idle if I let go of the throttle, but it would "idle" at 750 rpm with no hesitation as long as I pressed the throttle ever so slightly. On the second day I was able to get the engine to idle on its own, but only with the idle adjust screw fully open. It doesn't love to idle, but it's not hunting or anything - just kind of sounds like it's bogging at times. I verified vacuum leaks as well. While verifying ignition timing since I got it to idle, I got a little confused on what the FSM states: "Check that the marks on the pulley and indicator pin are aligned. Ignition Timing: Leading 5deg ATDC Trailing 20deg ATDC".
So do I align the leading mark to the pin at idle? Or do I set timing so that the leading mark is 5 deg AFTER the pin? For now, I set the leading mark to match the pin and it sounded okay... is that correct?
I haven't done a TPS check since I never suspected it to be bad. Everything seemed healthy before I rebuilt the engine since I only had a coolant seal failure. Would doing a TPS check improve idle as well? For reference, I have emissions delete and no BAC valve.
I'm having pretty similar issues too, I just rebuilt my engine and it doesn't like to idle. It's definitely flooding quite a bit but once it's started, the engine sounds really healthy in the 1000-2500 rpm range. On the first day it wouldn't idle if I let go of the throttle, but it would "idle" at 750 rpm with no hesitation as long as I pressed the throttle ever so slightly. On the second day I was able to get the engine to idle on its own, but only with the idle adjust screw fully open. It doesn't love to idle, but it's not hunting or anything - just kind of sounds like it's bogging at times. I verified vacuum leaks as well. While verifying ignition timing since I got it to idle, I got a little confused on what the FSM states: "Check that the marks on the pulley and indicator pin are aligned. Ignition Timing: Leading 5deg ATDC Trailing 20deg ATDC".
So do I align the leading mark to the pin at idle? Or do I set timing so that the leading mark is 5 deg AFTER the pin? For now, I set the leading mark to match the pin and it sounded okay... is that correct?
I haven't done a TPS check since I never suspected it to be bad. Everything seemed healthy before I rebuilt the engine since I only had a coolant seal failure. Would doing a TPS check improve idle as well? For reference, I have emissions delete and no BAC valve.
Ground the green 1-pin connector near the battery. Turn off all accessory electrical loads. Connect the timing light high tension lead to plug wire L1. Check that the yellow mark (5 deg ATDC) is aligned to the pin. If not, than rotate the CAS until they become aligned. Connect the timing light high tension lead to plug wire T1. Check that the red mark (20 deg ATDC) is aligned to the pin. If the yellow mark is lined up on plug wire L1, but the red mark is not lined up on plug wire T1 than your ECU needs to be replaced. Leading and trailing ignition timing cannot be adjusted independently as they are coupled together through the ECU.
Alright well I've exhausted pretty much everything apart from tearing the top end off and going through everything and it still won't idle. Any other recommendations before I go and do that cause I'd really prefer not to. Thanks!
Ground the green 1-pin connector near the battery. Turn off all accessory electrical loads. Connect the timing light high tension lead to plug wire L1. Check that the yellow mark (5 deg ATDC) is aligned to the pin. If not, than rotate the CAS until they become aligned. Connect the timing light high tension lead to plug wire T1. Check that the red mark (20 deg ATDC) is aligned to the pin. If the yellow mark is lined up on plug wire L1, but the red mark is not lined up on plug wire T1 than your ECU needs to be replaced. Leading and trailing ignition timing cannot be adjusted independently as they are coupled together through the ECU.
Ok cool, thanks so much for clarifying!! I didn't know whether the marks on the pulley were already 5 and 20 deg ATDC or not. Helps a ton.
i would do something to rig the throttle open enuf that it stays running, and spray some starting fluid under the upper intake manifold, and see if the rpms change. dont go overboard as it is flamable. id suspect a vaccum leak
but as far as timing if u set the pulley to the leading mark, and follow the FSM instructions on spining the cas so its lined up with the divot, pull the top cover off, and as it slides in make sure it stays about like this as it goes in, if it goes off one direction or the other, then timing is off u will have to make sure it matches what it looked like when positioned matching the divot .
( if you find it allways trys to spin off one direction or the other, when roughtly centered dropping it in, then the timing gear could be backwards in the engine, which is not really an issue as u can just spin the cas all the way 1 direction to make up for the difference)
So at this point I have triple checked my CAS and tried about every position on the Idle screw, I have triple checked all wires and hoses and the only way I can get it to idle at all is with the throttle cable tightened down so it idles at 2000 rpm for about 10 to 20 seconds before it dies. I sprayed a small amount of starter fluid in the intake and noticed the rpms changed drastically. Is this a suspected vacuum leak? Taking off intake manifold today to inspect and replace all my spider vacuum lines. Any ideas would be greatly appreciated as to what else I might be able to change/replace/inspect.
So at this point I have triple checked my CAS and tried about every position on the Idle screw, I have triple checked all wires and hoses and the only way I can get it to idle at all is with the throttle cable tightened down so it idles at 2000 rpm for about 10 to 20 seconds before it dies. I sprayed a small amount of starter fluid in the intake and noticed the rpms changed drastically. Is this a suspected vacuum leak? Taking off intake manifold today to inspect and replace all my spider vacuum lines. Any ideas would be greatly appreciated as to what else I might be able to change/replace/inspect.
No, if you sprayed starter fluid into your intake, your engine SHOULD change rpms. If you spray starter fluid around the throttle body, the RPMs should not change - if it does, you have a vacuum leak and the engine is sucking in air from where it's not supposed to. Once you verify that you don't have vacuum leaks, I would check to make sure your BAC valve is working properly. Or you could delete it along with a whole emissions delete kit so you don't have to worry about failing vacuum lines and such.
Upon further inspection my MAF was properly plugged in and I decided to take my entire intake manifold off. When I finished taking it off I noticed that I had missed plugging in a single wire from my harness. What does this go to and would it help to solve my problem? It is a part of the wires that run to the primary injectors. (Sorry for the bad pictures and messy engine it's been a long day) I will also go about replacing all my vacuum lines
OK sorry to hop back on this but I still haven't fixed my problem. I replaced my vacuum lines, fixed a messed up gasket on my BAC valve, and looked over everything. Still won't idle but starts really well. I removed my MAF in a last effort for some reason and it idled perfectly fine at exactly 3000 rpm before I covered the intake slightly and it died. Does this help anything in terms of a diagnosis or was it just a stupid move on my part?
Considering you've gone through just about everything, I'm wondering if it's just a compression thing. How much have you driven it since you started it up for the first time? Recently rebuilt rotaries don't love to idle and it takes about a 1000 miles before everything gets dialed in. Since your engine runs fine, a non-idle issue won't cause engine damage. I would just drive it as much as you can while keeping your foot on the gas at stoplights to build compression.
And to answer your question about the MAF, it seems like it's doing its job. You changed the amount of air going in by covering the intake slightly, and then it was no longer able to compensate since the MAF wasn't plugged in. If your MAF worked before the rebuild, I doubt it's broken, but you can get a new reman unit from O'Reilly's for $100 if you so wish.
I haven't even gotten to drive it yet cause I've been dealing with trying to have it just run. Should I get it to idle wherever it can and try to just drive it and see anything changes? The lowest I've been able to have it idle is like 2500 rpm, anything below that it stalls
I haven't even gotten to drive it yet cause I've been dealing with trying to have it just run. Should I get it to idle wherever it can and try to just drive it and see anything changes? The lowest I've been able to have it idle is like 2500 rpm, anything below that it stalls
Oh so your engine doesn't even run under 2500 rpm, even with your foot on the pedal? That does seem like it would be difficult to drive dealing with that unfortunately. Another option would be to call up some rotary shops to see if you can get some other info. Or post up in FC RX7 Facebook groups where there's more active people. I've posted several questions there and always got replies within minutes.
04-19-21, 05:18 PM
